Article

Relationships between leaf lifespan and structural defences in a low-nutrient, sclerophyll flora

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Abstract

Summary The spectrum between species with low leaf mass per area (LMA), short-lived leaves and high photosynthetic rate to those with high LMA, long-lived leaves and low photosynthetic rate is one of the major spectra of variation between plant species, and is of particular relevance to the ‘carbon-gain strategy’ of plants. In this study the relationship between physical properties of leaves and their lifespan was quantified for 17 sclerophyllous species from a nutrient-poor woodland in eastern Australia. Fracture properties of leaves (force of fracture, tissue toughness) and other leaf traits [LMA, thickness, dry-matter content (DMC), leaf area] were measured for each species and evaluated as predictors of leaf lifespan in cross-species and phylogenetic analyses, and for intercorrelation with one another. The LMA, mean force of fracture, leaf thickness and leaf area each explained approximately 30–40% of variation in leaf lifespan. Leaf toughness explained 25% of variation in leaf lifespan, and DMC 12%. Leaf toughness and DMC were correlated with each other, but not with leaf thickness. Leaf thickness and toughness were related closely to LMA, while DMC and LMA were only marginally correlated. Nutrients can be withdrawn prior to leaf death and redeployed elsewhere in the canopy when leaf death is initiated by a plant. However, when control is external to the plant these nutrients are lost. There may be advantages to increasing defence to give a high likelihood that the plant has control over the timing of leaf death.

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... For example, tissue density is the most important variable explaining the correlation between SLA and foliar toughness (Kitajima and Poorter 2010). Indeed, leaves with high tissue density generally have low SLA and therefore high foliar toughness, slow net photosynthetic rate, low N concentration, and long life span (Wright and Cannon 2001;Wright et al. 2004;Hanley et al. 2007). SLA appears to be a particularly good predictor of foliar toughness for plants like conifers with high investment in lignified tissue, whose ecological strategy to survive in inhospitable environments is to produce structurally reinforced, long-lived leaves (Reich et al. 1995). ...
... Plants have evolved several strategies to avoid, resist, and endure damage caused by insect herbivores; these include phenological, mechanical, chemical, and nutritional traits that affect insect performance or prevent feeding initiation or oviposition (Larsson 2002;Hanley et al. 2007;Fuentealba et al. 2017Fuentealba et al. , 2018. Foliar traits such as low SLA, high foliar toughness, and high fibre content are often associated with low vulnerability to herbivory (Wright and Cannon 2001;Hanley et al. 2007) because these traits increase biomechanical resistance to insects piercing the leaf, a natural prerequisite to feeding (Hochuli 1996;Wright and Cannon 2001;Wright et al. 2004;Hanley et al. 2007; Candidate models are ranked in the order of increasing differences in Bayesian Information Criterion (BIC). Model weights (ω m ) indicate the probability that a model is the best model in the candidate set (ΔBIC < 2). ...
... Plants have evolved several strategies to avoid, resist, and endure damage caused by insect herbivores; these include phenological, mechanical, chemical, and nutritional traits that affect insect performance or prevent feeding initiation or oviposition (Larsson 2002;Hanley et al. 2007;Fuentealba et al. 2017Fuentealba et al. , 2018. Foliar traits such as low SLA, high foliar toughness, and high fibre content are often associated with low vulnerability to herbivory (Wright and Cannon 2001;Hanley et al. 2007) because these traits increase biomechanical resistance to insects piercing the leaf, a natural prerequisite to feeding (Hochuli 1996;Wright and Cannon 2001;Wright et al. 2004;Hanley et al. 2007; Candidate models are ranked in the order of increasing differences in Bayesian Information Criterion (BIC). Model weights (ω m ) indicate the probability that a model is the best model in the candidate set (ΔBIC < 2). ...
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Article
Toughness of leaves is an important defense mechanism of plants against insect herbivores and is generally linked to leaf fibre content. We explored the anatomical basis and ecological role of needle toughness as a mechanism of defense against feeding initiation by second instar spruce budworm (Choristoneura fumiferana) emerging from diapause. We first aimed at determining relationships between needle physico-chemical traits and toughness (specific leaf area (SLA), nitrogen, carbon, fibre, and water content, and C/N ratio). Second, we tested the hypothesis that differences in needle toughness between balsam fir (Abies balsamea) and black spruce (Picea mariana) explain differences in the ability of young budworm to mine into a needle, asking whether nitrogen content or toughness is a better predictor of budworm mining success. Our results show first that needle toughness correlates with high cellulose content and that SLA is a good proxy. Second, needle toughness is a stronger predictor of mining success (defined as the number of larvae that entered a needle) by young budworm than is nitrogen content. Our results suggest that needle toughness can be an important defensive trait in conifers, as suggested by the low mining rate exhibited by second-instar spruce budworm larvae feeding on 1-year-old black spruce foliage. The foliage of this host is tougher and has higher fibre content than balsam fir foliage. Differences in needle toughness, and associated differences in resistance to folivores, might be an important component in adaptive suites of traits constituting the different life-history strategies of these two sympatric species.
... These traits are expected to vary along climatic and soil variation gradients, because of their expected links to either soil nutrient stress (LES traits, δ 15 N, Lth; Wright and Cannon 2001;Hodgson et al. 2011), temperature or climatic stress (LES traits, leaf area; Wright et al. 2005;Dong et al. 2020) or drought (leaf area, Lth, EWT, δ 13 C; Medeiros et al. 2019;Maréchaux et al. 2020). While high values of δ 13 C are known to reflect high long-term water-use efficiency, and thus drought tolerance (Farquhar et al. 1982;Pérez-Harguindeguy et al. 2013), δ 15 N relates to a plant's nitrogen acquisition strategy (Craine et al. 2015). ...
... This could explain the presence of acquisitive leaf traits (high SLA and leaf N) in less acidic soils for both vegetation layers (Wright & Cannon 2001). The lower relative importance of soil variables compared to climate proxies for the fern understory, on the other hand, might be because understory fern species respond less strongly to soil variation or that they respond to more small-scale soil variation than that measured at the 10 × 10 m plot-level in this study. ...
Article
Although the relative importance of climate in abiotic filtering is higher for woody than herbaceous species assemblages, it is unclear whether this pattern is also reflected between the woody overstory and herbaceous understory of forests. The understory might respond more to small‐scale soil variation, next to experiencing additional abiotic filtering through overstory effects on light and litter quality. We explored the proportional importance of climate and soil on the species, trait and (functional) diversity patterns of both the forest overstory and fern and lycophyte understory. Subtropical forest along an elevational gradient from 850 to 2100 m a.s.l. in Northern Taiwan. We measured nine functional traits expected to respond to soil nutrient or climatic stress for woody overstory species and understory ferns and lycophytes. Next, we performed parallel constrained ordinations on over‐ and understory species and trait composition, and multiple regression for species and functional diversity, using measured climate proxies and soil variables as predictors. Climate was more important than soil in predicting the species composition of both vegetation layers and trait composition of the understory. The stronger than expected effect of climate for the understory was likely due to fern and lycophytes’ higher vulnerability to drought, while the higher importance of soil for the overstory trait composition seemed driven by deciduous species. The environmental drivers affected different response traits in both vegetation layers, and the overstory had additional effects on understory traits, resuling in a disconnection of community‐level trait values across layers. Interestingly, species and functional diversity patterns could be almost exclusively explained by climate effects for both layers. This study illustrates that abiotic filtering can differentially affect species, trait and diversity patterns and can be highly divergent for forest overstory and fern understory vegetation, and should consequently not be extrapolated across vegetation layers.
... For example, the species Erica multiflora and Globularia alypum from drier sites in Greece and Algeria show similar results with respect to the occurrence of terpenic components (Llusià et al., 2009;Said et al., 2011). The plants existing under this kind of climate (dry and hot) had a lower photosynthetic capacity and a higher leaf nitrogen (N) and phosphorous (P) contents (Wright and Cannon, 2001). Furthermore, the high leaf nitrogen concentration is linked with lower leaf toughness during photosynthesis in order to enhance water conservation, because the dry-mass economics of leaf construction (leaf lifespan) and ...
... The increase in density and thickness and sclerophylly presence is thought to be a protection for plants facing inappropriate conditions; it may extend the leaf longevity under conditions of limited resources or drought (Fonseca et al., 2000). This method of protection in leaves works by diluting photosynthetic tissues with nonphotosynthetic tissues and leads to a reduction in the rate of photosynthesis due to lower levels of light-capture (Wright and Cannon, 2001). ...
Thesis
There are many factors shown to have beneficial effects on many crop plants. Here we investigate the impact of fertilizers and genetic variation on Rosmarinus officinalis L. measured by both oil yield and quality. Plants grown in a temperature-controlled greenhouse with a natural photoperiod and a controlled irrigation system were treated with seaweed fertilizer and an inorganic fertilizer of matching mineral composition but with no organic content. Treatments were either by spraying on to the foliage or watering direct to the compost. The essential oil was extracted by hydro-distillation with a Clevenger apparatus and analysed by gaschromatography mass-spectrometry (GC–MS) and nuclear magnetic resonance spectroscopy (NMR). The crop responded positively to the application of fertilizer when compared to the control (no fertilizer). The seaweed treatments caused a significant increase in oil amount and leaf area as compared with both inorganic treatments and the control regardless of application method. The application of cytokinin in seaweed form also had a positive role with plant growth and oil production. The chemical compositions of the plants were compared, and qualitative differences were found between fertilizer treatments, application methods, ages of the plant and different genotype. The difference in oil composition were influenced partly by applying seaweed fertilizer. A full chemical analysis of the essential oil was conducted in order to identify the main components. Nine compounds were determined. Eucalyptol and camphene were shown to make up more than half. The other compounds made up the remaining 30%. In general, oil yields are reduced in the older plants whether from those with applied fertilizer or the control. The different genotypes showed a highly significant difference in oil composition and yield compared with other factors affecting essential oil production showing that rosemary plants vary greatly and the correct cultivar should be chosen with reference to its intended final use.
... There are four major types of tests that are frequently used to measure leaf mechanical properties (Table 1; [17,18]): (1) shearing tests (also called scissoring, cutting tests) measure how much work is required to cut across a leaf with a single blade (against an anvil) or with a pair of blades (i.e., instrumented scissors) [19][20][21]; (2) punch tests, including punch-and-die and penetrometer tests, measure the maximum load required for the punch rod to penetrate a leaf [22][23][24][25]; (3) tensile tests (also called tearing tests) measure the force required to stretch and eventually tear a strip of leaf lamina [26][27][28]; and (4) bending tests (or flexural tests) measure the force required to bend a strip of leaf lamina that is placed on two supports [17,29] or entire leaf lamina with attached petiole [30,31]. These tests can measure mechanical properties of a leaf specimen (often rectangular strip) in different directions (vertical or horizontal to the lamina surface) and different tissue types (e.g., the major leaf veins or the lamina between veins). ...
... From a global plant perspective, increases in leaf sclerophylly can be associated with increases in leaf longevity, as several authors have reported positive relationships between LMA or physical properties with leaf life span (LL) (e.g., [4,6,18,21,119,120]. Focusing on the genus Quercus, a relationship between LL and LMA obtained from literature and personal measurements follows the same positive trend (Fig. 5). ...
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Article
Purpose of Review Defining the mechanisms behind and the leaf economic consequences of the development of sclerophylly in woody plants will allow us to understand its ecological implications, anticipate the potential for adaptation of different tree species to global change, and define new woody plant ideotypes for stress tolerance. Recent Findings Sclerophylly has evolved independently in different woody plant genera and has been traditionally considered as a stress-tolerance trait. However, the underlying drivers for this functional trait are still a matter of debate; it has been proposed as an adaptive response to miscellaneous stress factors, such as nutrient scarcity, drought stress, herbivory, and cold tolerance, and due to the large investment costs of sclerophylly, it is generally associated with a longer leaf life span. Summary The genus Quercus constitutes a unique living laboratory to understand global adaptive patterns along the leaf economic spectrum in forest trees. With more than 400 species, oaks are distributed along six zonobiomes and its versatility has resulted in a wide range of variations in leaf functional traits and contrasting adaptive strategies. However, although this wide variability cannot be explained alone by any of the ecological factors considered, such as drought, nutrient scarcity, low temperatures during vegetative period, and physical damage, neither any of them could be fully discarded. Noteworthy, our study also suggests that these constraints may have a synergistic effect, and from a functional point of view, we can conclude that in oaks leaf habit largely modulates the physiological implications of sclerophylly.
... The improved amount of food may therefore increase mite fecundity by increasing its feeding efficiency. Conversely, higher LMA may reduce mite performance through enhanced leaf resistance to herbivory (Walters and Reich 1999;Wright and Cannon 2001). In addition, light intensity would also influence the mite through changes in leaf food quality, such as nitrogen content, which is positively correlated with mite fecundity (Wermelinger et al. 1991). ...
... In addition, the amount of food per mesophyll cell may have been also increased, because the size of mesophyll cells is generally larger in plants grown at higher light intensity (Boardman 1977;Lichtenthaler et al. 1981). When the amount of food per unit leaf area and/or per single mesophyll cell increase, the mite can efficiently feed on the contents of mesophyll cells from a limited area, which may be one reason for the increased fecundity in the leaves with high LMA, although higher LMA possibly contributes to enhanced leaf resistance to herbivory (Walters and Reich 1999;Wright and Cannon 2001). This hypothesis is supported by our findings that both the daily area damage and area encompassing damage per egg decreased with increasing LMA. ...
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Article
We investigated feeding and fecundity of the two-spotted spider mite, Tetranychus urticae (Acari: Tetranychidae), on leaves of cucumber (Cucumis sativus) seedlings that had been acclimatized to different light intensities. Based on these data, we analyzed the relationships between mite performance (feeding and fecundity) and leaf properties. The cucumber seedlings were grown in controlled-environment chambers under different light intensities at a photosynthetic photon flux density of 50, 100, 150, 300, or 450 µmol m− 2 s− 1 until the first true leaves had expanded. Adult females were released on the adaxial surfaces of excised leaf samples from the seedlings of each treatment group and held under standardized light intensity (200 µmol m− 2 s− 1). Fecundity and leaf damage area increased and decreased, respectively, as the acclimatization light intensity increased, indicating indirect effects of light intensity on feeding and fecundity through changes in the host leaf properties. Leaf mass per area (LMA) and photosynthetic capacity, which increased as the acclimatization light intensity increased, was positively related to the fecundity, but was negatively related to the leaf damage area. The higher LMA and photosynthetic capacity results in an increased amount of mesophyll per unit leaf area. This would allow the mites to feed efficiently from a limited area, which may explain the increased fecundity on these leaves.
... This may be due to the limitation of soil nutrient availability across global grassland (Craine and Jackson 2010). Plants tend to have high nutrient resorption efficiency to maintain their growth under limited soil nutrient availability (Wright and Cannon 2001;Zong et al. 2018). The results of our study also indicated that N addition reduced PRE, which was in agreement with previous reports of N addition reducing PRE in forest, grassland, and shrubland ecosystems (Yuan and Chen 2015b;Su et al. 2021). ...
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Article
Knowledge of plant nutrient strategies is crucial for defining and predicting the patterns and mechanisms resulting from nitrogen (N) deposition. However, the impacts of N enrichment on plant nutrient strategies are unclear in global grasslands. We conducted a meta-analysis of 127 publications to synthesize the pathways underlying the responses of plant nutrient concentration and resorption to N addition across global grassland ecosystems. Our analysis indicated that N addition increased the N concentration in green and senesced leaves, the phosphorus (P) concentration in senesced leaves, and aboveground and belowground biomass by about 32%, 50%, 7%, 74%, and 19%, respectively. Meanwhile, it reduced N resorption efficiency (NRE) and P resorption efficiency (PRE) by about 9% and 6%, respectively. Nitrogen addition did not significantly affect green leaf P concentration. These responses were modulated by N application rates and humidity, and they differed among grassland types, plant groups, fertilizer types, and experimental durations. Nitrogen addition changed the relationship between N and P in green leaves and between NRE and PRE, but it did not alter the N:P ratio in senesced leaves. Our results suggest that N addition affects leaf nutrient concentrations and resorption in global grassland ecosystems, although such effects vary among grassland types and among plant functional groups. Nutrient resorption may be a critical pathway that mediates plant regulation of the coupled N:P balance. Changes in humidity due to climate change also mediate the response of plant nutrients to N addition and thereby affect the soil–plant nutrient cycles of grassland ecosystems under future N enrichment.
... The greater increment in LMA observed in plants growing on soils with low nutrient status is a structural consequence of anatomical and metabolic processes. These plants build leaves with a high investment in fibres, thick cell walls, sclerenchyma and important secondary plant compounds, which extends the lifespan and increase defence against herbivory and abiotic stress (Wright and Cannon 2001). Many of these structures being frequent in Cerrado species (Bieras et al. 2009;Rossatto et al. 2015). ...
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Article
Background The Cerrado of central Brazil—the world’s largest Neotropical savanna – is comprised of a mosaic of highly heterogeneous vegetation growing on an extremely diverse geologic and geomorphologic background. Geomorphic processes under stable tectonic and climatic conditions facilitated the development of diverse edaphic properties, which interact with disturbance events to form unique vegetation types. Scope In this review, we detail how the geophysical environment affects soil formation and evaluate the mechanisms through which edaphic conditions control vegetation structure, floristic diversity and functional diversity. Conclusion The influence of geomorphic processes on edaphic properties has a marked impact on the ecology and evolution of plant communities. Species exhibit morphological and physiological adaptations that optimise their successful establishment in particular soil conditions. Furthermore, fire disturbance alters these soil-vegetation associations further regulating the structural nature of these communities. Therefore, we propose an integrative view where edaphic, chemical and physical properties act as modulators of vegetation stands, and these conditions interact with the fire regime. The knowledge of plant edaphic niches, their functional traits related to resource acquisition and use, as well as the interaction of edaphic properties and disturbance regimes is paramount to research planning, conservation, and successful restoration of the full diversity of Cerrado vegetation types.
... As traits related to the nutritional quality of litter (Cornelissen et al., 2003;García-Palacios et al., 2016), which could be important in nutrient-transfer-related mechanisms of litter mixture effects (Hättenschwiler et al., 2005), we determined the C-to-N ratio (C:N) and concentrations of Ca, Mg and Na. As traits related to plant defence (Pérez-Harguindeguy et al., 2013;Wright & Cannon, 2001) and to litter recalcitrance, we determined the force to punch (Fp, the physical strength of leaves), and concentrations of lignin, tannins and total phenolics. We included litter C:N rather than N concentration, because it was shown that potential N transfer not only depends on N concentration, but also on the C available to decomposer organisms (Handa et al., 2014;Manzoni et al., 2008). ...
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Article
Litter decomposition is controlled by climate, litter quality and decomposer communities. Because the decomposition of specific litter types is also influenced by the properties of adjacent types, mixing litter types may result in non‐additive effects on overall decomposition rates. The strength of these effects seems to depend on the litter functional diversity. However, it is unclear which functional traits or combination of traits explain litter mixture effects and if these depend on the range of trait values and the ecosystems involved. These uncertainties hamper our ability to predict decomposition in plant communities. 2. We aimed at understanding whether and how functional diversity (measured as functional dispersion, FDis) influences litter decomposition, and how this influence varies among different climates and across decomposition stages. We calculated FDis based on litter traits related to nutrient concentrations or to litter recalcitrance, and tested whether these diversity measures and climatic parameters (soil moisture and temperature) explained litter mixture effects on decomposition. 3. Additive mixture effects (i.e. decomposition of mixtures equalling the mean decomposition of the single litter types) were common in most of the evaluated climates. Non‐additive, negative effects were mainly restricted to the driest and warmest sites, and decreased with time. Non‐additive effects increased in magnitude with the mixtures’ FDis, with positive effects being related to FDis in nutrient traits and negative effects being related to FDis in recalcitrance traits. 4. Synthesis: Litter mixing did not have strong effects on decomposition rates across the studied climatic gradient overall, and the direction and intensity of the mixture effects were context‐dependent. The effects were stronger and more negative in the dryer ecosystems. Where effects were found, functional diversity calculated from selected groups of traits (related to nutrients or litter recalcitrance) predicted mixture effects, especially where trait ranges were broad, though much of the variation remains unexplained. We propose that functional diversity metrics based on litter traits that are mechanistically relevant, applied to diverse site‐specific litter mixtures in different climates, can help to better understand under which conditions and in which direction litter diversity affects decomposition.
... SLA can also be used as a surrogate for other leaf traits such as leaf nitrogen, decomposition rate, and water use efficiency, all of which are important characteristics of wetland plants that are more difficult to measure (Wright et al., 2004, Pérez-Harguindeguy et al., 2013. SLA is frequently used to represent soil fertility as well as nutrient cycling (Knops & Reinhart 2000, de Bello et al., 2010, Pérez-Harguindeguy et al., 2013, and LDMC can represent nutrient retention (Wright & Cannon 2001). SLA and LDMC can reflect the fast-slow life history spectrum, as leaves with high SLA and low LDMC are indicative of fast-growing plants, whereas plants with low SLA and high LDMC are indicative of slower growing plants (Pérez-Harguindeguy et al., 2013). ...
Article
Monitoring is essential to restoration, but the standard metrics used to monitor wetland restoration do not explicitly account for function in plant communities. Functional traits may be a useful addition to the wetland monitoring toolkit, because they can represent aspects of ecosystem functioning that standard metrics may not. Our objective was to determine how abiotic factors that influence wetland community composition and structure relate to both functional leaf traits and standard vegetation monitoring metrics to determine if functional leaf traits could add a functional component to wetland monitoring. We surveyed 66 100-m² plots in 22 floodplain wetlands in Illinois that were restored between 1997 and 2010. We used plant species data to calculate the mean coefficient of conservatism (mean C) and richness, and collected leaves to determine community weighted means of specific leaf area (SLA) and leaf dry matter content (LDMC) at each plot. Hydrologic data were used to calculate variables related to frequency, depth, and duration of inundation, and soil samples were collected to determine soil pH, organic matter content, and nitrogen and phosphorous content at each plot. We used structural equation models to understand how predictor variables (hydrological variables, soil variables, canopy cover, time since restoration, and latitude) influenced each other, and ultimately how they influenced response variables (mean C, richness, percent non-native species cover, SLA, and LDMC). LDMC and SLA were poorly explained by predictor variables and had relatively few significant relationships within models. Predictor variables best explained variance in mean C, followed by percent non-native cover, richness, then LDMC and SLA. Mean C was positively influenced by canopy cover and negatively influenced by soil fertility, whereas richness was negatively influenced by latitude. There was a strong latitudinal gradient of species richness from north to south, such that southern plots were significantly more diverse and had less cover by non-native species than northern plots. Our research suggests that SLA and LDMC may not be well suited for use as wetland restoration monitoring tools in Midwestern floodplain wetlands, and that monitoring tools already in place may sufficiently reflect abiotic conditions.
... Plant species with small leaves often have shorter leaf lifespans and higher relative growth rates. 51 Because for many plants, relative growth rates are highly correlated with rates of photosynthesis, respiration, and nutrient uptake from environments, 52 it could result in a faster and higher level of PFAS accumulation in weeds via transport in the vascular system. This could be true for the annual herb Pu as suggested by many densely distributed small pores on its leaves ( Figure S2J). ...
... We also found that the correlation between plant leaf functional traits changed under long-term N addition conditions. This is similar to previous studies by Wright and Cannon (2001) and Pensa et al. (2010). Our results suggest that long-term nitrogen application tends to lead to closer relationships between traits. ...
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Article
Plasticity of plant functional traits plays an important role in plant growth and survival under changing climate. However, knowledge about how leaf functional traits respond to the multi-level N addition rates, multiple N compound and duration of N application remains lacking. This study investigated the effects of 2-year and 7-year N addition on the leaf functional traits of Leymus chinensis and Thermopsis lanceolata in a meadow grassland. The results showed that the type of N compounds had no significant effect on leaf functional traits regardless of duration of N application. N addition significantly increased the leaf total N content (LN) and specific leaf area (SLA), and decreased the leaf total P content (LP) and leaf dry matter content (LDMC) of the two species. Compared with short-term N addition, long-term N addition increased LN, LP, SLA, and plant height, but decreased the LDMC. In addition, the traits of the two species were differentially responsive to N addition, LN and LP of T. lanceolata were consistently higher than those of L. chinensis. N addition would make L. chinensis and T. lanceolata tend to "quick investment-return" strategy. Our results provide more robust and comprehensive predictions of the effects of N deposition on leaf traits.
... Under harsh abiotic conditions such as water stress, low SLA and high leaf C content (i.e., thick leaves) may promote resistance to cell-wall collapse under tension, in turn contributing to the maintenance of leaf function under extreme water deficits (Niinemets, 2001). Furthermore, low SLA and high leaf C content indicate physical toughness and/or long-lived leaves (Wright & Cannon, 2001), which in turn act to minimize cumulative damage by stressors such as wind, falling debris, and low temperatures (Ackerly, 2004). We observed lower CWMs for SLA, and higher CWMs for leaf C content, in the harsh habitat in our study area, for both ITV and mean metrics ( Figure 4). ...
Article
We considered two possibilities related to the contribution of intraspecific trait variation (ITV) to changes in functional community structure along a stress gradient in tundra vegetation. First, ITV could contribute to the success of plant species across the stress gradient by promoting optimal trait values for each condition along the gradient; thus, ITV enhances convergence toward optimal traits. Second, ITV of only a few dominant species aligns with the optimal trait, and ITV of other species promotes trait diversification within communities. Salluit, Québec, Canada (62°12’ N, 75°39’ W) Vegetation was surveyed under three different conditions (harsh, intermediate, and competitive) representing an environmental stress gradient. We assessed ITV across the gradient for four plant functional traits: leaf carbon (C) and nitrogen (N) contents, specific leaf area (SLA), and plant height. We assessed community weighted means (CWMs) and functional dispersion (FDis) for each of the four traits. These indices were calculated from mean trait values from all individuals across all habitats (mean‐CWM and ‐FDis), and from each habitat (ITV‐CWM and ‐FDis). For the four traits, increasing trends (leaf N content, SLA, and plant height) and decreasing trends (leaf C content) of mean‐CWM along the stress gradient were maintained and pronounced for ITV‐CWM. Comparisons between ITV‐ and mean‐FDis suggested that, except for leaf C content, ITV tends to reduce and increase FDis values at the abiotically stressful and competitive ends of the environmental stress gradient, respectively. ITV along the abiotic stress‐competition gradient appears to promote community‐level changes towards optimal traits. In particular, ITV in three traits (with the exception of leaf C content) may contribute to equalization of optimal trait values, and to “passage through environmental filtering” in harsh habitats. However, when species deal with competition for richer resources, only some dominant species may show optimal trait values. Therefore, ITV may allow for trait diversification within communities under competitive rather than harsh abiotic conditions.
... This adds an important ecological dimension to leaf longevity, which is known as a key trait for multiple functions for plant strategies, such as increasing stress tolerance and conserving nutrient, carbon and nutrient cycling (Edwards et al., 2014;Yu & He, 2017). We did, however, not observe the often observed trade-off between leaf lifespan and growth rate for other tree species and forests (Wright & Cannon, 2001;Cavender-Bares, 2019), suggesting that some leaf lifespan driven trade-offs are context-dependent. Whether the observed legacy effects of leaf life span on drought resilience is something particular for conifers, or also occurs across broadleaf species or other forests, remains to be tested. ...
... Furthermore, as shade leaves within individual trees generally have a higher SLA than sun leaves (Markesteijn et al., 2007;Rozendaal et al., 2006), a positive relationship between SLA and shade tolerance could be expected. However, the increased efficiency of light capture with increased SLA comes at a cost, as such leaves are more susceptible to herbivory and physical damage and hence are short-lived (Coley, 1983;Wright and Cannon, 2001). In our approach, both such leaf trait correlations and the woody pipes connected with the leaves are considered, with construction and maintenance costs increasing with increasing pipe length. ...
Article
Tropical forests are the most diverse terrestrial ecosystems and home to numerous tree species competing for resources in space and time. Functional traits influence the ecophysiological performance of tree species, yet the relationship between traits and emergent long-term growth patterns is poorly understood. Here, we present a novel 3D forest stand model in which growth patterns of individual trees and forest stands are emergent properties of leaf traits. Individual trees are simulated as 3D functional-structural tree models (FSTMs), considering branches up to the second order and leaf dynamics at a resolution of one cubic meter. Each species is characterized by a set of leaf traits that corresponds to a specific position on the leaf economics spectrum and determines light-driven carbon assimilation, respiration and mortality rates. Applying principles of the pipe model theory, these leaf scale processes are coupled with within-tree carbon allocation, i.e., 3D tree growth emerges from low-level processes. By integrating these FSTMs into a dynamic forest stand model, we go beyond modern stand models to integrate structurally detailed internal physiological processes with interspecific competition and interactions with the environment in diverse tree communities. For model calibration and validation, we simultaneously compared a large number of emergent patterns at both the tree and forest levels in a pattern-oriented modelling framework. At the tree level, the specific leaf area and correlated leaf traits determined the maximum height and age of trees, as well as their size-dependent growth rate and shade tolerance. Trait variations along the leaf economics spectrum led to a continuous transition from fast-growing, short-lived and shade-intolerant to slow-growing, long-lived and shade-tolerant trees. These emerging patterns resemble well-known functional tree types, indicating a fundamental impact of leaf traits on long-term growth patterns. At the forest level, a large number of patterns taken from lowland Neotropical forests were reproduced, indicating that our forest model simulates structurally realistic forests over long time spans. Our ecophysiological approach improves the understanding of how leaf level processes scale up to the tree and the stand level, and facilitates the development of next-generation forest models for species-rich forests in which tree performance emerges directly from functional traits.
... Although oaks are equipped with several drought-resistance strategies, such as deeply penetrating root systems, relatively high predawn water potential (Fotelli et al., 2000;Me´sza´ros et al. 2007), and efficient water-use (Abrams, 1990), drought-induced oak mortality is occurring worldwide (Haavik et al., 2015). Water shortage intensifies oak decline, affecting tree functional responses (Ackerly et al., 2000;Atkins and Travis, 2010;Matesanz et al., 2010), such as changes in leaves and fruit (Wright and Cannon, 2001;Sperlich et al., 2015). Hosseini et al. (2018), for instance, reported that Persian oaks showing moderate to severe decline had smaller leaves, and lower leaf biomass. ...
Article
Biotic and abiotic stressors are known to modify the morphology of forest trees. Nevertheless, there is little information on the effects of tree decline on leaf and fruit morphology of oaks. To understand morphological adaptations of Persian oak (Quercus brantii Lindl.) to oak decline, we compared leaves and fruit from healthy and declining Persian oaks from six populations in the Zagros Forest of Iran. Fruits and leaves were sampled from five healthy and five declining trees from each population (30 declining and 30 healthy trees total). Fifteen leaves and fruits were sampled from each tree, for a total of 900 leaves and 900 fruit. We measured fruit length and diameter, scar diameter, cupule length, cupule span diameter, and fruit cover length as well as leaf length, petiole length, maximum lamina width, width of the lamina base, and width of the lamina apex. The leaf area was estimated from the product of length, maximum width, and a shape coefficient. Leaf trichomes were examined with SEM and classified as either mostly stellate or non-stellate. Healthy Persian oaks from five of the six populations had larger leaves, with greater lamina area, when compared with declining individuals. Moreover, the trend was the same across all six populations. Leaves of declining oaks also had distorted trichomes. Moreover, declining Persian oaks had smaller (shorter) fruit. The impact of oak-decline on Persian oak morphology, however, varied greatly among the six populations, limiting leaf and fruit size as indices of oak-decline. Leaves and fruit are smaller in declining Persian oaks, and trichomes are degraded. Nevertheless, care must be taken in using these traits as reliable proxies for tree decline, simply because the effect varies among populations.
... Evidence from other invasive plants is mixed: LMA was smaller in the perennial herb Ageratina adenophora in two different introduced areas compared to native populations (Feng et al. 2009), whereas in the perennial Bunias orientalis, plants from naturalised populations had higher LMA values than native ones (Tewes and Müller 2018). In general, LMA is positively correlated with cell-wall mass (Onoda et al. 2004) and with leaf toughness (Wright and Cannon 2001), which probably explains the positive association between resistance and LMA across all populations in our study. LMA was similarly negatively associated with herbivore load in another invasive plant, Bunias orientalis, suggesting that LMA may play an important role in resistance against herbivores in invasive plants more generally (Tewes and Müller 2018). ...
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Intraspecific variation in growth and defence among plant populations can be driven by differences in (a)biotic conditions, such as herbivory and resources. Introduction of species to novel environments affects simultaneously herbivory encountered by a plant and resource availability both directly and via altered competitive environment. Here, we address the question of how growth (leaf mass per area (LMA), plant size) and resistance traits (leaf alkaloids, leaf trichomes, resistance to a generalist snail) vary and covary between native and introduced populations of the garden lupine, Lupinus polyphyllus. We focused specifically on evolved differences among populations by measuring traits from plants grown from seed in a common environment. Plants from the introduced populations were more resistant against the generalist snail, Arianta arbustorum, and they had more leaf trichomes and higher LMA than plants from the native populations. The composition of alkaloids differed between native and introduced populations, with the native populations having more diversity in alkaloids among them. Resistance was positively associated with plant size and LMA across all populations. Other trait associations differed between native and introduced areas, implying that certain trade-offs may be fundamentally different between native and introduced populations. Our results suggest that, for the introduced populations, the loss of native herbivores and the alterations in resource availability have led to a lower diversity in leaf alkaloids among populations and may facilitate the evolution of novel trait optima without compensatory trade-offs. Such phytochemical similarity among introduced populations provides novel insights into mechanisms promoting successful plant invasions.
... Because the N and P dynamics are tightly coupled in ecosystem processes (Ågren et al. 2012), understanding the mechanisms through which plants maintain the N and P balance in their leaves in response to P addition is challenging (Li et al. 2016;Yue et al. 2019). For example, in nutrient-poor soil, plants maintain their growth mainly through nutrient reabsorption, while in nutrientrich soils, plants might take up new nutrients through their roots to maintain growth and development (Aerts and Chapin III 1999;Wright and Cannon 2001). P addition may allow plants to take up more P from soil, and thereby reduces their dependence on internal P recycling (Gao et al. 2018;Mao et al. 2015;Yan et al. 2015). ...
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Background Changes in foliar nitrogen (N) and phosphorus (P) stoichiometry play important roles in predicting the effects of global change on ecosystem structure and function. However, there is substantial debate on the effects of P addition on foliar N and P stoichiometry, particularly under different levels of N addition. Thus, we conducted a global meta-analysis to investigate how N addition alters the effects of P addition on foliar N and P stoichiometry across different rates and durations of P addition and plant growth types based on more than 1150 observations. Results We found that P addition without N addition increased foliar N concentrations, whereas P addition with N addition had no effect. The positive effects of P addition on foliar P concentrations were greater without N addition than with N addition. Additionally, the effects of P addition on foliar N, P and N:P ratios varied with the rate and duration of P addition. In particular, short-term or low-dose P addition with and without N addition increased foliar N concentration, and the positive effects of short-term or low-dose P addition on foliar P concentrations were greater without N addition than with N addition. The responses of foliar N and P stoichiometry of evergreen plants to P addition were greater without N addition than with N addition. Moreover, regardless of N addition, soil P availability was more effective than P resorption efficiency in predicting the changes in foliar N and P stoichiometry in response to P addition. Conclusions Our results highlight that increasing N deposition might alter the response of foliar N and P stoichiometry to P addition and demonstrate the important effect of the experimental environment on the results. These results advance our understanding of the response of plant nutrient use efficiency to P addition with increasing N deposition.
... Specific leaf area (SLA) is known to define resource allocation strategies for acquisition and storage, thus reflecting important trade-offs between construction cost and survival under varied conditions (Poorter et al., 2008Iida et al., 2014). Also, leaves with low SLA exhibit high thickness and toughness that suggests increased resource allocation into defense than into growth (Wright and Cannon, 2001). This leads to greater leaf life span (Sterck et al., 2006), thus affecting overall leaf economic spectrum. ...
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This study quantifies the effect of low- to moderate-intensity anthropogenic activities and natural activities affecting less than 40% of the canopy cover on major plant functional traits and associated soil microbial diversity in western Himalayan temperate forests. Plots of 0.1 ha were placed in the temperate forests along disturbance gradient and were categorized based on lopping intensity, deadwood counts, grazing, and litter removal. Plots were classified into three classes, i.e., low disturbance intensity (LDI) and moderate disturbance intensities (MDI1 and MDI2) based on lopping activities and canopy cover. The study was conducted on functional traits related to growth and survival strategies of a species in a complex forest ecosystem. Furthermore, DNA was extracted and metagenome of soil samples was performed using Illumina MiSeq platform from three disturbance classes to study the effect of disturbance and plant traits on microbial diversity. Tree basal area was found to be most significantly affected by disturbance intensity. Total density was found to be greater for the LDI site. Specific leaf area (SLA) and crown cover (CC) were the most affected traits in the moderately disturbed sites, whereas maximum plant height (HT) and seed mass (SM) were least affected by disturbance. Soil microbial diversity was found to be negatively associated with disturbance index. Microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were found to be significantly higher in LDI sites. Disturbance level elicited variation in microbial community composition. Proteobacteria was the most abundant phylum and Phenylobacterium, DA101, and Candidatus solibacter were mainly abundant at the genus level. A decreasing level of disturbance due to the absence of human residences in the LDI site led to the dominance of Phenylobacterium (27%) which reduced to 18% in MDI1 site. Shannon alpha bacterial diversity and plant species diversity (H′) were found to be greatest for MDI2 site. In forests with varying levels of management, treefall gaps due to low levels of logging intensity might have a similar effect to those of reduced lopping intensities and deadwood count (due to natural disturbances) in the study sites. The study concludes that moderate disturbance is important for promoting species diversity and species richness (SR), but species having conservative ecological strategies would be more prone to continued disturbance intensity. Therefore, low- to moderate-level disturbance in such forests can be used as a model for natural treefall gaps, and moderate-level disturbance intensity plays a powerful role in buffering ecosystem processes.
... Among the leaf traits that have been widely used in studies about ecological attributes and plant defense we find at least six distinctive examples: a) leaf area (LA) which represents the balance between carbon assimilation and water loss through transpiration; b) specific leaf area (SLA), a trait that reflects the leaf building cost -especially in carbon -and is directly related to plant function [18]; c) thickness and density, scleromorphic characteristics that have important relationships the leaf mechanical properties and are related to the leaf life span and plant-herbivore interactions [19][20][21]; d) nutrient composition, such as nitrogen and phosphorus; e) secondary compoundsessential to protect the leaf epidermis against high light irradiance and herbivore attack [22]. Thus, it is expected that the ecological strategies adopted by plant species under different circumstances can be inferred based on these leaf traits [23,24]. ...
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ABSTARCT Leaf traits are analyzed as essential drivers for the evolutionary and ecological role of plant defense mechanisms. Plants show leaf trait variation as a response to the diverse environmental conditions, like different successional stages. Those variations can impact leaf herbivory rates and drive changes in the allocation of plant resources. In this study, we aimed at comparing the expression of leaf defenses in established plants over different successional stages in a tropical dry forest to understand how these defenses modify the plant–herbivore interactions based on herbivory rates. We analyzed physical leaf traits (specific leaf area, thickness, and density), nutrient content (N, P, and K), total phenolic compounds, and leaf herbivory, of the native tree species Aspidosperma pyrifolium and Cenostigma pyramidale, in early- and late-successional stage areas. Results showed that the plant investment in defenses varies according to the successional stage and that both species have similar defense strategies, confirming the resource availability hypothesis. Individuals from the early stage adopt a strategy to lower sclerophylly, higher nutrient content and less phenolic compounds, while the late-stage individuals showed an opposite behaviour. For both species in this study, the average percentage of leaf herbivory observed was 40% higher in the early compared to the late-stage area. Our data indicate that plant defenses are tightly coupled to sclerophylly and investments in secondary metabolites, and the environmental conditions of different successional stage drive that plasticity in such leaf traits.
... This leads to the main finding of our work, namely that LSC is evidently associated with LES variation, suggesting that additional nutrients seldom included in functional analyses may also be embroiled in the LES (Sardans et al. 2008;Laliberté et al. 2012;de la Riva et al. 2018). Indeed, plant growth requires at least 17 mineral elements used in leaves to support fundamental physiological processes (Marschner 2012) and leaf nutrient contents are supposedly closely related to SLA across species (Wright and Cannon 2001;Wright et al. 2004), likely because most elements end up in the cytoplasm rather than cell walls, which are indeed thinner for 'acquisitive' species. Moreover, the LES is fundamentally a trade-off between investment in structural polymers and metabolic machinery, which performance is guaranteed by sulfur and other mineral nutrients that are essential components of proteins. ...
Article
Sulfur is an essential macronutrient for plant primary metabolism. Its availability can modulate plant growth in most terrestrial ecosystems. However, its relationship with other leaf and nutrient traits, and hence its contribution to plant functioning, remains unclear. We analysed leaf and nutrient traits for 740 vascular plant species growing in a wide range of environmental conditions in Northern Italy. We determined whether leaf sulfur content per unit leaf dry mass (LSC) is associated with leaf economics spectrum, and whether its distribution among functional types (growth forms, leaf life span categories, and Grime’s CSR (Competitive, Stress-tolerant, Ruderal strategies) could help to elucidate adaptive differences within plant taxa. High LSC values were mainly associated with fast growing species representative of R- and C- strategy selection, thus the acquisitive extreme of plant economics, reflecting strong potential connections with ecosystem properties such as biomass production or litter decomposability. In general, LSC was significantly and positively correlated with leaf nitrogen content, and nitrogen to sulfur ratio was constant throughout growth forms, leaf life span and CSR strategies, and phylogenetic effects were evident. Our findings highlight that LSC variation is strongly associated with the leaf economics spectrum, suggesting that additional nutrients seldom included in functional analyses may also be embroiled within the context of plant conomics. However, different ratios among nitrogen and sulfur may be expected across different plant families, suggesting that deeper insight from functional groups can provide a bridge between plant stoichiometry and ecology, useful for the evaluation of ecological responses to global change.
... This strategy of adaptation to high levels of disturbance and low levels of stress is typical for ruderal species (Grime, 1974). On the contrary, LDMC is negatively correlated with relative growth rate and positively correlated with leaf toughness and leaf lifespan (Wright and Cannon, 2001). Indeed, leaves with high LDMC tend to be relatively hard and are therefore assumed to be more resistant to physical hazards, like drought tolerance and herbivory resistance (Louault et al., 2005;Pakeman, 2014;Blumenthal et al., 2020). ...
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In recent years, rainfed vineyards in the Mediterranean basin are being replaced by irrigated vineyards in some areas, a phenomenon that is expected to increase due to climate change. At the same time, the use of plant cover in vineyards has emerged as an alternative to other weed management practices (e.g., herbicide, tillage). Knowing how weed communities respond to these practices is essential to develop new and more sustainable vineyard management systems. However, there is a lack of research on this issue. This work examines, from a trait-based approach, the effects of weed management (herbicide, mowing, tillage), and deficit drip irrigation (irrigated, non-irrigated) on the functional structure of plant communities in a Mediterranean vineyard. Plant sampling was conducted from 2015 to 2018 in a previously established experiment in 2008. The experimental design was randomised blocks with four replications, including four management systems. Data for ten plant traits were collected from several databases and research work. The community-weighted mean of trait values were calculated, and RLQ and fourth-corner analyses were performed to establish the relationship between species-traits and management practices. In addition, functional groups were extracted by means of a cluster analysis on the RLQ ordination space and the Grime’s life strategy (CSR strategy) was computed to explore possible similarities with the functional structure of the community. A total of 29 herbaceous species were selected for their highest occurrence for statistical analysis. Results indicated that tillage and mowing were the main factors conditioning the functional structure of plant communities in this study. In general, weed management significantly affected leaf economics and regenerative traits, while irrigation influenced traits related to plant size. Phenological traits emerged as a major factor in understanding the response of plant communities to weed management practices. Furthermore, up to five functional groups were identified and associated with different management practices. Functional structure of the plant communities studied was consistent with CSR strategy, which showed a strong association with agricultural management. Irrigation favoured species with a more competitive strategy. Conversely, mowing in spontaneous plant cover limited the occurrence of these competitive species. This study provides knowledge about the ecology and plant traits that could contribute to the development of more sustainable weed management.
... Previous studies have shown that tree species from infertile soils usually have low leaf nutrient concentrations and higher NuRE values; thus, they will adopt a "conservative consumption" nutrient use strategy to ensure their survival and reproduction (Kobe et al. 2005;Yan et al. 2006). In contrast, tree species from nutrient-rich locations usually adopting a "resource spending" nutrient use strategy to grow (Wright and Cannon 2001;Zeng et al. 2017). In our research, the lower concentrations of nutrients in soil and leaves coupled with the high NRE and PRE (Fig. 2,3,4) indicate that PY in the two areas adopted a "conservative consumption" nutrient use strategy, EM in both areas adopted a "resource spending" nutrient use strategy. ...
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Background and aims Leaf nutrients resorption is critical for considerations of how plants use and recycle nutrients in terrestrial ecosystems. However, information on nutrient resorption and adaptation strategies of the same plant species growing in areas with different geological backgrounds remain poorly understood. Methods We investigated one natural plantation of Pinus yunnanensis Franch. (PY) and one introduced plantation of Eucalyptus maideni F. Muell. (EM) growing under the same climatic conditions but different geological backgrounds (limestone, karst area vs clasolite, non-karst area) in Yunnan Province, China. The C, N, and P concentrations, nutrient restriction, nutrient resorption efficiency, stoichiometric homeostasis, and plant adaptation strategy indicators were investigated. Results The results showed that soil concentrations of C, N, and P were significantly higher in the karst areas compared to the non-karst areas both of the two plantations. Elemental composition of specific plant organs differed significantly between the two sites, while within sites, different organs showed different elemental compositions. In addition, leaf N: P ratios and leaf P resorption efficiencies indicated that plantations in subtropical China are mainly limited by P, which was more evident in the non-karst area. The PY plantation in both areas showed a “conservative consumption” nutrient use strategy, whereas the EM plantation in the two areas showed a “resource spending” nutrient use strategy. Conclusions Plants need to adapt physiologically and morphologically to the harsh conditions in karst areas, resulting in lower growth rates and biomass, more conservative nutrient use, and a high capacity to retain nutrients in the biomass. The findings of this study indicated that trees could synergistically accommodate leaf stoichiometry and nutrient resorption efficiencies in response to different soil types. Overall, our results provide support that the geological background should be considered during the process of vegetation restoration.
... We believe that nitrogen addition may reduce the dependence of plants on internal P cycle to a certain extent. There is a balance between nutrients acquired by plants through nutrient resorption and nutrients acquired from soil, and this balance depends on the relative energy consumption of these two processes; plants tend to use the process that consumes less energy (Wright and Cannon 2001;Mao et al. 2013;Wang et al. 2014). Because Larix gmelinii can obtain more phosphorus from the outside environment and obtain more nutrients from its roots than from its needles, Larix gmelinii may be more likely to absorb nutrients from the soil. ...
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Human activities accelerate global nitrogen (N) deposition, and elevated N availability may alter the stoichiometric balance of nutrients and then affect nutrient absorption by plants. The boreal forest is considered one of the world’s most N-limited ecosystems, and its response to N deposition is already a hot issue. In order to explore how long-term nitrogen addition influences nutrient uptake and distribution in Larix gmelinii in a boreal forest, four N treatment levels (0, 25, 50 and 75 kg N ha⁻¹ yr⁻¹) have been applied in a boreal forest since May 2011. Nitrogen addition significantly reduced the soil pH, significantly changed the soil N availability, increased the total N and N/P in needles and fine roots, and decreased the total P in needles and the C/N in soil. Nitrogen addition significantly reduced nitrogen resorption efficiency, and its impacts on P resorption efficiency were not significant. Nitrogen addition significantly increased the root length, surface area and diameter of 4th- and 5th-order transport fine roots. The N and N/P of needles showed seasonal variation. The needle N concentration and N/P were positively correlated with N addition, while the needle P was negatively correlated with nitrogen addition. With increase in nitrogen addition, Larix gmelinii increased its investment in its belowground parts, which may explain why Larix gmelinii tended to put more C in long-lived roots to improve its C utilization efficiency. Given the P deficiency caused by N addition, Larix gmelinii may be more likely to absorb P from the soil and adjust its C distribution to meet its P demand rather than relying on internal nutrient resorption.
... Cornelissen et al. [30];2 Mantovani [31];3 Lorenzo et al.[32];4 Wright and Cannon[33];5 Witkowski and Lamont[34]. ...
... fitness in species with long-living leaves can more strongly rely on constitutive environmental tolerance rather than on plasticity, while fitness in species with short-living leaves can primarily depend on capacity to respond fast to environmental modifications (Figure 7a,b). Indeed, there is evidence of overall greater investments in structural and biochemical defences in longer-living than in shorter-living leaves (Coley, 1983;Matsuki and Koike, 2006;Wright and Cannon, 2001;Wright and Westoby, 2002). In contrast, in the case of short-living leaves, they do encounter a certain environmental variability, but the magnitude of environmental variability becomes progressively less as their lifespan decreases, and a severe stress might or might not occur at all during their lifespan. ...
Chapter
Phenotypic plasticity is the potential of a genotype to form different phenotypes in contrasting environments. Phenotypic plasticity is always present among plant leaves due to modularity of design such that individual leaves can acclimate to their own environment. Plasticity differs among genotypes, populations, and species and as the result plants vary in their capacity to reach the optimum phenotype and maximise fitness under different environmental conditions. Owing to high energy and carbon costs of plasticity, being most plastic does not always guarantee the maximum fitness, and the benefit of a given plastic modification depends on the rate of environmental variability, extent of plasticity, potential reversibility, and leaf longevity. There are extensive variations in the degree of plasticity, rate of plastic changes, and reversibility of different leaf chemical, physiological, and structural leaf traits. In particular, leaf chemical and physiological traits change faster and more reversibly than structural traits. Leaf photosynthetic plasticity is often structural, determined during leaf development, and therefore, largely irreversible, especially the light-dependent plasticity. Plant adaptability to the environment is driven by plasticity and ecotypic adaptation to environmental conditions and species from different plant functional types largely vary in the share of different adaptability components along resource availability gradients. Globally, the plastic component is expected to be greater in species from high resource habitats with higher leaf metabolic activity and leaf turnover and less in species from low resource habitats with opposite suite of leaf traits. Plant functional types with persistent leaves and low leafmetabolic activity rely primarily on high constitutive tolerance to survive adverse environmental conditions, whereas plant functional types with short leaf lifespan and high leaf metabolic activity survive adverse conditions by plastic trait modifications or avoidance (ephemerals). Future work should focus on understanding the global variation in leaf plasticity as driven by plant metabolic activity and rate of regulation of transcriptome and epigenome level changes.
... Cornelissen et al. [30];2 Mantovani [31];3 Lorenzo et al.[32];4 Wright and Cannon[33];5 Witkowski and Lamont[34]. ...
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Vascular epiphytes contribute up to 35% of the plant diversity and foliar biomass of flowering plants. The family Bromeliaceae is a monophyletic group of plants native to the Neotropics. Epiphytic bromeliads form associations with distinct groups of organisms but their relationship with foliar fungal endophytes remain underexplored. In this study we examined the relationship of foliar fungal endophytes to host photosynthetic pathways and associated ecophysiological traits. We sampled the fungal endophyte communities of 67 host individuals in six epiphytic bromeliad species differing in C 3 and crassulacean acid metabolism (CAM) photosynthetic pathways. We tested whether endophyte assemblages were associated with ecophysiological leaf traits related to host photosynthetic pathways. Our results indicate that (1) C 3 and CAM bromeliads host dissimilar endophyte assemblages, (2) endophyte communities in C 3 bromeliads are characterized by variable relative abundances of fungal orders; conversely, CAM associated endophyte communities were characterized by consistent relative abundances of fungal orders, and (3) endophyte communities in bromeliads are distributed along a continuum of leaf toughness and leaf water content. Taken together, our study suggests that host physiology and associated ecophysiological traits of epiphytic bromeliads may represent biotic filters for communities of fungal endophytes in the tropics.
... Even in area-based measures of P. tremula × alba and A. thaliana, where adult leaves have higher A sat , this photosynthetic advantage is lost under light-limited conditions ( Fig. 7a-c). Further, variation in photosynthesis and SLA have been associated with tolerance to additional environmental factors, including drought and herbivory, and with changes in growth strategy, such as leaf life-span and growth rate (Poorter, 1999;Wright & Cannon, 2001;Reich et al., 2003;Poorter et al., 2009;Niinemets, 2010;Dayrell et al., 2018). Because these traits are phase dependent, it is likely that, during a plant's lifetime, VPC contributes to variation in biotic and abiotic stress tolerance through changes in leaf morphology and photosynthesis, in addition to previously identified mechanisms (Stief et al., 2014;Cui et al., 2014;Arshad et al., 2017;Ge et al., 2018;Leichty & Poethig, 2019;Visentin et al., 2020). ...
Article
Plant morphology and physiology change with growth and development. Some of these changes are due to change in plant size and some are the result of genetically programmed developmental transitions. In this study we investigate the role of the developmental transition, vegetative phase change (VPC), on morphological and photosynthetic changes. We used overexpression of miR156, the master regulator of VPC, to modulate the timing of VPC in Populus tremula x alba, Zea mays and Arabidopsis thaliana to determine its role in trait variation independent of changes in size and overall age. Here we find that juvenile and adult leaves in all three species photosynthesize at different rates and that these differences are due to phase‐dependent changes in specific leaf area (SLA) and leaf N but not photosynthetic biochemistry. Further, we found juvenile leaves with high SLA were associated with better photosynthetic performance at low light levels. This study establishes a role for VPC in leaf composition and photosynthetic performance across diverse species and environments. Variation in leaf traits due to VPC are likely to provide distinct benefits under specific environments and, as a result, selection on the timing of this transition could be a mechanism for environmental adaptation.
... Even though Yongyou 12 cannot reach a high photosynthetic rate, it does not imply that it cannot reach a high yield. Thick cell wall can improve the toughness of leaves, the tolerance to physical disturbance, can protect plants from herbivores and pathogens and finally leads to a long life span (Coley 1983;Reich et al. 1991;Wright and Cannon 2001;Onoda et al. 2008Onoda et al. , 2017Hikosaka et al. 2009). It was reported that photosynthesis in rice plants during the grain-filling period contributes 60-100 % of the final grain carbon content (Yoshida 1981). ...
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The intraspecific variations of leaf structure and anatomy in rice leaves and their impacts on gas diffusion are still unknown. Researches about the tradeoff between structural compositions and intracellular chemical components within rice leaves are still lacking. The objectives of the present study were to investigate the varietal differences in leaf structure and leaf chemical compositions, and the tradeoff between leaf structural tissues and intracellular chemical components in rice leaves. Leaf structure, leaf anatomy, leaf chemical composition concentrations and gas exchange parameters were measured on eight Oryza sativa L. genotypes to investigate the intraspecific variations in leaf structure and leaf anatomy and their impacts on gas exchange parameters, and to study the tradeoff between leaf structural compositions (cell wall compounds) and intracellular chemical components (non-structural carbohydrates, nitrogen, chlorophyll). Leaf thickness increased with leaf mass per area (LMA), while leaf density did not correlate with LMA. Mesophyll cell surface area exposed to intercellular airspace (IAS) per leaf area, the surface area of chloroplasts exposed to IAS and cell wall thickness increased with LMA. Cell wall compounds accounted for 71.5 % of leaf dry mass, while mass-based nitrogen and chlorophyll concentrations decreased with LMA. Mesophyll conductance was negatively correlated with LMA and cell wall thickness. High LMA rice genotypes invest more leaf mass to cell wall and possess a low mesophyll conductance.
... This was consistent with our results that the F1 hybrids had the lowest PNUE [67.98 ± 4.15 µmol(CO2) g(N) -1 s -1 ; Fig. 3]. Onoda et al. (2004) found that there was a negative correlation between the proportion of N allocation to cell walls and leaf PNUE, which has been used in the determination of the efficiency of N-use resulting in growth (Garnier et al. 1995, Poorter and Evans 1998, Wright and Cannon 2001. At the same time, leaves with large LMA usually tend to have strong physical strength and longer leaf lifespans (Wright et al. 2004, Onoda et al. 2011. ...
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Photosynthetic capacity plays an important role in plant vegetative growth, and is often regarded as a key determinant of adaptability in plant species, including the hybrids. Interspecific hybridizations are common and can easily occur in Buddleja. The F1 hybrid investigated in this study is a newly discovered interspecific hybrid between B. crispa and B. officinalis, and it was found in the Sino-Himalayan region. In this study, the morphological traits, the stoichiometric characteristics and the gas-exchange traits in F1 hybrids and their parents were measured under the cultivation conditions. Buddleja F1 hybrids showed the high leaf mass per area, which was similar to B. officinalis. Although F1 hybrids presented a low light-saturated net photosynthetic rate, they did not reduced carbon cost by increasing the specific leaf area or decreasing the leaf dry mass per unit area. Compared to the parental species, F1 hybrids had low leaf C:N and C:P ratios, C concentration, as well as photosynthetic nitrogen-use efficiency. However, they had a great respiration efficiency through a markedly reduced rate of respiration. Furthermore, F1 hybrids showed similar photochemical efficiency to B. officinalis, which was significantly higher than that in B. crispa. These findings suggest that the F1 hybrids in our study show a high similarity to their parental species in the leaf economic spectrum and photosynthetic capacity.
... Both abiotic and biotic factors are important in explaining macroecological patterns in flower colours. The importance of the abiotic environment might not be surprising given the wealth of knowledge about environmental correlations in global patterns of other plant traits (Cunningham et al., 1999;Wright & Cannon, 2001;Wright et al., 2005;Moles et al., 2009Moles et al., , 2014. However, the flower colour literature has focused disproportionately on the effects of the pollinating and flowering communities (see Notes S4). ...
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There is a wealth of research on the way interactions with pollinators shape flower traits. However, we have much more to learn about influences of the abiotic environment on flower colour. We combine quantitative flower colour data for 339 species from a broad spatial range covering tropical, temperate, arid, montane and coastal environments from 9.25º S to 43.75º S with 11 environmental variables to test hypotheses about how macro‐ecological patterns in flower colouration relate to biotic and abiotic conditions. Both biotic community and abiotic conditions are important in explaining variation of flower colour traits on a broad scale. The diversity of pollinating insects and the plant community have the highest predictive power for flower colouration, followed by mean annual precipitation and solar radiation. On average, flower colours are more chromatic where there are fewer pollinators, solar radiation is high, precipitation and net primary production is low, and growing seasons are short, providing support for the hypothesis that higher chromatic contrast of flower colours may be related to stressful conditions. To fully understand the ecology and evolution of flower colour, we should incorporate the broad selective context that plants experience into research, rather than focussing primarily on effects of plant‐pollinator interactions.
... The highest LMA observed in R. arboreum observed in our study may be attributed to its greater leaf thickness. Wright and Cannon (2001) studied the relationship between physical properties of leaves in 17 sclerophyllous woody species in eastern Australia and concluded that leaf thickness and toughness were strongly related to LMA. Several other workers have also correlated leaf thickness with LMA (Niinemets 1999(Niinemets , 2001Vile et al. 2005). ...
Article
Variation in soil nutrient availability can influence the functional traits and performance of tree species in a forested landscape. We tested this hypothesis by studying the variations in leaf-traits, and N- and P-resorption efficiencies of a few evergreen (Myrica esculenta, Rhododendron arboretum and Lithocarpus dealbatus) and deciduous (Quercus griffithii, Engelhardtia spicata and Lyonia ovalifolia) tree species growing in montane subtropical old-growth and regenerating forests of Meghalaya, northeast India, varying in their soil characteristics. Trees of the old-growth forest stand, having greater soil total N and P, proved to be much efficient in their foliar nutrient resorption (mean = 42.0% for N and mean = 82.1% for P) and showed higher leaf nutritional quality compared to the regenerating forest stand. Deciduous species had greater N-resorption efficiencies (45.3–49.7%) than the evergreen species (23.6–56.9%) in the old-growth stand. However, in the regenerating stand, the evergreen species were better at resorbing both N (30.6–55.9%) and P (67.9–76.4%) from their leaves than the deciduous species (23.2–40.9% for N and 33.2–52.0% for P). Overall, phosphorus was the limiting nutrient for growth in both the functional groups, with relatively low concentrations in the soils of the two forest stands. The evergreen and deciduous trees in the old-growth forest are found to tightly conserve nutrients with higher leaf N and P concentrations and higher N- and P- resorption efficiencies than the regenerating forest stand. The study clearly indicates that soil fertility has profound effect on the internal nutrient cycling of evergreen and deciduous tree species.
... Wide variation in nutrient resorption efficiency was reported among different species (Aerts 1996;Killingbeck 1996;Aerts and Chapin 2000). Several factors have been attributed to this variation which include phloem transport rate (Chapin and Kedrowski 1983;Chapin and Moilanen 1991), leaf structural defenses (Wright and Cannon 2001), leaf expansion rate , sink strength (Nambiar and Fife 1991), and soil nutrient and moisture availability (Nambiar and Fife 1991;Enokiand and Kawaguchi 1999). The average percentage of nutrients that are resorbed back into the main plant tissues accounted for 62.1% for nitrogen and 64.9% for phosphorus on a global scale (Vergutz et al. 2012). ...
Article
Nutrient resorption (NR) from senescing leaves plays an important role in the conservation of nutrients in plants. The nutrient resorption efficiency depends on several factors including availability of soil nutrients, species type and leaf nutrient quality. Although several researchers have worked on the pattern of NR in deciduous and evergreen plants, it varied widely. Since the variations are species-specific and many functional groups prevailing in tropical and subtropical forests have not been studied, the understanding of NR pattern in varied functional groups remained incomplete. In this study, Nitrogen resorption efficiency (NRE) of four tree species belonging to different functional groups viz., Alnus nepalensis (non-leguminous nitrogen-fixing and deciduous), Lithocarpus dealbatus (broadleaved and evergreen), Pinus kesiya (coniferous and evergreen) and Schima wallichii (broadleaved semi-evergreen) were studied. NRE was greatest in Alnus nepalensis and Schima wallichii immediately before the maximum leaf fall and it decreased in the subsequent months. However, NRE in Lithocarpus dealbatus exhibited identical values across all the months in a year. In Pinus kesiya, the NRE was the lowest and it varied through six months. The nitrogen concentration in the leaves and NRE varied significantly among the species and across the months. The trees belonging to certain functional groups did not differ in their NREs in different months of a year due to the availability of alternate strategies to acquire nitrogen or being semi-/ evergreen in nature to cope up with their nutrient loss.
... A large survey involving the collection of leaves of many populations and species from across China, to assess variation in plant traits between terrestrial and wetland habitats (currently unpublished), provided samples with the appropriate species diversity and range of environmental conditions to test the hypothesis in this study. Leaf mass per area (LMA) broadly reflects carbon-based investments in foliar defense (Poorter, Niinemets, Poorter, Wright, & Villar, 2009;Wright & Cannon, 2001), bigger leaves are expected to be more vulnerable to wind stress for biomechanical reasons (Niklas, 1996), and the amount of plant availability of Si in the soil affects plant uptake (Garbuzov et al., 2011;Ma & Yamaji, 2006); hence, these three factors must be taken into account, because they might confound or mask any relationship between wind stress and Si accumulation. ...
Article
High foliar silicon (henceforth Si) concentration protects plant tissues against herbivory, but protection against several abiotic stressors has also been proposed, although the adaptive significance of these functions is still being debated. We aimed to explore the potential relationships between foliar Si content and chronic wind exposure across a large scale and multiple species and to analyse an overlooked alternative or complementary function of silicon in leaves: mechanical protection against wind. Mainland China. From July to September during 2012–2014. Two hundred and eighty‐two vascular plant species in predominantly herbaceous communities. We compiled a dataset for leaf silicon concentration ([Si]) across 27 sites and 153 herbaceous plots within the major climate zones of China. We hypothesized that evolutionary lineages that generally have high [Si] should show positive relationships between leaf [Si] and mean annual wind speed. Within major families with generally high [Si] (especially grasses, sedges and composites), leaf [Si] exhibits a consistently positive correlation with mean wind speed among species across China. For the seven widespread monocot species with high leaf [Si], including the globally distributed common reed (Phragmites australis), intraspecific variation in leaf [Si] exhibits the same consistent positive correlation with mean wind speed. Our findings suggest that high leaf [Si] is likely to have widespread adaptive value for wind exposure of leaves, at least in several very widespread families and species of herbaceous plants. Damage from wind is a danger for plants in many ecosystems, hence these findings are of global significance and indicate that further research into large‐scale variation of leaf Si and mechanical traits in relationship to wind exposure is likely to be illuminating.
... Leaf dry weight was determined with an analytic balance (precision of 0.01 mg) after 96 h of drying in an oven at 60°C. Leaf thickness was measured using a digital calliper (Mitutoyo® series 293, precision of 0.0001 mm), avoiding leaf veins (Wright and Cannon 2001;Rosado and de Mattos 2010). For succulents, only green tissue or photosynthetically active tissue was considered for measuring thickness (Vendramini et al. 2002). ...
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Background: Inselbergs are ancient rock outcrops with high biological diversity and endemism. They are common elements along the extension of the Atlantic Forest domain (AFd) and present large taxonomic (TD), functional (FD) and phylogenetic (PD) diversity. Aims: We investigated how the three dimensions of diversity changed across ecological and biogeographic scales by comparing TD, FD and PD of communities within and between two inselbergs. We expected converging FD and PD but distinct TD between outcrops, because of similar local environmental conditions in inselbergs and the long-term lineage isolation. Methods: We used the Rao index for calculating TD, PD and FD, and partitioned diversity into α (each inselberg), β (between inselbergs) and γ (whole sample) components. Phylogenetic signal was estimated to relate traits and phylogeny. To link environmental predictors to functional traits a redundancy analysis was run. Variation in TD, FD and PD was analyzed by general linear models with patch area and the two inselbergs as predictors. Results: The two inselbergs were taxonomically different (beta diversity), but showed convergence in their functional and phylogenetic diversity. The limited retention of phylogenetic signal suggests that different species may converge and respond similarly to environmental variables. Within inselbergs, larger patches displayed higher TD, FD and PD. Conclusions: Seeking conservation strategies for inselbergs is challenging since, despite their functional and phylogenetic similarity, endemic species make individual rock outcrops unique.
... Also, leaf life-span changes according to the cost of leaf construction, which in turn depends on nutritional and environmental conditions (Cordell et al., 2001). Finally, leaves with low SLA usually have long life-spans because structural strengthening makes them less susceptible to herbivory (Westoby et al., 2000;Wright and Cannon, 2001). The knowledge of these basic aspects of L. lucidum leaves, which have not been studied until now, and their relation to environmental conditions, will contribute to the comprehension of the mechanisms that facilitate the spread of this species in new areas. ...
... Two leaf blades adjacent to the main stem were removed from five -Si and five +Si plants (both insect-free) to determine the force of fracture of leaves (the force required to cut the lamina and midrib). Force of fracture was quantified using a purpose-built machine [18] using previously described procedures [16]. Remaining plant material was snap-frozen, freeze-dried, weighed and then milled prior to analysis for Si concentrations using X-ray fluorescence spectrometry as described by Johnson et al. [16]. ...
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Plants have evolved numerous herbivore defences that are resistance- or tolerance-based. Resistance involves physical and chemical traits that deter and/or harm herbivores whereas tolerance minimizes fitness costs of herbivory, often via compensatory growth. The Poaceae frequently accumulate large amounts of silicon (Si), which can be used for herbivore resistance, including biomechanical and (indirectly) biochemical defences. To date, it is unclear whether Si improves tolerance of herbivory. Here we report how Si enabled a cereal (Triticum aestivum) to tolerate damage inflicted by above- and belowground herbivores. Leaf herbivory increased Si concentrations in the leaves by greater than 50% relative to herbivore-free plants, indicating it was an inducible defensive response. In plants without Si supplementation, leaf herbivory reduced shoot biomass by 52% and root herbivory reduced root biomass by 68%. Si supplementation, however, facilitated compensatory growth such that shoot losses were more than compensated for (+14% greater than herbivore-free plants) and root losses were minimized to -16%. Si supplementation did not improve plant resistance since Si did not enhance biomechanical resistance (i.e. force of fracture) or reduce leaf consumption and herbivore relative growth rates. We propose that Si-based defence operates in wheat via tolerance either in addition or as an alternative to resistance-based defence.
... Leaf mass per area of giant dogwood increased more steeply with tree size than did the LMA of black locust (Figure 2a). This suggests that giant dogwood changes its leaf traits at a relatively stronger rate to extend leaf life span and increase stress tolerance at the mature stage (Wright and Cannon 2001, Wright et al. 2004, Onoda et al. 2017. However, the differences in leaf C of the two species remained unchanged as the trees grew ( Figure 2b). ...
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Tree species vary in how they invest resources to different functions throughout their life histories, and investigating the detailed patterns of ontogenetic changes in key functional traits will aid in predicting forest dynamics and ecosystem processes. In this context, we investigated size-dependent changes in key leaf functional traits and nitrogen (N) allocation trade-offs in black locust (Robinia pseudoacacia L., an N-fixing pioneer species) and giant dogwood (Cornus controversa Hemsl., a mid-successional species), which have different life-history strategies, especially in their light use. We found that the leaf mass per area and leaf carbon concentrations increased linearly with tree size (diameter at breast height, DBH), whereas leaf N concentrations decreased nonlinearly, with U- and hump-shaped patterns in black locust and giant dogwood, respectively. We also discovered large differences in N allocation between the two species. The fraction of leaf N invested in cell walls was much higher in black locust than in giant dogwood, while the opposite was true for the light harvesting N fraction. Furthermore, these fractions were related to DBH to varying degrees: the cell wall N fraction increased with DBH for both species, whereas the light harvesting N fraction of giant dogwood decreased nonlinearly and that of black locust remained constant. Instead, black locust reduced the fraction of leaf N invested in other N pools, resulting in a smaller fraction compared to that of giant dogwood. On the other hand, both species had similar fraction of leaf N invested in ribulose-1,5-bisphosphate carboxylase/oxygenase across tree size. This study indicated that both species increased leaf mechanical toughness through characteristic changes in N allocation trade-offs over the lifetimes of the trees.
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O presente trabalho propôs um agrupamento ecológico de espécies arbóreas da Floresta Ombrófila Mista (FOM) do Paraná a partir de uma abordagem funcional. Para tanto, foram calculadas métricas de diversidade funcional de três comunidades de FOM (Floresta Nacional de Irati – FNI, General Carneiro – GNC e São João do Triunfo – SJT) obtidas a partir dos valores de nove atributos funcionais das espécies presentes em cada comunidade, sendo estes: Área Foliar Específica (AFE), Massa da Semente (MS), Altura Máxima Potencial (AP), Densidade da Madeira (DM), Incremento Periódico Anual (IPA), Taxa de Mortalidade (M%), Síndrome de Dispersão (SD), Sistema Reprodutivo (SR) e Regime de Renovação Foliar (RF). Nestas comunidades foram selecionadas 78 espécies, utilizadas como uma amostra geral da FOM Paranaense, as quais foram agrupadas método de Cluster Hierárquico a partir do uso dos valores de seus atributos. Cada grupo gerado foi comparado estatisticamente com o uso Modelo Lineares Generalizados (GLM) e testes post hoc, interpretados também com o uso de Árvores de Decisão (AD) e Análise de Correlação Canônica (ACC). A comunidade SJT apresentou a maior diversidade funcional, justificada pela heterogeneidade ambiental de seus fragmentos, enquanto FNI presentou a menor diversidade e riqueza funcional, porém, com baixa divergência nos papéis funcionais de suas espécies, indicando uma condição ambiental mais estável. GNC, por sua vez, foi a comunidade com maior riqueza e divergência funcional, denotando que as espécies dominantes do local possuem papéis funcionais distintos. O agrupamento gerado a partir das 78 espécies revelou nove grupos de estratégias ecológicas, sendo estes: Pioneiras longevas, Secundárias Dispersas pelo Vento, Pioneiras de vida curta; Pioneiras; Secundárias facultativas; Tardias pequenas; Tardias, Secundárias oportunistas de clareiras e Secundárias Tardias. As características dos agrupamentos corroboram em grande parte com as teorias de estratégias ecológicas de alocação e compensação de recursos, formando grupos ecologicamente coerentes e que podem ser extrapolados para a FOM do Paraná. This survey proposes an ecological grouping of woody species from the Araucaria Mixed Forest (AMF) of Paraná state from a functional approach. For this purpose, functional diversity metrics were calculated for three AMF communities (Floresta Nacional de Irati – FNI, General Carneiro – GNC and São João do Triunfo – SJT) obtained from the values of nine functional traits of the species present in each community, these are: Specific Leaf Area (SLA), Seed Mass (MS), Maximum Potential Height (Hmax), Wood Density (WD), Periodic Annual Increment (PAI), Annual Mortality Rate (M%), Dispersal mode (DM), Reproductive System (RS) and Leaf Renewal (LR). Seventy-eight species were selected from these communities and used as a general sample for the Paraná state AMF, which were grouped using the Hierarchical Cluster method using their trait values. Each group was statistically compared using Generalized Linear Models (GLM) and post hoc tests, interpreted also using Decision Trees (DT) and Canonical Correlation Analysis (CCA). The SJT community had the highest functional diversity, justified by the environmental heterogeneity of its fragments, while FNI had the lowest diversity and functional richness, however, with low divergence in the functional roles of its species, indicating a more stable environmental condition. In other hand, GNC was the community with the greatest richness and functional divergence, denoting that the dominant species in this community plays distinct functional roles. The cluster generated from the 78 species revealed nine groups of ecological strategies, namely: Long-lived pioneers, Wind-dispersed Secondaries, Short-lived pioneers; Pioneers; Facultative secondaries; Small-size late trees; Late trees, Secondary Gap Opportunists and Late Secondary. The characteristics of the clusters largely corroborate the theories of ecological resource allocation and compensation strategies, forming ecologically coherent groups that can be extrapolated to the Paraná state AMF.
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Leaf nutrient resorption is one of the important mechanisms for nutrient conservation in plants. Element stoichiometry is crucial to characterizing nutrient limitations and terrestrial ecosystem function. Here, we use nitrogen (N) and phosphorus (P) resorption efficiencies (NRE and PRE) and their stoichiometry to evaluate the response patterns of leaf nutrient resorption efficiency (NuRE) to plant functional groups, species traits, climate, and soil nutrients on the global scale. In light of the findings from the global data set of published literature on N and P resorption by woody plants, we revisit the commonly held views that: The strong N fixation ability of N-fixers weakened the NRE, which was consistent with the general views. The NuRE was linearly negatively correlated with plant growth rate. The higher NuRE of evergreen species than deciduous plants revealed how leaf life span constrains nutrient conservation. From the perspective of NRE, PRE and their ratios, woody plants were limited by P in the tropical zone and the limiting nutrient gradually transformed into N in the temperate zone (23.43-66.57°). The NuRE of woody plants in the frigid zone was the largest than that of others implied that low temperature may limit the nutrient absorption by plant roots, thereby enhancing the retranslocation of nutrients by senesced leaves. Furthermore, Akaike weights analysis found that mean annual precipitation (MAP) and temperature (MAT), N-fixers, soil nutrients, and leaf life span have significant effects on nutrient resorption patterns, sequentially. Overall, these results showed that the plasticity of plant nutrient resorption patterns was strongly sensitive to plant functional groups and soil nutrients, but the regularity of NuRE on a global scale was controlled by temperature and precipitation. And the resorption stoichiometry pattern better interprets plant nutrient limitation and the synergy effect of N and P in plant and soil on multiple scales.
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The microlepidoptera, Bedellia somnulentella (Zeller), is an important pest of sweetpotato, Ipomoea batatas (L.) Lam. Damage by B. somnulentella occurs in the larval stage and when consuming the foliar mesophyll of I. batatas make the leaves brown, wrinkled, and reducing the photosynthetic area and the yield. The detection and management of this pest depends on knowing its biological cycle and identifying its natural enemies. The objectives of this study were to determine the life history of B. somnulentella feeding on I. batatas leaves and to survey parasitoids of this pest in the field. The duration and viability of B. somnulentella egg, larva, prepupa, pupa, and adult stages were evaluated under laboratory conditions. Cephalic capsule width was measured to determine the number of B. somnulentella instars, based on the Dyar rule and analyzed by the Akaike statistical model (AIC). The developmental period of B. somnulentella was 32.5 ± 0. 21 d with a viability of 75, 84, 100, and 84% for the egg, larva, prepupa, and pupa stages, respectively. The identification of this pest on the plants is possible from the third instar and in the pupal and adult stages. The parasitoid Conura sp. (Hymenoptera: Chalcididae) was identified parasitizing pupae of B. somnulentella and could be considered a potential natural enemy for the integrated management of this pest.
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Mangrove tree species show plasticity in their leaf morphological traits in different salinity zones. However, leaf morphological plasticity and its causes in different salinity zones are incompletely understood. To understand the mechanism of plasticity, this study investigated the responses of three dominant tree species Sundri (Heritiera fomes), Gewa (Excoecaria agallocha) and Goran (Ceriops decandra) of the Sundarbans to the salinity gradients. A total of 17 leaf parameters were measured and quantified. All collected data were analyzed using univariate and multivariate statistical tools to investigate leaf morphological plasticity. A wide range of phenotypic plasticity was observed in all leaf parameters studied among the salinity zones of the Sundarbans. One-way ANOVA and Tukey’s posthoc test revealed significant differences (P < 0.05) in all leaf parameters among the salinity zones and confirming that there was a high degree of phenotypic plasticity among the salinity zones of the Sundarbans. Petiole length (PL), leaf area (LA) and leaf length/petiole length (LL/PL) showed high level of plasticity among the salinity zones of the Sundarbans for each species of Sundri, Gewa and Goran. Plasticity index (PI) was developed in this study for each species studied. High level of phenotypic plasticity in these leaf traits reflects fitness of these species to different saline environments. Our results provide clear evidence that all the leaf parameters measured for three tree species viz., Sundri, Gewa and Goran effectively utilizes a plastic strategy in different salinity zones in the Sundarbans. Morphological trait plasticity could serve as powerful biological indicators to predict the shift of leaf morphology in upcoming environmental change events like sea level rise and reduction of fresh water flow from upstream.
Chapter
The geographic distribution of deciduous versus evergreen woody species has been intensively investigated, but the ecological significance of both leaf habits is still far from being fully understood. The purpose of this chapter is to review the factors that are related with the carbon gain of deciduous and evergreenoak species under Mediterranean environmental conditions. We will focus on the morphological, anatomical and chemical adaptations of evergreens necessary to guarantee leaf survival during the unfavorable part of the year. We will review the information available about the construction and maintenance costs associated with the leaf traits of deciduous and evergreenoak species. Moreover, we will compare these traits with those of non-Mediterranean oaks and species belonging to other families. One central leaf trait is the leaf mass per area (LMA), which depends on the leaf anatomy and chemical composition. Differences in LMA are related to photosynthesis and the costs of construction and maintenance. We will assess the differences in these traits between deciduous and evergreen oaks, the aim being to understand the coexistence of both leaf habits in certain environments.
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This article presents a broad view of the interactions between plants and arthropods in the Caatinga ecosystem, highlighting the role of climatic seasonality in the availability and quality of plant resources, as well as the effects of these factors in the production of plant chemical defenses, mutualistic interactions, and antagonistic interactions as herbivory. The indirect effects of one trophic level on another in the Caatinga ecosystem are also reported.The Caatinga and other dry forests share several characteristics, such as the prevalence of the biotic pollination system and the abiotic dispersion of seeds. The high frequency of plants with extrafloral Nectaries allows a wide range of interactions between plants and arthropods, but especially with ants. However, all these interactions present their costs and benefits in a variable way, with the main justification for the seasonality of abiotic factors. The Caatinga has been undergoing fragmentation due to anthropic actions and climate change is already showing criticism about various aspects of the ecology of this ecosystem. Thus, the breakdown or changes in the interactions cause multiple effects at several different biological levels that will have repercussions from the population level to the level of ecosystems, being essential the understanding of the ecological interactions in terms of forest dynamics so that only this way occurs properly. planning for restoration and best conservation practices in the Caatinga.
Thesis
Les objectifs de ce travail de thèse étaient : (i) identifier les principaux compromis et covariations d’un ensemble de traits foliaires relatifs à l’acquisition du carbone et (ii) caractériser la variabilité de ces traits en réponse à l’éclairement (plasticité phénotypique) et la diversité interspécifique de cette plasticité chez des espèces de forêt tropicale humide. Les mesures ont été réalisées sur des semis de 13 espèces d’arbres élevés en conditions contrôlées dans 3 traitements d’éclairements relatifs distincts. Une analyse coût-bénéfice des traits du bilan de carbone foliaire a été centrée sur les coûts de construction du métamère (CCmetm), le temps de retour sur investissement (PBT) et la mesure des durées de vie des feuilles (LLS). Une forte diversité interspécifique a été observée pour l’ensemble des traits étudiés. Les espèces se répartissent le long d’un axe opposant durée de vie des feuilles et LMA (masse surfacique) d’un côté, aux capacités photosynthétiques (Asat), PNUE (Asat/N), respiration (Rd) et teneurs en azote (Nm) de l’autre. Ces résultats sont en adéquation avec le schéma universel d’acquisition des ressources proposé par Wright et al. (2004). Les relations entre LLS et PBT sont faibles et l’ensemble des espèces amortissent très largement leur CCmetm. De manière générale, le classement des espèces est maintenu d’un traitement à l’autre et, à l’exception des coûts de construction, seuls de faibles effets d’interaction ont été observés entre espèces et traitements. Le calcul d’un indice de plasticité a également permis de montrer qu’en dépit d’une certaine diversité interspécifique de la plasticité phénotypique, aucune espèce n’était globalement plus « plastique » que les autres sur l’ensemble des traits considérés. Enfin, si les espèces pionnières se distinguent nettement par leurs attributs, leur degré de plasticité n’est pas différent de celui des espèces de sous-bois.
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Schinus terebinthifolia is a dioecious tree native to South America that has become an invasive weed in Florida, southern California, southern Arizona, Texas and Hawaii and has been naturalised in over 20 countries. Biological control is considered a viable long‐term control option for S. terebinthifolia because release from natural enemies appears to be at least partly responsible for its success in Florida. We examined leaf phenology of S. terebinthifolia over a period of 15 months at five sites in central and southern Florida to provide information that may help in predicting the impacts of potential biocontrol agents for this weed. We documented leaf lifespan, the seasonality of leaf development and abscission and the survivorship of leaves that emerged during either spring, summer or autumn. Average leaf lifespan was >4.5 months at all sites, and leaf phenology followed the seasons closely. Although S. terebinthifolia possesses leaves throughout the year, leaf production was greatest from April to September, and most leaves were abscised in February and March. Spring‐ and summer‐emerging leaves were also longer‐lived than leaves produced during autumn. These results suggest that leaves of S. terebinthifolia would be most vulnerable to herbivory during the spring and summer months when newly growing leaf tissue is most plentiful. Biocontrol agents capable of damaging these tissues during spring/summer might be an effective means of controlling this invasive weed.
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El cambio climático modificará el régimen hidrológico global a causa de alteraciones en la magnitud de la precipitación y temperatura, y su interacción con las condiciones físicas y de vegetación de cada lugar; esto representa un gran riesgo para la conservación de las especies, ya que implica variaciones en las condiciones que les son cruciales para su desarrollo. En respuesta a los factores abióticos y bióticos del hábitat, las plantas muestran gran variabilidad intraespecífica de rasgos, esta habilidad les permite sobrevivir, crecer y reproducirse en diversos escenarios. Estudiar la variabilidad intraespecífica de caracteres morfológicos conlleva a entender el potencial de respuesta de las especies a factores de alteración, como el cambio climático. El objetivo del presente estudio fue evaluar la variabilidad intraespecífica del área foliar (mm2), el área foliar específica (mm-2 mg), contenido de materia seca foliar (mg-1 g), densidad de madera (g cm-3) y grosor de corteza (cm) de 90 individuos de Cedrela odorata en tres bosques naturales con distintos regímenes de precipitación anual. A partir de la hipótesis de que C. odorata podría modular la magnitud de expresión de los caracteres morfológicos antes mencionados, de acuerdo con las diferentes condiciones de precipitación. Los resultados demostraron que los valores de los atributos funcionales variaron significativamente entre las poblaciones estudiadas; además, se evidenció que el taxón expresó sus rasgos en un eje de especialización adquisitivo-conservativo en el uso de los recursos. La variabilidad intraespecífica de rasgos en C. odorata podría ser un mecanismo de resiliencia ante el cambio climático.
Chapter
Die Gebiete mit mediterranem Klima nehmen nur einen sehr kleinen Anteil der Landoberfläche der Erde von etwa 2 % ein. Dennoch ist das mediterrane Biom hier von großem Interesse, da es zum einen sehr artenreich ist und zum anderen starken Erwärmungstrends ausgesetzt ist.
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Plants contain a vast array of compounds referred to as secondary metabolites that play no role in primary catabolic or biosynthetic pathways. Many of these metabolites influence important ecological interactions (e.g., deterring herbivores, protection against pathogens, allelopathy, symbiotic associations, seed germination of parasites, or interactions with pollinators). Others provide protection against ultraviolet radiation or high temperatures. We have already discussed some of these roles. In this chapter, we discuss the role of secondary compounds in allelopathic and plant-herbivore interactions. As an example of the metabolic versatility of plants, their responses to xenobiotics will be discussed in the context of phytoremediation. Plant-pathogen interactions are discussed in Chap. 10.1007/978-3-030-29639-1_14.
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Recent cladistic analyses are revealing the phylogeny of flowering plants in increasing detail, and there is support for the monophyly of many major groups above the family level. With many elements of the major branching sequence of phylogeny established, a revised suprafamilial classification of flowering plants becomes both feasible and desirable. Here we present a classification of 462 flowering plant families in 40 putatively monophyletic orders and a small number of monophyletic, informal higher groups. The latter are the monocots, commelinoids, eudicots, core eudicots, rosids including eurosids I and II, and asterids including euasterids I and II. Under these informal groups there are also listed a number of families without assignment to order. At the end of the system is an additional list of families of uncertain position for which no firm data exist regarding placement anywhere within the system.
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Analyses of nitrogen and phosphorus in the senesced leaves of 89 species of deciduous and evergreen woody perennials were used (1) to discover the limits of ultimate potential resorption (maximal withdrawal of nutrients from senescing leaves), (2) to determine a means by which resorption can be categorized as complete or incomplete, (3) to develop the concept of resorption proficiency (measured as the levels to which nutrients have been reduced in senesced leaves), (4) to compare resorption in evergreen vs. deciduous species, (5) to assess the impact of phylogeny on resorption, (6) to compare resorption in actinorhizal vs. non-nitrogen-fixing species, and (7) to consider the efficacy of using multiple measures of resorption to answer questions regarding the function and evolution of this process, rather than relying solely on analyses of resorption efficiency (percentage reduction of nutrients between green and senesced leaves). Concentrations of 0.3% nitrogen and 0.01% phosphorus in senesced leaves represent ultimate potential resorption of these nutrients in woody perennials. Resorption proficiency and potential resorption were quantitatively defined in two models that describe both resorption that is maximal and biochemically complete, and that which is not. Resorption is highly proficient in plants that have reduced nitrogen and phosphorus in their senescing leaves to concentrations below 0.7% and 0.05%, respectively. An important feature of knowing the levels to which nutrients can be reduced in senescing leaves is that these values offer an objective gauge by which to measure the success of resorption as a nutrient conservation mechanism. Evergreens were significantly more proficient at resorbing phosphorus than were deciduous species (0.045% vs. 0.067% P in senesced leaves, respectively) and plants capable of symbiotic nitrogen fixation were significantly less proficient at resorbing nitrogen than were nonfixers (1.6% vs. 0.9% N in senesced leaves, respectively). Resorption proficiency appeared to parallel some phylogenic trends, yet the influence of phylogeny was not so significant as to overwhelm the effects of recent selection. The ability of plants to reduce nitrogen in senescing leaves was significantly correlated with their ability to reduce phosphorus. Measurement and analysis of resorption proficiency, when coupled with concurrent consideration of potential resorption and resorption efficiency, should facilitate and expedite the ongoing attempt to resolve complex questions regarding the environmental constraints that influence resorption, and the selection pressures that have directed the evolution of this process.
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Parsimony analyses were conducted for 46 genera representing all subfamilies and tribes within Proteaceae using two chloroplast sequences: the gene atpB and the noncoding spacer region between atpB and rbcL. The spacer region was more variable than atpB and provided insertion and deletion data as well as nucleotide substitutions. The atpB and spacer region data sets were highly congruent (as indicated by the partition homogeneity test) and were analysed separately and combined. Both unweighted and weighted character states (3 : 1 correction for transition bias) for the atpB data resulted in very similar strict consensus trees. In addition, the large subfamilies Proteoideae and Grevilleoideae were analysed separately, using appropriate outgroups determined by the analyses with complete sampling. The results from the combination of data were better resolved and supported than the results from each separate data set, although the Grevilleoideae were highly unresolved in all analyses. Most subfamilies in the Proteaceae were essentially monophyletic, but most tribes and subtribes were not. Bellendena is weakly supported as the sister group to all remaining members of the Proteaceae. Monotypic Eidotheoideae is well supported as a member of Proteoideae. Carnarvonioideae and Sphalmioideae are strongly supported as closely allied to the Grevilleoideae, but their positions in relation to this subfamily are unresolved. Other unusual alliances supported by our molecular data are: Isopogon–Adenanthos–Leucadendron–Protea, Petrophile–Aulax, Cardwellia–Euplassa–Gevuina, and Opisthiolepis–Buckinghamia–Grevillea. The tree resulting from the combined data showed limited congruence with morphological characters (flower pairs, stylar pollen presentation, and ovule number). Congruence with chromosome number was minimal, but our tree does support previous hypotheses of multiple aneuploidy and chromosome doubling events. The African and South American genera included in our analysis are dispersed among various clades with taxa from Australia and Asia, suggesting a former Gondwanian distribution for Proteaceae.
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Chapter
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Chapter
Damage to leaves by herbivores can have a significant and extensive impact on growth and reproduction of plants (Marquis, 1984, 1992a, b; Marquis & Braker, 1993), which in turn can influence competitive outcomes and community composition (Janzen, 1970; Dirzo, 1984; Clark & Clark, 1985; Dirzo & Miranda, 1991). In tropical forests, approximately 11% of the annual leaf area produced is consumed by herbivores and pathogens (Coley & Aide, 1991), a resource loss equivalent to investments in reproduction (Bazzaz et al., 1987). This loss would be substantially higher except for the fact that plants allocate considerable resources to physical, chemical, and phenological defenses. Most of our understanding of the costs and benefits of defenses and of the interplay between defenses and herbivores is based on research on mature leaves. However, young expanding leaves are the most vulnerable stage during the life of a leaf. In tropical shade-tolerant species of plants, expanding leaves suffer 5–100 times the rates of damage from pathogens and herbivores as mature leaves (Coley & Aide, 1991). Seventy percent of the lifetime damage can occur during this small window of vulnerability. Many leaf developmental traits may therefore be the result of selection by herbivores and pathogens.
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1. The toughness of the midrib, secondary veins and lamina of mature leaves of Castanopsis fissa corresponded to the consumption pattern of caterpillars. Midrib and secondary veins were the toughest tissues and were consumed significantly less than the lamina, which was least tough. 2. Tertiary and higher order veins embedded in the lamina contributed most to lamina toughness but were less tough than secondary veins. Lamina toughness could be predicted by the cell-wall volume fraction of component tissues and by neutral detergent fibre content, confirming that these made leaves tough. 3. Young leaves had higher total soluble phenolics content. Mature leaves had lower phenolics but higher toughness. They were eaten less than young leaves which supports the hypothesis that toughness is the major deterrent to these herbivores.
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The fracture toughness of sun-leaves of 42 tropical tree species growing in Singapore was measured along a ‘least tough’ path using an instrumented cutting technique. Punch-and-die (penetrometer) tests were also conducted. Intercostal material was analyzed for crude fibre and crude protein (total nitrogen concentration × 6.25) and the ratio of the two, the index of sclerophylly, calculated for each species. Leaf anatomy was examined and specific leaf area was calculated. Thirty-seven of the species were from three definable plant communities, namely mangroves, trema belukar (secondary forest on undegraded sites) and adinandra belukar (secondary forest on highly degraded soils).
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General patterns of herbivory and plant defence are summarized for a range of tree species studied in a lowland rain forest of Panama. Species growing in comparable micro-habitats differed by more than three orders of magnitude in the rates of herbivorous damage to mature leaves. Over 70% of this interspecific variation was statistically accounted for by differences in leaf characteristics. Species having tough, fibrous leaves with low nutritional value suffered little herbivory. Concentrations of immobile defences such as tannins and fibre were higher in species with long-lived leaves. Among species, there was also a significant negative correlation between growth rate and defence, and a positive correlation between growth and herbivory. These results suggest that differences in defence among species are due to interspecific differences in intrinsic growth rates and not to differences in apparency. Theories of plant defence based on interspecific differences in growth rate and apparency are combined in a single general model of plant defence. This model follows Grime's triangular classification of plant strategies and assumes that quality of habitat and rate of disturbance are both important determinants of plant defence. Predictions are made as to the types of defensive properties expected in stress-tolerant, competitive and ruderal species.
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Fracture toughness was estimated for a 'least tough' path in the leaves of woody species from three sclerophyllous plant communities. Most of the species from Mediterranean, tropical heath forest and lowland tropical rain forest habitats had very tough leaves, with toughness generally 600-1300 J m-2, which is two to four times higher than soft-leaved tropical pioneer trees. The toughest leaf (2032 J m-2), Parishia insignis, came from the canopy of the lowland rain forest. Leaves from the shaded understorey of the rain forest did not appear any less tough than those from the canopy.Copyright 1993, 1999 Academic Press
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Leaves are most vulnerable to herbivory during expansion. We hypothesised that one factor favouring small leaves could be that smaller-leaved species have shorter expansion times and are therefore exposed to high levels of herbivory for a shorter period than large leaves. In order to test this hypothesis, leaf expansion time and leaf area loss were measured for 51 species from Sydney, Australia. Strong positive correlations were found between leaf length and area and leaf expansion time, confirming that small leaves do expand in a shorter time than large leaves. The amount of leaf area lost was highly variable (from 0.5 to 90% of total leaf area), but was significantly related to both leaf expansion time and log leaf area. The amount of leaf area lost was not significantly correlated with specific leaf area nor with the presence of distasteful substances in the leaves, but was lower on species with hairy expanding leaves.
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Relationships with climate and local resources are developed for soils, vegetation and tree foliage as well as levels of herbivory for the dominant eucalypts at sites representing a regional gradient in climate and local contrasts in landscape position. Indicators of site productivity such as soil nitrogen and phosphorus, canopy height and cover, foliar nitrogen and water, and average leaf area tended to increase as climate became more favourable. Many were also higher in locally richer parts of the landscape. In contrast, specific leaf weight, an indication of sclerophylly, decreased as climate and local resources became more favourable. Rates of herbivory tended to increase with increasing site productivity and the associated changes in soil, vegetation and foliar properties, in broad agreement with models relating herbivory to resource availability and plant vigour. We found no evidence to support models relating high herbivory to low-resource environments and plant stress. The apparent level of herbivore damage on mature leaves was highest at intermediate levels of resources; this could reflect interactions between resource availability, rates of herbivory and rates of leaf replacement. Implications of these findings are discussed with respect to ways of measuring herbivory, regional patterns in rates and levels of herbivory, and the regional distribution of rural dieback associated with high herbivory.
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summaryPrevious experiments have shown that leaf specific mass (LSM: the ratio of leaf dry mass lo area) was lower and leaf water content (LWC) was higher in annuals than in perennials, differences that are more generally found between fast-and slow-growing species. Leaf transverse sections of seven annual-perennial pairs of grass species grown in the laboratory were analyzed to elucidate the anatomical bases of these differences.Leaf thickness was similar in annuals and perennials, but leaf density was significantly higher in perennials. The proportion of the leaf volume occupied by mesophyll was higher in annuals, at the expense of the three other tissues (i.e. epidermis, sclerenchyma and vascular tissues). The cross-sectional area of mesophyll cells was higher in annuals than in perennials, but epidermal cell size was similar for both life-forms.The ranges of LSM (23.1–49.5 g m −2) and LWC (0.70–0.86 g g−1) displayed by the 14 species were large enough to examine the general relationships between these two parameters and various anatomical characters. LSM was significantly correlated with leaf density, but not with leaf thickness. The anatomical character that best explained interspecific differences in LSM was the volume of cell walls per unit leaf area (approximated by the sum: sclerenchyma + vascular tissues (including its living component) + cell wall components of mesophyll and epidermis). LWC was found to depend on leaf density, and interspecific differences in this parameter were best explained by the proportion of mesophyll protoplast (i.e. proportion of mesophyll minus proportion of mesophyll occupied by cell walls) in the transverse sections.The physiological and ecological implications of these findings are discussed in terms of a trade-off between leaf productivity and persistence.
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There is a number of reasons for studying the mechanisms controlling the structural integrity (largely expressed as fracture properties) of plants. The first is in terms of the plant itself—the plant has to be able to withstand the mechanical effects of wind, water, and gravity and grow in such a way that its integral parts remain intact and do not split open unannounced. This may sound a trivial statement, but it is the experience of engineers that it is much easier to design something which breaks than something which does not especially when, as with plants, there is an upper limit (if only an implied one) to the amount of material available for construction. To survive, the plant must, therefore, have mechanisms for resisting fracture (the initiation and propagation of cracks). By contrast, the plant can encourage and direct fracture by laying down abcission and dehiscence layers, which are very brittle. The fracture properties of plants are also important for the animals that feed upon them. Mechanical properties constitute a significant factor in palatability, which, for man, extends to mechanical properties during and after various processes in preparing plants as food.
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Leaves from different plants vary in photosynthetic capacity and in the carbon expended on growth and maintenance. Photosynthetic capacity, nitrogen concentration, longevity, and susceptibility to herbivore attack are all interrelated. Quantification of these relationships would allow a cost-benefit analysis of plant-herbivore interactions.
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Several leaf characteristics, including toughness and total phenols and condensed tannins, were measured in Australian rain forest leaves of different ages and related to observed herbivory rates. In most cases, toughness and chemical toxicity increased as leaves aged, and corresponding insect grazing decreased. Herbivory losses ranged from 4.7% to 32.5% leaf area losses, and were more positively correlated with toughness than with phenolics. It is suggested that a suite of factors, including physical and chemical characteristics of leaves as well as spatial and temporal factors, interact to create variation in grazing intensities.
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SUMMARYA single treatment with simulated acid rain [pH 3.0 delivered as a 30 min spray to glasshouse-grown seedlings of cabbage (Brassica oleracea L.)] caused extensive damage to the adaxial surface of the cotyledons. The extent of this injury was compared between plants which had been grown under different environmental conditions. Seedlings which were germinated and grown out of doors during springtime at a time of low minimum temperatures (full range: 7 to 32 °C) were less injured by the acid spray than were those grown in the glasshouse under warmer conditions (18 to 36 °C). The influence of temperature alone was studied further in controlled environments. Plants grown at 10 °C showed less damage from acid sprays, in terms of visible injury and in the effect on the subsequent rate of growth, than did those grown at 20 °C. In addition to the influence of low temperature, an insufficient supply of either water or nutrients during growth also reduced the extent of visible damage to the cotyledons from simulated acid rain. Estimates of the contact angles between water droplets and cotyledon surfaces, and SEM studies of the epicuticular wax, indicated that temperature–induced changes in the sensitivity of the cotyledon to acidity were not related simply to the wettability and morphology of the surface wax. The results indicate that laboratory or indoor experiments with stimulated acid rain should be interpreted cautiously; in the natural environment the direct effect of acidity on higher plants may change seasonally and spatially according to the plants’growing conditions.