No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Assembly theory applied to weed communities
Abstract
Community assembly is a branch of ecology that looks at how communities are assembled as they follow trajectories through time. A trajectory is controlled by biotic and abiotic constraints (filters) that act at multiple scales. From a total species pool, environmental and dispersal constraints control which species enter an ecological species pool. Within this pool, internal dynamics determine which of these species becomes part of the extant community. Environmental filters act by removing species that lack specific traits. Thus, traits are filtered, and with them, species. In this paper, we present the basic ecological theory of community assembly and address how it can be used in conjunction with a trait-based approach to understand and possibly predict how weed community structure changes in response to imposed filters such as tillage or crop rotation. Weed ecologists have struggled with the need to place our practical knowledge of agriculture and weeds into a broader theory, and there have been many calls to integrate ecology with agronomy and weed science. Community assembly might be one way to do so.
... The results in CH and IT sites highlighted the strong effect of the management in structuring the weed community, fostering an increase in non-dominant species when the exclusive niche of dominant species was partially vacated. This result puts in evidence that changes in control operations can lead to a rapid shift in species dominance, potentially resulting in drawbacks (here an increase in hard-tocontrol species like C. dactylon and C. rotundus) if not properly managed (Booth and Swanton 2002;Fried, Kazakou, and Gaba 2012;Mahaut et al. 2020). ...
... The lack of differences in PRN among systems confirms the plasticity of the weed community in response to management changes, affecting species composition but not on this particular trait. The reduction of T. officinale and O. stricta in the INN system compared to the BAUs might have led to the increase of another perennial species T. repens in INN systems (Figure 1a), reflecting a resilient trajectory in the evolution of the weed community (Booth and Swanton 2002). The increased frequency of T. repens in INN communities also helps explain the higher NFA trait observed compared with BAUs (Table 5; Figure 2b). ...
... Finally, we also observed changes in service-related response traits (BFF and DFF; Baraibar et al. 2021;Bàrberi et al. 2018;Booth and Swanton 2002). Our results demonstrated the effect of management practices on the distribution of service-related traits within the community. ...
... Explored how factors such as environmental filtering, local dispersal, and regional dispersal contribute to weed diversity within different crop types and landscape (Booth & Swanton, 2002;Bourgeois et al., 2020) Herbicide resistance Evolution Predict the likelihood or rate of resistance development and devise management strategies to mitigate it by reducing selection pressure (Jasieniuk et al., 1996;Maxwell et al., 1990) Weed community responses to tillage systems Succession theory Explore the potential relationship between reduced disturbance conditions and ecological succession theory (Zanin et al., 1997) Invasive species Neutral theory Framework for understanding how species invade and establish themselves in new environments (Herben et al., 2004) Agricultural management's impacts Intermediate disturbance hypothesis ...
... Assembly theory this theory offers a framework to explain the organization of native communities, exploring the mechanisms governing which plant species can coexist in a given environment, drawn from a regional species pool, and how they interact (Booth & Swanton, 2002;Keddy, 1992) (Figure 1). The theory is grounded in the concept that communities are not random assortments of species but rather structured outcomes formed by diverse ecological processes. ...
... This theory can help better understand the environmental filters that favour certain weed species, thereby indicating their potential to become invasive and problematic in the future. In weed research literature, Booth and Swanton (2002) discussed the concept of weed community assembly, specifically how weed community structure changes in response to filters such as tillage or crop rotation. Hubbell's Unified Neutral Theory (UNT), on the other hand, takes a more stochastic approach (Hubbell, 2001). ...
Weed science plays a vital role in mitigating the negative impacts of weeds in agriculture and natural ecosystems. However, the field has received criticism for its limited theoretical foundation and excessive focus on phenomenological and narrow scope. Our contention is that weed science needs to integrate more ecological theories to foster a deeper understanding of weed ecology, biology, and management. By embracing theoretical frameworks, weed science can enhance its ability to predict and explain weed dynamics, identify underlying mechanisms, and develop sustainable management strategies. This insight emphasizes the advantages of integrating theoretical approaches and offers practical recommendations to integrate ecological theory effectively into weed science research.
... We intend to highlight some of the common limitations in current cropping systems research and develop an ecological framework for cropping systems research incorporating this theoretical framework. The basis for our proposed research framework will be built upon some initial work from others (Booth and Swanton, 2002;Gaba et al., 2014;Smith and Mortensen, 2017) but modified and extended to a more comprehensive analysis of cropping systems with some new dimensions. This current study is not intended to conduct an overall systemic review of past cropping systems research but to highlight some general limitations. ...
... Community assembly implies that biological communities are assembled over time, and the membership in the community is limited by filters or constraints (biotic and abiotic factors) acting on the species pools (Weiher and Keddy, 1999). Originally, this theory was proposed for natural ecosystems, but Booth and Swanton (2002) correctly identified that this theory could apply equally well to agroecosystems to better understand weed dynamics. Furthermore, they extended this framework to use a trait-based approach to understand how weeds respond to various ecological filters via functional traits. ...
... The proposed framework tries to integrate several ecological approaches for cropping systems research proposed by others (Booth and Swanton, 2002;Gaba et al., 2014;Smith and Mortensen, 2017), but is modified with new dimensions to address the limitations of these existing frameworks. ...
We developed a research framework for cropping systems research focused on understanding weed dynamics. • Inability to compare, generalize and predict weed dynamics are the main limitations in many cropping systems research. • The pillars include quantifying func-tionality of the systems, functional traits of weeds and temporal dynamics. • This framework allow to understand weed dynamics and develop sustainable weed management strategies. A B S T R A C T CONTEXT: Cropping systems experiments are considered vital in devising sustainable weed management strategies. Many cropping systems studies were carried out to integrate several crop production practices that were previously tested in conventional small plot experiments and have agronomic objectives rather than weed management. Most cropping systems research lacks a research framework that enables an understanding of weed dynamics and provides sustainable weed management solutions. OBJECTIVES: This study aims to identify the prevailing limitations in most cropping systems research towards weed management and synthesize a common framework to conduct cropping systems experiments within an ecological framework. The inability to understand the mechanisms of weed suppression due to the diversity of agronomic practices in cropping systems, the inability to produce generalized conclusions, the limitations of statistical procedures to understand temporal weed dynamics and the inability to predict future weed dynamics due to lack of focus on weed persistence can be some of the fundamental limitations in most cropping systems research in weed management. METHODS: To overcome these limitations, we synthesized an ecological framework to design and analyze cropping systems research using some of the existing ecological theories. RESULTS AND CONCLUSIONS: The four pillars of the framework are 1. quantification of ecological functionality of cropping systems, 2. understanding the effect of cropping systems on weed functional traits. 3. understanding the weed seed persistence, and finally, 4. determining weed temporal dynamics. Others already have identified 2 the first two pillars, but we suggest modifications and address the research gaps to apply them to broader cropping systems. In short, our framework includes defining cropping systems using resource gradients and disturbance gradients to quantify cropping systems diversity, use of plant and seed functional traits to understand and predict weed dynamics and statistical approaches to understanding the temporal dynamics to realize both stochastic and deterministic processes that determine weed dynamics. SIGNIFICANCE: This proposed ecological framework will facilitate better design and analysis of cropping systems research by improving our understanding of how different cropping system components collectively and individually influence weed dynamics and how to utilize knowledge from cropping systems research to design cropping systems for better weed management.
... For efficient weed control, not just the amount of weeds, but also the community itself is decisive [26,38]. Some recent comprehensive surveys on weed communities in maize cropping systems across Germany revealed that weed species most commonly associated with maize cropping-summer annuals such as Solanum nigrum L., Amaranthus spp.-are rather scarce, whereas other, more generalist species dominate the weed flora on many maize fields [39][40][41][42]. ...
... In temperate European conditions, under old/traditional organic management, the row crop maize is usually sown in early May, mostly with 75 cm row width into an autumn-ploughed soil (CT), often after a winter fallow. The crop has a high nitrogen (N) and temperature demand, a slow juvenile development, and therefore, a low competitive munities as a whole-e.g., [38,40,41]-rather than focusing on one or a couple of weed species-e.g., [31,32,46,47]-or purely on weed biomass, density, diversity indices or community-averaged weed traits to describe the community under different management conditions-e.g., [6,23,[43][44][45]. ...
... and Ca. bursa-pastoris-have relatively high temperature requirements for emergence, which could be reached through shallow soil disturbance (seedbed preparation or MWC) [17,[61][62][63], and their predominant emergence time coincides with related management steps in maize production [8,25,26,31,38,40]. This is supported by the fact that these species are rather well represented throughout the maize fields in Germany [41]. ...
There are often negative side-effects associated with the traditional (silage) maize cropping system related to the unprotected soil surface. Reducing soil disturbance could enhance system sustainability. Yet, increased weed pressure and decreased nitrogen availability, particularly in organic agriculture, may limit the implementation of alternative management methods. Therefore, a field experiment was conducted at two distinct locations to evaluate the weed control efficiency of 18 organically managed silage maize cropping systems. Examined parameters were relative weed groundcover (GCweed) and its correlation with maize dry matter yield (DMY), relative proportion of dominant weed species (DWS) and their groups by life form (DWSgroup). Treatment factors comprised first crop (FC—winter pea, hairy vetch, and their mixtures with rye, control (sole silage maize cropping system—SCS)), management—incorporating FC use and tillage (double cropping system no-till (DCS NT), double cropping system reduced till (DCS RT), double cropped, mulched system (DCMS Roll) and SCS control), fertilization, mechanical weed control and row width (75 cm and 50 cm). The variation among environments was high, but similar patterns occurred across locations: Generally low GCweed occurred (below 28%) and, therefore, typically no correlation to maize DMY was observed. The number of crops (system), system:management and occasionally management:FC (group) influenced GCweed and DWS(group). Row width had inconsistent and/or marginal effects. Results suggest differences related to the successful inclusion of DCS and DCMS into the rotation, and to the altered soil conditions, additional physical destruction by shallow tillage operations, especially in the early season, which possibly acts through soil thermal and chemical properties, as well as light conditions. DCS RT could successfully reduce GCweed below 5%, whereas DCS NT and particularly DCMS (Mix) suffered from inadequate FC management. Improvements in DCMS may comprise the use of earlier maturing legumes, especially hairy vetch varieties, further reduction/omission of the cereal companion in the mixture and/or more destructive termination of the FC.
... Functional structure metrics elaborate upon taxonomic diversity by describing changes in plant community trait attributes. A functional approach can elucidate the effects of agronomic practices on weed community composition (Booth & Swanton, 2002) and weed-crop competition (Bennett et al., 2016;Derrouch et al., 2021;Funk & Wolf, 2016;Pakeman et al., 2015). Analysis of functional metrics enables predictions of weed community responses to farm practices across diverse settings because the effect of agricultural practices on species traits is expected to be consistent across different species pools (Booth & Swanton, 2002). ...
... A functional approach can elucidate the effects of agronomic practices on weed community composition (Booth & Swanton, 2002) and weed-crop competition (Bennett et al., 2016;Derrouch et al., 2021;Funk & Wolf, 2016;Pakeman et al., 2015). Analysis of functional metrics enables predictions of weed community responses to farm practices across diverse settings because the effect of agricultural practices on species traits is expected to be consistent across different species pools (Booth & Swanton, 2002). The ability to predict weed community response to management practices can help farmers design systems that are less conducive to the proliferation of problematic weeds. ...
... Community assembly theory can describe how cropping systems affect the functional structure of a weed community. Under this framework, geographic location, environmental conditions, and the internal dynamics of a system are filters that determine a plant community by allowing species with specific trait attributes to survive while filtering out those that do not meet a set of trait requirements (Booth & Swanton, 2002;Diamond, 1975;Weiher & Keddy, 1999). Agronomic practices filter weed communities because they impact the internal dynamics of a plant system, changing resource availability, biotic interactions, and habitat stability (Smith & Mortensen, 2017). ...
The use of multiple ecological weed management tactics may be an effective solution to weed management challenges associated with reducing tillage. An experiment was conducted to assess how soybean Glycine max (L.) Merr. density and cereal rye Secale cereale L. mulch biomass affected weed suppression and community assembly in no‐till production. Soybean was planted at five rates from 0 to 74 seeds m−2, and five cereal rye mulch levels were established from 0 to 2 times the ambient cereal rye biomass within each site–year. We assessed the effects of soybean density and cereal rye mulch biomass on weed suppression, weed community composition, and the functional structure of weed life cycle, emergence timing, seed weight, height, and specific leaf area traits. Weed suppression was influenced by a synergistic interaction between soybean density and cereal rye biomass. The functional dispersion (FDis) of all weed traits, when combined, was reduced by increased soybean density and mulch biomass, suggesting that high treatment intensities induced trait convergence. However, soybean density and cereal rye biomass had differing effects on the FDis and composition of individual traits, suggesting that these management practices represent unique filters during weed community assembly. Mulch biomass had a larger effect on annual weed suppression and weed community composition than soybean density. Farmers who utilize high biomass cover crop mulch for weed management may experience shifts in weed community composition toward an increased proportion of perennials and weeds with later emergence, heavier seeds, and shorter stature. Increasing soybean density may reduce perennial weed biomass, making it a valuable complement to high cereal rye mulch biomass. As such, weed management in no‐till soybean is enhanced by combining multiple practices, which can enable synergistic weed suppression and the management of diverse weed functional groups.
... This result is in line with a previous study by Guglielmini and Satorre (2004), relating CYNDA dispersal and tillage. On the other hand, despite the highly disturbing effect of planting operations on the original weed community, it is worth to note how the new communities structure changed over time to reach traits distribution similar to the condition before planting, particularly for response traits associated to competition (SLA-SW-CH), highlighting a resilient trajectory of the weed community evolution over time (Booth and Swanton, 2002). This finding clearly highlights how the resilience of the weed community and associated functional diversity could be related to organic management. ...
... The three systems showed more evident differences starting from Year 4, indicating a progressive differentiation over time from a common original condition. These differences were clearer on diversity and the distribution of traits than in community composition as showed by Fig. 4, highlighting than traits rather than species were filtered, and that management was leading the removal on the long run of those species lacking specific traits (Booth and Swanton, 2002). In particular, the ICC systems showed a reduction of total weed cover and species richness (Fig. 4a, 4b, Table 3) due to the presence of the cover crops (whose cover ranging between 25.5% in Year 4 (dry winter/spring period, Fig. 1) and 54.7% in Year 3 (data not showed), occupying weeds ecological niches Scavo et al., 2020;Navarro-Miró et al., 2019;Wayman et al., 2015). ...
... Other service-related traits (i.e., time of first flowering, flowering span, and supporting pollinators) were not filtered by the compared management Armengot et al. (2015) who found a relationship between tillage intensity and weed flowering-related traits. Despite the lack of significant differences, the INC showed a general higher relationship with these traits than other systems (Fig. 3), partially confirming the Armengot et al. (2015) findings, and suggesting a more evident differentiation over-time when the community evolution trajectory will become clearer (Booth and Swanton, 2002). ...
Biodiversity conservation and promotion of agroecology (including organic farming) are focused as priorities by European Commission, as reported in the Biodiversity and Farm to Fork Strategies. In this context, agricultural practices can be considered for their contribution to harnessing ecosystem services to sustain agricultural production, while minimising negative environmental effects. Among these, redesigning agricultural systems through diversification practices can be very promising by exploiting the natural biodiversity in space and time, and connecting farms with natural environments. Being an interface between above and belowground, spontaneous plants (i.e., the weeds) are considered valuable agroecosystem components that, if properly managed, provide ecosystem functions and services, and holding key role for biodiversity conservation within agroecosystems. In this study, we explored the response of spontaneous flora communities in terms of abundance, diversity, and functional traits to different soil and agrobiodiversity management strategies (soil ripping vs reduced tillage at orchard planting, soil tillage vs minimum/no tillage in orchard floor management over 5 years) and cover crop introduction in a new planted organic apricot orchard. Our results showed the strong impact of the planting operation on pre-existing spontaneous flora community structure but a resilient trajectory in the following years in recovering the previous community traits distribution. Interannual variability was the main factor affecting communities. However, the reduced tillage condition showed a conservative trend of the incidence of perennials in the community, while the introduction of cover crops generally decreased species richness and abundance. Understanding the mechanisms by which soil management practices affect weed communities can guide the designing of sustainable agroecosystems, preserving their functionality and biodiversity over time.
... Production systems with more diverse weed communities (e.g., higher number of species) tend to have a lower risk of suffering yield reductions due to interference (Adeux, et al., 2019;Storkey and Neve, 2018) and could contribute to reduce the unnecessary reliance on herbicides. Weed communities in agroecosystems are continuously changing due to interspecific differences in reproductive and death rates resulting from innate characteristics of each species and environmental and agricultural forces (Booth and Swanton, 2002). ...
... This point of view prompts the exploration of how plant communities change over time and how disturbance impacts those changes (Smith, 2015). Herbicides are likely the most influential factor for weed community assembly because they have the potential of eradicating or dramatically reducing the populations of susceptible species (Booth and Swanton, 2002;Ryan et al., 2010). Conversely, a few species which are either naturally tolerant to those herbicide programs or evolve resistance before eradication, will become predominant and drive the dynamics of the community. ...
... The constant value of richness in scenario G (Fig. 1) can be the result of a relatively consistent sensitivity to glyphosate in the weed community maintaining all species above eradication levels (Booth and Swanton, 2002). This is not surprising because glyphosate had been frequently used in the experimental area. ...
Herbicide programs change weed population density as well as weed community composition. The repeated use of a given program can result in a weed community that progressively becomes more difficult to manage or could lose its ability to provide ecosystem services. Simulation of those changes using stochastic models considering population dynamics of multiple species makes it possible to identify a priori potential community changes that might result from the use of a given herbicide program. The objectives of this work were to model the population dynamics of weed species under different herbicide programs and how those dynamics change weed community diversity over time. Weed population dynamics were stochastically modeled along ten years using population growth rate (lambda) for each species under different herbicide programs. Lambda values were obtained from an eight-year long, field experiment, and these were used to parameterize the stochastic ranges for the model for each weed species. Population trajectories were modeled for each individual species over ten years and the results were used to estimate richness, diversity, and evenness for each herbicide use scenario. The repeated use of glyphosate alone had a minimal effect on richness, but it caused a strong reduction in weed diversity and evenness. Programs with more mechanisms of action and the use of both preemergence and postemergence herbicides were slightly more likely to suffer the loss of weed species than programs with single or just a few herbicides. Conversely, the former had a higher probability of maintaining weed diversity and evenness than the latter. According to simulations, losses in weed community diversity are reversible, especially when highly competitive species were eradicated allowing other species with lower lambda to increase their populations. However, the eradication of species with low reproductive rates reduced diversity and evenness. The effects of herbicide programs on the weed community lasted for several years even after those programs were modified indicating that seed banks play a major buffering role in the rate of change of weed community composition. Thus, frequent changes in management interrupting the repeated use of specific weed control programs, even under high herbicide intensity use (i.e., number of applications and mechanisms of action), can help maintain weed diversity in agroecosystems.
... Finding an effective combination of tactics to organically manage the seed bank requires knowledge of how individual management practices and their combination interact with weed communities. Focusing on control of a single target species can lead to the dominance of other problem species and replenishment of the seed bank (Booth & Swanton, 2002). An alternative approach is to frame management practices as a series of community assembly filters that act on functional traits rather than individual species (Booth & Swanton, 2002). ...
... Focusing on control of a single target species can lead to the dominance of other problem species and replenishment of the seed bank (Booth & Swanton, 2002). An alternative approach is to frame management practices as a series of community assembly filters that act on functional traits rather than individual species (Booth & Swanton, 2002). Species with the appropriate combination of traits (morphological, physiological, or phenological) survive the filters imposed by a given cropping system (Menalled et al., 2022;Violle et al., 2007) and can contribute more seeds to the seed bank. ...
Knowledge of how agricultural management interacts with weed seed banks and emergent weed communities is crucial for proactive weed management. Though studies have detailed how differences in disturbance and nutrient applications between organic and conventional herbicide‐based systems affect weed communities, few have focused on these same factors in contrasting organic systems. This study assessed the seed banks and emergent weed communities from the most recent crop rotation cycle (2017–2022) of a long‐term experiment, which compared four organic grain and forage cropping systems differing in nutrient inputs and soil disturbance. The high fertility (HF) system received high‐rate nutrient applications, low fertility (LF) received low‐rate applications, enhanced weed management (EWM) focused on weed control through frequent soil disturbance, and reduced tillage (RT) prioritized soil health with less intense or frequent soil disturbance. Soil samples for greenhouse germination assays were collected at the beginning (2017) and end (2022) of the rotation to explore how these four systems influenced seed bank dynamics over time. Weed community biomass was also sampled in each crop during this time. Treatment effects on weed abundance, taxonomic diversity, and community‐weighted means and functional dispersion of weed traits were analyzed with generalized mixed‐effect models. The RT system had the highest weed seed bank taxonomic diversity, and EWM had the lowest. RT and LF had higher functional dispersion of traits than HF in the seed bank. Weed seed bank communities in HF and RT were characterized by short, small‐seeded, and early germinating weed species. However, seed banks were also labile: Differences between systems in seed density and all other mean trait values were dependent on the crop, which preceded seed bank sampling. Likewise, differences among emergent weed communities in the four systems depended on an interaction between crop species and their planting year. Results suggest that resource availability and intensity of disturbance act as weed community assembly filters in organic cropping systems. Organic growers seeking to design systems that balance weed management and production goals can use relatively low soil disturbance and nutrient application to increase weed community taxonomic or functional diversity without necessarily increasing weed biomass or seed bank density.
... It is often said that "one year seeding, seven years weeding" (Stephens 1982;Kropff et al. 1999). Conventional (Conv) and organic (Org) management systems (MS) have both different demands and options for the control of weed communities in crops (Booth and Swanton 2002). While herbicides are the main aspect of weed control in Conv MS, the principal option for weed control in Org MS is mechanical soil preparation and the use of cover crops. ...
... While herbicides are the main aspect of weed control in Conv MS, the principal option for weed control in Org MS is mechanical soil preparation and the use of cover crops. Such a MS is often less efficient when compared to herbicide application (Booth and Swanton 2002;Smith and Gross 2007;Legere et al. 2008). All other weed management systems (WMS) vary between Conv and Org MS (Smith et al. 2010). ...
Given the importance of different weed management systems (MS) for weed communities and soil seed bank, our aim was to study the impacts of organic (Org) and conventional (Conv) MS in tomato and sugar beet on the abundance of weeds and weed seed bank. The results have shown that in both crops the aboveground weed flora is dominated by 2–3 species in the Conv MS, while it is more diverse in the Org MS. In both crops the soil seed bank is less diverse when compared with the aboveground weed flora. Furthermore, a comparative analysis of the weed flora and soil seed bank has shown a high number of different weed seeds in the soil for tomato, unlike sugar beet, where a higher number of weeds was determined in the aboveground weed flora. In tomato, the soil seed bank is more diverse in Org MS (4.1 ± 1.5) than in Conv MS (3.8 ± 1.3), which was also true for the aboveground plant biodiversity (4.6 ± 1.1 vs. 3.6 ± 1.5 species, respectively). Also, although the differences in aboveground weed density and abundance in tomato were not statistically significant, seed bank reserves in the Org MS were significantly more abundant (40.4 ± 16.7 weed seeds vs. 4.5 ± 3.6 in Conv MS). This study has also shown that in sugar beet there were practically no differences between Org and Conv MS, even though the abundance of its aboveground weed flora was higher in Org MS (70.2 ± 29.4 vs. 38.1 ± 21.2 plants/m² in Conv MS). In conclusion, it can be said that although both MS had similar effects on weed management in tomato, for sugar beet Org MS has proven to be less effective in weed control.
... functional ecology, herbicides, management practices, mowing, response traits, tillage, vine, weed communities 1 | INTRODUCTION Since Booth and Swanton's seminal article (Booth & Swanton, 2002), there have been a large number of research studies using a trait-based approach that aimed to identify general rules explaining the effect of agricultural practices on arable weed communities (Fried et al., 2009b;Gunton et al., 2011;Ryan et al., 2010;Trichard et al., 2013). In this framework, agricultural practices are considered as filters that reduce the probability of presence of species that do not have suitable trait values, progressively replaced by more adapted weed species (Booth & Swanton, 2002;Fried et al., 2009b). ...
... functional ecology, herbicides, management practices, mowing, response traits, tillage, vine, weed communities 1 | INTRODUCTION Since Booth and Swanton's seminal article (Booth & Swanton, 2002), there have been a large number of research studies using a trait-based approach that aimed to identify general rules explaining the effect of agricultural practices on arable weed communities (Fried et al., 2009b;Gunton et al., 2011;Ryan et al., 2010;Trichard et al., 2013). In this framework, agricultural practices are considered as filters that reduce the probability of presence of species that do not have suitable trait values, progressively replaced by more adapted weed species (Booth & Swanton, 2002;Fried et al., 2009b). Weed community responses to particular practices, such as tillage, have been examined mostly in annual crops (Armengot et al., 2016;Plaza et al., 2015;Zanin et al., 1997). ...
Vineyards are an appropriate model for testing the filtering effect of management practices on weed communities, as a wide range of practices (tillage, herbicides and mowing) is implemented. The aim of this study is to highlight which trait values are selected by each practice in different environmental conditions, with special references to Grime's CSR strategies. A combination of a multivariate analysis (RLQ) and the fourth-corner analysis was used to analyse 400 floristic samples belonging to 100 vineyards in the wine-growing region of Bordeaux (France). The main structure of vineyard weed communities was shaped by the opposition between mowing, favouring hemicryptophytes with a competitive strategy, and soil tillage, favouring therophytes and nutrient-demanding species with a ruderal strategy. Secondly, the vineyard weed communities differed according to the trophic status of the soil. Vineyards on acidic, sandy soils with low organic matter were characterised by small-seeded annuals with a stress-tolerant strategy whereas vineyards with clayey, calcar-eous soils rich in organic matter, harboured larger perennial nitrophilous species with large seeds and a competitive strategy. Our study is the first to show that weed species responded consistently to two independent gradients with specific traits associated with disturbance (life cycle and SLA) and soil resources (plant height and seed mass) gradients. Based on knowledge of the soil characteristics, it becomes possible to predict which type of weeds will develop according to the combination of practices applied on the vineyard rows and inter-rows.
... In agroecosystems, management tactics represent distinct ecological filters of plant communities, selectively favoring some taxa while excluding others [9,43]. The results of our research confirmed that cropping systems have an overriding impact on weed community characteristics. ...
... Additionally, the relatively small size of the open top chambers and rainout shelters has been cited as a shortcoming of in situ climate manipulations [49], and could have masked our ability to detect the impacts of predicted warmer and drier climate conditions on weed communities across contrasting cropping systems. Yet, results underscore the importance that management decisions coupled with abiotic and biotic constraints have in determining the structure of agricultural weed communities [9]. ...
Understanding the impact of biological and environmental stressors on cropping systems is essential to secure the long-term sustainability of agricultural production in the face of unprecedented climatic conditions. This study evaluated the effect of increased soil temperature and reduced moisture across three contrasting cropping systems: a no-till chemically managed system, a tilled organic system, and an organic system that used grazing to reduce tillage intensity. Results showed that while cropping system characteristics represent a major driver in structuring weed communities, the short-term impact of changes in temperature and moisture conditions appear to be more subtle. Weed community responses to temperature and moisture manipulations differed across variables: while biomass, species richness, and Simpson’s diversity estimates were not affected by temperature and moisture conditions, we observed a minor but significant shift in weed community composition. Higher weed biomass was recorded in the grazed/reduced-till organic system compared with the tilled-organic and no-till chemically managed systems. Weed communities in the two organic systems were more diverse than in the no-till conventional system, but an increased abundance in perennial species such as Cirsium arvense and Taraxacum officinale in the grazed/reduced-till organic system could hinder the adoption of integrated crop-livestock production tactics. Species composition of the no-till conventional weed communities showed low species richness and diversity, and was encompassed in the grazed/reduced-till organic communities. The weed communities of the no-till conventional and grazed/reduced-till organic systems were distinct from the tilled organic community, underscoring the effect that tillage has on the assembly of weed communities. Results highlight the importance of understanding the ecological mechanisms structuring weed communities, and integrating multiple tactics to reduce off-farm inputs while managing weeds.
... Lathwal and Ahlawat (2011) also suggested crop rotation as one of the agronomic strategy for control of resistance in P. minor and reported higher grain yield of wheat grown on farmers' field without spraying any herbicides that adopted crop rotation. Any crop can be viewed in this sense as a filter that only allows specific weeds to get past its management practices (Booth and Swanton 2002). Crop rotation will change the selection pressures, preventing one weed from consistently succeeding snd establishing itself (Nichols et al. 2015). ...
Herbicide resistance has become one of the major unsustainability issues of the worlds' largest wheat (Triticum aestivum L.) ecosystems. In wheat, there is problem of herbicide resistance in Phalaris minor. Phalaris minor can cause wheat yield loss of 10-50% depending upon the density. We therefore, aimed to characterize herbicide use pattern and the factors responsible for the development of herbicide resistance against Phalaris minor in wheat based on data recording from 250 wheat growers of two contrasting agro-ecological regions viz. Bathinda (in southwestern) and Rupnagar (in sub-mountainous), Punjab in northwestern India. These results revealed that ~ 80-83% of respondent were using clodinafop, sulfosulfuron and pinoxaden herbicides against P. minor. On an average, farmers were applying 1.87-times of x-dose of total herbicides, but still getting only 70-82% control of P. minor. Albeit of perceived resistance, clodinafop was the most preferred herbicide against P. minor. The developed binary logistic regression model revealed that besides consistent application of herbicides of same mode of action, cultural variables viz. conservational method of sowing (zero tillage), time to first irrigation after sowing (< 24 days), days to reach field capacity moisture within 10 days and crop rotation followed were elucidated as a significant (p < 0.05) determinants of problem of herbicide resistance encountered by farmers. About 95.6% of farmers were using less water (225-300 L ha −1) and flood jet or hollow cone nozzles against the recommended practices (375 L ha −1 water and flat fan nozzle), therefore, contribute significantly towards the development of herbicide resistance against P. minor in wheat. Additionally, ~ 74% farmers followed delayed herbicide application against recommended time (30-35 days after sowing), which resulted in reduced efficacy of applied herbicides. About 75.6% respondents perceived poor quality of herbicides as prime cause for ineffectiveness of applied herbicides, while others believed that mono-cropping and over/under-dose of applied herbicides contributed to the evolution of resistance in P. minor. The 'β' coefficient values (Exp(β) = 0.754) of Logit model developed revealed that if farmers follow crop rotation, there are ~ 75.4% chances of decreased herbicide resistance in P. minor. Similarly, the farmers' who apply first irrigation within first 24 days after sowing have ~ 2.67-times higher chances of escaping the herbicide resistance, compared with those where first irrigation to crop is delayed (Exp(β) = 2.674). Therefore, addressing the complexities surrounding herbicide resistance in wheat ecosystems necessitates a multifaceted approach that integrates cultural practices, judicious herbicide application, and adherence to recommended agronomic techniques, such as crop rotation and timely irrigation, to effectively mitigate the evolution of resistance in P. minor.
... This could be achieved by either planting species of interest or allowing spontaneous vegetation to grow. Thus, the management of inter-rows plays a key role in the assembly of plant communities, acting as a filter that influences community structure (Booth & Swanton, 2002). Since the 1990s, Mendoza has undergone significant transformations, including the expansion of agricultural boundaries into higher lands that require the exploitation of groundwater (Barzola-Elizagaray & Engelman, 2020) and the subsequent removal of native vegetation. ...
Biodiversity plays a crucial role in supporting ecosystem functions and enhancing agroecosystem resilience to anthropogenic disturbances. The establishment of vineyards in natural areas with native vegetation is recognized as a significant driver of landscape fragmentation and biodiversity loss. This study was conducted in a vineyard surrounded by natural vegetation, including two riparian corridors serving as biological corridors, to assess the impact of vineyard management practices on biodiversity. Taxonomic and functional richness of dicotyledonous vegetation were evaluated across different zones: vineyard center, border, biological corridors, and surrounding natural areas. Vegetation surveys were conducted using fixed transects, and citizen science data were integrated to complement surveys and enhance species detection. The response of dicotyledonous species persisting within the vineyard to mowing practices was examined through phenology-related variables, focusing on six species from Asteraceae, Fabaceae, and Malvaceae families under mowed and non-mowed treatments. Results showed a significant decrease in taxonomic and functional richness toward the vineyard interior. Riparian corridors were identified as key contributors to species richness, positively influencing adjacent crop edges. Floral abundance and days in flower were notably reduced in mowed sectors, particularly affecting Malvaceae species. However, resilience to mowing was observed in species such as Thelesperma megapotamicum (Asteraceae) and Adesmia grandiflora (Fabaceae), indicating their potential for use as native cover crops. These findings highlight the necessity of maintaining or restoring areas with shrub and tree elements to enhance vertical heterogeneity and provide resources for biodiversity. Integrating these conservation measures with vineyard management can contribute to sustainable and ecologically responsible grape cultivation.
... ENMs use associations between environmental variables and a species' occurrence data to define climatic conditions of suitability for its presence (Guisan andThuiller 2005, Dudík et al. 2007). Although the definition of ecological niche includes abiotic conditions and biotic interactions for a species to persist (Wiens 2011), some authors suggest that macroscale environmental conditions determine all possible suitable areas that meet the physiological requirements of a species, whereas biotic interactions determine the subset of these areas that remain suitable after accounting for species interactions and impacts of species on limiting resources (Belya and Lancaster 1999, Booth and Swanton 2002, Soberón 2007, Chase and Myers 2011, Mittelbach and Schemske 2015. ...
Here, we aimed to assess the role of historical (climate events) and the current geographical and ecological features in the evolutionary history of a clade of New World jays. Using an ellipsoid-based approach relying on environmental climatic layers and occurrence data, we tested whether closely related taxa in the clade Cyanocorax colliei + C. formosus + C. morio occupy ecologically different environmental spaces throughout their mostly allopatric distribution in a semihomogeneous landscape, and whether they have been influenced by similar processes given the geographical and ecological context of the Mesoamerican lowland tropical forests. We reconstructed palaeo-distributions to assess the effects of climate shifts on their current patterns of distribution. Additionally, we assess the importance of areas that could function as environmental barriers between taxa. Our results at the species level show evidence for niche divergence for two of the three species pairs. Geographical transferences (areas of suitability inferred by the model) seem to have good explanatory power for current subspecies distribution and variation. At the subspecies level, we find no evidence for niche divergence; the observed parapatric and allopatric distributions seem instead associated with historical environmental differences and ecological barriers limiting the connection between populations with similar niche requirements.
... Trait-based approaches provide a relevant framework to better understand how weed communities shift in response to climate and management changes (Richner et al., 2015). Functional trait values at the community level respond to environmental filtering (e.g., climate change) (Lavorel & Garnier, 2002) and anthropogenic drivers (e.g., agricultural practices) (Booth & Swanton, 2002;Damour et al., 2018). This approach assumes that only certain species with specific trait values will persist within communities in particular climate and management conditions. ...
Spontaneous plant communities have undergone considerable constraints due to human‐mediated changes. Understanding how plant communities are shifting in response to land management and climate changes is necessary to predict future ecosystem functioning and improve the resilience of managed ecosystems, such as agroecosystems. Using Mediterranean weed communities as models of managed plant communities in a climate change hotspot, we quantified the extent to which they have shifted from the 1980s to the 2020s in response to climate and management changes in vineyards. The weed communities of the same 40 vineyards in the Montpellier region were surveyed using the same protocol in spring, summer, and autumn, for two years, with a 40‐year interval (1978–1979 vs. 2020–2021). In four decades, the annual range of temperatures (i.e., the difference between the warmest month's and the coldest month's mean temperatures) increased by 1.2°C and the summer temperatures by 2°C. Weed management diversified over time with the adoption of mowing that replaced the chemical weeding of interrows. Chemical weeding is now mostly limited to the area under the row. Current weed communities were 41% more abundant, 24% more diverse, and with a less even distribution of abundance across species than the 1980s communities at the vineyard level. Modern communities were composed of more annual species (57% of annual species in the 1980s vs. 80% in the 2020s) with lower community‐weighted seed mass and were composed of fewer C4 species. They had higher community‐weighted specific leaf area, higher leaf dry matter content, and lower leaf area than the 1980s weed communities. At the community level, the onset of flowering was earlier and the duration of flowering was longer in the 2020s. Climate change induced more stress‐tolerant communities in the 2020s while the diversification of weed management practices favored less ruderal communities. This study shows that plant communities are shifting in response to climate change and that land management is a strong lever for action to model more diverse and eventually more desirable weed communities in the future.
... It has been shown that the removal of native vegetation by tillage creates a large number of gap ecological niches that favor plant species colonization (Czerwiński et al., 2018). Consequently, tillage alters the species composition of weed communities, in which perennial species shifted to annual species, and increases the community evenness index (Booth and Swanton, 2002) but does not change diversity indices such as species richness and the Shannon-Weiner index (Leǵère et al., 2005;Randriamalala et al., 2012;Barroso et al., 2015). Tillage imposed environmental filtering, an artificial deterministic process, on the weed community and therefore altered the drivers of weed community assembly (Alarcoń et al., 2018). ...
Introduction
Understanding how human activities affect biodiversity is needed to inform systemic policies and targets for achieving sustainable development goals. Shallow tillage to remove Artemisia ordosica is commonly conducted in the Mu Us Desert. However, the impacts of shallow tillage on plant community species diversity, phylogenetic structure, and community assembly processes remain poorly understood.
Methods
This study explores the effects of shallow tillage on species diversity including three a-diversity and two b-diversity indicators, as well as phylogenetic structure [phylogenetic diversity (PD), net relatedness index (NRI), and nearest taxon index (NTI)]. Additionally, this research analyzes the effects of shallow tillage on the community assembly process.
Results and discussion
The results showed that the a-diversity index, b-diversity index, and PD of the shallow tillage (ST) communities were significantly higher than those of the non-shallow tillage (NT) communities, and the phylogenetic structures of both the ST and NT communities tended to be differentiated, with competitive exclusion being the main mechanism of plant assembly. However, shallow tillage increased the relative importance of the stochastic processes dominated by dispersal limitation, mitigating plant competition in the communities. This conclusion was supported by the Raup–Crick difference index-based analysis.
Conclusion
Therefore, for the ecological restoration of the Mu Us Desert, species with adaptability and low niche overlap should be selected to increase the utilization efficiency of the environmental resources. The results of this study provide a foundation for policy development for ecosystem management and restoration in the Mu Us Desert.
... Rapidity is maximized with self-pollination, as autogamous seed set is not dependent on the occurrence of any (biotic or abiotic) event [86]. Weeds are regarded as pioneer flora of early stages of secondary successions [87], and their frequent annual cycle is often correlated with self-pollination [88] according to the "time-limitation" hypothesis of crucial importance in the typically highly disturbed agroecosystem. For example, Amaranthus retroflexus, characterized by flowers devoid of attractiveness and by almost total selfpollination [89], represents the ideotype of weeds as it already produces mature seeds just a few weeks after emergence [90]. ...
The growing interest in safeguarding agroecosystem biodiversity has led to interest in studying ecological interactions among the various organisms present within the agroecosystem. Indeed, mutualisms between weeds and pollinators are of crucial importance as they influence the respective survival dynamics. In this review, the mutualistic role of flower visitors and the possible (often predominant) abiotic alternatives to insect pollination (self- and wind-pollination) are investigated. Mutualistic relations are discussed in terms of reward (pollen and/or nectar) and attractiveness (color, shape, scent, nectar quality and quantity), analyzing whether and to what extent typical weeds are linked to pollinators by rigid (specialization) or flexible (generalization) mutualistic relations. The entomofauna involved is composed mainly of solitary and social bees, bumblebees, Diptera, and Lepidoptera. While some of these pollinators are polylectic, others are oligolectic, depending on the shape of their mouthparts, which can be suited to explore the flower corollas as function of their depths. Consequently, the persistence dynamics of weed species show more successful survival in plants that are basically (occasional insect pollination) or totally (self and/or wind pollination) unspecialized in mutualistic relations. However, even weed species with typical abiotic pollination are at times visited during periods such as late summer, in which plants with more abundant rewards are insufficiently present or completely absent. Many typically insect-pollinated weeds can represent a valid indicator of the ecological sustainability of crop management techniques, as their survival dynamics are closely dependent on the biodiversity of the surrounding entomofauna. In particular, the presence of plant communities of species pollinated above all by butterflies (e.g., several Caryophyllaceae) gives evidence to the ecological compatibility of the previous agronomic management, in the sense that butterflies require certain weed species for oviposition and subsequent larva rearing and, therefore, provide further evidence of plant biodiversity in the environment.
... 1. Cover Crops: Cultivation of cover crops help to suppress the growth of some weed species while allowing others to thrive [7]. Cover crops are widely cited as critical for weed control on organic farms, and they have been the focus of several weed management studies as it reduces more than 50% of weed biomass than fallow one. ...
... When assessing the level of weed infestation in arable fields, it is also worth determining species diversity [3]. Individual species of plants side effects do not act independently of each other and form certain communities [4]. The species composition of weeds in an area is affected by many factors, including the type of climate, soil structure, pH, and topography [5]. ...
Delayed sowing of winter cereals or unfavorable weather conditions in autumn may make it impossible to carry out herbicide treatment in autumn. In such cases, weed control should be started in the spring. During this time, the plantation should be protected as effectively as possible because the weeds are at an advanced stage of growth. Therefore, they are less sensitive to applied herbicides. In the treatment, it is worth using a mixture of different mechanisms of action. Studies were conducted to evaluate the effectiveness of a band of tribenuron-methyl, and MCPA applied as soluble granules in spring control of dicotyledonous in winter cereals. The biological efficacy of herbicides was estimated in the 25 field experiments on winter cereals in Poland. Postemergence, a spring application of tribenuron-methyl + MCPA, effectively controls the majority of weed species present in spring: Anthemis arvensis, Brassica napus, Capsella bursa-pastoris, Centaurea cyanus, Lamium purpureum, Matricaria chamomilla, Tripleurospermum inodorum, Stellaria media and Thlaspi arvense. Satisfactory control was confirmed for Veronica persica, Viola arvensis, and Galium aparine. Tribenuron-methyl with MCPA is recommended for application to winter cereals in spring. To prevent the development of resistance in weeds, it is advantageous to combine two active substances.
... Since 2008, a no-till system was practiced in Beni-Fouda field, but biannual rotation appears to be ineffective at weed control and significantly reducing herbicide use. Due to the turnover of seed stock or the planting of crop rotations with identical dates, which has produced results similar to those of our study, this type of rotation demonstrated some stability in weed seed density and diversity [22], but it is unclear what function the various crops served as filters for the weed community as described by [40]. On other hand, According to [38], fields with species-rich communities are generally correlated with marginal environmental conditions such as the adoption of a mixed crop-livestock system that relies on both livestock and crop production and uses extensive practices compared to more intensive cereal cropping systems which is the case of our field in the Beni-Fouda site. ...
Weeds are a major threat to crop yield and quality but an important component of the agro-system. Estimating the response of weed species to cultural practices is crucial to selecting weed control methods. The study was realized in Setif, a Mediterranean semi-arid region in northeastern Algeria, on two fields (Beni-Fouda and Rmada) practicing the direct seeding since 2008 The experiment was carried out over two campaign years (2015-2017) to examine the effects of rotations compared to monoculture on weed diversity and abundance. Among 40 species inventoried , dicotyledons are the best represented, with 85% (34/40) of the species, belonging to 15 families, the Asteraceae have nearly 27.5% of the total inventoried flora. Monocotyledons are composed of just the Poaceae, comprising 15% of the total flora. Between the two fields, the diversity indices show controversial values and a great dissimilarity is noted. The wheat-crop and rotations at Beni-Fouda (W/T/L/V) were distinguished by both high species diversity and low dominance, while the same treatments (W/T/L/P) at the Rmada site showed strong dominance with low diversity. The results indicate potential changes in the dominance of weed species between the two fields and the impact of the rotations on weeds is insignificant.
... According to the 'assembly rules' of ecological communities (Keddy 1992;Booth and Swanton 2002), the filters that regulate the assembly of a weed community are the availability of resources and physical and chemical disturbances by actual and previous agricultural practices (Gaba et al. 2014). At high crop densities, competition for light can be the primary factor modulating weed community structure (Ballaré et al. 1997;Batlla et al. 2000;Poggio 2005;Poggio and Ghersa 2011;Gaba et al. 2014). ...
... Moreover, management practices presented contrasting effects, detrimental or beneficial, on target species and on target groups, except for the narrow endemics that did not respond to management factors. This differential effect is probably the result of the distinct disturbance regime resulting from each management, that filtered out from the community specific species or traits, and simultaneously, increased available niches for others (Booth and Swanton, 2002;Fried et al., 2012;Storkey et al., 2010). ...
Arable plant diversity has been dramatically declining due to agriculture intensification, with several arable species currently included in national Red Lists. This is particularly relevant in the case of plant communities of the traditional Mediterranean agricultural systems. Despite the current knowledge about the factors affecting this diversity, it is not clear how these communities, which have likely evolved under the pressure of ploughing for millennia, depend on this regular soil disturbance. This is an important issue nowadays, because current management practices focused on the conservation of the ground vegetation cover, to protect soil and other biological groups, often exclude ploughing. In this paper, we test the hypothesis that traditional ploughing is favourable to more specialist arable plants, predictably more dependent on the regular soil disturbance. We address this issue in a Mediterranean agricultural system, the traditional olive groves of Southern Portugal, which is characterized by the annual ploughing of soil. A total of 90 plots containing 1350 sampling quadrats were sampled, and all plant species identified. We categorized plants in four target groups of conservation interest , and then used a joint species distribution model to model their occurrence in relation to three management practices: ploughing, cultivation and low-intensity grazing, using abandoned olive groves as reference level. Results suggest that ploughing is a key factor for the maintenance of arable plant diversity. Ploughing had a positive effect on the occurrence of rare arable plants, archaeophytes and on several Red listed species. In order to conserve these high value plant communities and endangered plant species, we recommend incentivizing ploughing using reduced tillage techniques (e.g. chisel ploughing) on these traditional Mediterranean agricultural systems.
... In agroecosystems, weed and carabid communities are often composed of multiple species of various functional traits including mass parameters (Booth & Swanton, 2002;Pufal & Klein, 2013). But based on the above, knowing the structure of functional body mass in the carabid community may suffice to produce relatively accurate predictions about strength of seed predation pressure (Eilersen & Sneppen, 2019;Vucic-Pestic et al., 2010). ...
Seed choice in seed-feeding omnivorous carabid beetles (Coleoptera: Carabidae) is influenced by numerous ecological factors, including the chemical and physical properties of seed species. Previous work has shown that seed chemistry can drive seed selection decisions by carabids only when the size and mass of seed species are within certain limits. In a model system composed of eight carabid species and seeds of three brassicaceous weeds, we explored predator-to-seed mass relationships and their impact on seed choice by carabids. We show that carabid-to-seed mass ratio scaling relationships are likely to drive seed choice when seed species of different mass are presented to carabid species varying in body mass. Smaller seed species in the experiments were more preferably chosen by smaller carabid species, and mass of the preferable seed species increased as a function of the body mass of carabid species. The taxon-specific mass of carabid predators in relation to the species-averaged mass of available seeds was the main driver of seed choice decisions in the model system under study. These mass-driven changes in seed preferences suggest that feeding interactions between carabid and seed species in agricultural fields are likely driven by mass-structured dynamics. Given this, the intensity of predation pressure imposed by carabids on seed species in the field may potentially be determined by the match/mismatch between the distribution of seed mass in the weed community and the structure of functional body mass in the carabid community.
... The abiotic environment influences community assembly by restricting which species can be established at the site and by constraining the function of successful colonists (Belyea & Lancaster, 1999;Booth & Swanton, 2002). On the other hand, environmental constraints are assumed to remain constant for long enough that communities approach equilibrium and the outcome of many assembly rules that are resource-based is more likely to be detected (Colorado, 2015). ...
... Beyond the case studies presented here, the large geographical extent covered by AWME makes it a particularly valuable resource to address questions where (i) a sufficiently large environmental gradient may not be present in national or regional surveys, like macroecological patterns or climate change effect prediction (space-for-time substitution) or (ii) an effect may be hypothesised to change with scale. Potential future studies using AWME could (a) test the abundant-centre hypothesis (Sagarin & Gaines, 2002) which assumes that a species becomes more abundant at the centre of its range, where the environmental conditions are most favourable, (b) test the theory of species assembly (Booth & Swanton, 2002) according to hierarchical filters starting from a true regional pool, (c) predict responses to climate change and/or extreme events using a time-for-space substitution, (d) predicting the spread of invasive or troublesome weeds by identifying combinations of management practices, soil and climates suitable for these species to establish, (e) disentangling the effects of management systems and single management measures and (f) examining relationships between weed management, weed abundance/weed pressure and weed diversity. ...
Over the last 30 years, many studies have surveyed weed vegetation on arable land. The ‘Arable Weeds and Management in Europe’ (AWME) database is a collection of 36 of these surveys and the associated management data. Here, we review the challenges associated with combining disparate datasets and explore some of the opportunities for future research that present themselves thanks to the AWME database. We present three case studies repeating previously published national scale analyses with data from a larger spatial extent. The case studies, originally done in France, Germany and the UK, explore various aspects of weed ecology (community composition, management and environmental effects and within‐field distributions) and use a range of statistical techniques (canonical correspondence analysis, redundancy analysis and generalised linear mixed models) to demonstrate the utility and versatility of the AWME database. We demonstrate that (i) the standardisation of abundance data to a common measure, before the analysis of the combined dataset, has little impact on the outcome of the analyses, (ii) the increased extent of environmental or management gradients allows for greater confidence in conclusions and (iii) the main conclusions of analyses done at different spatial scales remain consistent. These case studies demonstrate the utility of a Europe‐wide weed survey database, for clarifying or extending results obtained from studies at smaller scales. This Europe‐wide data collection offers many more opportunities for analysis that could not be addressed in smaller datasets; including questions about the effects of climate change, macro‐ecological and biogeographical issues related to weed diversity as well as the dominance or rarity of specific weeds in Europe.
... A suitable conceptual framework to understand, predict and manage a floristic change of a weed community is the community assembly theory (Weiher and Keddy 1999;Storkey et al. 2010). Thus, crop management practices can be conceptualized as "filters" that prevent or favor the establishment and growth of a certain weed species present in the weed community that is feasible to colonize a site (Booth and Swanton 2002;Cardinale et al. 2006). CC represent a potential and important biological management "filter", because they may compete with weeds for solar radiation, water and/or nutrients, potentially reducing ("filtering") the abundance of a weed species with a high competitive capacity (Smith and Gross 2007). ...
The aim of this study was to determine if different mixtures and monocultures of cover crops (CC) reduce aerial dry matter, number and diversity of autumn-winter weeds. Two experiments with different CC species were implanted in the INTA Pergamino Agricultural Experimental Station (Pergamino, Buenos Aires, Argentina, 33° 51´ S, 60° 34´W) in 2018 and 2019. The species used were: Avena sativa, Triticosecale and Vicia villosa. Mixtures and monocultures of CC were used, in different proportions and densities, and were compared with a chemical fallow. Two cuts of CC were made aboveground at tillering and milk grain stages (Z 2.5 and 7.3, respectively) to obtain aerial dry matter of CC (ADMcc, g.m⁻²), ADM of weeds (ADMw, g.m⁻²) and number of weeds (weeds.m⁻²). Moreover, weed species were identified and Shannon diversity and evenness indices and effective specific richness were calculated. In 2018, the highest ADMcc was recorded in Avena sativa at Z 2.5 as well as the highest weed density. At Z 7.3, the highest ADMcc was recorded in Avena sativa, Triticosecale and their mixture. At that stage, the highest ADMw was recorded in the chemical fallow. In 2019, the 3:1 Avena sativa/Vicia villosa mixture showed the highest ADMcc and diversity of weed community showed non-significant differences from the chemical fallow at Z 2.5. There were non-significant differences in ADM among CC and diversity of weed community in the CC was practically null at Z 7.3. At both stages, the highest number of weeds and ADMw was observed at chemical fallow, whereas in CC, non-significant differences were detected. The results obtained indicate that CC reduce the number, ADMw and diversity of the weed community, regardless of the mixtures used.
... However, in the study of weed infestation in crops, the diversity of weeds and the dominance of individual species are also very important [Sobiech et al. 2018]. The unfavorable impact of the community of several dominant species of weeds may be greater than in the case of their greater biodiversity [Booth and Swanton 2002]. Taking into account the above statement, it appears question about the importance of weed number and biomass regulation for shaping their biodiversity. ...
The aim of the experiment was to assess the effect of cropping system and as well as various methods of weed control on the biodiversity of the weed community of dent maize, narrow-leaved lupine and spring oat. The data used in the study came from a three year field experiment carried out at the Experimental Station in south-eastern Poland (50°42'N, 23°16'E). The following factors were studied: 1. Cropping system – sole cropping and strip intercropping; 2. Weed control – mechanical and chemical. Changes in the diversity of the segetal flora are analysed using the species richness index (S), the Shannon-Wiener diversity index (H’), the Margalef index (R), the Simpson dominance index (D) and Pielou’s evenness index (J’). The use of chemical weed control increased the diversity of the weed community in all species tested compared to mechanical weed regulation. Chemical weed regulation significantly decreased the value of Simpson dominance index due to the limitation of the occurrence of dominant weed species. Strip intercropping increased weed biodiversity, however, the influence of cropping systems depended on the crop species and the weed control
method used.
... Functional groups of vegetation are defined by family classification and phenology, which can give rise to functional traits among species (Hou et al., 2013) due to their ecological processes (Rogers et al., 2019). Community assemblies can follow trajectories through time that are controlled by biotic and abiotic constraints that act at multiple scales (Booth and Swanton 2002). Examples exist where functional group assembly theory can provide a framework for advancing invasive ecologies (Pearson et al., 2018) and responses to fire histories (Cianciaruso et al., 2010). ...
The relationship between species phenology and spectral separability is essential to determine the optimal remote sensing sampling period to maximise spectral separability of vegetation species. However, this relationship in many native grasses, introduced grasses and herbs, shrubs, and vine species in tropical savannas is unknown. We measured the in-situ hyperspectral response of monospecific vegetation stands of several understorey species representing different functional groups over phenological stages (throughout dry and wet seasons) using a non-imaging spectrometer. We present a spectral library of both native and introduced species of a tropical savanna environment. We analysed the data using continuum removal to highlight absorption features. Most understorey species displayed a photosynthetic spectral response with increased greenness at the end of the wet season that progressively declined as vegetation dried out. For some species, there were seasonally dependent differences in absorption features with spectral differences between the late wet and early dry season, and late dry and early wet seasons. We resampled the data to the spectral range typical of drone-mounted hyperspectral sensors (i.e., 150 bands between 400 and 1000 nm), which omits the water absorption features of the SWIR. These findings suggest an ideal sampling period for measuring outdoor canopy reflectance of understorey species, which will promote methodological improvements of hyperspectral data capture. The use of a VNIR only hyperspectral sensor will exclude the important regions of the spectrum for plant spectral identification including non-pigment bands for water, nitrogen and cellulose. The results have implications for determining the completeness of rehabilitation assessing reestablishment among indigenous species across mine sites under rehabilitation.
... The herb richness and herb composition present in a crop field depend, on the one hand, on the ability of the species to "reach" the community or assemble through dispersion or regeneration processes, and, on the other, on the adaptations that allow the species to "thrive" in those specific ecological conditions, as well as on the availability of certain resources and the internal dynamics created by the crop (Booth and Swanton 2002). Agronomic management practices modify all these conditions and are a main selection factor of herbaceous species. ...
the most conservative pattern, with the lowest number of new species and species lost, due to the presence of the cover crop. Both the most intensively managed system (CM) and the most diverse and least intensive one (SA) had the highest number of new species recorded over time, which led to highly specialized assemblages, with worldwide distributed and herbi-cide resistant species in the first case and secondary forest species, in the second. We conclude that the promotion of organic management and agroforestry systems, especially highly divers and successional agroforestry sytems would favour herb assemblages with high conservation value and prevent the establishment of globally distributed species.
... The seed bank is composed of both new and old seeds that have been shed and disseminated across landscapes and regions, and these serve as pools of genetic material for future generations (Gandıá et al., 2022). The traits preserved in this way contribute to future weed populations by allowing seeds to bypass filters such as unfavourable environmental conditions and weed management measures, and hence the soil seed banks provide several opportunities for weeds to establish themselves in the plant populations (Booth and Swanton, 2002;Yang et al., 2021). Examination of seed banks can reveal important insights about what species may have been in previous standing vegetation in addition to their function as a reservoir for future populations (Ambrosio et al., 2004;Hopfensperger, 2007). ...
Navua sedge (Cyperus aromaticus) is threatening crops, pasture species and natural ecosystems in Pacific Island countries and northern Queensland, Australia. To aid future management efforts of this exotic invasive weed, research was conducted to understand the soil seed bank dynamics of pastures invaded by Navua sedge. Six grazing properties were chosen across two landscapes, coastal and inland/upland, with areas that had Navua sedge infestations in Queensland, Australia. At each site, soil was collected from two soil depths, 0-5 and 5-10 cm, and from plots with high and low infestation levels of Navua sedge. It was observed that the soil seed bank dynamics varied significantly between these study sites. Navua sedge was the dominant species in the soil seed bank at all the sites contributing between 62% to 95% of the total seed bank, while pasture seeds occupied only 3% to 24%. Broadleaf seeds were even lower in abundance, showing between 2% to 13% of the total seed count. The abundance of Navua sedge seed present in the soil was significantly correlated with the aboveground biomass of Navua sedge (r=0.53, p=0.006), but no correlation was found with the infestation age of Navua sedge. Based on this work, it is clear that the seed bank of Navua sedge is very large and concentrated within the top 0-5 cm of the soil, with, 83% of total Navua sedge seeds being in this layer. It was also noted that, although, high infestation plots had significantly higher number of seeds than low infestation plots, more than 18,000 Navua sedge seeds/m ² were still found in the 0-5 cm soil layer of plots regarded as low infestation. We suggest that insights achieved from our soil seed bank study may be used to devise management strategies to minimise the impact of Navua sedge weed in critical grazing and agricultural areas.
... Dispersal restrictions determine which species reach a given location (Booth & Swanton 2002). They provide biotic regulation of ecosystem services in Antarctica's ice-free soils (Pertierra et al. 2021). ...
We set out to document the diversity and distribution of bryophytes in Admiralty Bay and thereby enable the identification of patterns in local diversity and their possible drivers. Combining data extracted from different sources and recent collections, we documented the presence of 63 species. Similarity analyses of moss species diversity in relation to underlying geology and ornithogenic influence identified an identical cophenetic correlation coefficient of 0.744 for both factors. The Sørensen index was < 0.6, indicating that the groups share < 60% of the species recorded. The data showed that the selected filters (ornithogenic soils, non-ornithogenic soils and different geological extracts) did not underlie consistent species groupings, and we conclude that other environmental and topographical factors are likely to be responsible for shaping the moss community structure in Admiralty Bay. To enable effective management of Antarctic Specially Managed Area (ASMA) No. 1 and Antarctic Specially Protected Area (ASPA) No. 128, robust assessments of the local ecosystem and biodiversity are necessary to assist in the decision-making processes mandated under the Antarctic Treaty System, one of whose founding principles is the preservation of the Antarctic ecosystem.
... Additionally, it is possible that differences in weed communities between treatments influenced the total weed biomass at the time of cabbage harvest. Disturbance-based events such as tillage can act as strong filters on weed community assembly, leading to dominant species (Booth and Swanton, 2002;Smith and Mortensen, 2017). Higher weed diversity in no-till/no-tarp, in particular, may have served to suppress some dominant, high-biomass weed species, including A. retroflexus. ...
Small-scale vegetable farmers are interested in cover crops and reduced tillage, but scale-appropriate technology and equipment are necessary to expand these practices to the growing segment of small farms. We sought to determine the efficacy of tarps, an increasingly popular tool on small farms, to end overwintering cover crops and provide weed suppression for subsequent no-till cabbage production. In three fields over two seasons in Maine, we grew a winter rye (Secale cereale L.) and hairy vetch (Vicia villosa L.) cover crop, which we managed by a factorial combination of tillage (no-till, till) and tarp-ing (tarp, no-tarp) in June, followed by a transplanted cabbage crop (Brassica oleracea L. var. Capitata) in July. Within each treatment, subplots were either weeded by hand or left unweeded. Cover crop biomass ranged from 2.8 to 4.5 MgÁha 21. Mean cabbage weights in the novel no-till system (no-till/tarp) were greater than (year 1) or equal to (year 2) those in tillage-based systems (till/no-tarp and till/tarp). In year 1, the mean cabbage weight in weeded subplots was 48% greater in no-till/tarp than in till/no-tarp systems. In unweeded subplots, this difference was 270%, highlighting the efficacy of the no-till/tarp system to reduce the impact of weeds. In year 2, weed biomass was higher with all treatments than it was in year 1, and unweeded subplots failed to produce marketable heads (i.e., >300 g). The mean cabbage weight in weeded subplots was equal among no-till/tarp, till/tarp, and till/no-tarp systems. Tarping had a strong effect on weed biomass and weed community composition measured at the time of cabbage harvest in unweeded subplots. In year 1, weed biomass at the time of cabbage harvest with tarp treatments was less than half that with no-tarp treatments. Tarps effectively facilitated the cover crop mulch-based no-till system. We propose that this system is an adaptive strategy for farmers affected by climate change. However, both cover crop production and tarping shorten the growing season. We discuss tradeoffs and opportunity costs using the metric of growing degree days.
Peanut (Arachis hypogaea L.) and maize (Zea mays L.) are essential crops for Ghana's economy and food security, but weed infestation poses a significant threat to their cultivation. Crop rotations influence weed communities, but little is known about these processes in peanut-cropping systems in West Africa. This study investigated the impact of different crop rotations and input levels on weed communities in Ghana over 3 yr. Results showed that low inputs (absence of herbicide and fertilization) favored species richness, while higher input levels (weed control with herbicides and fertilizer use) reduced it. Diversity and evenness were also affected by inputs, with varying patterns across locations and seasons. Weed population growth rates (λ) varied significantly by location and treatment; all management programs resulted in increasing weed populations. Principal component analysis revealed distinct associations between weed species and crop management. The majority of weed species exhibited a generalist behavior and did not associate with a particular management. However, billygoat weed (Ageratum conyzoides L.) and Benghal dayflower (Commelina benghalensis L.) were positively associated with high-input systems, while purple nutsedge (Cyperus rotundus L.) exhibited strong associations with low and medium inputs. The weed-crop rotation dynamics described here demonstrate how management drives the selection of weed species that are more pervasive and interfere with important food crops in Ghanaian agriculture.
Increased agricultural weed diversity is associated with reduced dominance of competitive weeds that reduce crop yields. In addition, diverse weed communities can promote biodiversity at other trophic levels and enhance ecosystem services. For both reasons, there is increasing interest in the relationship between agricultural management and weed diversity. Existing information in this area is limited, relative to the large number of influential factors, but knowledge is increasing rapidly. We conducted a scoping review to determine when, where, and how weed diversity has been evaluated in relation to management. From an initial set of 10 236 items retrieved from Web of Science and Scopus, 7198 were screened and 331 were included. The median publication year was 2015. Nearly half of all studies were conducted in Europe (n = 161, 49%). Organic cropping systems were included in 48 studies (15%). Tillage was the most common management factor (n = 111, 34%), followed by crop rotation (n = 73, 22%). There were 135 studies in which management factors were implemented for six or more years (41%). Most studies included measurements of species richness (n = 265, 80%) and/or Shannon-Wiener diversity (n = 145, 44%). Overall, this review identified a small and heterogenous-but quickly growing-body of literature on weed diversity. Priority areas for future research should include weed diversity beyond field crops in temperate environments, weed seedbanks, functional diversity, and best practices for measuring weed diversity. K E Y W O R D S agroecology, biodiversity, ecosystem services, integrated weed management, sustainable agriculture, weed community assembly
El monocultivo de un puñado de especies de gran densidad calórica domina la agricultura contemporánea y ha resultado en una erosión de la agrobiodiversidad, problemas ambientales, dependencia de insumos externos al campo y dietas de reducida diversidad de nutrientes y sabores. No obstante, en las comunidades dominadas por una agricultura de subsistencia, a menudo indígenas, persisten bastiones de agricultura y dieta diversificadas. Actualmente, existen en Latinoamérica movimientos importantes para rescatar esta agrobiodiversidad; sin embargo, la mayoría se limita a la diversificación de cultivos, con prácticas como rotaciones de estos, cultivos intercalados, o el uso de cultivos de cubierta. Las arvenses, agrobiodiversidad vegetal asociada a los cultivos, abundante en los sistemas agrícolas, pero no sembrada, no son consideradas frecuentemente en esta discusión. Las arvenses son componentes esenciales de muchas agriculturas tradicionales, donde incrementan la diversidad funcional de los agroecosistemas y contribuyen a la nutrición humana. En México, verbigracia, se usa el término "quelite" para describir plantas del campo no sembradas, pero comestibles. En otras partes del continente americano también se encuentran numerosos quelites, plantas que muchos productores perciben como "malezas". En este trabajo discutimos el concepto de los "quelites", su origen en la agricultura tradicional de México, su significado en el presente, y su potencial para el futuro. Demostramos, con doce ejemplos, que los quelites no se limitan a Mesoamérica, sino que siempre han formado parte de los sistemas agrícolas en el continente americano. Nuestra meta es difundir el concepto de los quelites más allá de la agricultura tradicional en México para fomentar el uso de estas plantas promisorias. Concluimos el artículo con sugerencias de estrategias para lograr esta meta.
The monoculture of a handful of energy-dense crops that dominates contemporary agriculture has resulted in an erosion of agrobiodiversity, environmental issues, agroecosystem dependency on off-farm inputs, and diets with poor diversity in nutrients and flavors. However, diversified agriculture persists in communities characterized by subsistence farming, many of them Indigenous. Although movements across Latin America aim to rescue agrobiodiversity, they are widely limited to cropping system diversification, including practices such as crop rotations, intercropping, and cover crops. The agrobiodiversity of plants associated with crops, often labeled as weeds, is commonly not considered in this context. Yet edible weeds are the essential components of traditional food systems where they increase the functional diversity of agroecosystems and contribute to human nutrition. In Mexico, the term “quelite” describes noncultivated but edible plants growing on a crop field. Across the American continent, there are nutritious quelites that are commonly perceived as “weeds.” In this article, we discuss the concept of quelites, their origin in traditional Mexican agriculture, their significance for agroecosystem diversification, and their potential for the future. We demonstrate, with 12 examples, that quelites have always been part of agroecosystems across the Americas. We aim to spread the concept of quelites beyond traditional farming in Mexico to promote the use of these promising plants. We conclude the article with suggestions for strategies to achieve this goal. Please refer to Supplementary Materials, Full text Spanish version of this article, for a full text Spanish version of this article.
Faced with the biodiversity extinction crisis and climate change, alternative approaches to food production are urgently needed. Decades of chemical-based weed control have resulted in a dramatic decline in weed diversity, with negative repercussions for agroecosystem biodiversity. The simplification of cropping systems and the evolution of herbicide resistance have led to the dominance of a small number of competitive weed species, calling for a more sustainable approach that considers not only weed abundance but also community diversity and composition. Agroecological weed management involves harnessing ecological processes to minimize the negative impacts of weeds on productivity and maximize biodiversity. However, the current research effort on agroecological weed management is largely rooted in agronomy and field-scale farming practices. In contrast, the contributions of landscape-scale interventions on agroecological weed management are largely unexplored (e.g., interventions to promote pollinators and natural enemies or carbon sequestration). Here, we review current knowledge of landscape effects on weed community properties (abundance, diversity, and composition) and seed predation (a key factor in agroecological weed management). Furthermore, we discuss the ecological processes underlying landscape effects, their interaction with in-field approaches, and the implications of landscape-scale change for agroecological weed management. Notably, we found that (1) landscape context rarely affects total weed abundance; (2) configurational more than compositional heterogeneity of landscapes is associated with higher alpha, beta, and gamma weed diversity; (3) evidence for landscape effects on weed seed predation is currently limited; and (4) plant spillover from neighboring habitats is the most common interpretation of landscape effects on weed community properties, whereas many other ecological processes are overlooked. Strikingly, the drivers of weed community properties and biological regulation at the landscape scale remain poorly understood. We recommend addressing these issues to better integrate agroecological weed management into landscape-scale management, which could inform the movement towards managing farms at wider spatiotemporal scales than single fields in a single season.
The aim of this study was to investigate the niche mechanism and diversity of weeds in drip-irrigated and machine-harvested cotton fields in north Xinjiang, China. The dominant classes of weeds in 25 cotton fields under drip-irrigated and machine-harvested in 5 regions of north Xinjiang were investigated by seven-grade visual method, and converted to important value data, the 20 main weeds niche breadth and niche overlap were caculated on the basis of the data above. The ecological similiarity revealed by DCA sorting and minimum spanning tree of graph theory cluster analysis is drawed on the basis of the niche overlap value. The results show that Convolvulus arvensis L., Chenopodium album L., Amaranthus retroflexus L., Solanum nigrum L., Phragmites australis (Cav.) Trin. ex Steud., Setria viridis (L.) Beauv., Abutilon theophrasti Medicus., Hibiscus trionum L., Echinochloa crusgalli (L.) Beauv., nine species of weeds, which are the dominant species (malignant weeds) in drip-irrigated and machine-harvested cotton fields in North Xinjiang, have wide niche. The niche overlap values of S. nigrum L. and C. album L., A. theophrasti Medicus. and A. retroflexus L., H. trionum L. and E. crusgall (L.) Beauv., A. retroflexus L. and E. crusgalli (L.) Beauv. are higher. The minimal spanning tree method based on niche overlap value to reflect similar degree of the ecological needs of the weeds, 20 main weeds will be divided into 4 groups. DCA ordination of 20 main weeds comprehensive ecological needs of 25 sampling sites: the vicious weeds all gathered at the central sorting chart, the distinction is obvious with the general weed and the corresponding of DCA ordination chart with minimal spanning tree is better. The minimal spanning tree by its focus on the results of which show that weeds are the most similar to the ecological requirements, but not be used for the no adjacent species, and no clear that the ecological relationship between them, the DCA sorting can reflect the ecology similar relations between all weeds wholely, though this method will lose a small amount of ecological information through the data conversion. Therefore, the two methods will be combined, complementary advantages, the superiority is obvious. Along with drip irrigation age years increase, S. nigrum L., C. arvensis L., C. album L. and so on, between dominant value of nine species of malignant weeds and the drip irrigation age years has the remarkable regression relations.
Spontaneous plant communities have undergone considerable constraints due to human-mediated changes. Understanding how plant communities are shifting in response to land management and climate changes is necessary to predict future ecosystem functioning and improve the resilience of managed ecosystems, such as agroecosystems. Using Mediterranean weed communities as models of managed plant communities in a climate change hotspot, we quantified to which extent they have shifted from the 1980s to the 2020s in response to climate and management changes in vineyards. In four decades, the annual range of temperatures (i.e. the difference between the warmest month's and the coldest month's mean temperatures) increased by 1.2°C and the summer temperatures by 2°C. Weed management diversified over time with the adoption of mowing that replaced the chemical weeding of inter-rows. Current weed communities were 41% more abundant, 24% more diverse and with a less even distribution of abundance across species than the 1980s communities at the vineyard level. Modern communities were composed of more annual species (57% of annual species in the 1980s versus 80% in the 2020s) with lower lateral spreadability and seed mass and were composed of fewer C4 species. They had higher community-weighted specific leaf area, higher leaf dry matter content and lower leaf area than 1980s weed communities. At the community level, the onset of flowering was earlier and the duration of flowering was longer in the 2020s. Climate change induced more stress-tolerant communities in the 2020s while the diversification of weed management practices over time filtered less competitive communities. This study shows that plant communities are adapting to climate change and that land management is a strong lever for action to model more diverse and functional plant communities in the future.
In recent years, trait-based research on zooplankton has gained importance to enable comprehensive interpretation of ecosystem processes, but this approach is still limited in inland waters. Wetlands, one of the most important inland water resources, provide many ecological and economic services in the ecosystem, but like all other water bodies in the world, they are under threat of deterioration and depletion for various reasons. In this study, the taxonomic structure of the zooplankton community in Lake Manyas, one of the important wetlands of Türkiye, as well as their functional characteristics such as body size (small, large) and feeding strategies (microphagous, raptorials) were investigated monthly between 2019 and 2020. The hypothesis that environmental variables influence the species composition and functional groups of zooplankton was tested, given that their structure is shaped by environmental gradients. A total of 62 taxa, including rotifer-dominated, cosmopolite and eutrophication indicator species, were identified. These taxa categorized into three functional groups dominated by small microphagous. Although the zooplankton structure had a high taxonomic diversity, functional homogeneity was observed which reflected a low grazing rate in the ecosystem. Albeit water temperature and total organic carbon significantly affected the distribution of all functional groups, each dominant taxa interacted with different environmental variables. Changing environmental conditions in the lake affected the presence and/or quantity of the zooplankton functional groups (ZFGs). The results showed that ZFGs are strongly associated with environmental conditions and that the response of trait-based functional groups to environmental changes can provide useful knowledge about aquatic ecosystem’s health.
The use of herbicide combinations is a common practice in modern agriculture. However, unexpected results may be observed due to herbicide and weed diversity, therefore, highlighting the need for a predictive strategy. To this end, a data set was made based on recent studies. This data set included herbicide attributes, such as active ingredient, chemical family, and mode of action, and weed attributes, namely, species, clade, type of leaves, family, and lifespan. Globally, additive interactions (46.30%) were more frequent than antagonistic (29.09%) and synergistic (24.61%) ones. The occurrence of these herbicide interactions with regard to herbicide and weed features is also discussed. Moreover, mesotrione and glyphosate have been, respectively, identified as the most promising or inadequate herbicides in predicting beneficial mixtures. The resulting global trend could guide farmers in their choice of beneficial herbicide companions.
This book covers key areas of Geography, Environment and Earth Sciences. The contributions by the
authors include photosynthesis, oxygen content, K-T boundary, volcanism, Alpha radioactivity,
Contaminated environmental materials, Surface ozone, effect of ozone on plants, long-term ozone
monitoring, summer heat waves, peak ozone concentrations, monitoring the ozone, spatial and temporal
ozone variability, above ground biomass, below ground biomass, carbon sinks, green house gases, soil
organic carbon, agro-ecosystems, biodiversity, climate change, weed communities, , land management,
wastewater treatment, membrane bio-reactor, solidification. This book contains various materials suitable
for students, researchers and academicians in the field of Geography, Environment and Earth Sciences
Ecological communities are structured by combinations of biotic and abiotic factors acting at different spatial scales. However, the relative influence of the different scale‐related variables on assemblage composition is poorly understood, despite being key to the effective and efficient management of fluvial ecosystems. We took advantage of the relatively recent and well‐studied history of salmonid introductions in Patagonia to evaluate if non‐native species show different patterns of association with abiotic factors depending on the spatial scale of the environmental filter. We used a hierarchical approach to characterised environmental variables at the basin and reach scales to assess their influence on the presence, abundance and structure of the salmonid assemblages in breeding streams. We saw no evidence that presence/absence patterns of salmonid distribution were driven by landscape variables, except for those basins with physical environmental barriers to colonisation. However, we did find evidence for relative abundances being influenced by climatic and geomorphological variables (e.g., precipitation and relief). Our results do not support a scenario in which any of the salmonid species modulates the distribution of the other species, suggesting that interference has played only a minor role in determining current fish distribution in fluvial systems of the region. Instead, current patterns of presence and abundance of salmonids are best explained as the product of environmental filters. Our findings contribute to our understanding of the ecology of individual species and provide insight into the mechanisms structuring fish assemblages in Southern Hemisphere's lotic systems.
Background and Aims
Decomposition is a major ecosystem process which improves soil quality. Despite that, only a few studies have analysed decomposition in an agricultural context, while most agrosystems (e.g. vineyards) are facing decreasing soil quality. The objective of this study is to understand the impacts of both pedoclimate and weed management on the mass loss of vineyard weed communities during the early stages of the decomposition process through their functional properties.
Methods
In 16 Mediterranean vineyards representing both a pedoclimate and a soil management gradient, we measured the mass loss of green aboveground biomass of 50 weed communities during decomposition in standard conditions and key leaf traits of dominant species (e.g. leaf dry matter content, LDMC, leaf lignin to nitrogen ratio, lignin:N). Both the mean (i.e. community weighted means, CWM) and diversity (i.e. Rao index) were computed at the community level. Path analysis was used to quantify the effects of agro-environmental filters on the mass loss of weed communities through their functional properties.
Key Results
Tillage and mowing filtered more decomposable communities compared to chemically weeded communities (16% and 8% of higher mass loss after two months of decomposition). Path analysis selected weed management practice type as the main factor determining mass loss through its effect on functional properties while soil and climate had minor and no effects respectively. Chemical weeding favoured communities with higher investment in resistant leaves (e.g. 38% higher lignin:N, 22% lower leaf nitrogen content) which resulted in lower mass loss compared to tilled and mowed communities. Mowing favoured communities with 47% higher biomass and with 46% higher nitrogen content.
Conclusions
Weed management influenced significantly weed mass loss, while pedoclimate had little effect. Our results suggest that mowing is a promising alternative to herbicide use, favouring higher biomass, nitrogen content and decomposability potential of weeds.
Weed seeds present in the soil seedbank represent the most persistent threat to successful crop production. Despite our efforts with such selection pressures as herbicide technology, tillage, and mechanical and manual weed control, weeds continue to persist and challenge our weed management strategies. In this chapter, we explore five agronomic practices that influence the persistence of weed seeds in the soil seedbank. Topics include tillage, the role of light penetration into the seedbank, crop rotation, cover crops and livestock pasture, and manure management. Of the agronomic practices highlighted in this chapter, tillage, pasture, and grazing management were the most significant variables influencing long‐term weed seedbank dynamics. Research must continue to address the ecological significance of weed seedbanks and the agronomic practices that may contribute to the management of a persistent weed seedbank.
It is over twenty years since Jared Diamond focused attention on the possible existence of assembly rules for communities. Since then there has been a proliferation of studies trying to promote, refute or test the idea that there are sets of constraints (rules) on community formation and maintenance (assembly). This timely volume brings together carefully selected contributions which examine the question of the existence and nature of assembly rules with some rigour and in some detail, using both theoretical and empirical approaches in a variety of systems. The result is a balanced treatment which encompasses a wide range of topics within ecology including competition and coexistence, conservation and biodiversity, niche theory, and biogeography. As such it provides much to interest a broad audience of ecologists, while also making an important contribution to the study of community ecology in particular.
(1) Multiple stable states in ecosystems have been proposed on theoretical grounds, and examples have been offered, but direct tests of the predictions are lacking. A boundary between states exists if: (i) a system when disturbed from one state to another does not return to its original state once the cause of the disturbance returns to its original value; and (ii) a second factor takes over and holds the system in the new state. We examine these predictions for two stable states in the woodlands of the Serengeti-Mara ecosystem in East Africa. (2) Woodlands in natural areas of savannah Africa have declined over the past 30 years. Three general hypotheses have been proposed: (i) expanding human populations have concentrated elephants into protected areas, elephants then caused the decline of woodlands but man-induced fires prevented regeneration (two stable states); (ii) fires caused the decline and also prevented recovery (one stable state); (iii) fires caused the decline while elephants inhibited recovery through density-dependent mortality of seedlings (two stable states). (3) Two time periods, the 1960s when woodlands changed fastest and the 1980s when grasslands prevailed, produced four specific hypotheses. (i) `The 1960s elephant hypothesis' and (ii) `the 1960s fire hypothesis' hold that elephants and fire, respectively, caused woodland change. (iii) The `1980s elephant hypothesis' and `the 1980s fire hypothesis' hold that these factors, respectively, prevented woodland recovery. (4) From experiment and observation of seedling recruitment, mortality due to combinations of burning rates, elephant browsing, wildebeest trampling, and antelope browsing was estimated and used to model tree population dynamics; predictions for rates of decline and increase were compared with independent estimates from aerial photographs. (5) Maximum rates of elephant and antelope browsing could not have caused the observed decline of woodlands in the 1960s. The most conservative burning rates in the 1960s, without elephants, could have caused a decline consistent with the 1960s fire hypothesis. (6) The combined impact of fire and browsing most closely matched the observed rate of woodland loss. (7) Wildebeest grazing in the 1980s reduced dry grass and minimized fire incidence. The model predicted that fire mortality and wildebeest grazing could not maintain the present grassland state. (8) The present high elephant density was sufficient to prevent an increase in the woodlands consistent with the 1980s elephant hypothesis. Wildebeest trampling and other browsers ensures that the vegetation is currently stable in a grassland state. (9) Thus, an external perturbation, such as fire, was necessary to change the vegetation from woodland to grassland. Elephants were unable to cause such a change. Once the grassland was formed, however, elephants were able to hold it in that state. These results are consistent with the third general hypothesis that there are two stable states of woodland and grassland, the latter maintained by herbivores. (10) Simulation of conditions in the 1890s suggests that the rinderpest epidemic combined with elephant hunting could have caused the woodland regeneration observed before the 1950s. Therefore, (i) savannah woodlands may regenerate in pulses as evenaged stands, and (ii) there may have been more grassland in Africa before 1890. This longer time-scale view of the dynamics of vegetation has implications for the conservation of elephants and their habitats.
Periphytic algae were experimentally manipulated over a 20-week period to evaluate the influence of environmental fluctuations and community age on succession and community stability. Environmental fluctuations were generated by periodically transferring artificial substrata between stations in an oligotrophic lake during 9 or 10 weeks. Developing communities exposed to induced fluctuations of two- and four-week periods did not track the fluctuations. Instead, succession was slowed and followed a trajectory intermediate between those of unmanipulated control communities representing the two extremes of the fluctuation cycles. The fluctuations favored the growth of some early successional taxa while strongly suppressing the growth of at least one late successional taxon. Responses of other late successional taxa were intermediate. After ending the fluctuations two separate experiments assessed adjustment stability (''resilience'') by following convergence of the ''fluctuating'' communities and of ''early successional stage'' communities to a control during a recovery period lasting 10 or 11 weeks. The detection of convergence depended on the community property measured. Although the total density of the fluctuating and control communities had converged 3 weeks into the recovery period, taxonomic composition did not converge during the recovery period, presumably because both sets of communities were still far from maturity and therefore the control was moving toward maturity almost as rapidly as the fluctuating communities. The total density and taxonomic composition of the early successional stage communities had not converged to those of the control by the end of the recovery period. Slow community recovery in this oligotrophic lake is in agreement with theoretical work showing increased recovery time in model ecosystems with reduced nutrient input.
Links between plant traits and the environment, i.e. sets of plant attributes consistently associated with certain environmental conditions, are the consequence of the filtering effect of climatic, disturbance and biotic conditions. These filters determine which components of a species pool are assembled into local communities. We aimed at testing for consistent association between plant traits and climatic conditions along a steep regional gradient, divided into 13 climatically homogeneous sectors, in central‐western Argentina. We analyzed 19 vegetative and regeneration traits of the 100 most abundant species along the gradient. For each trait, we tested for homogeneity of frequencies of different categories between sectors and the regional species pool, using the χ ² statistic. We rejected H 0 in 71% of the pair‐wise comparisons, which strongly suggests a ‘filtering effect’ of climatic factors on key plant functions. Vegetative traits were filtered more often than regeneration traits. Specific leaf area, life span, ramification, canopy height, leaf weight ratio, carbon investment into support tissue and pollination mode were the traits showing differences in the largest number of pair‐wise comparisons.
This is probably the first attempt to detect, on a quantitative, statistically conservative basis, consistent linkages between climatic factors and numerous plant traits, over a broad spectrum of environmental conditions and plant growth forms. We discuss the advantages and limitations of this approach in predicting vegetation structure and functioning under present environmental conditions, and those expected for the next century as a consequence of global change.
It is over twenty years since Jared Diamond focused attention on the possible existence of assembly rules for communities. Since then there has been a proliferation of studies trying to promote, refute or test the idea that there are sets of constraints (rules) on community formation and maintenance (assembly). This timely volume brings together carefully selected contributions which examine the question of the existence and nature of assembly rules with some rigour and in some detail, using both theoretical and empirical approaches in a variety of systems. The result is a balanced treatment which encompasses a wide range of topics within ecology including competition and coexistence, conservation and biodiversity, niche theory, and biogeography. As such it provides much to interest a broad audience of ecologists, while also making an important contribution to the study of community ecology in particular.
It is over twenty years since Jared Diamond focused attention on the possible existence of assembly rules for communities. Since then there has been a proliferation of studies trying to promote, refute or test the idea that there are sets of constraints (rules) on community formation and maintenance (assembly). This timely volume brings together carefully selected contributions which examine the question of the existence and nature of assembly rules with some rigour and in some detail, using both theoretical and empirical approaches in a variety of systems. The result is a balanced treatment which encompasses a wide range of topics within ecology including competition and coexistence, conservation and biodiversity, niche theory, and biogeography. As such it provides much to interest a broad audience of ecologists, while also making an important contribution to the study of community ecology in particular.
It is over twenty years since Jared Diamond focused attention on the possible existence of assembly rules for communities. Since then there has been a proliferation of studies trying to promote, refute or test the idea that there are sets of constraints (rules) on community formation and maintenance (assembly). This timely volume brings together carefully selected contributions which examine the question of the existence and nature of assembly rules with some rigour and in some detail, using both theoretical and empirical approaches in a variety of systems. The result is a balanced treatment which encompasses a wide range of topics within ecology including competition and coexistence, conservation and biodiversity, niche theory, and biogeography. As such it provides much to interest a broad audience of ecologists, while also making an important contribution to the study of community ecology in particular.
It is over twenty years since Jared Diamond focused attention on the possible existence of assembly rules for communities. Since then there has been a proliferation of studies trying to promote, refute or test the idea that there are sets of constraints (rules) on community formation and maintenance (assembly). This timely volume brings together carefully selected contributions which examine the question of the existence and nature of assembly rules with some rigour and in some detail, using both theoretical and empirical approaches in a variety of systems. The result is a balanced treatment which encompasses a wide range of topics within ecology including competition and coexistence, conservation and biodiversity, niche theory, and biogeography. As such it provides much to interest a broad audience of ecologists, while also making an important contribution to the study of community ecology in particular.
This chapter addresses heterogeneity in the context of scale. Scale is emerging as one of the critical problems that must be adequately considered if different ecological studies are to be either compared in a corroboration or contrasted in a refutation. Some argument in the ecological literature is misdirected because the contentions are differently scaled and so are not competitive (e.g., Belsky, 1986, 1987 versus McNaughton, 1985,1986, as discussed in Brown and Allen, 1989). Disparately scaled ecological situations cannot be compared in any simple way, even if superficially it appears that it is the same community or site that is being addressed.
Crop rotation is thought to reduce weed density and maintain species diversity, thus preventing the domination of a few problem weeds. Because cropping sequence dictates other agricultural management practices, variations in weed populations between cropping systems may be the direct result of crop rotation, the result of different weed management practices associated with crop rotation, or both. Studies that fail to separate the effects of crop rotation from weed management may generate misleading results. A 10-yr crop rotation study was undertaken to study the dynamics of the standing weed vegetation in Zea mays L., Glycine max L., and Triticum aestivum L. The present paper compared total weed density and diversity between monocultures and rotations under three levels of weed management. Weed management accounted for 37.9% of the variation in total weed density, whereas crop rotation accounted for only 5.5%. Weed density varied between monocultures and rotations in plots where herbicides were applied. The effectiveness of rotations in reducing weed density was dependent upon the crop. Margalef's species richness index (D(MG)), a measure of diversity, varied among weed management strategies, with 38.4% of the variance attributed to this factor. In the 10th year, when all plots were sown with Z. mays, few cumulative effects of crop rotation were apparent, with two exceptions. In weedy and herbicide-treated plots, weed density was higher on plots cropped with Z. mays the previous year. Also, under these weed management treatments, including a cereal in the crop rotation reduced weed density. Crop rotation, when used in combination with herbicides, provides additional weed control and is therefore an effective tool in integrated weed management.
An ecological landscape consisting of discrete interconnected patches was constructed in the laboratory. Each patch in the landscape was a 1-litre aquatic microecosystem containing producers and consumers. Species invaded and spread throughout the landscape in a specific sequence following prescribed invasion pathways. Species distribution among landscape patches was heterogeneous and converged to one of several alternative states despite identical initial conditions. Differences in structure which developed among patches were the result of the assembly processes which occurred in each patch and among interconnected patches. Variance in species composition increased as a function of distance from the patches that served as entry points for invasions into the landscape. The development of organization at the landscape level results from the interplay between the assembly of individual patches and the constraints imposed on each patch by invasion among patches. Differences in invasion success and persistence led to the development of alternative community states. -from Authors
1. An ecological landscape consisting of discrete interconnected patches was constructed in the laboratory. Each patch in the landscape was a 1-litre aquatic microecosystem containing producers and consumers. 2. Species invaded and spread throughout the landscape in a specific sequence following prescribed invasion pathways. 3. Species distribution among landscape patches was heterogeneous and converged to one of several alternative states despite identical initial conditions. 4. Differences in structure which developed among patches were the result of the assembly processes which occurred in each patch and among interconnected patches. Variance in species composition increased as a function of distance from the patches that served as entry points for invasions into the landscape. 5. The development of organization at the landscape level results from the interplay between the assembly of individual patches and the constraints imposed on each patch by invasion among patches. 6. Differences in invasion success and persistence led to the development of alternative community states.
In 2 of 3 fields, similarity indices indicated that experimental plots having different resource supply rates diverged in species composition with time. There was some evidence of convergence both within and between fields on plots with similar resource supply rates, but divergence was also common, especially at high rates of nutrient supply. Much of the divergence indicated by similarity indices can be explained by plot-to-plot differences in the initial abundances of 3 dominant species: Agropyron repens, Poa pratensis and Schizachyrium scoparium. High N treatments favored A. repens if it was present, but led to major increases in P. pratensis or S. scoparium if A. repens was absent. Results suggest that plots will converge at high N levels. -from Authors
The ability to predict the composition of communities from environmental factors is a central goal of community ecology. We carefully selected a pool of species and subjected it to a range of environmental factors to determine which factors were able to filter out subsets of species. We began with a pool of 20 species and sowed them into 120 wetland microcosms representing 24 different habitat treatments and monitored them for 5 yr. The treatments were fertility, water depth, fluctuations in water depth, soil texture, leaf litter, length of the initial growing season, and invasion by Typha. After 5 yr 14 species persisted; no rare species survived. The experimental communities differed from random expectation and were assembled by rules that constrained their organization. There were strong and consistent effects of fertility, water level, and leaf litter on community composition. Community assembly was modeled as a series of environmental filters. Some aspects of assembly were deterministic: trajectories were constrained within two "pathway basins" and species rank abundances were significantly concordant within treatments. Other factors indicated that assembly has a strong stochastic component: 50% of species were present only occasionally and we cannot accurately predict species ranks. Community stochasticity did not show any clear patterns among treatments.
(1) The mechanisms by which communities of mangrove ants develop are examined. (2) Eighty-one small mangrove islands in the Florida Keys were surveyed for ant species. Islands varied four orders of magnitude in size. (3) Each of the five major species was found only on islands of a certain minimum size (MSR) or larger. (4) For two species, termed Primary species, experimental introductions showed that the MSR was due to island unsuitability. For two other species, termed Secondary species, the MSR was shown to be the result of competitive interactions with the Primary species. (5) Experiments involving the two Primary species showed that either was capable of preventing the invasion of the other species. Simultaneous introduction experiments showed that one species invariably invaded while the other invariably became extinct. (6) Behavioural interactions between all pairs of the species were tested in arena experiments. The patterns of aggression and avoidance were consistent with, and presumed to be the cause of, the experimental results and patterns of geographical distribution.
1. This paper describes the effectiveness of a range of bracken control and heathland restoration treatments (cutting, spraying with asulam, and seed sowing, in factorial combination) at a Calluna and a grass heath in Breckland over 10 years. 2. In the grass heath, 13 species were recorded during the 10 years, although in most plots two species were dominant: Festuca ovina which was sown, and Deschampsia flexuosa which colonized naturally. Festuca ovina rapidly colonized the seeded plots, but Deschampsia flexuosa appeared 5 years later. After 10 years D. flexuosa was co-dominant on many plots. 3. On the Calluna heath, 13 vascular and three bryophyte species were found. The sown species Calluna was found mainly on seeded plots, especially where the bracken was cut. Agrostis capillaris, Dicranum scoparium and Galium saxatile were most abundant on plots where the bracken was cut twice yearly. Other species appeared independent of treatment, reflecting low abundance, ubiquitous distributions, or clumped distributions. Two clonal species, Carex arenaria and Calamagrostis epigejos, invaded in large patches where cover of other heath species was negligible. 4. Most of the species colonizing the restored areas had higher Ellenberg nitrogen-indicator values than the dominant heathland species, indicating that soil fertility may be too high for successful heathland restoration. 5. The results are discussed in relation to practical conservation management and vegetation dynamics.
The floristically distinct shrub communities of the Mediterranean climatic regions of southern California and central Chile display similarities in vegetation structure. Similar trends in the representation of various features of growth-form and leaf morphology are found in the different parts of equivalent elevation-aspect mosaics in the two areas. Quantitatively-determined growth-form `types', comprised of groups of phenetically similar species, show strong similarities both in their composition and distributions through the two mosaics. It is argued that in Mediterranean climatic regions with hot, dry summers similar environmental selection results in similar structural-functional systems. Despite these similarities, there are also some noticeable discrepancies between the two communities. The matorral vegetation of Chile possesses a significantly greater diversity, both of species and growth forms, than does the chaparral vegetation-type in California. This distinction, along with the more open nature of the vegetation at the lower elevation sites in Chile, can be attributed to a much more intensive land-use history in the matorral. An analysis of the influence of phylogeny of the evolution of aspects of morphology in the shrubs shows that, if phylogenetic constraints do exist, they can very frequently be overcome by environmental selection. Multivariate analysis is used to show, in respect of the characters considered, that a species is often more similar phenetically to a taxonomically finrelated species than it is to the other members of the same family, or even genus.
Competition has been shown to be an important factor in natural systems. Yet, its effect on community structure remains poorly understood and is often disputed. Null models have been employed by researchers in recent years, but these generally suffer from a lack of power estimation and unclear distinction between statistical significance and biological importance. Models that employ an appropriate alternative hypothesis allow for powers estimates and for quantitative evaluation of the effects of competition. We have developed methodologies to (1) allow for testing the significance of competition in natural communities, (2) determine the power of these estimates, and (3) produce maximum likelihood estimates of interaction parameters or these communities. Using these methologies we show that small mammal communities at the interface between Valdivian temperate rain forest and Patagonian steppe in southern South America appear significantly and importantly structured by competition, although we cannot distinguish between resource competition, interference competition, and apparent competition. Secondarily, we show that the geographic origin of the component species (Valdivian vs. Patagonian) is relatively more important than their habitat affinities in structuring these communities.
Plant invasions are a serious threat to natural and managed ecosystems worldwide. The number of species involved and the extent of existing invasions renders the problem virtually intractable, and it is likely to worsen as more species are introduced to new habitats and more existing invaders move into a phase of rapid spread. We contend that current research and management approaches are inadequate to tackle the problem. The current focus is mostly on the characteristics and control of individual invading species. Much can be gained, however, by considering other important components of the invasion problem. Patterns of weed spread indicate that many species have a long lag phase following introduction before they spread explosively. Early detection and treatment of invasions before explosive spread occurs will prevent many future problems. Similarly, a focus on the invaded ecosystem and its management, rather than on the invader, is likely to be more effective. Identification of the causal factors enhancing ecosystem invasibility should lead to more-effective integrated control programs. An assessment of the value of particular sites and their degree of disturbance would allow the setting of management priorities for protection and control. Socioeconomic factors frequently play a larger part than ecological factors in plant invasions. Changes in human activities in terms of plant introduction and use, land use, and timing of control measures are all required before the plant invasion problem can be tackled adequately. Dealing with plant invasions is an urgent task that will require difficult decisions about land use and management priorities. These decisions have to be made if we want to conserve biodiversity worldwide.
This study attempts to identify Plant Functional Types (PFTs) within the scrub vegetation of the stabilized sand dunes of the Doñana National Park (southwestern Spain) and to explore possible links with ecosystem function. Two 10‐km long transects were sampled along a gradient of water table depth from elevated and dry dunes to a border area close to the salt marsh.
A matrix of cover values for 20 woody species × 58 plots and a matrix of 24 morphological and physiological traits × 20 species were analysed by means of DCA and TWINSPAN to identify the main vegetation types and PFTs. In order to know the predominant plant traits, the matrix of 20 species × 58 plots was multiplied by the 24 traits × 20 species matrix. The resulting 24 traits × 58 plots matrix was analysed by means of DCA.
The main vegetation types coincide with the previous descriptions of the Park with Juniperus phoenicea woodland and xerophytic species dominating the top of the dunes and hygrophytic species with isolated Quercus suber trees in the depressions. Previous classifications of Mediterranean woody plants resulted in two main PFTs. The present analysis confirmed these two groups: maquis versus garrigue , but added four new groups. The analysis of the traits × plots matrix revealed that the main trend of variation is related to the water table gradient, while the traits related to the species of mature plant communities had little weight in the analysis because these communities are restricted to isolated patches.
Abies grandis, Taxus brevifolia, Thuja plicata, or any combination of these may dominate old-growth mesic forests of the Bitterroot Canyons, western Montana. Similar sites need not develop similar, relatively stable forests. This is shown by (i) anomalous distributional patterns of tree species, (ii) broad overlap of tree species abundance in environmental space (shown by ordination and discriminant analysis of stands in environmental space), and (iii) weak or undetectable correspondence of species × stand and site factor × stand matrices (multiple regressions of compositional dissimilarity against environmental differences; also, canonical correlation and Mantel tests). Since a one-to-one mapping from site factors to species composition in old-growth vegetation is a fundamental tenet for applications of the climax concept, caution is warranted where the concept is to be applied within a narrow range of site factors or to insular communities.
Invasive indigenous (IN) or nonindigenous (NI) plant species can alter various properties of plant communities, including
species diversity, primary productivity, interactions between species, stability, and rates or pathways of successional recovery
of a community following disturbance (Ramakrishnan and Vitousek 1989; Versfeld and van Wilgen 1986; Vitousek 1990; Vitousek
and Walker 1989; Walker and Vitousek 1991). They can also alter the actual disturbance regime (Breytenbach 1986; Hughes et
al. 1991; Vitousek 1990). Studies of ecosystem processes are usually not focused on a particular organism but on the linkages
between organisms and their environment. Examination of the flow of energy, water, or nutrients through an ecosystem can provide
a sensitive measure of the degree to which invasive plants alter indigenous ecosystems. Successful management of communities
and ecosystems containing invasive species involves (1) assessing whether the invaders have significantly altered the ecosystem
from its preinvasion condition, (2) recognizing and measuring specific community and ecosystem properties potentially being
altered by the invader, and (3) developing strategies that return communities and the associated ecosystem processes to the
preinvasion state (if such is deemed desirable by management goals).
In this study, plant functional types are understood as groups of plants with similar biological traits displaying significant optima or maxima on a gradient plane of resource supply and disturbance intensity. The biological traits refer to expansion, vegetative regeneration, generative reproduction, dispersal and seed bank longevity.129 vegetation samples were taken in an agricultural landscape in southwestern Germany, covering a wide range of terrestrial vegetation types – but with the exception of forests and wetlands. For each site, also soil data were recorded. Mean daily soil moisture was estimated with a simple model. Soil moisture, balanced nitrogen supply and available phosphorus were combined into a factor ‘resource supply’. In addition, disturbance intensity was estimated for each site. This factor was based on (1) frequency of disturbance, (2) disturbance depth below or above the soil surface, and (3) proportion of the area affected by a discrete disturbance event. 30 plant groups with similar biological characteristics resulted from a cluster analysis, based on a compilation of 19 biological traits for a regional species pool. Logistic regression on a gradient plane of disturbance intensity and resource supply yielded response curves for 28 groups. The dependent variable was defined as the probability of encountering all members of a group in a sample. 17 groups display a significant response curve on the gradient plane. Plants with a potential for long‐ range dispersal are concentrated on sites with low or high disturbance intensities (e.g. fallow land, fields, lawns). On sites with medium disturbance intensity (e.g. meadows) and low to medium resource supply, small‐range dispersal predominates. There are no distinct trends concerning seed bank longevity. The potential for vertical and lateral expansion increases with decreasing disturbance intensity. Only at medium disturbance intensities does vertical expansion correlate positively with resource supply. Rapid detachment of daughter individuals occurs more often on productive sites than on less productive sites. Diversity of groups with similar biological traits is highest on sites with medium disturbance intensities.
A common goal in functional type research is to find a useful classification that defines the dynamic behaviour of groups of species in relation to environmental variation. Long‐term data sets on the dynamics of forests are difficult to obtain; thus, it would be useful if more readily available data, such as that on morphological and life history characters, could be used to derive groups that reflect the dynamics of the species. We used a 30‐yr data set on the dynamics of subtropical rainforests in Australia to derive classification based on the dynamics of the species and compared this classification with groups of species derived by other approaches. Functional types were derived for ca. 80 tree species using subjective, deductive and data‐driven approaches. The subjective classification used was a pioneer to late successional grouping. The deductive classification was an extension of the vital attribute approach.
Two data sets were used for the data‐based classifications, one based on morphological, life history and phenological characters (morphological data) readily available from taxonomic descriptions and another based on long‐term observations on the establishment, growth and death of all individuals on permanent plots (dynamic data).
SAHN (Sequential, Agglomerative, Hierarchical and Nested) clustering techniques were used for the numerical classifications. There was some similarity between the classification based on dynamic characters and the subjective and deductive classifications. The classification based on the readily available morphological characters showed less similarity with other classifications. However, the morphological data could be used to predict group membership in the dynamic classification using discriminant analysis with 87% accuracy. Thus, it appears that surrogate classifications might be found to describe the dynamics of the subtropical rainforest site. Further exploration and testing at other sites is required, especially to link the functional classification to specific perturbations.
Previous work on trait correlation patterns has contributed to the identification of broad patterns of plant distribution along environmental gradients in vegetation. However, these general trends may conceal subtle mechanisms of response that are specific to particular types of disturbance. To address this, we propose a generic methodology for the analysis of traits, using herb‐dominated vegetation as a model.
Hypothetical biological traits are identified for testing against disturbance gradients. The traits were selected for their perceived relevance to disturbance response generally, but also include a specific focus on domestic livestock grazing. The analysis is structured hierarchically to enable attributes to be analysed within major life forms. A different selection of traits is identified as being relevant to each major life form.
Flexible adaptation in the use of the trait set is suggested as a way of comparing functional response to disturbance over a series of locations. For example, assemblages will vary in their representation of the major life forms, and it may be relevant to analyse traits within a subset of these life‐form groups. Because individual studies encompass a limited range of environmental variation, and local floras may be constrained by their evolutionary context, similar approaches need to be tested over a range of vegetation types and geographic situations. A significant advance in functional trait analysis could be achieved if individual studies provide explicit descriptions of their evolutionary and ecological context from a global perspective.