Plant Trait Composition Research Articles

Environmental conditions differently shape leaf, seed and seedling trait composition between and within elevations of tropical montane forests

The composition of plant functional traits varies in response to environmental conditions due to processes of community assembly and species sorting. However, there is a lack of understanding of how plant trait composition responds to environmental conditions at different spatial scales and across the plant life cycle. We investigated the trait composition of leaves (specific leaf area), seeds (seed mass) and seedlings (initial seedling height) across elevations and within elevations in relation to soil and light conditions in a tropical montane forest in southern Ecuador. We surveyed traits and communities of adult trees, seeds and seedlings on nine plots at three elevations (1000–3000 m a.s.l.) and calculated community‐weighted mean trait values to analyse trait variation across and within elevations. In addition, we measured two environmental factors (soil C/N ratio and canopy openness) to quantify local‐scale variation in environmental conditions within elevations. We found that community‐weighted means of specific leaf area, seed mass and initial seedling height decreased consistently with increasing elevation. Within elevations, mean trait values of trees, seeds and seedlings responded differently to local‐scale environmental conditions. Specific leaf area decreased with increasing soil C/N ratio, and initial seedling height decreased with increasing canopy openness. Seed mass was associated neither with soil nor with light conditions. Our findings show that broad‐scale and local‐scale processes differently shape the composition of leaf, seed and seedling traits in tropical forests, indicating a scale‐dependence in trait–environment associations. Furthermore, plant traits corresponding to different life stages were related differently to environmental conditions within elevations. Community assembly processes may therefore lead to differences in species sorting at early and late plant life stages.

Relationships between Environmental Factors and Functional Traits of Macrophyte Assemblages in Running Waters of Greece

The analysis of plant trait composition has raised significant interest among freshwater ecologists as a complementary approach for assessing the effects of environmental change on ecosystem functions. In this study, we investigated patterns of functional traits of the aquatic macrophyte assemblages of 74 lotic ecosystems of Greece, and we identified associations between species traits and environmental variables (hydromorphological and physicochemical parameters) through testing the hypothesis that the environmental features determine the spatial structure of traits. We allocated 12 traits to a total of 39 hydrophyte species, and we conducted RLQ and fourth corner analysis to explore relationships between species, trait composition, and environmental gradients. Based on the results of the RLQ, a hierarchical cluster analysis was conducted to identify groups of plants that share common trait characteristics. Plants were discriminated into five discrete groups based mostly on their life form (e.g., free-floating, rooted submerged etc.) and their ecological preference for nitrogen levels. Hydromorphological parameters had a higher contribution than physicochemical variables in explaining the total variance of the trait data, with water abstraction, channel substrate, and hydrologic alteration being the most important. Our analysis did not reveal significant bivariate relationships between single traits and environmental parameters, although the five groups of macrophyte assemblages appeared to associate with certain environmental gradients. Free-floating and emergent plants were related to higher concentrations of nutrients, whereas rooted submerged plants were related to higher oxygen concentration and increased pH. In addition, free-floating plants were highly associated with metrics of hydromorphological change. Our findings showed clear discrimination of macrophytes based on their functional composition and association of traits with environmental gradients. Thus, further research could explore whether macrophyte functional groups can serve as indicators of environmental change and the overall ecosystem health.

The Functional Structure of Tropical Plant Communities and Soil Properties Enhance Ecosystem Functioning and Multifunctionality in Different Ecosystems in Ghana

Plant functional traits are useful in tracking changes in the environment, and play an important role in determining ecosystem functioning. The relationship between plant functional traits and ecosystem functioning remains unclear, although there is growing evidence on this relationship. In this study, we tested whether the functional structure of vegetation has significant effects on the provision of ecosystem services. We analysed plant trait composition (specific leaf area, leaf carbon and nitrogen ratio, isotopic carbon fraction, stem dry matter content, seed mass and plant height), soil parameters (nutrients, pH, bulk density) and proxies of ecosystem services (carbon stock, decomposition rate, invertebrate activity) in twenty-four plots in three tropical ecosystems (active restored and natural forests and an agroforestry system) in Ghana. For each plot, we measured above-ground biomass, decomposition rates of leaves and invertebrate activity as proxies for the provision of ecosystem services to evaluate (i) whether there were differences in functional composition and soil properties and their magnitude between ecosystem types. We further aimed to (ii) determine whether the functional structure and/or soil parameters drove ecosystem functions and multifunctionality in the three ecosystem types. For functional composition, both the leaf economic spectrum and seed mass dimension clearly separated the ecosystem types. The natural forest was more dominated by acquisitive plants than the other two ecosystem types, while the non-natural forests (agroforest and restored forest) showed higher variation in the functional space. The natural forest had higher values of soil properties than the restored forest and the agroforestry system, with the differences between the restored and agroforestry systems driven by bulk density. Levels of ecosystem service proxies and multifunctionality were positively related to the functional richness of forest plots and were mainly explained by the differences in site conditions. Our study demonstrated the effects of functional forest structure on ecosystem services in different forest ecosystems located in the semi-deciduous forest zone of Ghana.

Functional traits of alpine plant communities show long‐term resistance to changing herbivore densities

AbstractHerbivores shape vegetation by suppressing certain plant species while benefitting others. By thus modifying plant species functional composition, herbivores affect carbon cycling, albedo, vegetation structure and species' interactions. These effects have been suggested to be able to counteract the effects of increasing temperatures on vegetation in alpine environments. Managing the dominant large ungulates in these ecosystems could thus provide a tool to mitigate climate change effects. However, it is possible that legacy effects of past grazing will dampen ungulate impacts on vegetation. We shed a light on this topic by investigating the short‐ and long‐term effects of varying sheep densities on the plant trait composition in the Norwegian alpine tundra with centuries‐long of intensive grazing history. In the first part of our study, we quantified the effects of sheep on the plant community functional trait composition at different elevations and under moderate and low productivity in. We combined data from two long‐term (14 and 19 yr) sheep fence experiments and showed that differences in sheep densities did not affect plant trait composition, irrespective of productivity. However, in the second part of our study, we showed that the plant trait composition in mainland (that has been grazed for centuries) differed from vegetation on islands which have been herbivore‐free. Taken together, these results suggest that sheep have an effect on the alpine plant communities on historical time scales covering centuries, but that the resulting sheep grazing resistant/tolerant communities may not respond to shorter‐term (14 and 19 yr) changes in sheep densities, that is, at temporal scales relevant for ecosystem management. Furthermore, we showed that the plant trait composition at the site with low productivity had gone through a temporal trait change independent of sheep treatment, potentially due to increased temperatures and precipitation, suggesting that sheep may not be able to counteract climatic impacts in the areas with centuries‐long grazing history.

Impact of long‐term water level drawdown on functional plant trait composition of northern peatlands

Abstract Understanding how plant communities respond to increased evaporation and consequent water level drawdown (WLD) is critical for predicting the functioning of northern peatlands under climate change. Functional traits provide a quantitative link between vegetation and ecosystem functions and, therefore, constitute a useful concept for predicting responses to climate change. We studied the impact of long‐term experimental WLD on vascular plant and moss traits at a rich fen, poor fen and bog. Vegetation change was followed over a 15‐year period. In the final study year, the traits of the most common plant species were measured from control and WLD areas at each peatland type. We found equally high interspecific trait variation for Sphagnum mosses and vascular plants while the intraspecific variation was greater in the mosses. Community‐weighted mean (CWM) traits varied between sites; WLD had the strongest impact on those traits that the dominant plant group originally had high values for, and in most cases, WLD further increased these values. In the vascular‐plant‐dominated rich fen, WLD led to taller plants with a greater specific leaf area, features that under the prevailing water table were also greatest at that site. In the bog, characterized by dense Sphagnum moss stands with small individuals, WLD further enhanced these properties that increase the ability of a moss stand to remain moist under drier conditions. The poor fen was transitional between the two extremes, both in its vegetation composition and in its trait responses. Structural equation models (SEM) showed that WLD in the fens, indirectly via other traits, increased photosynthetic capacity while the impact in the bog site was the opposite. In the poor fen and bog, WLD directly increased vascular plant respiration while the increase in the rich fen was through other traits. WLD directly increased and decreased Sphagnum respiration in the poor fen and bog, respectively. Overall, the traits of the vascular plant and Sphagnum communities in the bog were more dependent on each other than they were in the fens. Based on these findings, it is evident that fens and bogs respond differently to WLD. This should be considered when predicting the effects of climate change on peatland carbon cycling. A free Plain Language Summary can be found within the Supporting Information of this article.

Leaf traits and phylogeny explain plant survival and community dynamics in response to extreme drought in a restored coastal grassland

Abstract Climate change will increase uncertainty in restoration outcomes due to greater water stress and other abiotic filters that limit plant survival. Drought‐related plant functional traits can help species withstand filters in a semi‐arid environment. Our objective was to provide guidance for selecting species to improve restoration success in a changing climate. We planted 12 native species in ambient rainfall and under 60% rain‐out shelters in an invaded coastal grassland in central California. We measured survival and size annually for 4 years and quantified plant community and trait composition in the third and fourth years. We measured growth rate, specific leaf area (SLA), leaf C:N, leaf lobedness and leaf δ13C of all planted species and dominant extant species, and evaluated the effect of treatments, traits and phylogenetics on mortality risk using Cox proportional hazards. Native perennial species cover was greater, whereas thatch depth and per cent cover of shrubs and non‐native annual grasses were lower, on drought plots. Drought plots had lower community‐weighted leaf C:N and higher leaf lobedness. Planted species with resource conservative traits, such as higher leaf lobedness and lower growth rate, had lower mortality risk. Increased plasticity of morphological traits (SLA and lobedness) was associated with decreased mortality risk, whereas increased plasticity of physiological traits (leaf C:N and δ13C) and risk was positively correlated. Trait plasticity explained a greater degree of plant mortality risk compared to absolute trait values. Plants that were more phylogenetically related to the surrounding plant community had lower mortality risk. Traits of planted species that were important for determining plant mortality in this coastal grassland may be conserved, which was supported by a phylogenetic signal (Blomberg's K = 0.380, Pagel's λ = 0.830) in leaf C:N. Synthesis and applications. Our results suggest that leaf traits and phylogenetics could serve as plant selection criteria for reducing plant mortality risk during drought, thereby improving restoration outcomes. Because some traits have a phylogenetic signal that explains drought survival, restoration practitioners could expand the use of trait‐based selection for closely related species when restoring other arid‐ and semi‐arid ecosystems. ​

Modern pollen rain predicts shifts in plant trait composition but not plant diversity along the Andes–Amazon elevational gradient

AbstractAimsTerrestrial ecosystems are changing in biodiversity, species composition and functional trait composition. To understand the underlying causes of these changes and predict the long‐term resilience of the ecosystem to withstand future disturbances, we can evaluate changes in diversity and composition from fossil pollen records. Although diversity can be well estimated from pollen in temperate ecosystems, this is less clear for the hyperdiverse tropics. Moreover, it remains unknown whether functional composition of plant assemblages can be accurately predicted from pollen assemblage composition. Here, we evaluate how community‐weighted mean (CWM) traits and diversity indices change along elevation.LocationAmazon–Andes elevation gradient in Peru.MethodsWe used 82 modern pollen samples and 59 vegetation plots along the elevation gradient, and calculated CWM traits and diversity indices for each pollen sample and vegetation plot. We also quantified the degree to which taxa are over‐ or underrepresented by their pollen, by dividing the relative pollen abundance by the relative basal area abundance in the nearby vegetation survey plots (i.e. the R‐rel values).ResultsWe found that CWM wood density increased, and CWM adult height and leaf area decreased with elevation. This change was well predicted by pollen assemblages, indicating that CWM trait–environment relationships based on pollen abundance data provide meaningful results. Diversity (richness, Shannon and Simpson) decreased with elevation for vegetation plots, but these trends could not be observed from pollen assemblages.ConclusionsOur results demonstrate that more research is needed to develop methods that lead to accurate diversity estimates from pollen data in these tropical ecosystems, but that CWM traits can be calculated from pollen data to assess spatial shifts in functional composition. This opens opportunities to calculate CWM traits from fossil pollen data sets in the tropics, with broad implications for improving our understanding and predictions of forest dynamics, functioning and resilience through time.

Few large trees, rather than plant diversity and composition, drive the above-ground biomass stock and dynamics of temperate forests in northeast China

Large trees, as the versatile provider of ecosystem services, are the most susceptible to episodic disturbance regimes such as extreme climate and biotic agents across the globe, and hence, largely determine forest demographic processes. Despite the recognized fundamental ecological significance of large-diameter trees to above-ground biomass (AGB) stock, relatively little is known about their distinctive role, interplaying with abiotic and biotic drivers, in shaping forest AGB dynamics (i.e., gain and loss) at regional or larger extents. Here, we hypothesized that the AGB of few large trees drives AGB stock and dynamics (gain and loss) better than species diversity and trait composition in temperate forests along topography and soil gradients. We analyzed two repeated forest inventories data from 700 plots (including 74,300 adult trees) across 15 plots in temperate forests of northeastern China, including old-growth and disturbed forests. A steady net AGB change increase was found for 13 of the 15 plots. Despite disturbed forests were recovering from post-logging disturbance with a lower density of large-diameter trees and AGB stock than old-growth plots, disturbed forests had higher AGB gain, net AGB change and lower AGB loss than old-growth forests. The largest trees (i.e. top 1% AGB or diameter) were consistently more important for explaining AGB stock, gain and loss compared to plant diversity and trait composition. Besides, the elevation-related topographic factors were more direct determinants of forest AGB accumulation than soil nutrients, and also exerted the indirect impacts via increasing the dominance of resource-conservative trees, stand structural diversity and top 1% large trees. Overall, we highlight the key overruling effect of top 1% large trees on AGB stock and dynamics in response to local environmental factors. This study could improve our understanding of the multiple ecological mechanisms underlying the global change drivers of forest AGB stock and dynamics.

Voles mediate functional trait diversity along a resource gradient

Abstract Disentangling the effect of multiple ecological processes on plant trait composition is complicated by the fact that both top‐down and bottom‐up processes may affect similar traits. We examined the interacting role of resource variation and vole herbivory on functional trait patterns in an annual California grassland. We manipulated vole herbivory via exclosures at eight grassland sites along a steep resource gradient and measured plant composition and functional traits over 3 years. Plants with resource acquisitive functional traits were favoured at sites with increasing resources. Vole herbivory influenced community‐weighted mean (CWM) leaf nitrogen (N) and seed mass, suggesting these traits may mediate plant susceptibility to vole herbivory. After 3 years, CWM leaf N increased in the absence of the voles, as did CWM seed mass, although this increase in CWM seed mass only occurred at higher resource sites. Vole exclusion at high‐resources sites also increased the functional diversity of leaf N and seed mass by the end of the experiment. Overall, environmental filtering primarily structured the dominant plant trait strategies, but vole herbivory also influenced the functional diversity of traits that influence herbivore susceptibility, particularly at resource‐rich sites. Thus, habitat filtering and herbivory can operate on different dimensions of plant functional composition to influence the species and functional composition of communities. A free Plain Language Summary can be found within the Supporting Information of this article.

Resource-enhancing global changes drive a whole-ecosystem shift to faster cycling but decrease diversity.

Many global changes take the form of resource enhancements that have potential to transform multiple aspects of ecosystems from slower to faster cycling, including a suite of both above- and belowground variables. We developed a novel analytic approach to measure integrated ecosystem responses to resource-enhancing global changes, and how such whole ecosystem slow-to-fast transitions are linked to diversity and exotic invasions in real-world ecosystems. We asked how 5-yr experimental rainfall and nutrient enhancements in a natural grassland system affected 16 ecosystem functions, pools, and stoichiometry variables considered to indicate slow vs. fast cycling. We combined these metrics into a novel index we termed "slow-fast multifunctionality" and assessed its relationship to plant community diversity and exotic plant dominance. Nutrient and rainfall addition interacted to affect average slow-fast multifunctionality. Nutrient addition alone pushed the system toward faster cycling, but this effect weakened with the joint addition of rainfall and nutrients. Variables associated with soil nutrient pools and cycling most strongly contributed to this antagonistic interaction. Nutrient and water addition together, respectively, had additive or synergistic effects on plant trait composition and productivity, demonstrating divergence of above- and belowground ecosystem responses. Our novel metric of faster cycling was strongly associated with decreased plant species richness and increased exotic species dominance. These results demonstrate the breadth of interacting community and ecosystem changes that ensue when resource limitation is relaxed.

Above‐ and below‐ground biodiversity jointly regulate temperate forest multifunctionality along a local‐scale environmental gradient

Abstract Tree diversity has been shown to promote a broad range of ecosystem functions in forests. However, how important these effects are in driving ecosystem multifunctionality in natural forests, relative to other drivers, such as below‐ground biodiversity (e.g. soil microbial diversity), community‐level functional traits and environmental conditions, remains poorly understood. Here, we hypothesize that tree species or phylogenetic diversity (PD), stand structure, functional traits and soil microbial diversity jointly regulate temperate forest multifunctionality (FM) along a local‐scale environmental gradient. Using repeated census data from a 25‐ha old‐growth temperate forest, we first quantified eight ecosystem functions and properties related to above‐ and below‐ground nutrient cycling. We then used these to estimate ecosystem multifunctionality using both averaging and multiple threshold (50%, 75% and 95%) approaches. Finally, we used structural equation models to explore how different facets of tree (tree species, functional and PD) and soil (bacteria, fungi and nematode diversity) biodiversity influence ecosystem multifunctionality, as well as how these relationships are modulated by stand structural attributes and environmental conditions (topography and soil nutrients). Forest multifunctionality was positively related to stand structural complexity but negatively related to acquisitive traits (i.e. community‐weighted mean of specific leaf area). Plant PD had no significant direct effect on FM, but it had a significant indirect effect via increased stand structural complexity. The effect of soil microbial diversity on FM increased with increasing threshold levels of FM and outperformed tree diversity and environmental conditions at the highest threshold level (i.e. 95%). Forests on steep slopes had lower levels of ecosystem multifunctionality due to decreased stand structural complexity. Soil nutrients were responsible for regulating FM via plant trait composition and, to a lesser extent, via tree diversity, stand structure and soil microbial diversity. Synthesis. Plant PD, stand structure and soil microbial diversity jointly regulated FM, and these effects were influenced by local‐scale changes in environmental conditions. Soil microbial diversity was a key driver of highly multifunctional forests, whereas conservation of complex stand structure and conservative trait dominance could enhance mean values of multiple functions.

Succession of a broad-leaved Korean pine mixed forest: Functional plant trait composition

Abstracts A longstanding goal of ecology and conservation biology is to understand the climatic and biological controls of forest succession. However, the patterns and mechanisms that guide forest succession, especially within broad-leaved forests, remain unclear. We collected leaf traits and abiotic data across a 200-year chronosequence within a broad-leaved Korean pine forest in northeastern China. We focused on five key leaf traits related to resource acquisition and competition by quantifying the community-weighted trait distributions for specific leaf area (SLA), leaf dry matter concentration (LDMC), leaf nitrogen content (Nmass (g/kg)), leaf phosphorus content (Pmass (g/kg)) and the ratio of nitrogen content to phosphorus content (Nmass/Pmass). We also studied how these traits respond to changing environmental variables (climatic, soil and topographical) during succession. Redundancy analysis was used to examine the importance of the environmental variables in shaping the successional variation in plant traits. Our results revealed the following. Older forests differed significantly from younger forests in species composition and trait distribution. For example, SLA, leaf N and P content and the N/P ratio tended to increase and then decrease throughout the community during forest succession (p

Uncovering traits in recovering grasslands: A functional assessment of oil and gas well pad reclamation

Oil and gas exploration has disturbed extensive areas of grassland in North America. Reclamation of this human footprint is only a first step towards ecological recovery. A trait-based approach may provide a mechanistic understanding of biological and edaphic filters influencing longer-term plant community assembly on reclaimed sites. Using taxonomic indices, trait community weighted means (CWM), and functional diversity (FDQ) combined with multivariate models, we compared biological and edaphic properties of 18 reclaimed well pads in Alberta (Canada), to proximate native grasslands. These well pads were certified reclaimed under two reclamation criteria (old, new). Consistent with practices in other regions, newer criteria emphasize using native plant species in place of historically-used introduced agronomic species. We found significant differences between reclaimed and undisturbed reference soil properties (e.g., pH, electrical conductivity), with greater differences on sites reclaimed using the older criteria (e.g., lower TOC, higher bulk density). Plant trait composition also differed between reclaimed and undisturbed sites, with a lower prevalence of short, native, xeric species, with semi-abundant seed production and large seed weight on reclaimed sites. We found a strong trait-environment relationship underlying trait composition difference. While not significantly different in overall trait composition from new sites, old sites included higher prevalence of introduced species, dispersed by animals, preferring mesic conditions, and high seed production. The increased cover of introduced species reduced trait FDQ and led to an arrested succession. New sites included higher prevalence of tall, native species preferring hydric conditions, therophytes, geophytes, and species with low dispersal capacity. The use of native seed with higher FDQ on new sites seemed to alleviate arrested succession; However, biological trait filters (e.g., tall, hydric preference) and altered edaphic properties, might continue to drive differences between reclaimed and reference sites. Our results suggest that even as practices and policies evolve, reclamation does not fully alleviate the legacy effects of this industrial disturbance. We have demonstrated how trait-based approaches can inform recovery assessment and future reclamation best practices. We must go beyond simply seeding with native species for recovery of plant communities – the traits of these native species matter too.

The importance of physiological, structural and trait responses to drought stress in driving spatial and temporal variation in GPP across Amazon forests

Abstract. The capacity of Amazon forests to sequester carbon is threatened by climate-change-induced shifts in precipitation patterns. However, the relative importance of plant physiology, ecosystem structure and trait composition responses in determining variation in gross primary productivity (GPP) remain largely unquantified and vary among models. We evaluate the relative importance of key climate constraints to GPP, comparing direct plant physiological responses to water availability and indirect structural and trait responses (via changes to leaf area index (LAI), roots and photosynthetic capacity). To separate these factors we combined the soil–plant–atmosphere model with forcing and observational data from seven intensively studied forest plots along an Amazon drought stress gradient. We also used machine learning to evaluate the relative importance of individual climate factors across sites. Our model experiments showed that variation in LAI was the principal driver of differences in GPP across the gradient, accounting for 33 % of observed variation. Differences in photosynthetic capacity (Vcmax and Jmax) accounted for 21 % of variance, and climate (which included physiological responses) accounted for 16 %. Sensitivity to differences in climate was highest where a shallow rooting depth was coupled with a high LAI. On sub-annual timescales, the relative importance of LAI in driving GPP increased with drought stress (R2=0.72), coincident with the decreased importance of solar radiation (R2=0.90). Given the role of LAI in driving GPP across Amazon forests, improved mapping of canopy dynamics is critical, opportunities for which are offered by new satellite-based remote sensing missions such as GEDI, Sentinel and FLEX.

Temporal stability of aboveground biomass is governed by species asynchrony in temperate forests.

Understanding the effects of plant species diversity and trait composition on aboveground biomass is a central focus of ecology and has important implications for biodiversity conservation. However, the simultaneous direct and indirect effects of soil nutrients, species asynchrony, functional trait diversity, and trait composition for explaining the community temporal stability of aboveground biomass remain underrepresented in natural forests. Here, we hypothesized that species asynchrony relative to soil nutrients, functional trait diversity, and trait composition plays a central role in stabilizing the community temporal stability of natural forests. We tested this hypothesis using a structural equation model based on 10-year continuous monitoring data (i.e., three-time repeated forest inventories) in both second-growth and old-growth temperate forests in northeast China. Our results showed that the community temporal stability of aboveground biomass was driven by a strong direct positive effect of species asynchrony in both second-growth and old-growth temperate forests, whereas functional trait diversity and composition (i.e. community-weighted mean of leaf nitrogen content) were of additional importance in an old-growth forest only. Functional trait diversity decreased community-weighted mean of leaf nitrogen content in an old-growth forest, whereas this relationship was non-significant in a second-growth forest. Soil nutrients had non-significant effects on the community temporal stability of both second-growth and old-growth forests. Species asynchrony was the direct determinant of the community temporal stability of aboveground biomass in temperate forests. The direct effect of species asynchrony increased with forest succession, implying that temporal niche differentiation and facilitation increase over time. This study suggests that managing forests with mixtures of both early and late successional species or shade intolerant and tolerant species, not only species diversity, is important for maintaining forest stability in a changing environment. We argue that the species asynchrony effect is crucial to understand the underlying ecological mechanisms for a diversity-biomass relationship in natural forests.

Effects of livestock grazing on soil, plant functional diversity, and ecological traits vary between regions with different climates in northeastern Iran.

Understanding the responses of vegetation characteristics and soil properties to grazing in different precipitation regimes is useful for the management of rangelands, especially in the arid regions. In northeastern Iran, we studied the responses of vegetation to livestock grazing in three regions with different climates: arid, semiarid, and subhumid. In each region, we selected 6–7 pairwise sampling areas of high versus low grazing intensity and six traits of the present species were recorded on 1 m2 plots—five grazed and five ungrazed in each area. The overall fertility was compared using the dissimilarity analysis, and linear mixed‐effect models were used to compare the individual fertility parameters, functional diversity indices, and species traits between the plots with high and low grazing intensity and between the climatic regions. Both climate and grazing, as well as their interaction, affected fertility parameters, functional diversity indices, and the representation of species traits. Grazing reduced functional evenness, height of the community, the representation of annuals, but increased the community leaf area. In the subhumid region, grazing also reduced functional richness. Further, grazing decreased the share of annual species in the semiarid region and seed mass in the arid region. Larger leaf area and seed mass, smaller height and lower share of annuals were associated with intensive grazing. Species with large LA and seed mass, lower height and perennials can be therefore presumed to tolerate trampling and benefit from high nutrient levels, associated with intensive grazing. By providing a detailed view on the impacts of overgrazing, this study highlights the importance of protection from grazing as an effective management tool for maintaining the pastoral ecosystems. In general, the composition of plant traits across the pastures of northeastern Iran was more affected by intensive grazing than by the differences in climate.

Linkages between Macrophyte Functional Traits and Water Quality: Insights from a Study in Freshwater Lakes of Greece

Freshwater ecologists have shown increased interest in assessing biotic responses to environmental change using functional community characteristics. With this article, we investigate the potential of using functional traits of the aquatic plants to assess eutrophication in freshwater lakes. To this end we collected macrophyte and physicochemical data from thirteen lakes in Greece and we applied a trait-based analysis to first identify discrete groups of macrophytes that share common functional traits and then to assess preliminary responses of these groups to water quality gradients. We allocated 11 traits that cover mostly growth form and morphological characteristics to a total of 33 macrophyte species. RLQ and fourth corner analysis were employed to explore potential relationships between species, trait composition and environmental gradients. In addition, a hierarchical cluster analysis was conducted to discriminate groups of plants that share common trait characteristics and then the position of the groups along the environmental gradients was assessed. The results showed total phosphorus, chlorophyll-a, conductivity, pH and Secchi disk depth as main drivers of the environmental gradients. Hierarchical cluster analysis showed a clear separation of macrophyte assemblages with discrete functional characteristics that appeared to associate with different environmental drivers. Thus, rooted submerged plants were related with higher Secchi disk depth, conductivity and alkalinity whereas rooted floating-leaved plants showed a preference for enriched waters with phosphorus and nitrogen. In addition, free-floating plants were related positively with nitrogen and increased pH. Although we did not identify specific trait patterns with environmental drivers, our findings indicate a differentiation of macrophytes based on their functional characteristics along water quality gradients. Overall, the presented results are encouraging for conducting future monitoring studies in lakes focused on the functional plant trait composition, as expanding the current approach to additional lakes and using quantifiable functional characteristics will provide more insight about the potential of trait-based approaches as ecological assessment systems.

Land-use history influence the vegetation in coniferous production forests in southern Sweden

During the last centuries, land use in Europe intensified, which has led to a drastic decrease in the cover of semi-natural grasslands. In Sweden, much of the lost grasslands was turned into forest. This study investigated if species typical of managed grasslands could be found in coniferous production forests more than 80 years after grassland management ceased. Species and trait composition for plants was investigated in two types of forest differing in land use history (meadow in the 1870s or continuous coniferous forest), and in reference grasslands. The average plant species richness as well as the richness of grassland indicator species were 30% higher in forests with a history as meadow compared to in forests with a history as forest, hence clear signs of historical grassland management in today’s forests. Compared with forests with continuous coniferous history, vegetation in forests with a meadow history tended to be more similar to reference grassland regarding both plant species and especially plant trait composition. The study provides proof of remnant grassland populations in coniferous production as the source for the biodiversity of clearcuts, rather than seed dispersal or seed bank survival. The result highlights the importance of land use for biodiversity of clearcuts, and points to the potential value of forests with a history of meadow in grassland conservation and restoration.

Factors of variation in beech forest understory communities on waste heaps left by historical Zn-Pb ore mining

The species trait-environment relationships in understory vegetation were carried out on metalliferous sites created by historical Zn–Pb mining (S Poland), on which natural revegetation took place. The study sites were 31 small heaps of waste rock covered by an 80–120 year old beech forest. The sites were described in terms of plant coverage, species richness and composition, and the composition of plant traits. Three types of understory communities that were identified were compared for environmental variables and plant parameters. Despite a high concentration of heavy metals in soils, namely Cd, Pb, and Zn, the degree of shading by the tree canopy was the main factor determining variation in understory communities. The understories that developed in low and strong shading were similar to some extent: They had high number of species, and they were characterized by a high proportion of the ancient forest species. The species composition changed substantially with increasing coverage of trees; mixed strategy plants withdrew, while the stress tolerant species became more abundant. The other predictor of community structure was the ratio of Cd to Ca, which was responsible for the decrease of woody plants and the endangered species. This study proved that, in the case of highly complex and productive ecosystems, even with a high degree of contamination with heavy metals, the biotic factors play a primary role.

The invasion of abandoned fields by a major alien tree filters understory plant traits in novel forest ecosystems

The abandonment of agricultural use is a common driver of spontaneous reforestation by alien trees. The N-fixing black locust (Robinia pseudoacacia L.) is a major alien invader of old fields in Europe. Here we show that canopy dominance by this tree may filter the frequency distribution of plant functional traits in the understory of secondary woodlands. Higher soil C/N ratio and available P are associated with black locust stands, while higher soil phenols associate with native tree stands. These environmental effects result in differences in understory flowering periods, reproduction types and life forms. Our findings emphasize the effect of a major alien tree on functional plant trait composition in the early stages of spontaneous reforestation of abandoned lands, implying the development of a novel forest ecosystem on a large geographical scale.