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Plant height and evolutionary games
Abstract
In plants, investment in height improves access to light, but incurs costs in construction and maintenance of the stem. Because the benefits of plant height depend on which other height strategies are present, competition for light can usefully be framed as a game-theoretic problem. The vertical structure of the world's vegetation, which is inefficient for plant growth, can then be understood as the outcome of evolutionary and ecological arms races. In addition, game-theoretic models predict taller vegetation on sites of higher leaf area index, and allocation to reproduction only after an initial period of height growth. However, of 14 game-theoretic models for height reviewed here, only one predicts coexistence of a mix of height strategies, a conspicuous feature of most vegetation. We suggest that game-theoretic models could help account for observed mixtures of height strategies if they incorporated processes for coexistence along spectra of light income and time since disturbance.
... 21 showed that when weighted to the community level, plant height was the only trait that increased with rising temperature, mainly due to turnover of taller species. In particular, height is considered to be a crucial trait for species' C acquisition strategy due to its dominant role in light competition and its strong correlations with numerous traits for C cycling [27][28][29][30][31] . These studies, along with others, have suggested that ecosystem functions related to plant height, especially C cycling processes, will change rapidly in response to climate change 27,32,33 . ...
... These results indicate that rising temperature plays a dominant role in altering plant community composition at our warming experimental site where water is typically not limited. Height is identified as a key trait for plant ecological strategy, especially for light competition 27,[29][30][31]33 . The competitive advantage of taller species for light may serve as the underpinning mechanism for species turnover or species loss in a community, especially under fertilization or warming 21,22,27,30,33 . ...
... By relieving temperature limitation in cold ecosystems, warming may promote plant growth and light competition. Taller plants can position their leaves in the upper canopy and thus have a competitive advantage for light interception over shorter plants 29,30 , which can lead to changes in plant community composition and structure. In our warming experiment, we found a dramatic decline in light intensity from the top of the canopy to the ground surface, which indicated a strong shading effect of taller plants (Supplementary Fig. 13). ...
Growing evidence indicates that plant community structure and traits have changed under climate warming, especially in cold or high-elevation regions. However, the impact of these warming-induced changes on ecosystem carbon sequestration remains unclear. Using a warming experiment on the high-elevation Qinghai-Tibetan Plateau, we found that warming not only increased plant species height but also altered species composition, collectively resulting in a taller plant community associated with increased net ecosystem productivity (NEP). Along a 1,500 km transect on the Plateau, taller plant community promoted NEP and soil carbon through associated chlorophyll content and other photosynthetic traits at the community level. Overall, plant community height as a dominant trait is associated with species composition and regulates ecosystem C sequestration in the high-elevation biome. This trait-based association provides new insights into predicting the direction, magnitude and sensitivity of ecosystem C fluxes in response to climate warming.
... A suite of traits known as the 'agricultural weed syndrome' (Vigueira et al., 2013), including rapid growth, high nutrient use efficiency, seed dormancy, seed dispersal and herbicide resistance, have been reported in different weedy rice populations (Chauhan & Johnson, 2011;Gu et al., 2005;Sales et al., 2008;Shivrain et al., 2010;Thurber et al., 2010). For example, some weedy rice will grow taller than adjacent rice cultivars (Reagon et al., 2011;Sun et al., 2019), which can help the weeds access more light and heat (Falster & Westoby, 2003). Some weedy rice populations flower earlier than the crops they invade, a strategy that allows them to escape being collected by humans (Ellstrand et al., 2010). ...
... BHA weedy rice tends to be taller than aus cultivars (Reagon et al., 2011), and in the U.S. rice fields, BHA weeds usually tower over commonly grown tropical japonica dwarf varieties. Increasing plant height can enhance the competitiveness of agricultural weeds through the most straightforward way of accessing more light and heat (Falster & Westoby, 2003;Liu et al., 2018), although there are also potential disadvantages such as the cost of construction and maintenance of the stem or the susceptibility to lodging (Falster & Westoby, 2003;Liu et al., 2018). Although more than half of these QTLs showed evidence of selection, we were unable to identify the most plausible candidates in most of these. ...
... BHA weedy rice tends to be taller than aus cultivars (Reagon et al., 2011), and in the U.S. rice fields, BHA weeds usually tower over commonly grown tropical japonica dwarf varieties. Increasing plant height can enhance the competitiveness of agricultural weeds through the most straightforward way of accessing more light and heat (Falster & Westoby, 2003;Liu et al., 2018), although there are also potential disadvantages such as the cost of construction and maintenance of the stem or the susceptibility to lodging (Falster & Westoby, 2003;Liu et al., 2018). Although more than half of these QTLs showed evidence of selection, we were unable to identify the most plausible candidates in most of these. ...
Weedy rice ( Oryza spp.) is a weedy relative of the cultivated rice that competes with the crop and causes significant production loss. The BHA (blackhull awned) US weedy rice group has evolved from aus cultivated rice and differs from its ancestors in several important weediness traits, including flowering time, plant height and seed shattering. Prior attempts to determine the genetic basis of weediness traits in plants using linkage mapping approaches have not often considered weed origins. However, the timing of divergence between crossed parents can affect the detection of quantitative trait loci (QTL) relevant to the evolution of weediness. Here, we used a QTL‐seq approach that combines bulked segregant analysis and high‐throughput whole genome resequencing to map the three important weediness traits in an F 2 population derived from a cross between BHA weedy rice with an ancestral aus cultivar. We compared these QTLs with those previously detected in a cross of BHA with a more distantly related crop, indica . We identified multiple QTLs that overlapped with regions under selection during the evolution of weedy BHA rice and some candidate genes possibly underlying the evolution weediness traits in BHA. We showed that QTLs detected with ancestor–descendant crosses are more likely to be involved in the evolution of weediness traits than those detected from crosses of more diverged taxa.
... Дикие овощи устойчивы к различным биотическим и абиотическим стрессовым факторам в их естественной среде обитания. Таким образом, эти растения приобрели узкоспециализированную морфологию и синтезировали разнообразный набор вторичных растительных метаболитов, таких как полифенолы и витамины [10]. Несмотря на проведенные исследования по выявлению некоторых биологически активных соединений и минеральных компонентов, химический состав сныти мало изучен [11]. ...
... Физиологическая суточная норма потребления железа составляет 15-18 мг. В случае разработки обогащенного железом продукта питания содержание железа в готовом продукте должно быть не менее 15%, в случае разработки функционального продукта содержание железа должно быть не ниже 30% от суточной нормы его потребления 10 . Учитывая высокую долю макроэлемента кальция (1135 мг / 100 г), физиологическую суточную потребность в нем в количестве 1200 мг, также в качестве рекомендаций можно предложить разработку продукции, обогащенной кальцием, или функциональной направленности 11 при условии дальнейших исследований форм кальция. ...
Relevance . Aegopodium podagraria L. is a promising source of biologically active substances for use in functional and specialized food systems.
Methods . The objects of the study were ordinary dried leaves with a moisture content of 8.5%. Dried Aegopodium podagraria is prepared from leaves of goutweed, grown in the conditions of Kuzbass. When carrying out the research, the following test methods were used: the mass fraction of iron was determined according to GOST 26928-86 by the colorimetric method, the mass fraction of phosphorus according to methodological instructions 4.1.3217-14, the mass fraction of calcium according to the “Guide to methods for analyzing the quality and safety of food products” (Skurikhin I.M., Tutelyan V.A. Moscow, 1998), vitamin C content according to GOST 24556-89, mass fraction of dietary fiber according to GOST R 54014-2010 (enzymatic-gravimetric method), mass fraction of protein according to GOST 54607.7-2016 (Kjeldahl method), mass fraction of ash according to GOST 5901-2014, mass fraction of ash according to GOST 5901-2014, mass concentration of zinc and copper according to GOST 33842-2016.
Results . The article is the first to show the high content of ordinary ascorbic acid in dried leaves of Aegopodium podagraria , the proportion of which is 168 mg / 100 g, which allows recommending the ascorbic acid as an ingredient with increased antioxidant activity. According to research, the total amount of minerals is 18.65%. The high iron content should be noted: 118.9 ± 33.3 mg / 100 g, which is more than 600% of the daily intake. Of the macroelements, the content of phosphorus (144.8 ± 40.5) and calcium (1134.8 ± 158.9) is high, which satisfies the daily physiological norm of their consumption by 12% and 94%, respectively. The content of copper and zinc does not exceed their maximum permissible concentration (5 mg/kg), which indicates the safety of use in food production technologies. The data obtained make it possible to calculate the percentage of the addition of dried Aegopodium podagraria into product formulations to obtain enriched or functional products.
... Height is a key trait in the global spectrum of plant form and function (Diaz et al., 2016). It represents the economic trade-off between investment in structural tissues, stem maintenance, and access to light (Falster & Westoby, 2003). Taller plants are linked to increased biomass, acting as carbon sinks (Moles et al., 2009), and woody debris of taller plants such as trees slows decomposition (Gora et al., 2019 and references therein). ...
... Therefore, particularly since the acquisition of arborescence in the late Devonian (Stein et al., 2007), plant height can tell us a great deal about total ecosystem function (Moles et al., 2009), and has been used extensively to provide key ecological contexts for swamp dwelling plants of the Carboniferous (Philips & DiMichele, 1992;DiMichele et al., 2013). However, the light-competitive advantage of height depends on the relative height of other species within the paleo-or modern plant community rather than the absolute height of a species (Falster & Westoby, 2003), complicating inferences for fossil communities. Although plant height scored modestly as a potential paleo-functional trait (6) in our semi-quantitative evaluation, because of its importance in affecting ecosystem-scale and Earth system processes outlined above it ranked relatively highly as an ESE trait (score = 5.4; Figs 3, 4; Table S1). ...
A minuscule fraction of the Earth's paleobiological diversity is preserved in the geological record as fossils. What plant remnants have withstood taphonomic filtering, fragmentation, and alteration in their journey to become part of the fossil record provide unique information on how plants functioned in paleo‐ecosystems through their traits. Plant traits are measurable morphological, anatomical, physiological, biochemical, or phenological characteristics that potentially affect their environment and fitness. Here, we review the rich literature of paleobotany, through the lens of contemporary trait‐based ecology, to evaluate which well‐established extant plant traits hold the greatest promise for application to fossils. In particular, we focus on fossil plant functional traits, those measurable properties of leaf, stem, reproductive, or whole plant fossils that offer insights into the functioning of the plant when alive. The limitations of a trait‐based approach in paleobotany are considerable. However, in our critical assessment of over 30 extant traits we present an initial, semi‐quantitative ranking of 26 paleo‐functional traits based on taphonomic and methodological criteria on the potential of those traits to impact Earth system processes, and for that impact to be quantifiable. We demonstrate how valuable inferences on paleo‐ecosystem processes (pollination biology, herbivory), past nutrient cycles, paleobiogeography, paleo‐demography (life history), and Earth system history can be derived through the application of paleo‐functional traits to fossil plants.
... Increased investment in growth can be allocated to roots, stems or leaves. Higher investment into stem elongation can be particularly beneficial as it allows the vine to reach higher into the canopy quickly and, thus, gain more light for photosynthesis (Falster and Westoby 2003;Llorens and Leishman 2008). However, investment into stem elongation must be balanced adequately with the other needs of the vine to survive and reproduce. ...
... The first strategy was associated with fast growth, exemplified by D. odorata and I. cairica which showed high SLAs and high mean stem growth rates under both canopy and edge conditions. Having fast stem growth rates and high stem biomass allocation is beneficial for vines as it allows individuals to compete with others through early access to canopy light (Falster and Westoby 2003;Llorens and Leishman 2008). High SLA provides leaves with more efficient energy capture to invest into growth (Poorter and Bongers 2006), although it also indicates that these species are likely to be short-lived (Westoby et al. 2004). ...
To compare the capacity of native and exotic vine species established under a rainforest canopy, a comparison of growth rates and resource allocation was made amongst five exotic vine species that are serious and common invaders and two common native vine species under two light conditions reflective of edge and interior canopy conditions. All species experienced heavy reductions in growth parameters in the low-light treatment, but three exotic species showed stronger growth under the low light. All exotic species had higher plasticity in leaf morphology showing a significant increase in SLA under low light. Native vines may have a lower capacity to change leaf morphology in shade, as a result of local adaptation to edge habitats. Higher SLA under both low and high light conditions suggests that exotic vines species are able to exploit a range of forest conditions better than the native species. Three species, Anredera cordifolia , Araujia sericifera and Cardiospermum grandiflorum , appear particularly capable of invading rainforest interiors. Individuals produced few leaves, focusing resources on roots and stems suggesting a response to reach the canopy quickly. With their long-distance seed dispersal, plasticity in leaf SLA and high RGR, these species appear most likely to invade undisturbed rainforest.
... We also hypothesized that these species would have lower C i :C a and higher N area , as predicted by least-cost optimality theory (Wright et al. 2003). We further hypothesized that at drier and hotter sites, plants would be smaller-statured (Bruelheide et al. 2018;Falster and Westoby 2003) because long xylem vessels are prone to drought-induced embolisms, which are disadvantageous in drier environments (Liu et al. 2019a). Contrary to what has been observed globally, we hypothesized that plant height would be only weakly (positively) influenced by the amount of light (measured as photosynthetic photon flux density), given that these steppes are relatively open environments where competition for light is low. ...
... Instead, we found that tall plants had leaves with a high mass per area (forest steppe, Fig. 4e), or high dry matter content (typical steppe, Fig. 4f), suggesting that high LMA or LDMC enhanced vigor and promoted taller individuals. We were surprised to find that there was no relationship between leaf size and height, given that a combination of being tall and having larger leaves should generally result in more competitive plants across a range of environments (Falster and Westoby 2003). Strong selection for a narrow range of heights (Fig. S4) could explain the weak coordination between height and leaf area (Fig. 4, Fig. S7). ...
Despite being Earth’s largest biome and a key contributor to global energy budgets, arid regions (or drylands) are critically understudied relative to mesic ecosystems. Here we clarify how dryland species vary in their functional traits across environmental gradients.
We measured nine traits reflecting resource use for 68 species inhabiting dryland steppe communities across northwestern China. We tested predictions from various theoretical frameworks including the leaf economics spectrum, leaf energy balance theory and least-cost optimality theory.
Species on drier or sunnier sites had smaller leaves with higher LMA, higher leaf nitrogen concentration per area (Narea), and a greater drawdown of CO2 during photosynthesis (i.e., lower Ci:Ca) suggesting higher photosynthetic water use efficiency. Leaf nitrogen per mass and plant height (typically < 1.4 m for all species) did not vary with climate or with soil properties. Trait-trait relationships showed little patterning in relation to climate or soil. Traits of forbs were more strongly influenced by environmental properties than those of the shrubs, trees, or grasses sampled.
We investigated variation in plant traits that influence carbon economy, water use and competitive interactions, and found that in dry and low fertility environments, dryland steppe species exhibited a mixture of resource acquisitive (e.g. high Narea) and conservative leaf traits (e.g. high LMA). Our results demonstrate the utility of applying multiple theoretical frameworks to better understand variation in resource use strategies among co-occurring species.
... The leaf morphology of plants is closely related to their physiological needs, and a change in leaf morphology is a manifestation of adaptation to different habitats [57,58]. In this study, under drought treatment, the leaf area and specific leaf area of E. oxyrhinchum, A. linifolium, and H. pulchella decreased to varying degrees (Figure 4), which can help to reduce carbon depletion for building and upkeep the stems and leaves, meanwhile to reduce transpiration and improve the water storage capacity [59,60]. Adjustment of these plant functional traits is beneficial to adapt to the desert environment characterized by drought, torridity and strong radiation, and indicate the trade-off between adaptation to the environment and optimal function of ephemeral plants, thereby maximizing resource use and energy accumulation while ensuring survival [56]. ...
... A. linifolium has the smallest biomass, small leaf area and specific leaf area, and has the shortest life span and was not associated with other traits. These characteristics not only reduce the costs of growth, ensure seed quality, but also facilitate rapid completion of the life cycle, thereby greatly reducing the risks of drought [59]. This is consistent with what we have previously considered to be a drought avoidance strategy for ephemeral plants [11] and we consider this survival strategy of rapid access to resources for growth and rapid reproductive success to be a ruderal plant [61]. ...
In the context of global climate change, changes in precipitation patterns will have profound effects on desert plants, particularly on shallow-rooted plants, such as ephemeral plants. Therefore, we conducted an experiment on artificial control of precipitation for four dominant ephemeral plants, Erodium oxyrhinchum, Alyssum linifolium, Malcolmia scorpioides, and Hyalea pulchella, in the southern edge of Gurbantunggut Desert. We measured the importance value and some growth parameters of the four species under increased or decreased precipitation and constructed trait correlation networks for each of the four species. We also compared the response of increased or decreased precipitation to vegetation coverage. The results show that drought significantly reduced the survival rate, seed production and weight, and aboveground biomass accumulation of ephemeral plants. The four ephemeral plants showed different tolerance and response strategies to precipitation changes. E. oxyrhinchum and M. scorpioides can avoid drought by accelerating life history, and E. oxyrhinchum, A. linifolium, and H. pulchella can alleviate the negative effects of drought by adjusting leaf traits. However, the response of different species to the wet treatment was not consistent. Based on the results of the trait correlation network, we consider A. linifolium belongs to the ruderal plant, E. oxyrhinchum and M. scorpioides belong to the competitive plants, and H. pulchella belongs to the stress-tolerant plant. The outstanding trait coordination ability of E. oxyrhinchum makes it show absolute dominance in the community. This indicate that ephemeral plants can adapt to precipitation changes to a certain extent, and that distinct competitive advantages in growth or reproduction enabled species coexistence in the same ecological niche. Nevertheless, drought significantly reduces their community cover and the ecological value of ephemeral plants. These findings established the basis to predict vegetation dynamics in arid areas under precipitation changes.
... 55 Game-theoretic models predict taller plants to have larger leaf size, which could be attributed to resource utilization and support costs. 56 Taller plants are more likely to intercept more light, while photosynthesis is the basis of plant growth, 57 and is associated with leaf size and ability on radiation loading. On another hand, supporting cost and water utilization of leaf area increase with height. ...
... In tropical rainforest, species replacement is driven by light competition as light is the most limiting resource in vertically developed tropical forests (Fauset et al. 2017;Rozendaal et al. 2020). During tropical forest succession, there is a rapid build-up of the forest canopy, resulting in a marked vertical light gradient with less light in the forest understory (i) Investing in height or crown growth to increase light interception (LIE, light interception per unit aboveground biomass) (Hikosaka et al. 1999;Falster and Westoby 2003), and/or (ii) Utilizing the intercepted light more efficiently for their growth (i.e., light use efficiency, LUE) (Valladares and Niinemets 2008;Onoda et al. 2014). Tree species differ in their light competition strategies by Communicated by Yoshiko Iida. ...
Light competition is thought to drive successional shifts in species dominance in closed vegetations, but few studies have assessed this for species-rich and vertically structured tropical forests. We analyzed how light competition drives species replacement during succession, and how cross-species variation in light competition strategies is determined by underlying species traits. To do so, we used chronosequence approach in which we compared 14 Mexican tropical secondary rainforest stands that differ in age (8–32 year-old). For each tree, height and stem diameter were monitored for 2 years to calculate relative biomass growth rate (RGR, the aboveground biomass gain per unit aboveground tree biomass per year). For each stand, 3D light profiles were measured to estimate individuals’ light interception to calculate light interception efficiency (LIE, intercepted light per unit biomass per year) and light use efficiency (LUE, biomass growth per intercepted light). Throughout succession, species with higher RGR attained higher changes in species dominance and thus increased their dominance over time. Both light competition strategies (LIE and LUE) increased RGR. In early succession, a high LIE and its associated traits (large crown leaf mass and low wood density) are more important for RGR. During succession, forest structure builds up, leading to lower understory light levels. In later succession, a high LUE and its associated traits (high wood density and leaf mass per area) become more important for RGR. Therefore, successional changes in relative importance of light competition strategies drive shifts in species dominance during tropical rainforest succession.
... It may be due to the availability of the essential nutrients in the Tithonia leaf powder, which accelerate the cell division and elongation for increasing the plant height. Plant height is a foremost determinant of a plant's ability to compete for light (Falster and Westoby, 2003) which is one of the required inputs for photosynthesis. The number (7) of leaves per plant was a maximum value in T4 and T5; meanwhile, all the other treatments except T6 showed a relatively higher number of leaves than the T1 (control). ...
Tithonia diversifolia is a genus of flowering plants and its leaves have been used to improve fertility and soil properties by supplying organic matters and nutrients. This experiment was done to study the effect of compost with powdered Tithonia leaves on okra yield and to select the optimal quantity of Tithonia leaves for obtaining the optimum yield of okra in the sandy regosol soil conditions. This experiment was carried out in a completely randomized design with five replicates with the following treatments; T1 - recommended chemical fertilizers (control), T2 - compost 140 g alone, T3 - compost 140 g + 15 g powdered Tithonia leaves (PTL), T4 - compost 140 g + 30 g PTL, T5 - compost 140 g + 45 g PTL, T6 - compost 140 g + 60 g PTL. These fertilizers were applied as the basal application to each polybag (0.07 m2), while the top dressing was not applied in this experiment. The results revealed that compost with PTL application had effects on the number of pods per plant, the number of seeds per pod, pod length, pod girth, single pod weight, fresh pod weight per plant and marketable pod yield. Further, it was found that T4 was more suitable for obtaining a better marketable pod yield of okra in sandy regosol soil conditions. Based on the results obtained, it can be concluded that 2 kg m-2 compost with 0.43 kg m-2 powdered Tithonia leaves as the basal application could be used in okra cultivation.
... It is probable that the intense growth of shoots led to a decline in stem radial growth rate, as a strong incentive is given TABLE 7 Linear regression slopes of the relationship between relative growth increment (RGI) and predictor environmental variables (air temperature (T A ), air relative humidity (RH), soil volumetric water content (SWC) and photosynthetically active radiation (PAR)) in control (C), air humidification (H) and soil irrigation (I) treatments during different sampling periods (weeks of the year). to height growth over diameter growth in forest stands where light competition takes place (Falster and Westoby, 2003). This point is indirectly supported by the weaker impact of environmental factors on RGI dynamics in the second subperiod (Table 6). ...
Introduction
Global warming promotes geographical variability in climate, although the trends differ for the lower and higher latitudes of the Northern Hemisphere. By the end of the current century, the climate models project an increase of up to 20–30% in summer precipitation for northern Europe, accompanied by an increase in atmospheric humidity. Information on the effects of increasing precipitation and air humidity on the performance of northern trees is scant.
Methods
We studied the effects of artificially elevated air relative humidity (RH) and soil moisture on growth, phenology and needle/shoot morphology of 5-year-old Norway spruce ( Picea abies ) saplings at the Free Air Humidity Manipulation (FAHM) experimental site in eastern Estonia. The trees were subjected to three treatments: C – control, ambient conditions; H – air humidification, mean relative humidity ~ + 5%; I – soil irrigation, precipitation +15%. Trees from pure stands were sampled from three experimental plots per treatment in 2022.
Results
The needle morphology of P. abies was insensitive to moderate changes in air humidity and soil water content in northern mesic conditions. In contrast, the humidity treatments significantly affected shoot size, which decreased in the following order: C > I > H. This finding indicates a certain deceleration of the development of trees’ assimilating surface under elevated air humidity. The humidity manipulation did not influence the timing of bud burst, but the trees differentiated between two phenological forms – early-and late-flushing forms. Trees growing under elevated RH exhibited slower growth rates compared to trees in C and I treatments. The early-flushing trees grew faster, while the late-flushing trees performed better under increasing environmental humidity.
Conclusion
At high latitudes, the increasing precipitation and concomitant rise in atmospheric humidity counteract the enhancement of trees’ growth and forest productivity predicted for boreal forests due to global warming. Given that the late phenological form of P. abies is more tolerant of wetter climates and less threatened by late spring frosts, it has a greater potential to adapt to regional climate trends predicted for northern Europe.
... Height is a key plant characteristic that distinguishes potential fitness variation across individual plants in an ecosystem (Moles et al., 2009;Nagashima and Hikosaka, 2011). It is a crucial attribute of the ecological strategies used by woody plants to ensure their long-term survival in challenging environments (Díaz et al., 2016;Falster and Westoby, 2003). In this study, the Euryops floribundus shrub showed more investment in plant height growth on the north-facing slopes than on south-facing slopes at Upper Mnxe and Manzimdaka, respectively. ...
Mountainous grassland landscapes are severely threatened by the proliferation of shrub encroachment. So far, it remains unclear though how slope aspect coupled with land disturbances linked to the proximity of homesteads to communal grazing sites affects the distribution, density and structure of the encroaching shrubs in these grassland ecosystems. In this study, we investigated the role that slope aspect plays in determining the density and structure of an encroaching shrub species Euryops floribundus N.E. Br in three communal grazing sites located at varying distances from rural homesteads in a semi-arid mountainous grassland in the Eastern Cape Province of South Africa. Three sites were strategically chosen in Cala communal grazing lands in an encroached mountainous grassland landscape that depicted north and south-facing slope aspects. The selected sites were Tsengiwe; a site located in close proximity to homesteads at a distance of less than 100 m, Upper Mnxe situated at an intermediate distance ranging from 200 to 800 m away from homesteads and Manzimdaka, which was located furthest from homesteads at a distance greater than 1600 m. In each site and corresponding slope aspect, the density and structure of the shrub E. floribundus were evaluated on 36 randomly distributed plots, yielding a total of 108 plots across all sites. We found that shrub density was significantly higher (50%) on the north-facing slope compared to the south-facing slope in Tsengiwe, the site located near homesteads. Shrub height was significantly higher (53 and 17%) on the north-facing slope compared to the south-facing slope at Upper Mnxe and Manzimdaka, which were located at intermediate and furthest distances from the homesteads. Notably, shrub height was significantly lower (37%) in the north-facing slope compared to the south-facing slope in Tsengiwe. Following a similar pattern to shrub height, total stem number was significantly higher (20 and 85%) in the north-facing slope compared to the south-facing slope at Upper Mnxe and Tsengiwe, respectively. Shrub crown area was higher (33 and 11%) in the north-facing slope compared to the south-facing slope at Upper Mnxe and Manzimdaka, respectively. A strong positive relationship was established between the height of shrubs and their longest crown diameter, shortest crown diameter and shrub crown area across all sites, suggesting that the investigated shrub species E. floribundus employs its structural characteristics to survive, and thrive and this was more evident in the north-facing slope. The results highlight the importance of considering the proximity of homesteads into account in ecological studies, and puts emphasis on improved understanding of the vegetation patterns shaped by shrub encroachment in mountainous grasslands, which is crucial in the development of effective land management strategies.
... In closed-canopy systems globally, plants exhibit intense competition for light, prioritizing vertical growth to attain elevated positions within the canopy, thereby enhancing their capabilities to intercept light (Hirose andWerger 1995, Falster andWestoby 2003). Light competition is especially strong in many tropical rainforests as they have a dense canopy, resulting in a marked decrease in irradiance from the canopy to the forest floor (Fauset et al. 2017). ...
In closed‐canopy systems globally, plants exhibit intense competition for light, prioritizing vertical growth to attain elevated positions within the canopy. Light competition is especially intense in tropical rainforests because of their dense shaded stands, and during forest succession because of concomitant changes in vertical light profiles. We evaluated how the height growth of individual tree differs among forest light strata (canopy, sub‐canopy and understorey) and successional guilds (early, mid‐ and late successional species) during secondary succession in a Mexican rainforest. Fourteen secondary forest stands differing in time since agricultural abandonment (1–25 years) were monitored for seven consecutive years. For each stand and census year we estimated relative light intensity (RLI) for each height and categorized trees into forest light strata: understorey (RLI ≦ 33.3%), sub‐canopy (33.3% ≦ RLI ≦ 66.6%) and canopy (RLI ≧ 66.6%), and into successional guilds based on the literature. We estimated two measures of height growth: absolute height growth (HG abs , cm year ⁻¹ ) calculated as the difference in tree height between two consecutive censuses, and biomass partitioning to height growth (HG bp , in kg kg ⁻¹ × 100) calculated as the percentage of total aboveground biomass growth partitioned to height growth. Earlier in succession, trees for all strata had greater HG abs and HG bp , resulting in rapid vertical forest development. HG abs was fastest for canopy trees, followed by sub‐canopy and understorey trees. These differences in HG abs among strata, combined with their inter‐specific variation and continuous recruitment of small individuals, lead to a rapid differentiation in tree sizes and increase stand structural heterogeneity. HG bp was greater for understorey and sub‐canopy trees than for canopy trees, reflecting ontogenetic changes in the light competition strategy from growth to persistence. With succession, both HG abs and HG bp decreased, most strongly for canopy trees, probably because of an increased exposure to drought stress. These successional changes stabilize stand size structure and reduce the rate of development.
... As the community develops further, canopy closure within the forest increases. If early-successional and transitional trees attempt to emerge above the canopy, they will have narrower and thinner crowns, taller stems, and increased investment in stem construction and maintenance for tree support [55], water transport [56], and other physiological functions. However, narrow crowns lead to insufficient photosynthesis, reduced carbon reserves within the trees, and, consequently, a decrease in individual growth rates. ...
Neighborhood competition influences tree growth, which can affect species composition and community succession. However, there is a lack of understanding regarding how dominant tree species at different successional stages of forest communities respond in terms of crown architecture and functional traits during their growth process to neighborhood competition. In this study, we analyzed the responses of average annual basal area increment (BAI), crown architecture, and leaf functional traits of early-successional species (Cunninghamia lanceolata and Pinus massoniana), transitional species (Alniphyllum fortunei and Choerospondias axillaris), and late-successional species (Elaeocarpus duclouxii and Castanopsis carlesii) to neighbor competition in a secondary evergreen broad-leaved forest. We found that the BAI of all species is negatively correlated with competition intensity. Notably, early-successional and transitional species exhibited a more rapid decline in growth rates compared to late-successional species in response to increased competition. Among these tree species, the response of crown structure to neighbor competition exhibited variation. Early-successional and transitional species displayed a negative correlation between the competition index and crown area (CA)/diameter, while a positive correlation emerged between the lowest branch height (LBH)/height. Conversely, late-successional species followed the opposite trend. In terms of leaf functional traits, specific leaf area (SLA) showed heightened sensitivity to neighborhood competition, with a positive correlation between SLA of all tree species and the competition index. Furthermore, water use efficiency (WUE) demonstrated negative correlations with the competition index in early-successional and transitional trees, while a positive correlation emerged with late-successional trees. These findings suggest that early-successional and transitional trees prioritize vertical canopy growth, whereas late-successional trees tend to favor horizontal canopy expansion in response to neighboring competition. Additionally, early-successional and transitional trees experience more significant suppression of radial growth rate. Our research contributes to a deeper understanding of the underlying mechanisms driving changes in species composition and community succession.
... Allometric partitioning theory (APT) offers a framework explaining how biomass is distributed among plant organs (Grime, 2001), grounded in metabolic and biomechanical constraints (Enquist and Niklas, 2002;Falster and Westoby, 2003;Peng et al., 2022). This theory, referred to as the fixed allometric effect or apparent plasticity, anticipates leaf biomass scaling with the ¾ power of stem and root biomass. ...
Background and Aims
Understanding biomass allocation among plant organs is crucial for comprehending plant growth optimization, survival and responses to global change drivers. Yet, mechanisms governing mass allocation in vascular plants from extreme elevations exposed to cold and drought stresses remain poorly understood.
Methodology
We analyzed organ mass weights and fractions in 258 Himalayan herbaceous species across diverse habitats (wetland, steppe, alpine), growth forms (annual, perennial taprooted, rhizomatous, cushiony), and climatic gradients (3500–6150 m elevation) to explore whether biomass distribution adhered to fixed allometric or optimal partitioning rules, and how variation in size, phylogeny, and ecological preferences influence their strategies for resource allocation.
Key Findings
Following the optimal partitioning theory, Himalayan plants distribute more biomass to key organs vital for acquiring and preserving limited resources necessary for their growth and survival. Allocation strategies are mainly influenced by plant growth forms and habitat conditions, notably temperature, water availability, and evaporative demands. Alpine plants primarily invest in belowground stem bases for storage and regeneration, reducing aboveground stems while increasing leaf mass fraction to maximize carbon assimilation in their short growing season. Conversely, arid steppe plants prioritize deep roots over leaves to secure water and minimize transpiration. Wetland plants allocate resources to aboveground stems and belowground rhizomes, enabling them to resist competition and grazing in fertile environments.
Conclusions
Himalayan plants from extreme elevations optimize their allocation strategies to acquire scarce resources under specific conditions, efficiently investing carbon from supportive to acquisitive and protective functions with increasing cold and drought. Intraspecific variation and shared ancestry did not significantly alter Himalayan plants' biomass allocation strategies. Despite diverse evolutionary histories, plants from similar habitats have developed comparable phenotypic structures to adapt to their specific environments. This study offers new insights into plant adaptations in diverse Himalayan environments and underscores the importance of efficient resource allocation for survival and growth in challenging conditions.
... -1 which was 7.155gm. The result of the present study showed that by increasing the seeding rate plant height was increased, this was opposite to the result of the previous studies which confirmed that equally high plants were recorded for both seed rates, demonstrating that an increase in seed rate does not always lead to an increase in plant height (Falster et al., 2003 andGeorgieva et al., 2020). The number of primary branches was negatively related to the seeding rate, due to increase competition between plants for growth factors, which finally reduced the (2011) confirmed that dry matter yield increased significantly (p<0.05) as the nitrogen fertilization level increased from 200 kg/ha to 400 kg/ha, but the fresh yield was not significantly different according to nitrogen fertilization level (p<0.05). ...
This study was conducted to evaluate the influence of seeding rates and nitrogen application on the growth, forage yield, and its components of different vetch varieties under rainfed conditions of sulaimani region during the growing season of 2020-2021. The field experiment was conducted in a split-split plot layout arrangement with a randomized complete block design (RCBD) with three replications. The main plots were fertilizer applications (no fertilization 0Kg N/ha and fertilization 40Kg N/ha), and subplots consisting of five varieties of vetch obtained from Agricultural Research Centre-Sulaimania were (V1(Morrd), V2 (Rook), V3 (Excel), V4 (Clima), and V5 (Namoi)), while sub-sub plots were two different seeding rates (40 Kg/ ha and 60 Kg/ha). The result of this investigation showed that the application of nitrogen fertilizer caused to increase in some growth traits of vetch such as no. of branches. plant-1 , no. of leaves. plant-1 , the weight of leaves. plant-1 and root length, green forage yield, dry forage yield, dry matter%, fresh leaf%, fresh leaves/stem ratio, dry leaf%, and dry leaves/stem ratio. Variety 2 (Rook) gave the highest value for most growth traits, green forage yield, and dry forage yield, but the lowest dry matter% was obtained by this variety, and variety 1 (Moord) was the best among other varieties for forage yield components such as fresh leaf%, fresh leaves/stem ratio, dry leaf%, and dry leaves/stem ratio. By increasing the seeding rate plant height, and weight of leaves. plant-1 , green forage yield, dry forage yield, fresh stem%, and dry stem% were increased but other growth traits and dry matter% decreased. Cluster analysis results indicate the presence of high variability based on agro-morphological traits between five varieties of vetch used in this study thus, the improvement of this crop is possible through the breeding techniques.
... They are closely related to the biophysical and biochemical processes of ecosystems. H governs light access (Falster and Westoby 2003) and seed dispersal distance (Thomson et al. 2011), while DBH influences water transport and mechanical support within the plant, and also affects leaf biomass. The relationship between these variables reflects the trade-off in the 'growth versus survival' life strategy. ...
The tree height–diameter at breast height (H–DBH) and crown radius–DBH (CR–DBH) relationships are key for forest carbon/biomass estimation, parameterization in vegetation models and vegetation–atmosphere interactions. Although the H–DBH relationship has been widely investigated on site or regional scales, and a small amount of studies have involved CR–DBH relationships based on plot-level data, few studies have quantitatively verified the universality of these two relationships on a global scale. Accordingly, this study first evaluated the ability of 29 functions to fit the H–DBH and CR–DBH relationships for six different plant functional types (PFTs) on a global scale, based on a global plant trait database. Results showed that most functions were able to capture the H–DBH relationship for tropical PFTs and boreal needleleaf trees relatively accurately, but slightly less so for temperate PFTs and boreal broadleaf trees. For boreal PFTs, the S-shaped Logistic function fitted the H–DBH relationship best, while for temperate PFTs the Chapman–Richards function performed well. For tropical needleleaf trees, the fractional function of DBH could satisfactorily capture the H–DBH relationship, while for tropical broadleaf trees, the Weibull function and a composite function of fractions were the best choices. For CR–DBH, the fitting capabilities of all the functions were comparable for all PFTs except boreal broadleaf trees. The Logistic function performed best for two boreal PFTs and temperate broadleaf trees, but for temperate needleleaf trees and two tropical PFTs, some exponential functions demonstrated higher skill. This work provides a valuable foundation for parameterization improvements in vegetation models, and some clues to forest field investigations.
... Although the investigated climate-trait relationships were mostly consistent across broadly defined habitats, we found several habitat-specific relationships. For instance, the increase in plant height along the Mediterranean and temperature gradients could be explained by the longer growing season and higher light availability, which both increase competition for light in warmer regions 42,43 . In forest habitats, the decrease in plant height along the Mediterranean gradient could be attributed to the limiting effects of higher temperatures and lower water availability on the growth of canopy trees. ...
Ecological theory predicts close relationships between macroclimate and functional traits. Yet, global climatic gradients correlate only weakly with the trait composition of local plant communities, suggesting that important factors have been ignored. Here, we investigate the consistency of climate-trait relationships for plant communities in European habitats. Assuming that local factors are better accounted for in more narrowly defined habitats, we assigned > 300,000 vegetation plots to hierarchically classified habitats and modelled the effects of climate on the community-weighted means of four key functional traits using generalized additive models. We found that the pre-dictive power of climate increased from broadly to narrowly defined habitats for specific leaf area and root length, but not for plant height and seed mass. Although macroclimate generally predicted the distribution of all traits, its effects varied, with habitat-specificity increasing toward more narrowly defined habitats. We conclude that macroclimate is an important determinant of terrestrial plant communities, but future predictions of climatic effects must consider how habitats are defined. Predicting the effects of a changing climate on the diversity and functioning of the ecosphere requires an understanding of how climate drives the distribution of plant species and ecosystem properties 1,2. Ecosystem functioning, such as productivity and nutrient cycling, is strongly determined by the functional composition of the plant community 3-6. Functional traits represent species' life-history strategies 7 , and are often summarized with a few main, largely independent , axes of variation, such as the fast-slow continuum 8 , as reflected in the leaf-economics spectrum 9 , the species' reproductive strategy 10 , the plant size spectrum 7 , and the continuum of collaboration with mycorrhizal fungi 11. A foundational, yet globally weakly supported, assumption in trait-based ecology is that the geographical distribution of dominant functional traits in plant communities is shaped by macro-environmental gradients, independently of taxonomy 12-14. Here, we addressed this assumption by studying the consistency of macroclimate-trait relationships among European plant communities.
... (Zeng et al., 2021) found that a timely irrigation in reviving and jointing period of wheat would gain a relatively high yield, which was similar to our results. Soil water at the reviving and jointing stages of wheat greatly influences the formation of pre-anthesis biomass, so a moderate irrigation can accelerate the process of biomass into grains (Falster and Westoby, 2003;Zeng et al., 2021). Besides, (Yao et al., 2015) found that severe drought in the early growth period of winter wheat could affect its aboveground growth and development, and this harmful effect could not be compensated later. ...
North China Plain suffers from the world's most severe water scarcity and groundwater depletion due to intensive irrigation for agricultural production. It is imperative to reduce irrigation water consumption while safeguarding crop production and food security. This study conducted a quantitative analysis with deficit irrigation strategies for winter wheat using a water-driven AquaCrop model. After model calibration and validation with field experimental data, we analyzed the irrigation water demand, crop yield, and water productivity (WP) of winter wheat under various deficit irrigation scenarios. A set of optimal irrigation schedules were proposed for different climate years, which significantly mitigated irrigation water usage while sustaining high yields and WPs. The results indicated that despite the irrigation water demand of winter wheat under the future climate scenario was slightly higher than that in the historical period, their crop water sensitive periods (reviving, jointing, and flowering) remained the same. Therefore, we recommended adopting the same deficit irrigation schedules for the historical and future periods. In wet years, adopting a 50% deficit irrigation strategy only reduced crop yields by less than 5% compared with full irrigation, but it saved 1000-1100 m 3 of water per hectare and contributed a WP higher than 1.88 kg/m 3. While in normal and dry years, an optimal 25% deficit irrigation could sustain over 96% of the maximum yield, meanwhile it could save 650-800 m 3 /ha of water and achieve almost the same WP as full irrigation. These climate-smart irrigation strategies adapting to diverse climatic conditions largely mitigate agricultural water consumption while maximizing crop productivity and water use efficiency, which are essential for achieving precision irrigation and sustainable water management under a changing climate.
... To estimate FD, we selected eight plant traits that are associated with ecological functions (Bjorkman et al., 2018;Diaz et al., 2016), including woodiness (i.e., woody or herbaceous), plant maximum height (PH max , m), wood density (WD, g cm −3 ), seed mass (SM, mg), specific leaf area (SLA, mm 2 mg −1 ), leaf carbon content per leaf dry mass (LC mass , mg g −1 ), leaf nitrogen content per leaf dry mass (LN mass , mg g −1 ), and leaf phosphorous content per leaf dry mass (LP mass , mg g −1 ). PH max represented the tradeoff between light competition ability and water transport risk (Falster and Westoby, 2003;Thomson et al., 2018) and has been used to predict stand biomass and ecosystem primary productivity (Saatchi et al., 2011;Šímová et al., 2018;Wang et al., 2019). WD represents the trade-off between mechanical support strength and vertical growth rate (Swenson and Enquist, 2007) and was associated with the capability of plants to resist environmental stress (Kraft et al., 2010;Kunstler et al., 2016;Larjavaara and Muller-Landau, 2010). ...
The Convention on Biological Diversity seeks to conserve at least 30% of global land and water areas by 2030, which is a challenge but also an opportunity to better preserve biodiversity, including flowering plants (angiosperms). Herein, we compiled a large database on distributions of over 300,000 angiosperm species and the key functional traits of 67,024 species. Using this database, we constructed biodiversity-environment models to predict global patterns of taxonomic, phylogenetic, and functional diversity in terrestrial angiosperms and provide a comprehensive mapping of the three diversity facets. We further evaluated the current protection status of the biodiversity centers of these diversity facets. Our results showed that geographical patterns of the three facets of plant diversity exhibited substantial spatial mismatches and nonoverlapping conservation priorities. Idiosyncratic centers of functional diversity, particularly of herbaceous species, were primarily distributed in temperate regions and under weaker protection compared with other biodiversity centers of taxonomic and phylogenetic facets. Our global assessment of multifaceted biodiversity patterns and centers highlights the insufficiency and unbalanced conservation among the three diversity facets and the two growth forms (woody vs. herbaceous), thus providing directions for guiding the future conservation of global plant diversity.
... As a measure of a plant's capacity to strive for space and light (Long et al., 2015a), H measures the shortest distance from the plant stem base to the tallest sucker or shoot in the canopy. As a result, H is associated with acquiring carbon (Falster and Westoby, 2003). ...
Identifying soil characteristics associated with the plant's resource use and acquisition strategy at different scales could be a crucial step to understanding community assembly and plant strategy. There is an increasing trend that plant functional properties can be an important driver of ecosystem functioning. However, major knowledge gaps exist about how soil abiotic properties, shape species diversity, above-ground biomass (AGB) and plant functional diversity in the Bawangling tropical forest (TCF) of Hainan island. Hence we hypothesized that plant functional traits and above-ground biomass would be strongly associated with soil abiotic factors, given their direct relationship to soil resource acquisition and use. Here, we used twelve plant functional traits (FTs), above-ground biomass (AGB), and five soil nutrients in the Bawangling tropical cloud forest of Hainan Island by using a polynomial regression model and multivariate correlations to show relationships and identify how plants allocate their limited resources to adapt to their surroundings. Various phytosociological attributes were assessed, and an importance value index (IVI) value was calculated for each species to determine the dominant species. More than half of the total variations could be attributed to interspecific variations in H, DBH, LA, LMA and LDW. From a taxonomic perspective, we found that species-level variance was more significant for plant functional traits and soil nutrients like TN, AP, TP, and OM. On the other hand, variation in specific stem density (SSD), leaf thickness (LT), leaf phosphorus (LP) and leaf soluble sugar (LS) was an exception for these tendencies. Among soil nutrients, soil nitrogen and phosphorus significantly impact the species and functional traits. Furthermore, the soil AN and TP we also found to have a comparatively strong positive relationship with above-ground biomass (AGB) as compared with other soil nutrients. The morphophysiological functional traits showed a trade-off between conservative and acquisitive resource usage. These variations suggested that the relationships of functional traits, AGB, and species with soil nutrients, mainly AN and TP in tropical cloud forests can directly affect the growth, reproduction, and survival of the species and are beneficial for the species' co-existence and maintenance of biodiversity.
... This suggests that niche partitioning is dominant, but the early increases in allocation to roots stimulate greater capture of soil resources early in the season as well, which support greater plant growth across the entire season. By contrast, when soil nutrient availability is high, quinoa plants shift more biomass aboveground and the changes in light characteristics caused by the accumulating biomass stimulates plants to shift their allocation to greater leaf size to increase their competitiveness for light (Falster and Westoby 2003;Murphy and Dudley 2009). Kin plants do not do this, even though they have greater accumulated shoot biomass than non-kin plants, suggesting that they are suppressing leaf size expansion, a potential indication of kin selection. ...
Plants have the ability to recognize their kin neighbors, which may be a beneficial trait that increases inclusive fitness, by suppressing individual growth to support the combined growth of the group. However, the advantages of kin cooperation (known as kin selection theory), may differ across environmental gradients, with competition between related individuals potentially being detrimental under resource limitation (following niche partitioning theory). The study aimed to understand how quinoa (Chenopodium quinoa (Willd)) plants grow with kin or with non-kin under different nutrient supply rates. Plants were grown in treatments' post-germination for 70 days. Biomass accumulation, allocation to organs, and organ traits related to resource acquisition were measured at the end of the experiment. Total mass and shoot mass were greater for plants grown with kin than with non-kin across nutrient treatments. Plants grown with kin had greater root allocation than with non-kin under low and high nutrients. Allocation to leaves, specific leaf area, and average leaf mass were greater for plants grown with non-kin than kin under high-nutrient supply, but did not differ under low-nutrient supply. Allocation to stem was greater for plants grown with kin than non-kin under high-nutrient supply, but did not differ under low-nutrient supply. Specific taproot length and specific stem length were respectively positively and negatively related to increased fertility, but unrelated to kinship. Our results suggest that both niche partitioning and kin selection processes may be at play in quinoa, depending on whether soil nutrient competition is more important. Under both situations, quinoa plants always grew better with kin than non-kin regardless of soil nutrient conditions.
... Forest community structure can be critical in determining plant growth, as competition for light encourages taller growth (Falster & Westoby, 2003). Disturbances such as thinning that reduce competition between trees can result in increases in diameter at breast height at the expense of height growth (Deng et al., 2019), and crown length may be greater so that crown base height is lower in more openly spaced stands (Pinkard & Neilsen, 2003). ...
Many forest types globally have been subject to an increase in the frequency of, and area burnt by, high‐severity wildfire. Here we explore the role that previous disturbance has played in increasing the extent and severity of subsequent forest fires. We summarise evidence documenting and explaining the mechanisms underpinning a pulse of flammability that may follow disturbances such as fire, logging, clearing or windthrow (a process we term disturbance‐stimulated flammability). Disturbance sometimes initiates a short initial period of low flammability, but then drives an extended period of increased flammability as vegetation regrows. Our analysis initially focuses on well‐documented cases in Australia, but we also discuss where these pattens may apply elsewhere, including in the Northern Hemisphere. We outline the mechanisms by which disturbance drives flammability through disrupting the ecological controls that limit it in undisturbed forests. We then develop and test a conceptual model to aid prediction of woody vegetation communities where such patterns of disturbance‐stimulated flammability may occur. We discuss the interaction of ecological controls with climate change, which is driving larger and more severe fires. We also explore the current state of knowledge around the point where disturbed, fire‐prone stands are sufficiently widespread in landscapes that they may promote spatial contagion of high‐severity wildfire that overwhelms any reduction in fire spread offered by less‐flammable stands.
We discuss how land managers might deal with the major challenges that changes in landscape cover and altered fire regimes may have created. This is especially pertinent in landscapes now dominated by extensive areas of young forest regenerating after logging, regrowing following broadscale fire including prescribed burning, or regenerating following agricultural land abandonment.
Where disturbance is found to stimulate flammability, then key management actions should consider the long‐term benefits of: ( i ) limiting disturbance‐based management like logging or burning that creates young forests and triggers understorey development; ( ii ) protecting young forests from disturbances and assisting them to transition to an older, less‐flammable state; and ( iii ) reinforcing the fire‐inhibitory properties of older, less‐flammable stands through methods for rapid fire detection and suppression.
... Maximum height (MH) Downloaded from EUCLID database (Slee et al. 2015) Growing tall confers a competitive advantage for light from above. But it incurs costs of investment in support and supply (Givnish 1982;Loehle 2000;Westoby et al. 2002;Falster and Westoby 2003). Greater height growth is associated with site 'productivity' (Moles et al. 2009) and might be expected to coordinate with more 'productive' than 'conservative' strategies. ...
Context The radiation of eucalypts into almost every Australian environment offers valuable insights to plant ecological strategies. Aims We aimed to assess the degree to which functional traits across different organs are independent or reflect coordinated strategies in southern eucalypts. Methods We applied ordinary and phylogenetic generalised least squares regressions to 164 southern Australian taxa, examining the network of pairwise relationships between 10 functional traits representing aspects of stature, leaf economics, reproduction and post-fire regeneration. We examined coordination and modularity in this network and estimated how phylogeny affects observed trait correlations. Results Stem and stature traits were generally independent of reproductive traits, with Specific Leaf Area the most connected trait, being correlated with traits from all organs. Resprouting ability was also connected to several traits. Species able to resprout basally, but not epicormically, were on average shorter, stouter, with higher stem sapwood density, thinner bark, smaller leaves and lower Specific Leaf Area than those able to resprout using both methods. Taxa resembled their relatives; phylogenetic signal was significant for all continuous traits except Relative Height, ranging from Pagel’s Lambda λ = 0.37 (Relative Bark Thickness) to λ = 0.82 (Specific Leaf Area). Phylogenetic analyses showed weakened correlations for most (but not all) trait pairs. However, most moderate relationships on the trait correlation network also displayed correlated evolution. Conclusions Stature, stem, leaf and reproductive traits and fire response of eucalypts are somewhat coordinated, principally through leaf economics. Trait combinations that confer ecological competence on eucalypt taxa in present-day conditions are likely to have been similarly favoured throughout their evolutionary history. Implications This supports theory of coordinated plant strategies.
... Additionally, with the annual temperature increasing at 1 ℃, the plant height, leaf length and width would decrease by 4.65 cm, 2.81 cm and 0.39 mm (Table S4), respectively. Previous studies showed that the individuals with taller height and larger leaves had more powerful competitiveness because of their advantages in harvesting light, the source of primary productivity [43,44]. Therefore, the compact plant type of the populations from high latitude might suggest the downregulated competitiveness when temperature increases. ...
Background
Global warming could have a significant impact on plant adaptation to local environments. Widespread species provide a useful model to examine the population dynamic under climate change. However, it is still unclear how widespread aquatic species respond to rapidly changing environments. Wild-rice Zizania latifolia is an emergent macrophyte widely distributed across East Asia. Here, 28 Z. latifolia natural populations covering above 30 latitudes were transplanted in a common garden.
Results
The growth, photosynthesis and reproduction traits were quantified and compared among populations, and pairwise relationships among geographic, genetic and growth traits were estimated. Results showed that, in the common garden, the high-latitude populations grew in small size indicating weaker competitiveness in warmer temperatures; the low-latitude populations had no sexual reproduction, suggesting that low-latitude individuals stood little chance to migrate successfully to higher latitude. Significantly positive correlations among the distances of genetic, geographic and biological traits for populations indicated that both isolation by distance and isolation by environment models affected the genetic pattern of populations, and phenotypic traits of Z. latifolia populations might be determined genetically.
Conclusions
All our results suggested that, despite widespread, the genetically determined differentiation of Z. latifolia populations causing growth and reproduction traits could not rapidly acclimate to the accelerated increase of temperature, which implies this widespread species could fail to cope with global warming via migration.
... Plant height is also closely related to leaf area (Falster and Westoby, 2003), therefore positive relationships between leaf area and plant height are likely to lead to a positive correlation between seed mass and leaf area. In our study, there were also consistent and positive correlations between seed mass and leaf area, suggesting that the correlations between leaf area and seed mass are conserved across life-forms. ...
Although variation in seed mass can be attributed to other plant functional traits such as plant height, leaf size, genome size, growth form, leaf N and phylogeny, until now, there has been little information on the relative contributions of these factors to variation in seed mass. We compiled data consisting of 1071 vascular plant species from the literature to quantify the relationships between seed mass, explanatory variables and phylogeny. Strong phylogenetic signals of these explanatory variables reflected inherited ancestral traits of the plant species. Without controlling phylogeny, growth form and leaf N are associated with seed mass. However, this association disappeared when accounting for phylogeny. Plant height, leaf area, and genome size showed consistent positive relationship with seed mass irrespective of phylogeny. Using phylogenetic partial R ² s model, phylogeny explained 50.89% of the variance in seed mass, much more than plant height, leaf area, genome size, leaf N, and growth form explaining only 7.39%, 0.58%, 1.85%, 0.06% and 0.09%, respectively. Therefore, future ecological work investigating the evolution of seed size should be cautious given that phylogeny is the best overall predictor for seed mass. Our study provides a novel avenue for clarifying variation in functional traits across plant species, improving our better understanding of global patterns in plant traits.
... Maximum plant height is one of the core components of plant ecological strategy, reflecting the ability to compete for light and accumulate carbon stocks at the expense of investment in stem production (Westoby, 1998;Falster and Westoby, 2003). In addition, plant height is correlated with facilitated seed dispersal, lifespan and seed mass (Moles et al., 2009;Díaz et al., 2016). ...
Among the characteristics of alien plant species that are likely to influence invasion success, those that capture variation in relation to distribution and environmental requirements in their native range are of special interest. Similarly, traits such as maximum height, specifc leaf area (SLA) and seed dry mass, related respectively to vegetative growth, resource use strategy, and reproductive effort and dispersal ability, have been found to vary
with invasiveness. Australian Acacia species (‘wattles’) present an exceptional natural experiment for identifying traits linked with invasiveness, while applying the source-area framework and controlling for the environmental conditions within the native range. We combine large-scale data sets of the distribution and functional traits of wattles with high-resolution climate surfaces to re-examine the effect of range size, environmental niche breadths and functional traits in determining invasion status (not introduced, casual, naturalized, or invasive) in wattles. We extracted occurrence records of 1036 wattle species (96% of all species in the genus) in Australia from the Atlas of Living Australia. For each species, we calculated the range size through the minimum convex polygon, and environmental niche breadths by matching occurrence records with WorldClim long-term average climate conditions. We extracted trait values from AusTraits and gap-filled when certain values were not known. We compared the obtained values, grouping wattle species by their introduction (not introduced vs introduced species) and invasion statuses, and calculated functional hypervolumes for each of
the groups and overlaps between pairs of them. We found the performance of introduced wattle species to be profoundly influenced by their historical environment; species with broader distributions and climate niche breadths in their native range were more likely to become invasive. Trait strategies for wattles that enhance invasion consisted of maximizing plant height to promote competitive ability, displaying medium-to-high SLA values for enhanced photosynthetic activity and relative growth rate, and intermediate values of seed mass for successful establishment and sufficient seed output and dispersal.
... The scenarios allowed us to conclude that resource competition does not apply to all smaller plants even if it exists in response to N enrichment. Potential height is an essential aspect of the ecology of plant species (Falster and Westoby 2003), and plants harboring capability to adjust their height strategically could better adapt to growth under continuous N input. ...
Background and aims
N enrichment is a major driver of plant species loss worldwide. Nevertheless, its impacts on local species assemblages (i.e., β-diversity), another essential but often overlooked index of biodiversity, remain uncertain. Moreover, whether or how C input changes the effects of N enrichment on plant biodiversity are poorly understood.
Methods
We addressed the questions using location test of continuous input of a gradient of both N (n = 5) and labile C (n = 3) in a semi-arid grassland, conducted a five-year survey of plants biodiversity in each plot annually, and analyzed their variations and correlations.
Results
N enrichment made plant α-diversity lose and plant production increase, which enhanced over time. The responses of different species varied, and plant communities shifted from stochastic to deterministic assembly during the five-year survey. The effects of N enrichment on plant biodiversity could be significantly relieved by a lower rate of labile C input. In this case, a lower rate of labile C enhanced coexistence of plant species (based on data of number and height), especially for certain taller species; but a higher rate of labile C input was opposite.
Conclusion
A lower labile C treatments under N enrichment alleviated the negative responses of plant biodiversity over time. Plant species that could adjust their height strategically may better adapt to varied N and C addition and play important roles in plant communities assembly. All provided novel prospects in prediction and prevention of biodiversity reduction in semi-arid grasslands.
... Resource niche differentiation is conventionally quantified by comparing the species-specific capacity to acquire and/or use various resources (e.g., light, water, and nutrients) (Silvertown, 2004). For example, taller trees can acquire more light than shorter ones, and thus perform better under interspecific than intraspecific competition (Williams et al., 2021), so relative growth rate is a useful indicator for the differential capacity to acquire light among tree species (Falster & Westoby, 2003;King, 1981;Reich et al., 1998). Coexisting species may have different strategies for the use of water and have variable water-use efficiencies, especially in regions subject to water stress (Kulmatiski et al., 2019;Silvertown et al., 2015). ...
The migration of trees induced by climatic warming has been observed at many alpine treelines and boreal–tundra ecotones, but the migration of temperate trees into southern boreal forest remains less well documented. We conducted a field investigation across an ecotone of temperate and boreal forests in northern Greater Khingan Mountains of northeast China. Our analysis demonstrates that Mongolian oak ( Quercus mongolica ), an important temperate tree species, has migrated rapidly into southern boreal forest in synchrony with significant climatic warming over the past century. The average rate of migration is estimated to be 12.0 ± 1.0 km decade ⁻¹ , being slightly slower than the movement of isotherms (14.7 ± 6.4 km decade ⁻¹ ). The migration rate of Mongolian oak is the highest observed among migratory temperate trees (average rate 4.0 ± 1.0 km decade ⁻¹ ) and significantly higher than the rates of tree migration at boreal–tundra ecotones (0.9 ± 0.4 km decade ⁻¹ ) and alpine treelines (0.004 ± 0.003 km decade ⁻¹ ). Compared with the coexisting dominant boreal tree species, Dahurian larch ( Larix gmelinii ), temperate Mongolian oak is observed to have significantly lower capacity for light acquisition, comparable water‐use efficiency but stronger capacity to utilize nutrients especially the most limiting nutrient, nitrogen. In the context of climatic warming, and in addition to a high seed dispersal capacity and potential thermal niche differences, the advantage of nutrient utilization, reflected by foliar elementomes and stable nitrogen isotope ratios, is also likely a key mechanism for Mongolian oak to coexist with Dahurian larch and facilitate its migration toward boreal forest. These findings highlight a rapid deborealization of southern Asian boreal forest in response to climatic warming.
... Previous studies showed that the individuals with taller height and larger leaves had more powerful competitiveness because of their advantages in harvesting light, the source of primary productivity (Falster and Westoby, 2003;Craine et al., 2013). Therefore, the compact plant type of the populations from high latitude might suggest the downregulated competitiveness when temperature increases. ...
The global warming could have significant impact on plant adaptation to local environments. Widespread species provides a useful model to examine the population dynamic under climate change. However, it is still unclear how widespread aquatic species response to rapidly changing environments. Wild-rice Zizania latifolia is an emergent macrophyte widely distributed across East Asia. Here, 28 Z. latifolia natural populations covering above 30 latitudes were transplanted in a common garden. The growth, photosynthesis and reproduction traits were quantified and compared among populations, and pairwise relationships among geographic and genetic variables were estimated. Results showed that, in the common garden, the high-latitude populations grew in small size indicating weaker competitiveness in warmer temperatures; the low-latitude populations had no sexual reproduction, suggesting that low-latitude individuals stood little chance to migrate successfully to higher latitude. Significant positive correlations among the distances of genetic, geographic and morphological traits for populations indicated that both isolation by distance and isolation by environment models affected the genetic pattern of populations, and phenotypic traits of Z. latifolia populations might be genetically determined. All our data suggest that Z. latifolia would be inadaptable to the global warming, indicating that this species would be at least at risk of local extinction in the warmer future.
... Plant height varied substantially depending on the species considered and the stage of development (Fig. 2). Differences in height were due to the genetic characteristics and growth habit of each cover crop species (Falster and Westoby, 2003), and to their ability to take up nitrogen during the vegetative stage (Jiang et al., 2020). Height is also correlated with the life span, seed mass and time to maturity, and is a major determinant of the ability of a species to compete for light (Moles et al., 2009). ...
Abstract
Context or problem
Conservation agriculture is a sustainable farming system designed to enhance agroecosystem productivity, adaptability, and the conservation of natural resources and biodiversity, while reducing production costs. In the context of northern Benin, understanding the role of cover crops in biomass production and soil improvement is crucial for promoting and adopting conservation agriculture practices.
Objective or research question
This study aimed to contribute valuable insights into the growth performance and impact of 10 cover crop species in the Okpara and five in Angaradebou regions of northern Benin.
Methods
The study employed a split-block design to assess cover crop growth during the rainy season of 2018. Plant density, height, aboveground biomass, and grain productivity were measured. In the subsequent season, the experimental setup was transformed into a strip-split plot design to evaluate how soil cover management, specifically mulched cover (M) or standing cover (L), influenced soil ground cover, water infiltration, soil moisture, and weed density.
Results
The findings of the study indicated that Sesbania rostrata and Mucuna pruriens produced the tallest plants in the Okpara region, while Crotalaria juncea, Brachiaria ruziziensis, and Crotalaria retusa were the tallest in the Angaradebou region. Brachiaria ruziziensis, Crotalaria juncea, Crotalaria ochroleuca, and Sesbania rostrata exhibited the highest biomass production. In terms of yield components, Crotalaria ochroleuca and Crotalaria juncea performed well in seed production per pod, while Mucuna pruriens and Cajanus cajan had the highest seed weight. Regarding ground cover, Brachiaria ruziziensis demonstrated the highest performance, with 60% and 89% ground cover as mulch and standing cover, respectively, followed by Stylosanthes guianensis. Plots with better ground cover exhibited higher soil moisture retention (7–13%) and hydraulic conductivity (0.0015 cm s−1 - 0.002 cm s−1), as well as lower weed densities (55–69 weeds m−2). Stylosanthes guianensis and Sesbania rostrata showed the best soil moisture retention (11% and 13%, respectively), followed by Crotalaria juncea, Mucuna pruriens, and Brachiaria ruzisiensis (13%).
Conclusions
The study highlighted the agronomic performance of 10 cover crops under conservation agriculture and their potential to positively impact soil physical properties and weed dynamics in northern Benin.
Implications or significance
These cover crops have the potential to diversify cotton-based cropping systems in the region, thereby enhancing their sustainability. However, further investigation is needed to explore the effects of these cover crop species on intercrop combinations and crop and cover crop sequences under the specific agroecological conditions of northern Benin.
... A high seed mass increases seedling establishment in temperate grasslands , but usually trades off with reproductive output see Figure S5 for the tradeoff between seed mass and seed number in our focal species). An investment in height leads to a greater light interception (Falster & Westoby, 2003), and low SLA is related to a more efficient resource acquisition (Westoby, 1998). Thus, we expect these three functional traits to also be relevant for population growth in interspecific competition, albeit with different optimal trait values (see Figure 1a-c). ...
Alien plants experience novel abiotic conditions and interactions with native communities in the introduced area. Intra- and interspecific selection on functional traits in the new environment may lead to increased population growth with time since introduction (residence time). However, selection regimes might differ depending on the invaded habitat. Additionally, in high-competition habitats, a build-up of biotic resistance of native species due to accumulation of eco-evolutionary experience to aliens over time may limit invasion success. We tested if the effect of functional traits and the population dynamics of aliens depends on interspecific competition with native plant communities. We conducted a multi-species experiment with 40 annual Asteraceae that differ in residence time in Germany. We followed their population growth in monocultures and in interspecific competition with an experienced native community (varying co-existence times between focals and community). To more robustly test our findings, we used a naïve community that never co-existed with the focals. We found that high seed mass decreased population growth in monocultures but tended to increase population growth under high interspecific competition. We found no evidence for a build-up of competition-mediated biotic resistance by the experienced community over time. Instead, population growth of the focal species was similarly inhibited by the experienced and naïve community. By comparing the effect of experienced and naïve communities on population dynamics over 2 years across a large set of species with a high variation in functional traits and residence time, this study advances the understanding of the long-term dynamics of plant invasions. In our study system, population growth of alien species was not limited by an increase of competitive effects by native communities (one aspect of biotic resistance) over time. Instead, invasion success of alien plants may be limited because initial spread in low-competition habitats requires different traits than establishment in high-competition habitats.
... In that case, an indicator, referred to as the Gini index [7], was proposed to quantify income inequality by calculating the ratio of the area between the Lorenz curve and the egalitarian line to the area below the egalitarian line. There are many mathematical equations that can be used to describe the Lorenz curve [8][9][10][11][12][13][14][15][16][17][18][19]. There is also the Theil index of inequality [20,21] which can be partitioned into inter-group components and intra-group components [22]. ...
Measuring the inequality of leaf area distribution per plant (ILAD) can provide a useful tool for quantifying the influences of intra- and interspecific competition, foraging behavior of herbivores, and environmental stress on plants’ above-ground architectural structures and survival strategies. Despite its importance, there has been limited research on this issue. This paper aims to fill this gap by comparing four inequality indices to measure ILAD, using indices for quantifying household income that are commonly used in economics, including the Gini index (which is based on the Lorenz curve), the coefficient of variation, the Theil index, and the mean log deviation index. We measured the area of all leaves for 240 individual plants of the species Shibataea chinensis Nakai, a drought-tolerant landscape plant found in southern China. A three-parameter performance equation was fitted to observations of the cumulative proportion of leaf area vs. the cumulative proportion of leaves per plant to calculate the Gini index for each individual specimen of S. chinensis. The performance equation was demonstrated to be valid in describing the rotated and right shifted Lorenz curve, given that >96% of root-mean-square error values were smaller than 0.004 for 240 individual plants. By examining the correlation between any of the six possible pairs of indices among the Gini index, the coefficient of variation, the Theil index, and the mean log deviation index, the data show that these indices are closely related and can be used interchangeably to quantify ILAD.
... The DBH can be easily obtained through field surveys, while the tree height is more difficult to measure, and constructing accurate height-diameter (H-DBH) models will improve the accuracy of tree height predictions [5,10]. In addition, H-D models are not only used as part of estimating biomass and carbon stocks but are also utilized by foresters and ecologists to assess a tree's access to light resources, competition with neighboring trees, or stand quality [11][12][13][14]. ...
Accurate estimates of tree height (H) are critical for forest productivity and carbon stock assessments. Based on an extensive dataset, we developed a set of generalized mixed-effects height–DBH (H–D) models in a typical natural mixed forest in Northeastern China, adding species functional traits to the H–D base model. Functional traits encompass diverse leaf economic spectrum features as well as maximum tree height and wood density, which characterize the ability of a plant to acquire resources and resist external disturbances. Beyond this, we defined expanded variables at different levels and combined them to form a new model, which provided satisfactory estimates. The results show that functional traits can significantly affect the H–D ratio and improve estimations of allometric relationships. Generalized mixed-effects models with multilevel combinations of expanded variables could improve the prediction accuracy of tree height. There was an 82.42% improvement in the accuracy of carbon stock estimates for the studied zone using our model predictions. This study introduces commonly used functional traits into the H–D model, providing an important reference for forest growth and harvest models.
... Some other studies attribute the reasons for cooperation to subjective altruism or prosociality [22,23,24] when human society are taken as a reference. However, if the tragedy can only be avoided when higher-level incentives are invoked, why non-human organisms can avoid overexploiting the resources on which they depend [25,26,27]. ...
Introducing environmental feedback into evolutionary game theory has led to the development of eco-evolutionary games, which have gained popularity due to their ability to capture the intricate interplay between the environment and decision-making processes. However, current researches in this field focus on the study to macroscopic evolutionary dynamics in infinite populations. In this study, we propose a multi-agent computational model based on reinforcement learning to explore the coupled dynamics between strategies and the environment in finite populations from a bottom-up perspective. Our findings indicate that even in environments that favor defectors, high levels of group cooperation can emerge from self-interested individuals, highlighting the significant role of the coupling effect between the environment and strategies. Over time, the higher payoff of defection can be diluted due to environmental degradation, while cooperation can become the dominant strategy when positively reinforced by the environment. Remarkably, individuals can accurately detect the inflection point of the environment solely through rewards, when a reinforcing positive feedback loop are triggered, resulting in a rapid increase in agents' rewards and facilitating the establishment and maintenance of group cooperation. Our research provides a fresh perspective on understanding the emergence of group cooperation and sheds light on the underlying mechanisms involving individuals and the environment.
... A range of morphological, reproductive, and dispersal characteristics, as well as habitat suitability and establishment success, influence the presence and success of weeds (Pyšek et al. 2009, Mashau et al. 2021. Tall plants have a greater dispersal distance (Thomson et al. 2011) and competitive ability (Falster and Westoby 2003), thus favouring their dispersal and establishment success potential. Culm height is positively correlated to invasive capacity in grasses (Mashau et al. 2021). ...
Digitaria is a large pantropical genus, which includes a number of economically problematic agricultural weeds. Difficulties in species identification and the circumscription of the genus have previously hindered progress in understanding its evolution and developing a stable classification. We investigate the evolutionary history of Digitaria by combining two approaches: (i) phylogenetic analyses of the currently available Sanger sequence data with previously unpublished sequences mainly from South East Asia, and (ii) newly generated genomic data from low-copy nuclear genes obtained using the Angiosperms353 probe kit, with new data mainly from Madagascar. Both methods gave congruent results. The combination of these results allowed us to confirm a new clade structure within Digitaria lineages, in partial agreement with the previous morphology-based classifications. We confirm that Digitaria as traditionally circumscribed is not monophyletic, comprising Anthephora, Baptorhachis, Chaetopoa, and Chlorocalymma. We present an inference of key character evolution with morphological support for clades with spikelets arranged in binate and ternate groups, with variable trichome morphology, spikelet length, and culm length. Geographical clade structure is also observed. No phylogenetic signal of weedy function was observed.
... Las interacciones biológicas entre los componentes de los Si pueden ser positivas o negativas, la competencia por luz, el agua y los nutrientes se acentúa cuando los recursos son limitados (Falster y Westoby, 2003). La fijación de nutrientes y transferencia de los mismos, el mejoramiento del suelo, del microclima y el confort animal son ejemplos de respuestas positivas (Ludwig et al., 2001;Nishimura et al., 2002). ...
Antecedentes: De la revisión bibliográfica se generó un análisis de los valores y beneficios que generan los sistemas silvopastoriles (Si) en asocio con Leucaena leucopcephala (Lam.) de Wit., con especial referencia a manejo agronómico, integración árbol-pasto, densidad, intervalos de corte, producción y calidad nutricional de la biomasa. El objetivo fue recopilar información existente sobre el uso de leucaena como forraje.Metodología: Se revisaron artículos publicados desde 1999 a 2022. Los años con mayor producción científica fueron 2016, 2020, y 2014, con 8, 7 y 6 obras respectivamente, 2000 y 2004 no registraron artículos. Se obtuvo bibliografía de temas diversos, que citan la importancia de posible integrar leguminosas en los pastizales para incrementar la carga animal por hectárea, incrementar peso y producción de leche, en comparación con los sistemas que solo emplea pastos como alimento de los animales. Resultados: Los Si con asocio de leucaena constituyen una de las mejores alternativas para incrementar la ganancia de peso en la ganadería principalmente en zonas semisecas, ya que en ellos se hace un uso más eficiente del espacio y se obtiene un alimento de mejor calidad nutricional, mayor aporte de materia seca (MS), proteína cruda (PC), menor contenido de fibra detergente neutro (FDN) y de fibra detergente ácido (FDA). Conclusiones: Dentro de las condiciones a considerar en este sistema se debe tener presente la densidad la altura de corte, fecha y forma de siembra para obtener el mayor volumen de forraje por época.
... We expected large-statured plants to dominate in sunlit microsites where the density of herbaceous competitors is high. As herbaceous plant density increases, greater height allows taller plants to overtop neighbors, providing greater energetic returns on the structural costs associated with growing taller (Givnish 1982;Keddy and Shipley 1989;Keddy et al. 2002;Falster and Westoby 2003;Cahill et al. 2008). We predicted microsites with greater canopy cover and earlier-leafing trees would favor species with high specific leaf area (SLA) reflecting the photosynthetic advantages experienced by species with broad, thin leaves in shaded environments (Givnish 1988;Westoby 1998). ...
Functional traits influence plant distributions along broad environmental gradients leading species to occupy communities where their traits enable them to successfully establish and compete for resources. Trait differences are also expected to influence plant distributions and diversity at finer spatial scales within communities. However, relatively few empirical studies have examined the extent to which interspecific trait variation predicts local species-environment distributions. We surveyed herbaceous plants within a heterogeneous acid bedrock glade in south-central Wisconsin to elucidate how traits influence local plant distributions and diversity. Using quadrat-scale environmental covariates (soil depth, canopy openness, and neighborhood tree phenology) and species functional trait means (SLA, vegetative height, and seed mass), we modeled variation in local species distributions as well as plant diversity across 361 quadrats distributed evenly in a 1 ha study plot. Functional traits predictably mediated individualistic species distributions along local gradients in soil depth and canopy openness as well as differential plant responses to variation in canopy leaf phenology. Small-seeded herbs occurred in shallow soil microsites while the prevalence of large-statured plants increased with canopy openness. Local species richness and functional trait dispersion were greatest in microsites near canopy gaps where sun-adapted and shade-adapted plant species co-occur and in microsites surrounded by later-leafing trees. Interspecific trait differences influence local species distributions and shape spatial patterns of diversity within heterogeneous plant communities like bedrock glades. The parallels between local plant distributions within this heterogeneous community and regional plant distributions across the landscape suggest trait-mediated ecological sorting influences plant distributions along environmental gradients similarly across spatial scales.
... On the one hand, leaf traits of leaf area (LA), specific leaf area (SLA), and leaf dry matter content (LDMC) in phenotype [14], and the macronutrient C, N and P support light capture ability due to the material basis [15], while their stoichiometric ratio reflects leaf structure and nutritional efficiency [16]. On the other hand, plant size includes plant diameter at breast height (DBH) and plant height [17]. Previous studies have shown a significant correlation between leaf functional traits and plant size [18]. ...
Citation: Hu, X.; He, Y.; Gao, L.; Umer, M.; Guo, Y.; Tan, Q.; Kang, L.; Fang, Z.; Shen, K.; Xia, T. Strategy Trade-Off of Predominant Stress Tolerance Relative to Competition and Reproduction Associated with Plant Functional Traits under Karst Forests. Abstract: The Grime (1974) CSR framework posits that ecological strategies of competition, stress tolerance and ruderal reflect plants' adaptability to their survival environments. Karst forests are crucial for terrestrial ecosystem functions. However, how karst forests regulate plant functional traits in ecological strategy to adapt to infertile habitats remains unclear. Therefore, we surveyed fifty-three karst forest plots and measured plant functional traits involving the plan diameter at breast height (DBH), height, leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon (LC) and nitrogen (LN) and phosphorus (LP) with the leaf water content (LWC). We calculated CSR components on the individual and community levels introduced by community-weighted means (CWM) using the 'StrateFy' calculator. Principal component analysis (PCA) and Mantel's test were used to investigate trait correlations with CSR components. Our results showed that stress tolerance (S) contributed an average 65.88% and 63.63% in individuals and communities, respectively, followed by competition (C) at 25.82% and 29.63%, and the least, ruderal (R), at 8.30% and 6.74%. Different plant functional traits exhibited different variations, coupled with significant correlations between CSR components and PC1 scores (except for CWM− LA, SLA and LDMC). Component S increased with the increase in CWM− LC and C:N ratio, and decreased with the increase in CWM− DBH, Height, LWC, LN, and N:P ratio, while it was the opposite for C and R, highlighting strategic trade-offs associated with plant functional traits. Mantel's test revealed varied key trait combinations for each strategy. In conclusion, the predominant stress tolerance strategy relative to competition and ruderal is a result of trade-offs regulating karst forests, in association with plant functional traits. The disentangled CSR strategies provide insights into theoretically understanding functional maintenance for infertile forest ecosystems as an evolutional regulation mechanism.
Background
Salt stress is one of the most common abiotic stresses, reducing plant growth and productivity. Thus, the development of suitable management practices to minimize the deleterious effects of salt stress has become necessary.
Aims
This study was conducted to investigate the possible mechanisms underlying salt tolerance conferred by jasmonic acid (JA).
Methods
Salt‐stressed wheat seedlings were supplemented with 1 mM JA and/or 1 mM ibuprofen (IBU), an inhibitor of endogenous JA biosynthesis, in the culture medium.
Results
The obtained results showed that salt stress significantly decreased shoot and root dry weight production and relative water contents. This was associated with a noteworthy reduction in leaf and root ascorbate (AsA) concentrations, as well as glutamine synthetase (GS), glutamate synthase (GOGAT), and glutamate dehydrogenase (GDH) activities. Exogenously supplied JA did not affect GS and GOGAT activities in leaves and roots of salt‐treated seedlings. However, noticeable enhancements were observed in growth, AsA concentrations, as well as GDH activities. Likewise, the inhibition of JA biosynthesis by IBU application was accompanied by a significant decrease in seedlings’ growth associated with a noticeable reduction in AsA concentrations and GDH activities. The decreases in growth and GDH activities were also obtained following inhibition of AsA biosynthesis by lycorine (Lyc) application. By contrast, increased GDH activities and enhanced growth were obtained following exogenous AsA supplementation, with or without JA biosynthesis inhibition.
Conclusions
The findings implied that exogenous JA enhanced AsA biosynthesis and induced GDH activity, which further promoted the growth of wheat seedlings in salt‐stressed conditions. Therefore, the stimulation of AsA biosynthesis and GDH activity through JA application in the rhizosphere may be suggested as a vital strategy for strengthening the salt tolerance of wheat plants, at least at the seedling stage.
Under the influence of global change, precipitation amounts and extreme precipitation frequency during non- growing seasons in mid-high latitude grasslands have been increasing. However, the ecological effects of non- growing season precipitation in the desert steppe have long been overlooked due to an insufficient under-
standing of the correlative mechanisms linking non-growing season precipitation to plant growth. Therefore, a 3- year non-growing season precipitation manipulation experiment was conducted to reveal the response of desert steppe plants to non-growing season precipitation changes. Our study indicates that, by influencing water budget and availability, non-growing season precipitation directly or indirectly impacted community structure, plant biomass allocation, and water-carbon utilization intensity. Adaptive strategies of communities and plants included: ① Dominant species enhanced their dominance in the community to adapt to non-growing season precipitation changes. ② Stipa krylovii exhibited different biomass allocation strategies in response to non- growing season precipitation variations. Plants in the precipitation shading plots tended to allocate biomass to the roots, while those in the precipitation increase plots favored aboveground development. ③ Persistent drought during the growing season intensified early insufficient development of plants in the precipitation shading plots. Upon entering the wet period, plants in the precipitation shading plots shifted into a compensatory growth mode with high water-carbon activity intensity, while those in the precipitation increase plots entered a moderate growth mode with relatively low water-carbon activity intensity. Additionally, our study found that the regulatory effects of non-growing season precipitation were more pronounced in the growing seasons with less precipitation in the early to middle stage. Moreover, increased non-growing season precipitation enhanced plant water use efficiency (WUE) and strengthened their resilience to drought conditions. Our study suggests that the ecological role of non-growing season precipitation may be further highlighted in the future climate change pattern. Given the worldwide increase in frequency of extreme precipitation events, particular vigilance should be paid to the underlying long-term adverse effects of severe droughts during the non-growing season. Our findings provide new insights and valuable experimental observational evidence for the climate change impact assessment and response in xerophytic grassland ecosystems.
Willow herb (Epilobium spp.) is a medicinal plant that is used for various purposes in the traditional medicine and food industries. In this research, an attempt was made to assess morphological and phytochemical variations in eight Epilobium species (E. hirsutum, E. Parviflorum, E. roseum, E. algidum, E. anatolicum, E. confusum, E. frigidum, and E. lanceolatum). The species were collected from natural habitats during the flowering period. Analysis of variance showed a significant variation among the studied species for measured morphological and phytochemical traits. Total phenolic content varied from 194.64 ± 1.17 to 309.10 ± 5.59 mg g-1 DW, total flavonoids ranged from 39.03 ±0.21 to 56.14 ±0.67 mg g-1 DW, and antioxidant activity differed from 43.03 ± 2.20 to 101.36 ± 3.68 mg g-1 DW. The results showed that E. frigidum is the richest source of natural antioxidants among the studied species, and also has the highest seed and leaf lengths. Antioxidant activity was significantly correlated with bioclimatic variables. However, the dendrogram based on morphological traits was relatively different from that based on all phytochemical variables. In conclusion, the remarkable variation among species for the morphological and phytochemical traits may be exploited in the breeding programs of the genus Epilobium. How to cite: Abbasi Karin Sh, Karimzadeh G, Mohammadi Bazargani M. 2023. Interspecific morphological and phytochemical variation in the willow herb (Epilobium spp.) medicinal plant. J Plant Physiol and Breed. 13(2): 15-27.
Philosophers often treat beliefs as propositional attitudes that entail taking the content as true. However, there exist certain mental states, such as delusions, that challenge this dogmatic norm, leading some researchers to question its validity. This chapter delves into that philosophical inquiry that surrounds the nature of beliefs and establishes a contrastive perspective in cases of delusion, self-deception, sectarian influence, and scientific negationism. We should explore the notion of privileged access to our own mental states acknowledging the importance of self-ascription as being more indirect than commonly believed. We may find that self-ascription is a result of our mindreading ability applied to ourselves and there could be a plausible biological evolution of the cognitive mechanism that underlies. This chapter discusses the evolutionary escalation of mindreading in humans, reviews philosophical accounts of mindreading, and evaluates different theories of belief self-attribution. It concludes with the implications for understanding belief-related phenomena and their cognitive underpinnings.
Background
Seed quality, an important determinant of germination and vigor potential, can be improved through seed priming. This study was therefore aimed at assessing the effects of steeping duration and inoculum concentration on the germination and seedling growth of five seed crops through priming with growth-promoting rhizobacteria.
Methods
Broth cultures of five bacterial strains, belonging to Providencia vermicola (2 strains), P. rettgeri (2 strains), and Bacillus cereus (1 strain), isolated from rhizosphere were used for priming in the study. Seeds of cowpea ( Vigna unguiculata ), soybean ( Glycine max ), sorghum ( Sorghum bicolor ), sesame ( Sesamum indicum ), and okra ( Abelmoschus esculentus ) were used as experimental materials. To determine the effects of steeping duration, viable seeds of the respective crops were primed with broth cultures of the respective isolates and allowed to stand for a known duration (1, 2, 3, 4, or 5 h). Then, another set of viable seeds was steeped in varying concentrations of the bacterial cultures for a period that was determined to be the optimal steeping duration in the first experiment.
Result
At the expiration of both experiments, final germination, mean germination time, germination index, and vigor index of the respective seeds were estimated. Generally, higher final germination and seedling vigor index values were restricted to shorter steeping periods for cowpea and soybean. With respect to inoculum concentration, there was no consistent pattern with the parameters.
Conclusion
The study revealed the primacy of steeping duration over inoculum concentration with respect to bacterial priming.
Aim
Mangrove canopy height is a key metric to assess tidal forests' resilience in the face of climate change. In terrestrial forests, tree height is primarily determined by water availability, plant hydraulic design, and disturbance regime. However, the role of water stress remains elusive in tidal environments, where saturated soils are prevalent, and salinity can substantially affect the soil water potential.
Location
Global.
Time Period
The canopy height dataset provides a global snapshot of the maximum mangrove height geographical distribution for the year 2000. Climate and environmental variables extend over the period 1970–2018.
Major Taxa Studied
Mangroves.
Methods
We use global observations of maximum canopy height, species richness, air temperature, and seawater salinity—a proxy of soil water salt concentration—to explore the causal link between salinity and mangrove stature.
Results
Our findings suggest that salt stress limits mangrove height. High salinity favours more salt‐tolerant species, narrowing the spectrum of viable traits. Highly salt‐tolerant mangroves have evolved to cope with high salt concentrations in the soil, but this adaptation comes at a cost. They typically have lower rates of photosynthesis and growth, resulting in reduced productivity and smaller stature compared to more salt‐sensitive mangrove species. This suggests a causal link between salinity, biodiversity, and tree height, where high salinity selects for more salt‐tolerant species that tend to be less productive and shorter.
Conclusions
We hypothesize that the salinity‐induced limit to mangrove canopy height is the direct result of a reduction of primary productivity, an increment in the risk of xylem cavitation, and an indirect consequence of the decrease in biodiversity. As sea‐level rise enhances coastal salinisation, failure to account for these effects can lead to incorrect estimates of future carbon stocks in Tropical coastal ecosystems and endanger preservation efforts.
Plant traits are informative for ecosystem functions and processes and help to derive general rules and predictions about responses to environmental gradients, global change and perturbations. Ecological field studies often use 'low-throughput' methods to assess plant phenotypes and integrate species-specific traits to community-wide indices. In contrast, agricultural greenhouse or lab-based studies often employ 'high-throughput phenotyping' to assess plant individuals tracking their growth or fertilizer and water demand. In ecological field studies, remote sensing makes use of freely movable devices like satellites or unmanned aerial vehicles (UAVs) which provide large-scale spatial and temporal data. Adopting such methods for community ecology on a smaller scale may provide novel insights on the phenotypic properties of plant communities and fill the gap between traditional field measurements and airborne remote sensing. However, the trade-off between spatial resolution, temporal resolution and scope of the respective study requires highly specific setups so that the measurements fit the scientific question. We introduce small-scale, high-resolution digital automated phenotyping as a novel source of quantitative trait data in ecological field studies that provides complementary multi-faceted data of plant communities. We customized an automated plant phenotyping system for its mobile application in the field for 'digital whole-community phenotyping' (DWCP), capturing the 3-dimensional structure and multispectral information of plant communities. We demonstrated the potential of DWCP by recording plant community responses to experimental land-use treatments over two years. DWCP captured changes in morphological and physiological community properties in response to mowing and fertilizer treatments and thus reliably informed about changes in land-use. In contrast, manually measured community-weighted mean traits and species composition remained largely unaffected and were not informative about these treatments. DWCP proved to be an efficient method for characterizing plant communities, complements other methods in trait-based ecology, provides indicators of ecosystem states, and may help to forecast tipping points in plant communities often associated with irreversible changes in ecosystems.
An important aim of plant ecology is to identify leading dimensions of ecological variation among species and to understand the basis for them. Dimensions that can readily be measured would be especially useful, because they might offer a path towards improved worldwide synthesis across the thousands of field experiments and ecophysiological studies that use just a few species each. Four dimensions are reviewed here. The leaf mass per area-leaf lifespan (LMA-LL) dimension expresses slow turnover of plant parts (at high LMA and long LL), long nutrient residence times, and slow response to favorable growth conditions. The seed mass-seed output (SM-SO) dimension is an important predictor of dispersal to establishment opportunities (seed output) and of establishment success in the face of hazards (seed mass). The LMA-LL and SM-SO dimensions are each underpinned by a single, comprehensible tradeoff, and their consequences are fairly well understood. The leaf size-twig size (LS-TS) spectrum has obvious consequences for the texture of canopies, but the costs and benefits of large versus small leaf and twig size are poorly understood. The height dimension has universally been seen as ecologically important and included in ecological strategy schemes. Nevertheless, height includes several tradeoffs and adaptive elements, which ideally should be treated separately. Each of these four dimensions varies at the scales of climate zones and of site types within landscapes. This variation can be interpreted as adaptation to the physical environment. Each dimension also varies widely among coexisting species. Most likely this within-site variation arises because the ecological opportunities for each species depend strongly on which other species are present, in other words, because the set of species at a site is a stable mixture of strategies.
We use a fitness-generating function (G-function) approach to evolutionary games. The G-function allows for simultaneous consideration of strategy dynamics and population dynamics. In contrast to approaches using a separate fitness function for each strategy, the G-function automatically expands and contracts the dimensionality of the evolutionary game as the num-ber of extant strategies increases or decreases. In this way, the number of strategies is not fixed but emerges as part of the evolutionary process. We use the G-function to derive conditions for a strategy's (or a set of strategies) resistance to invasion and convergence stability. In hopes of relating the proliferation of ESS-related terminology, we define an ESS as a set of strategies that is both resistant to invasion and convergent-stable. With our definition of ESS, we show the following: (1) Evolutionarily unstable maxima and minima are not achievable from adaptive dynamics. (2) Evolutionarily stable minima are achievable from adaptive dynamics and allow for adaptive speciation and divergence by additional strategies – in this sense, these minima provide transition points during an adaptive radiation and are therefore unstable when sub-ject to small mutations. (3) Evolutionarily stable maxima are both invasion-resistant and convergent-stable. When global maxima on the adaptive landscape are at zero fitness, these combinations of strategies make up the ESS. We demonstrate how the number of co-existing strategies (coalition) emerges when seeking an ESS solution. The Lotka-Volterra competition model and Monod model of competition are used to illustrate combinations of invasion resistance and convergence stability, adaptive speciation and evolutionarily 'stable' minima, and the diversity of co-existing strategies that can emerge as the ESS.
Windthrow was assessed following a convective storm in a stand of tropical savanna in Kakadu National Park, northern Australia. Over an area of 3 ha, 79 out of 810 trees (9.8%) were damaged; 27 of them were either uprooted or snapped off at the trunk. Logistic regression showed that both species and tree height were significant determinants of the probability of wind damage. Branch loss and either uprooting or trunk snapping was highest in the canopy sub-dominant Eucalyptus porrecta. Damage was lowest in the sub-dominant trees Erythrophleum chlorostachys, a species which is relatively resistant to termite damage, and Terminalia ferdinandiana, a deciduous species which is generally shorter than the main canopy dominants. Damage was intermediate in the two most common canopy dominants, Eucalyptus tetrodonta and E. miniata. Wind damage was greatest in trees taller than 9 m and relatively minor in trees below this height. Wind disturbs savanna trees in a manner opposite to that of fire, because wind damage is greatest in taller trees, whereas fire damage is greatest in smaller trees. This, coupled with significant within-patch variability in the extent of wind damage, may act to increase small-scale environmental heterogeneity in savannas.
Based on the premise that competition for light is the most important selection pressure on leaf height in forest herbs, presents a game theoretic model for the evolution of this trait which balances the structural costs of a given height increment over an opponent with the resultant photosynthetic benefits. Herbs growing in areas with sparse herbaceous cover are unlikely to be next to and thus under an opponent. Hence, they reap little advantage by being taller, whereas the opposite is true in areas of dense cover. Therefore, the evolutionarily stable strategy favors greater leaf height in productive herb communities having dense coverage than in less productive communities with sparse coverage. In deciduous, cool temperate forests, winter photosynthesis may be limited more by leaf temperature than by light intensity, and thus may favor recumbent basal leaves in evergreen or wintergreen species and seasonal morphs. These ideas are confirmed by data on plant height and coverage from a study along a topographic gradient from a dry oak woods, through a mesic forest, to a floodplain forest. Maximum leaf height roughly doubles with each 7% increase in herbaceous cover, corresponding to quantiative predictions based on independent measures of the allometry of support tissue as a function of leaf height. The low stature of evergreen herbs favored by winter conditions appears to restrict their occurrence to dry, sterile sites with low coverage by summer competitors, and may be another factor favoring an association between evergreenness and soil poverty in temperate forest herbs. Patterns of leaf height among orchids native to the NE United States correspond to qualitative predictions of the model. Extensions of the model are sketched for herbs in open habitats; woody plants; higher leaves in reproductive individuals; selection on flower or fruit height; evolution of altruism along relatives. If a species occurs in herbaceous communities of high density only when its neighbors are close relatives, selection may favor the evolution of lower, more 'altruistic' leaf heights than with unrelated competitors. Aster macrophyllus, which usually has basal leaves even though it occurs in dense herb communities, is a possible case of altruism in that its stands are nearly monospecific and appear to be maintained by allelopathic compounds. -Author
The growth and physiological characteristics of canopy trees are expected to differ systematically from those of understory trees on the basis of size-dependent aspects of biomechanics, resource availability, and life history. Although such differences have previously been noted, there has been relatively little effort to quantify these in terms of interspecific allometric relationships. Asymptotic maximal height (H-max) is advocated as a measure of the size of dicotyledonous woody plants for this purpose. Height diameter (H-D) relationships in 38 species within six genera of Malaysian rain forest trees are well described by an asymptotic model, and thus provide a basis for estimating H-max using static observational data. Three important aspects of tree growth strategies are shown to be predictable on the basis of these values: average tree growth rates are positively related to H-max, while wood density and the initial allometric slope of (species-specific) H-D relationships are negatively related to H-max. These patterns may be explained by an association of low light levels with slow growth and high density wood in understory species; the latter property may in turn allow for relatively high allometric slopes of H-D relationships in saplings of small-statured species. Analyses that control for phylogenetic differences provide evidence that such interspecific allometric patterns are the product of convergent evolution. These results are consistent with the idea thee much ecological variation within species-rich taxa of southeast Asian rain forest trees is related to differentiation along a vertical axis of tree size.
To analyze the effect of leaf angle on light competition among individual plants, a simple model for photosynthesis of an individual plant in a dense stand was developed. The model assumes that each plant has a particular leaf angle that determines the light-extinction coefficient (K). Light climate of a target plant is determined by the K values both of its own and of its neighbors, while light absorption of a target is determined by its own K. Evolutionarily stable K (ESK) values (the K values at which photosynthesis of a target plant having any other K values is smaller than that of its neighbors) were calculated. The ESK value was found to depend both on total leaf area of the stand and on the degree in which neighboring plants affect light climate of each other. The ESK value is always higher than the K value that maximizes canopy photosynthesis when light interception by neighbors occurs. Ecological roles of vertical (low K) and horizontal (high K) leaves are discussed. Horizontal leaves may be advantageous in light competition because the ability of light interception is higher in such leaves. Vertical leaves may be favored in clonal plants whose ramets are closely spaced (phalanx type) because photosynthetic capacity of the whole clone is greater if K is low.
Models have been formulated for monospecific stands in which canopy photosynthesis is determined by the vertical distribution of leaf area, nitrogen and light. In such stands, resident plants can maximize canopy photosynthesis by distributing their nitrogen parallel to the light gradient, with high contents per unit leaf area at the top of the vegetation and low contents at the bottom. Using principles from game theory, we expanded these models by introducing a second species into the vegetation, with the same vertical distribution of biomass and nitrogen as the resident plants but with the ability to adjust its specific leaf area (SLA, leaf area∶leaf mass). The rule of the game is that invaders replace the resident plants if they have a higher plant carbon gain than those of the resident plants. We showed that such invaders induce major changes in the vegetation. By increasing their SLA, invading plants could increase their light interception as well as their photosynthetic nitrogen-use efficiency (PNUE, the rate of photosynthesis per unit organic nitrogen). By comparison with stands in which canopy photosynthesis is maximized, those invaded by species of high SLA have the following characteristics: (1) the leaf area index is higher; (2) the vertical distribution of nitrogen is skewed less; (3) as a result of the supra-optimal leaf area index and the more uniform distribution of nitrogen, total canopy photosynthesis is lower. Thus, in dense canopies we face a classical tragedy of the commons: plants that have a strategy to maximize canopy carbon gain cannot compete with those that maximize their own carbon gain. However, because of this strategy, individual as well as total canopy carbon gain are eventually lower. We showed that it is an evolutionarily stable strategy to increase SLA up to the point where the PNUE of each leaf is maximized.
Since the fitness of each individual organism in a biological community may be affected by the strategies of all other individuals in the community, the essential element of a game exists. This game is an evolutionary game where the individual organisms (players) inherit their strategies from continuous play of the game through time. Here, the strategies are assumed to be constants associated with certain adaptive parameters (such as sunlight conversion efficiency for plants or body length in animals) in a set of differential equations which describe the population dynamics of the community. By means of natural selection, these parameters will evolve to a set of strategy values that natural selection, by itself, can no longer modify, i.e. an evolutionarily stable strategy (ESS). For a given class of models, it is possible to predict the outcome of this evolutionary process by determining ESSs using an ESS maximum principle. However, heretofore, the proof of this principle has been based on a limited set of conditions. Herein, we generalize the proof by removing certain restrictions and use instead the concept of an ecological stable equilibrium (ESE). Individuals in a biological community will be at an ESE if fixing the strategies used by the individuals results in stable population densities subject to perturbations in those densities. We present both necessary and sufficient conditions for an ESE to exist and then use the ESE concept to provide a very simple proof of the ESS maximum principle (which is a necessary condition for an ESS). A simple example is used to illustrate the difference between a strategy that maximizes fitness and one that satisfies the ESS maximum principle. In general they are different. We also look for ESEs in Lotka—Volterra competition and use the maximum principle to determine when an ESE will be an ESS. Finally, we examine the applicability of these ideas to matrix games.
A comprehensive scheme is presented which provides qualitative models of vegetation dynamics in communities subject to recurrent disturbance. The scheme has been derived to deal mainly with terrestrial communities dominated by higher plants, but may be more widely applicable.The scheme utilizes a small number of life history attributes termed vital attributes which pertain to the potentially dominant species in a particular community. Three main groups of vital attributes are recognized, relating to the method of persistence of species during a disturbance and to their subsequent arrival, to their ability to establish and grow to maturity following the disturbance, and to the time taken for them to reach critical stages in their life history.In the application of the scheme, each major species is first categorized into a species type, determined by its specific attributes in the first two vital attribute groups. The interaction between various species, based on their species types and life stage attributes, then yields a replacement sequence which depicts the major shifts in composition and dominance which occur following a disturbance. Although 30 species types are recognized, only 15 distinct patterns of behaviour are displayed in replacement sequences.Examples of replacement sequences for two different forest communities are provided.The degree to which vital attributes are robust properties of a species is explored in relation to different disturbance frequencies and intensities, and to the seasonal time of disturbance.
The evolutionary consequences of asymmetric competition between species are poorly understood in comparison with symmetric competition. A model for evolution of body size under asymmetric competition within and between species is described. The model links processes operating at the scale of the individual to that of macroscopic evolution through a stochastic mutation–selection process. Phase portraits of evolution in a phenotype space characteristically show character convergence and parallel character shifts, with character divergence being relatively uncommon. The asymptotic states of evolution depend very much on the properties of asymmetric competition. Given relatively weak asymmetries between species, a single equilibrium point exists; this is a local attractor, and its position is determined by the intra- and interspecific asymmetries. When the asymmetries are made stronger, several fixed points may come about, creating further equilibrium points which are local attractors. It is also possible for periodic attractors to occur; such attractors comprise Red Queen dynamics with phenotype values that continue to change without ever settling down to constant values. From certain initial conditions, evolution leading to extinction of one of the species is also a likely outcome.
When plants are competing, larger individuals often obtain a disproportionate share of the contested resources and suppress
the growth of their smaller neighbors, a phenomenon called size-asymmetric competition. We review what is known about the
mechanisms that give rise to and modify the degree of size asymmetry in competition among plants, and attempt to clarify some
of the confusion in the literature on size asymmetry. We broadly distinguish between mechanisms determined primarily by characteristics
of contested resource from those that are influenced by the growth and behavior of the plants themselves. To generate size
asymmetric resource competition, a resource must be “pre-emptable.” Because of its directionality, light is the primary, but
perhaps not the only, example of a pre-emptable resource. The available data suggest that competition for mineral nutrients
is often size symmetric (i.e., contested resources are divided in proportion to competitor sizes), but the potential role
of patchily and/or episodically supplied nutrients in causing size asymmetry is largely unexplored. Virtually nothing is known
about the size symmetry of competition for water. Plasticity in morphology and physiology acts to reduce the degree of size
asymmetry in competition. We argue that an allometric perspective on growth, allocation, resource uptake, and resource utilization
can help us understand and quantify the mechanisms through which plants compete.
An individual-based model of plant competition for light that uses a definition of plant functional types based on adaptations for the simultaneous use of water and light can reproduce the fundamental spatial and temporal patterns of plant communities. This model shows that succession and zonation result from the same basic processes. Succession is interpreted as a temporal shift in species dominance, primarily in response to autogenic changes in light availability. Zonation is interpreted as a spatial shift in species dominance, primarily in response to the effect of allogenic changes in water availability on the dynamics of competition for light. Patterns of succession at different points along a moisture gradient can be used to examine changes in the ecological roles of various functional types, as well as to address questions of shifts in patterns of resource use through time.Our model is based on the cost-benefit concept that plant adaptations for the simultaneous use of two or more resources are limited by physiological and life history constraints. Three general sets of adaptive constraints produce inverse correlations in the ability of plants to efficiently use (1) light at both high and low availability, (2) water at both high and low availability, and (3) both water and light at low availabilities.The results of this type of individual-based model can be aggregated to examine phenomena at several levels of system organization (i.e., subdisciplines of ecology), including (1) plant growth responses over a range of environmental conditions, (2) population dynamics and size structure, (3) experimental and field observations on the distribution of species across environmental gradients, (4) studies of successional pattern, (5) plant physiognomy and community structure across environmental gradients, and (6) nutrient cycling.
Root competition inhibits root proliferation. All else equal, a plant should invest roots in a nutrient patch devoid of roots rather than one already occupied by roots. Less clear is how a plant should respond to intra-plant versus inter-plant root competition. We consider three responses for how a plant may select habitats based on intra-versus inter-plant root competition: inter-plant avoidance, resource matching, or intra-plant avoidance. The first assumes that plants prefer to have their own space and preferentially proliferate roots away from neighboring plants. The second response, based on the ideal free distribution, assumes that plants invest so as to equalize average returns from roots, regardless of the identity of the neighboring roots. The third, based on game theory, assumes that the plant proliferates roots so as to maximize whole-plant fitness, in which case it is better to proliferate plants among a neighbor's roots than to continue proliferating amongst one's own roots. To test among these models we grew beans (Phaseolus varigaris, var. Kenya) in a greenhouse under two planting scenarios. Both scenario were tested under 0.5 and 0.1strength of nutrient solution. Under scenario A (fence-sitters), two split-root plants each shared two patches by virtue of having roots in each. Under scenarioB (owners) two plants each had their own patch. The results supported the game theory model of intra-plant avoidance (whole plant habitat selection). Fence-sitters produced 150% more root mass per individual than owners. Owners produced 90% more yield (dry mass of pods) than fence-sitters. Furthermore, owners had significantly higher shoot-root ratios than fence-sitters. These effects did not vary with high or low nutrient levels. The over-proliferation of roots under inter-plant competition (fence-sitters) was manifest by the tenth day after planting. In short, the fence-sitters engaged in a tragedy of the commons in which they competed with each other through root proliferation. At the ESS, the fitness maximizing strategy of the individual is to sacrifice collective yield in a quest to `steal' nutrients from its neighbor. The research has three implications. First, plants may be able to assess and respond to local opportunities in a manner that maximizes the good of the whole plant. Second, nutrient foraging as a game may provide a fresh perceptive for viewing root competition either intra-specifically or inter-specifically. Third, it may be possible to increase the yield of certain crop species by breeding more `docile' cultivars that do not overproduce roots in response to inter-plant competition.
The canopy structure of a stand of vegetation is determined by the growth patterns of the individual plants within the stand and the competitive interactions among them. We analyzed the carbon gain of individuals in two dense monospecific stands of Xanthium canadense and evaluated the consequences for intra-specific competition and whole-stand canopy structure. The stands differed in productivity, and this was associated with differences in nitrogen availability. Canopy structure, aboveground mass, and nitrogen contents per unit leaf area (N
area) were determined for individuals, and leaf photosynthesis was measured as a function of N
area. These data were used to calculate the daily carbon gain of individuals. Within stands, photosynthesis per unit aboveground mass (P
mass) of individual plants increased with plant height, despite the lower leaf area ratios of taller plants. The differences in P
mass between the tallest most dominant and shortest most subordinate plants were greater in the high-nitrogen than in the low-nitrogen stand. This indicated that competition was asymmetric and that this asymmetry increased with nitrogen availability. In the high-nitrogen stand, taller plants had a higher P
mass than shorter ones, because they captured more light per unit mass and because they had higher photosynthesis per unit of absorbed light. Conversely, in the low-nitrogen stand, the differences in P
mass between plants of different heights resulted only from differences in their light capture per unit mass. Sensitivity analyses revealed that an increase in N
area, keeping leaf area of plants constant, increased whole-plant carbon gain for the taller more dominant plants but reduced carbon gain in the shorter more subordinate ones, which implies that the N
area values of shorter plants were greater than the optimal values for maximum photosynthesis. On the other hand, the carbon gain of all individual plants, keeping their total canopy N constant, was positively related to an increase in their individual leaf area. At the same time, however, increasing the leaf area for all plants simultaneously reduced the carbon gain of the whole stand. This result shows that the optimal leaf area index (LAI), which maximizes photosynthesis of a stand, is not evolutionarily stable because at this LAI, any individual can increase its carbon gain by increasing its leaf area.
Optimization models help us to test our insight into the biological constraints that influence the outcome of evolution. They serve to improve our understanding about adaptations, rather than to demonstrate that natural selection produces optimal solutions.
A spatial and mechanistic model is developed for the dynamics of transition oak-northern hardwoods forests in northeastern North America. The purpose of the model is to extrapolate from measurable fine-scale and short-term interactions among individual trees to large-scale and long-term dynamics of forest communities. Field methods, statistical estimators, and model structure were designed simultaneously to ensure that parameters could be estimated from data collected in the field. This paper documents eight aspects of a three-year study to calibrate, test, and analyze the model for the nine dominant and subdominant tree species in transition oak-northern hardwoods forests: 1) Design and structure of the model. The model makes population dynamic forecasts by predicting the fate of every individual tree throughout its life. Species-specific functions predict each tree's dispersal, establishment, growth, mortality, and fecundity. Trees occupy unique spatial positions, and individual performance is affected by the local availability of resources. Competition is mechanistic; resources available to each tree are reduced by neighbors. Although the model was developed to include light, water, and nitrogen, the version described here includes only competition for light (shading and light-dependent performance) because the field data provide little evidence of competition for nitrogen and water over the range of sites examined. 2) Estimates of the model's parameters for each species. The estimates reveal a variety of "strategic trade-offs" among the species. For example, species that grow quickly under high light tend to cast relatively little shade, have low survivorship under low light, and have high dispersal. In contrast, species that grow slowly under high light tend to cast relatively dark shade, and to have high survivorship under low light and low dispersal. These trade-offs define one of two dominant "axes" of strategic variation. 3) Community level predictions of the model. The model predicts succession from early dominance by species such as Quercus rubra and Prunus serotina, to late dominance by Fagus grandifolia and Tsuga canndensis, with Betula alleganiensis present as a gap phase species in old-growth stands. The model also predicts that old-growth communities will have intraspecifically clumped and interspecifically segregated spatial distributions. 4) An error analysis that identifies community level predictions that are robust given the level of sampling uncertainty in the study. This analysis translates the statistical uncertainty associated with each parameter estimate into statistical uncertainty in the model's predictions. The robust predictions include those mentioned in aspect (3) above. 5) Sensitivity of the model to changes in initial conditions and to changes in the three parameters not included in the error analysis. For example, the model predicts that initial abundances continue to affect community composition well into succession (>300 yr for some species). 6) Tests of the system- and community-level predictions of the model against independent data gleaned from other studies. These tests support the predictions found to be robust in the error analysis, including those predictions mentioned in aspect (3) above. 7) Modeling experiments that determine which aspects of individual performance and inter-neighbor competition are responsible for each of the: robust predictions identified in aspect (4) above and tested in aspect (6) above. This analysis reveals a wide variety of causal relationships, with most parameters contributing to at least one community level phenomenon. 8) An explanation of the diversity of individual level causes identified in aspect (7). The two "axes" describing most of the strategic variation among the species (see [2]), provide a simple explanation of community level pattern in terms of individual level processes.
Within plant communities seed mass often varies over 3 to 5 orders of magnitude, yet simple evolutionary models predict a single optimum seed mass. Here we explore a class of models where seed mass determines 1) the number of seeds produced via a size number trade-off and 2) competitive ability plants arising from large seeds are assumed to have a competitive advantage over those derived from small seeds. In this setting the existence of a single-species global ESS seed mass requires the competitive advantage of large seeds over small ones to be unbounded. If there is a limit on the competitive advantage that large seeds obtain then it is always possible to find a smaller seed mass that will successfully invade. In such circumstances there might be a multi-species coevolutionarily stable coalition of several species each with a different seed mass. In this way a wide range of seed masses could be promoted by evolution. In general the adaptive landscape generated by these models is extremely flat leading to slow evolutionary dynamics. The implications of these results for the interpretation of observational, comparative and experimental studies are discussed.
The debate over the relative importance of natural selection as compared to other forces affecting the evolution of organisms is a long-standing and central controversy in evolutionary biology. The theory of adaptationism argues that natural selection contains sufficient explanatory power in itself to account for all evolution. However, there are differing views about the efficiency of the adaptation model of explanation. If the adaptationism theory is applied, are energy and resources being used to their optimum? This book presents an up-to-date view of this controversy and reflects the dramatic changes in our understanding of evolution that have occurred in the last twenty years. The volume combines contributions from biologists and philosophers, and offers a systematic treatment of foundational, conceptual, and methodological issues surrounding the theory of adaptationism. The essays examine recent developments in topics such as phylogenetic analysis, the theory of optimality and ess models, and methods of testing models.
This chapter explores some of the trade-offs and underlying constraints on stem adaptations for energy capture, and analyzes how such adaptations may limit the distribution of species along gradients, and shape the structure and physiognomy of plant communities. Such analysis provide important insights into the determinants of plant stature, crown geometry, phyllotaxis, the location of tree lines, the zonation of aquatic plants, and the shift in understory dominance from shrubs to herbs along forested gradients. The primary functions of support and competition impose four principal constraints on stem adaptations for energy capture viz. mechanical stability, mechanical safety, photosynthetic efficiency, and whole plant growth and competitive ability. Each of these constraints is discussed briefly. On the basis of this optimality criterion, the optimal form, biomechanical properties, and growth dynamics of stems in a particular ecological context should be set by five major trade-offs involving the constraints. These trade-offs involve the balance between safety vs growth and competitive ability; growth vs photosynthetic requirements; mechanical vs photosynthetic efficiency; initial vs continuing costs; and structural parasitism vs self-support. Each of these trade-offs is discussed and the resulting implications for ecological trends in stem form, resource allocation, and growth dynamics are analyzed. Context specificity is the key feature that distinguishes biomechanical ecology from pure biomechanics, and allows insights derived from functional morphology and biomechanics to illuminate ecological and evolutionary issues.
The amount of effort organisms should put into reproducing at any given time has been a matter of debate for many years. Early models suggested a simple rule of thumb: iteroparity should be favored when juvenile survival is relatively variable and semelparity when adult survival is relatively variable. When more mathematically complex models were developed, these simple conclusions were found to be special cases. Variability can select toward iteroparity or semelparity depending on a number of factors irrespective of relative adult/juvenile survival (e.g, the density-independent models of Orzack and Tuljapurkar). Using new techniques, we estimate the ESS reproductive effort for stage-structured models in density-dependent and stochastic conditions. We find that variability causes significant changes in reproductive effort, these changes are often small (+/- 10% of determinstic ESS effort, but up to 50% change in some instances), and the amount that effort increases or decreases depends on many factors (e.g., the deterministic population dynamics, the vital rates affected by density, the amount of variation, the correlations between the vital rates, the distribution from which the variation is drawn, and the deterministic ESS effort). In a variable environment, semelparity is the ESS in only 3.5% of cases; iteroparity is the rule.
The problem of scale has been a critical impediment to incorporating important fine-scale processes into global ecosystem models. Our knowledge of fine-scale physiological and ecological processes comes from a variety of measurements, ranging from forest plot inventories to remote sensing, made at spatial resolutions considerably smaller than the large scale at which global ecosystem models are defined. In this paper, we describe a new individual-based, terrestrial biosphere model, which we label the ecosystem demography model (ED). We then introduce a general method for scaling stochastic individual-based models of ecosystem dynamics (gap models) such as ED to large scales. The method accounts for the fine-scale spatial heterogeneity within an ecosystem caused by stochastic disturbance events, operating at scales down to individual canopy-tree-sized gaps. By conditioning appropriately on the occurrence of these events, we derive a size-and age-structured (SAS) approximation for the first moment of the stochastic ecosystem model. With this approximation, it is possible to make predictions about the large scales of interest from a description of the fine-scale physiological and population-dynamic processes without simulating the fate of every plant individually. We use the SAS approximation to implement our individual-based biosphere model over South America from 15° N to 15° S, showing that the SAS equations are accurate across a range of environmental conditions and resulting ecosystem types. We then compare the predictions of the biosphere model to regional data and to intensive data at specific sites. Analysis of the model at these sites illustrates the importance of fine-scale heterogeneity in governing large-scale ecosystem function, showing how population and community-level processes influence ecosystem composition and structure, patterns of aboveground carbon accumulation, and net ecosystem production.
The evolution of age at maturity under exploitation competition in a patchy environment is modelled using both an analytical approach and computer simulations. Maturity is defined as the switch from allocating resources to growth to allocating them to reproduction, and fitness is measured as lifetime energy allocation to reproduction. Explicit consideration of resources and their exploitation brings about frequency dependence. As a consequence, whenever two or more individuals jointly exploit a patch, the ESS is to mature later and at larger size than at the age and size maximizing the fitness measure. An adaptive response to the presence of competitors thus aggravates the depression of fecundity resulting from competitive resource depletion. In some cases two individuals in a patch should grow larger and mature later than a single individual in a patch of the same size, even though in the first case the individual resource share is halved. The effects of patch size, number of competitors, within-patch mortality and whole-patch destruction rate on the predicted age and size at maturity are discussed.
This paper demonstrates a new analysis of photon flux partitioning among species and an evaluation of the efficiency of photon flux capturing in terms of biomass investment. For that purpose, distributions of aboveground biomass, leaf area, and photon flux density (PPFD) were determined with the stratified harvest method in a stand of a tall herbaceous community on a floating fen at the time of peak standing crop. The stand contained 11 species and the photon flux absorbed by each species in the stand was estimated. Three tall dominant species absorbed 75% of the incident PPFD, while eight short subordinate species absorbed 2.5%. Tall species in the canopy received higher PPFD averaged over leaf area (@?"a"r"e"a). However, the PPFD absorbed per unit aboveground biomass (@?"m"a"s"s) of the tall species was not higher than that of the subordinate species. @?"m"a"s"s is a product of the leaf area ratio (LAR, the ratio of leaf area to aboveground biomass) and @?"a"r"e"a. There was a trade-off relationship between LAR and @?"a"r"e"a. To have a high @?"a"r"e"a, plants place their leaves at higher positions in the canopy, which necessarily decreases LAR. Aboveground biomass was regarded as an investment (cost) to capture PPFD (benefit). @?"m"a"s"s, as a ratio of benefit to cost, indicates an efficiency of biomass investment to capture photon flux. Tall species appeared to have an advantage over subordinate species in receiving a large fraction of incident PPFD, while subordinate species have an advantage in efficiently using their biomass to capture PPFD.
In temperate grasslands, the relative importance of above‐ground competition for light compared to below‐ground competition for water and nutrients is hypothesized to increase with increasing precipitation. Thus, competition for light is likely to exert an increasing influence on canopy structure and species composition as precipitation increases. We quantified canopy structure, light availability and changes in species composition at seven sites across the central grassland region of the United States to determine how these properties change across a precipitation gradient. Across the region, there was a disproportionate increase in leaf area and canopy height with increasing precipitation, indicating that plants become taller and leafier across the gradient. Leaf area index increased by a factor of 12 across the gradient while above‐ground net primary productivity increased by a factor of only 5.5. As precipitation increased, there was decreased light availability at the soil surface, increased seasonal variability in light transmission, increased biomass and leaf area at higher canopy layers and an increased proportion of tallstatured species. These observed changes in canopy structure support the prediction that competition for light increases in importance with increasing precipitation.
Conflicts between animals of the same species usually are of ``limited
war'' type, not causing serious injury. This is often explained as due
to group or species selection for behaviour benefiting the species
rather than individuals. Game theory and computer simulation analyses
show, however, that a ``limited war'' strategy benefits individual
animals as well as the species.
We present and apply a method for analyzing size-dependent patterns of resource acquisition by individuals within stands of competing plants. Our approach relies on curve-fitting to relate empirical measures of resource acquisition with various aspects of plant size and form. These relationships are referred to as size-uptake relationships (SURs). We demonstrate the use of this approach by characterizing the size dependence of light and nitrogen acquisition within developing stands of birch seedlings. Results of a number of phenomenological studies have predicted that competition for light is expected to be size asymmetric and that competition for belowground resources is expected to be size symmetric. Our study provides the first direct empirical test for these hypotheses. Application of the SUR approach largely confirms predictions regarding the size-dependent nature of light and belowground resource (nitrogen) acquisition. The uptake of nitrogen by birch seedlings was size symmetric, regardless of which aspect of size we considered (i.e., root mass, root length, root surface area, number of root tips, number of mycorrhizal root tips). In contrast, light interception was size asymmetric in relation to height and leaf area, but size symmetric in relation to total plant biomass. Differences in the degree of size-asymmetry of light acquisition between different measures of size were driven by the nature of the allometric relationships between plant height, biomass, and leaf area. SURs offer a tool for exploring some of the mechanistic processes related to resource-based interactions. Using this approach, we demonstrate that it is possible to characterize simultaneously the size-dependent patterns of multiple resources within competing plant populations. We suggest that this approach may prove valuable for identifying how size-dependent patterns of resource acquisition vary through ontogeny. We conclude with a discussion of the need for a more mechanistic understanding of plant-plant interactions and the role that the SUR approach can play towards this goal.
A game-theoretical model of tree growth balances the advantages of height for light interception against height-related costs, such as increased maintenance respiration, that reduce the energy available for stem growth. The model predicts an evolutionarily stable strategy (ESS) for trees of even-aged stands. This ESS consists of a prolonged interval of height growth that terminates when the trees reach 87% of the theoretical break-even height, at which stem maintenance and root and leaf renewal costs require all available photosynthate, leaving none for wood production. Tests of the model with data from forest yield tables indicate that 1) average-sized trees of even-aged stands follow the predicted ESS until reaching at least 70-90% of their maximum height; 2) trees that are larger than average have thicker-than-expected trunks to withstand disproportionately greater wind forces in the upper canopy; 3) height growth may cease in very old stands, as predicted; and 4) height growth appears to cease gradually rather than suddenly. Features that are not in the model but might favor a gradual cessation of height growth include the greater wind exposure of the upper canopy and unpredictable environmental variation. The general success of the model suggests that competition for light is the primary factor responsible for the evolution and maintenance of the arboreal life form. -from Author
While differential equations have been commonly used to model the population dynamics of biological systems, it is uncommon for such models to include the evolutionary potential of the species being modeled. As a consequence, the focus of such models has generally been directed toward ecological stability rather than on evolutionary stability. Here, an evolutionary game approach to modeling is presented that allows for a very clear distinction between ecological and evolutionary stability. Necessary conditions are given for each type of stability so that they may be studied separately. In order to include evolution into management models, we are faced with two fundamental questions: what is evolving, and where is it evolving to? In the evolutionary game theory presented here, the ‘what’ are parameters in the differential game model associated with characteristics of the species that are clearly adaptive (such as sunlight conversion efficiency for plants or body length in animals), which we call strategies. The ‘where’ is the evolutionarily stable strategies (ESS) to which these parameters can evolve. These strategies can be determined using the ESS maximum principle presented here. The ESS maximum principle when used with appropriate models, has the capacity to predict the evolutionary response of biological systems subject to a wide range of inputs, including physiographic changes, harvesting, and the introduction or removal of new species and/or resources. Applications are discussed in terms of some typical managed ecosystems. A detailed example, illustrating use of the theory, is given in which the treatment of cancer with drugs is ‘simulated’.
A game model was developed to examine the evolutionarily stable strategy for the architecture of herbaceous plants. The clones which were considered consisted of leaves, vertical stems and horizontal stems. It was assumed that tall vertical stems are advantageous in light competition with neighbors, and that long horizontal stems decrease self-shading. The model analysis predicted the following four correlations between environmental conditions and the evolutionarily stable architecture of herbaceous plants. (1) A clone allocates all resources to leaves, nothing to vertical or horizontal stems, and forms a rosette in open habitats with low clone density. (2) A clone allocates resources only to leaves and to horizontal stems, but nothing to vertical stems, and creeps on the ground in closed habitats with low clone density. (3) A clone allocates resources only to leaves and to vertical stems, but nothing to horizontal stems, and grows gregariously in open habitats with high clone density. (4) A clone allocates resources to leaves, to vertical stems, and to horizontal stems in closed habitats with high clone density.
The growth and reproductive schedule of terrestrial plants can be usefully studied as the dynamic optimal allocation of material between different organs. This idea, pioneered by Dan Cohen, has been formalized as an optimal control problem and analysed using Pontryagin's maximum principle or dynamic programming. Here, I review several examples of dynamic resource allocation models. First, the seasonal timing of reproduction of annuals is discussed. This can be extended to plants with multiple vegetative organs and the optimal shoot-root balance is assessed. Secondly, the growth schedule over multiple seasons is examined, and the reproductive effort, the leaf phenology of deciduous perennials, and the conditions under which perenniality is more advantageous than annuality are considered. With some modifications, the same model can handle intermittent reproduction and monocarpic perennials (one large reproduction after many years). Thirdly, growth in an unpredictably fluctuating environment is analysed for the case in which a sudden disturbance (herbivory or fire) removes the photosynthetic system altogether, followed by recovery using stored material, and for the case in which environmental productivity fluctuates in a Markovian process. Finally, the optimal level of chemical defence against herbivory is formalized and used to explain the intensity of alkaloid defence decreasing with leaf age. These examples illustrate the usefulness of dynamic resource allocation models in understanding plant life-history adaptation.
Available data generally do not support the hydraulic limitation hypothesis. There was no significant correlation between ln-transformed KP,LA and tree height (2–25 m) for 17 trees of 11 temperate species ( Fig. 2, Pearson’s r = −0·16, P = 0·54). Values of KP,LA for tall temperate trees and short tropical plants overlapped ( Figs 1 and 2; Becker et al. 1999 ). Comparison within species is preferable; there were slight inverse trends between KP,LA and height for two species and large variation in KP,LA among studies for a third species with trees of similar height measured at four different sites ( Fig. 2). In a comparison of five tropical species, KP,LA was again uncorrelated with tree height (18–35 m), although some trees were not well-watered ( Andrade et al. 1998 ; Goldstein et al. 1998 ) so soil resistance may have become limiting. Whole-plant conductance normalized by LAI (leaf area per ground area) did not significantly differ between short (3–5 m) and tall (9–14 m) Acer saccharum (Fig. 5 in Dawson 1996). Saliendra, Sperry & Comstock (1995) did find that juveniles (
A model was developed to examine the ESS sapling growth waiting for future gap formation under closed canopy. Assumptions are: a sapling has two parts, a trunk and a photosynthetic part, and allocates annual photosynthates to these two parts; and a sapling with a larger photosynthetic part has a larger production rate, but a sapling with a larger trunk is more successful in competition after gap formation. The ESS growth schedule of a sapling typically consists of three phases: (1) the sapling first allocates all annual photosynthates to the photosynthetic part, then (2) it allocates annual photosynthates both to its trunk and to photosynthetic part, and both parts grow simultaneously, and finally (3) it also allocates annual photosynthates to both parts, but the size of the photosynthetic part stays constant due to annual loss, and only the trunk size increases. A sapling should allocate photosynthates more to the trunk if mortality or probability of gap formation is large. However, a sapling should allocate photosynthates more to the photosynthetic part if large trunks are strongly advantageous in competition after gap formation.
To determine the effect of tree dimensions on the rate of height growth a model was constructed relating tree weight to total height and R, the ratio of crown weight to trunk weight. The model is based on the assumption that the trunk buckling safety factor is constant. If trees also maintain a constant R as they grow then the rate of height growth is maximized by R=0.17. In addition, the height growth rate increases as the buckling safety factor decreases. These predictions of optimal form for height growth are appropriate for shade intolerant, successional species growing in dense stands. Dimensional measurements of self thinning Populus tremuloides indicate near optimal dimensions for height growth. Trees ranging from 7 to 19 m in height had trunks which were only 50% thicker than the minimum required to prevent them from buckling under their own weight, and had a mean R of 0.13. This ratio of crown weight to trunk weight is significantly lower than the optimal value, but the predicted height growth rate for R=0.13 is 99% of that predicted for R=0.17.
We present a general framework for modelling adaptive trait dynamics in which we integrate various concepts and techniques from modern ESS-theory. The concept of evolutionarily singular strategies is introduced as a generalization of the ESS-concept. We give a full classification of the singular strategies in terms of ESS-stability, convergence stability, the ability of the singular strategy to invade other populations if initially rare itself, and the possibility of protected dimorphisms occurring within the singular strategy''s neighbourhood. Of particular interest is a type of singular strategy that is an evolutionary attractor from a great distance, but once in its neighbourhood a population becomes dimorphic and undergoes disruptive selection leading to evolutionary branching. Modelling the adaptive growth and branching of the evolutionary tree can thus be considered as a major application of the framework. A haploid version of Levene''s soft selection model is developed as a specific example to demonstrate evolutionary dynamics and branching in monomorphic and polymorphic populations.
Three new studies suggest that tall trees experience increased hydraulic stress in drawing water from the soil into their canopies. They adjust to this by various homeostatic mechanisms, such as reducing the leaf area/conducting stem ratio. These mechanisms partly mask the hydraulic consequences of increased tree height in some measures of plant–water interactions, and have implications for the hydraulic limitations hypothesis and the fractal networks transport hypothesis.
A behavior or strategy which is evolutionarily stable must be both optimal and stable. The strategy must be optimal in that it maximizes the expected fitness of all the individuals using it. In addition, the strategy must be resistant to invasion by a mutant. The difference between the Nash solution of game theory and the ESS used in ecology is that the Nash solution only satisfies an optimality criterion and not an evolutionary stability criterion. We extend the ESS definition of Maynard Smith and Price so that it can be applied directly to two-strategy evolutionary games. The concept of a balanced game is introduced, and necessary conditions are derived which are similar to the Nash necessary conditions. The balanced game necessary conditions may be used for direct calculation of ESS candidates. These results are used to examine the optimal flowering time of an annual plant experiencing competition from neighboring plants. The plant competition model is general, and the results may be applied to a wide range of interference competition problems.
We present a model for the evolutionary dynamics of seed size when there is a trade-off between seed size and seed number, and seedlings from large seeds are better competitors and have a higher precompetitive survival than seedlings from small seeds. We find that strong competitive asymmetry, high resource levels, and intermediate harshness of the precompetitive environment favor coexistence of plants with different seed sizes. If the evolution of seed size is mutation-limited and single mutations have only a small phenotypic effect, then an initially monomorphic population reaches the final evolutionarily stable polymorphic state through one or more discrete evolutionary branching events. At each such branching event, a given lineage already present in the population divides into two phenotypically diverging daughter lines, each with its own seed size. If the precompetitive survival of seeds and seedlings is high for small and large seeds alike, however, evolutionary branching may be followed by the extinction of one or more lineages. Various results presented here are model-independent and point the way to a more general evolutionary bifurcation theory describing how the number and stability properties of evolutionary equilibria may change as a consequence of changes in model parameters.
In a crop monoculture, the most competitive individuals will gain a disproportionate share of the limiting resource in the environment, and are thus favored by natural selection. However, a partitioning of limited assimilates to organs for competition requires a reduced partition to grain production. Reflecting on this problem, Donald proposed that natural selection through competition would generally result in `over-growth' of some resource-foraging organs, which may be termed `growth redundancy'. According to Donald, an important way to increase the yield potential in annual seed crops would be to develop a `communal' ideotype that minimizes growth redundancy. Selection through competition within a crop seems to be an ideal topic for analysis using game theory, because the optimal strategy for each plant depends on what the other plants do. As a consequence, there are conflicts of interest between the individuals in a crop population and the optimizing process is actually a noncooperative game in which each individual is a player which optimizes its strategy, given other player's strategies. A game theoretical model of this kind is presented in this paper, and corroborates the Donald's view. It is shown that the optimal resource partition maximizing a crop's yield is never evolutionarily stable, implying a high incidence of growth redundancy in modern crop plants. Growth redundancy represents a particular version of the famous `tragedy of the commons'.
Frequency-dependent selection is so fundamental to modern evolutionary thinking that everyone `knows' the concept. Yet the term is used to refer to different types of selection. The concept is well defined in the original context of population genetics theory, which focuses on short-term evolutionary change. The original concept becomes ambiguous, however, when used in the context of long-term evolution, where density dependence becomes essential. Weak and strong frequency dependence, as distinguished in this article, refer to two very different forms of selection.
Differential game theory is applied to the analysis of evolutionarily stable strategies (ESS) in this article. A general form for the evolutionary differential game is introduced in the case of intra-specific competition, and a connection between the ESS and the mathematical Nash solution concept is indicated. A dynamic ESS is found for the height growth strategies of trees. A hierarchical model is introduced to account for different time constants in simultaneous selection processes. Differential evolutionary games are compared with static evolutionary games utilizing the hierarchical approach.