Plant Trait Composition Research Articles

Integrating trait-based empirical and modeling research to improve ecological restoration.

A global ecological restoration agenda has led to ambitious programs in environmental policy to mitigate declines in biodiversity and ecosystem services. Current restoration programs can incompletely return desired ecosystem service levels, while resilience of restored ecosystems to future threats is unknown. It is therefore essential to advance understanding and better utilize knowledge from ecological literature in restoration approaches. We identified an incomplete linkage between global change ecology, ecosystem function research, and restoration ecology. This gap impedes a full understanding of the interactive effects of changing environmental factors on the long‐term provision of ecosystem functions and a quantification of trade‐offs and synergies among multiple services. Approaches that account for the effects of multiple changing factors on the composition of plant traits and their direct and indirect impact on the provision of ecosystem functions and services can close this gap. However, studies on this multilayered relationship are currently missing. We therefore propose an integrated restoration agenda complementing trait‐based empirical studies with simulation modeling. We introduce an ongoing case study to demonstrate how this framework could allow systematic assessment of the impacts of interacting environmental factors on long‐term service provisioning. Our proposed agenda will benefit restoration programs by suggesting plant species compositions with specific traits that maximize the supply of multiple ecosystem services in the long term. Once the suggested compositions have been implemented in actual restoration projects, these assemblages should be monitored to assess whether they are resilient as well as to improve model parameterization. Additionally, the integration of empirical and simulation modeling research can improve global outcomes by raising the awareness of which restoration goals can be achieved, due to the quantification of trade‐offs and synergies among ecosystem services under a wide range of environmental conditions.

Assessing non-intended effects of farming practices on field margin vegetation with a functional approach

To assess the unwanted side effects of farming practices on non-target plants, we used a nationwide survey of the vegetation of arable field margin strips. The vegetation was surveyed during two years (2013, 2014) in 430 field margins distributed over all agricultural regions of France. We used two complementary multivariate, trait-based approaches to examine how ten plant traits were related to ten environmental variables describing abiotic conditions, landscape factors, field margin management and in-field practices. Generalized additive mixed models were also developed to assess how the same environmental variables correlated with species richness, functional diversity and relative richness of agrotolerant versus hemerophobic species. Traits responded primarily to an environmental gradient of landscape diversity and field margin management. For instance, narrow field margin strips, frequent management and presence of a ditch favoured annual plants, small size at maturity and perennial plants, respectively. The second environmental gradient affecting plant traits was related to field size and intensity of in-field farming practices. On this gradient, fertilizer drift appeared to have a much stronger effect on plant trait composition of field margin strips than herbicide drift. The relationship between species richness, or functional diversity, and environment was consistent with the trait-based approach: the two former variables were negatively correlated with agriculture intensification (e.g. field size). However, this analysis also highlighted new covariates, such as a negative relationship between frequency of herbicide use and species richness. Some of the observed patterns seemed to be driven by differential responses of agrotolerant versus hemerophobic species, with the latter being more species-rich under organic than under conventional farming. Despite efforts to reduce nitrogen inputs since the 2000s, our results shows that N-fertilization still has significant non-intended effects on field margin vegetation. More generally, increasing the width of field margin strips, keeping or restoring semi-natural elements (ditches, hedges) in the field boundary, and lowering the number of management events may promote grassland plant species more typical of semi-natural habitats.

The combined impacts of experimental defaunation and logging on seedling traits and diversity.

Animals can have both positive (e.g. via seed dispersal) and negative (e.g. via herbivory) impacts on plants. The net effects of these interactions remain difficult to predict and may be affected by overhunting and habitat disturbance, two widespread threats to tropical forests. Recent studies have documented their separate effects on plant recruitment but our understanding of how defaunation and logging interact to influence tropical tree communities is limited. From 2013 to 2016, we followed the fate of marked tree seedlings (n = 1489) from 81 genera in and outside experimental plots. Our plots differentially excluded small, medium and large-bodied mammal herbivores in logged and unlogged forest in Malaysian Borneo. We assessed the effects of experimental defaunation and logging on taxonomic diversity and plant trait (wood density, specific leaf area, fruit size) composition of seedling communities. Although seedling mortality was highest in the presence of all mammal herbivores (44%), defaunation alone did not alter taxonomic diversity nor plant trait composition. However, herbivores (across all body sizes) significantly reduced mean fruit size across the seedling community over time (95% confidence interval (CI): -0.09 to -0.01), particularly in logged forest (95% CI: -0.12 to -0.003). Our findings suggest that impacts of mammal herbivores on plant communities may be greater in forests with a history of disturbance and could subsequently affect plant functional traits and ecological processes associated with forest regeneration.

Phylogenetic diversity and plant trait composition predict multiple ecosystem functions in green roofs

Plant selection and diversity can influence the provision of key ecosystem services in extensive green roofs. While species richness does predict ecosystem services, functional and phylogenetic community structure may provide a stronger mechanistic link to such services than species richness alone. In this study, we assessed the relationship between community-weighted trait values from four key leaf and canopy functional traits (plant height, leaf area, specific leaf area, dry leaf matter content), functional diversity, and phylogenetic diversity to ten different green roof functions, including ecosystem multifunctionality, in experimental polycultures. Functional traits of dominant plant species were a major driver for indicators of multiple green roof functions, such as substrate nitrate-N, substrate phosphorus, aboveground biomass and ecosystem multifunctionality. In contrast, functional diversity alone increased substrate organic matter. Moreover, both functional/phylogenetic diversity and identity predicted canopy density, substrate cooling. This study highlights the first line of evidence that distinct aspects of phylogenetic and functional diversity play a major role in predicting multiple green roof services. Therefore, we provide further evidence that to maximize green roof functioning, a very careful selection of plant traits and polycultures are needed.

Biodiverse cities: the nursery industry, homeowners, and neighborhood differences drive urban tree composition

AbstractIn arid and semiarid regions, where few if any trees are native, city trees are largely human planted. Societal factors such as resident preferences for tree traits, nursery offerings, and neighborhood characteristics are potentially key drivers of urban tree community composition and diversity, however, they remain critically understudied. We investigated patterns of urban tree structure in residential neighborhoods of the Salt Lake Valley, Utah, combining biological variables, such as neighborhood and plant nursery tree species and trait composition, and sociological data comprised of resident surveys and U.S. Census data. We sampled nine neighborhoods that varied in household income and age of homes. We found more tree species were offered in locally owned nurseries compared with mass merchandiser stores and yard trees at private residences were more diverse than public street trees in the same neighborhoods. There were significant differences among neighborhoods in street and yard tree composition. Newer neighborhoods differed from older neighborhoods in street tree species composition and trait diversity, while neighborhoods varying in affluence differed in yard tree composition. Species richness of yard trees was positively correlated with neighborhood household income, while species richness of street trees was negatively correlated with home age of neighborhood residences. Tree traits differed across neighborhoods of varying ages, suggesting different tree availability and preferences over time. Last, there was a positive correlation between resident preferences for tree attributes and the number of trees that had those attributes both in residential yards and in nursery offerings. Strong relationships between social variables and urban tree composition provides evidence that resident preferences and nursery offerings affect patterns of biodiversity in cities across Salt Lake Valley. These findings can be applied toward efforts to increase taxonomic and functional diversity of city trees in semiarid regions in ways that will also provide ecosystem services of most interest to residents.

Elevation predicts the functional composition of alpine plant communities based on vegetative traits, but not based on floral traits

The functional diversity and composition of plant traits within communities are tightly linked to important ecosystem functions and processes. Whereas vegetative traits reflecting adaptations to environmental conditions are commonly assessed in community ecology, floral traits are often neglected despite their importance for the plants’ life cycle. The consideration of floral traits covers important aspects such as sexual plant reproduction and pollinator diversity, which remain unobserved in studies focussing on vegetative traits only. To test whether vegetative and floral traits differ in their responses to elevation, we measured morphological and chemical traits of plant species occurring in pastures at seven elevations in the Austrian Alps. Variation in functional composition was examined using the concept of n-dimensional hypervolumes and vector analysis. Our data show that vegetative and floral traits vary differently with the elevational gradient. Whereas vegetative traits changed in a predictable manner with elevation, floral traits did not specifically respond to elevation. Overall variation in vegetative traits mainly resulted from phenotypical differences between plants in different elevations, whereas total variation in floral traits was a result from a high variation within communities. The assessment of functional changes in vegetative and floral traits along mountain slopes thus reveals different patterns in plant responses to elevation and may help to generate testable hypotheses on functional responses to current climate warming.

Sustained functional composition of pollinators in restored pastures despite slow functional restoration of plants.

Habitat restoration is a key measure to counteract negative impacts on biodiversity from habitat loss and fragmentation. To assess success in restoring not only biodiversity, but also functionality of communities, we should take into account the re‐assembly of species trait composition across taxa. Attaining such functional restoration would depend on the landscape context, vegetation structure, and time since restoration. We assessed how trait composition of plant and pollinator (bee and hoverfly) communities differ between abandoned, restored (formerly abandoned) or continuously grazed (intact) semi‐natural pastures. In restored pastures, we also explored trait composition in relation to landscape context, vegetation structure, and pasture management history. Abandoned pastures differed from intact and restored pastures in trait composition of plant communities, and as expected, had lower abundances of species with traits associated with grazing adaptations. Further, plant trait composition in restored pastures became increasingly similar to that in intact pastures with increasing time since restoration. On the contrary, the trait composition of pollinator communities in both abandoned and restored pastures remained similar to intact pastures. The trait composition for both bees and hoverflies was influenced by flower abundance and, for bees, by connectivity to other intact grasslands in the landscape. The divergent responses across organism groups appeared to be mainly related to the limited dispersal ability and long individual life span in plants, the high mobility of pollinators, and the dependency of semi‐natural habitat for bees. Our results, encompassing restoration effects on trait composition for multiple taxa along a gradient in both time (time since restoration) and space (connectivity), reveal how interacting communities of plants and pollinators are shaped by different trait–environmental relationships. Complete functional restoration of pastures needs for more detailed assessments of both plants dispersal in time and of resources available within pollinator dispersal range.

Plant functional assemblages as indicators of the resilience of grassland ecosystem service provision

Ecosystems provide a variety of ecosystem services (ES), which act as key linkages between social and ecological systems. ES respond spatially and temporally to abiotic and biotic variation, and to management. Thus, resistant and resilient ES provision is expected to remain within a stable range when facing disturbances. In this study, generic indicators to evaluate resistance, potential resilience and capacity for transformation of ES provision are developed and their relevance demonstrated for a mountain grassland system. Indicators are based on plant trait composition (i.e. functional composition) and abiotic parameters determining ES provision at community, meta-community and landscape scales. First the resistance of an ES is indicated by its normal operating range characterized by observed values under current conditions. Second its resilience is assessed by its potential operating range − under hypotheses of reassembly from the community’s species pool. Third its transformation potential is assessed for reassembly at meta-community and landscape scales. Using a state-and-transition model, possible management-related transitions between mountain grassland states were identified, and indicators calculated for two provisioning and two regulating ES. Overall, resilience properties varied across individual ES, supporting a focus on resilience of specific ES. The resilience potential of the two provisioning services was greater than for the two regulating services, both being linked to functional complementarity within communities. We also found high transformation potential reflecting functional redundancy among communities within each meta-community, and across meta-communities in the landscape. Presented indicators are promising for the projection of future ES provision and the identification of management options under environmental change.

Species pools and environmental sorting control different aspects of plant diversity and functional trait composition in recovering grasslands

Summary Succession theory argues that the taxonomic and functional structure of assembling communities is regulated by the interplay of local environmental conditions and regional factors such as available species pools or landscape configurations that moderate dispersal. Yet, the relative importance of these factors and whether they control different aspects of community structure, for example species diversity or the composition of plant traits, is not well understood. This limits predictions of spatial variation in successional outcomes. We explored patterns of species diversity and traits in recovering calcareous grasslands that varied in environmental conditions, age, past and present spatial landscape configuration, as well as in the propagule pressure they receive from historical grasslands that have large and functionally distinct species pools. Mixed‐effects modelling and multimodel inference were used to dissect the leading drivers of species diversity and functional composition. Propagule pressure from the regional species pools of old grasslands during early stages of grassland re‐assembly was an important determinant of community structure, with significant effects not only on species diversity but also on the composition of traits related to resource economics. Such species pool effects exceeded positive influences of environmental heterogeneity on species richness and confounded well‐known diversity–environment and trait–environment relationships. As an orthogonal axis of community assembly, environmental sorting occurred along a gradient of soil texture that discriminated species according to their canopy height and – to a smaller extent – phenology. Additionally, high grassland perimeter–area ratios favoured specialist species richness and increased the proportion of species with predicted poor epizoochorous and wind dispersal. Synthesis. We provide empirical evidence that both species pool effects and local environmental sorting operate during community assembly of recovering calcareous grasslands, but that they influence different aspects of plant community structure. Further, we show that geographic variation in propagule pressure from large and functionally distinct source species pools can confound diversity–environment and trait–environment relationships. Therefore, besides accounting for environmental factors, considering the location of source species pools, as well as their compositional and functional characteristics, is a prerequisite for robust predictions of contingencies in taxonomic and functional community structure of successional habitats.

Environmental filtering and spatial processes in urban riparian forests

AbstractQuestionsWhat are the spatial processes structuring plant trait composition in urban riparian forest communities at different spatial scales? What are the relative roles of local conditions (including historical aspects), landscape context and spatial processes in the community assembly of these forests?LocationMontréal, Québec, Canada.MethodsSpecies plant composition was inventoried in 57 riparian forests located along a gradient of urbanization. To analyse plant communities in terms of their trait composition, community‐weighted means were calculated using eight functional traits. Forests were characterized by local (physical features, hydrological regime and historical disturbances) and landscape (surrounding land use) variables. Spatial processes structuring communities were assessed using Moran's eigenvector maps and asymmetric eigenvector maps. The relative importance of these three subsets (local, landscape and spatial variables) on tree, shrub and herb functional composition was quantified by variation partitioning using redundancy analyses.ResultsFunctional patterns in riparian forests resulted primarily from environmental filtering (local and landscape variables). Local conditions, especially flood intensity, exerted an overriding selection pressure on functional composition of riparian plant communities. Urbanization seemed to act indirectly on trait patterns through the alteration of hydrological disturbances caused by on‐going and historical land transformation. Nevertheless, dispersal along rivers was also a significant structuring force, while overland dispersal was negligible.ConclusionsOur study highlights that under severe natural disturbance regimes, the effect of natural filters outweighed the negative effects of urban filters. However, the alteration of natural flooding processes by human activities is also a major mechanism influencing plant trait composition in urban riparian communities as forests subjected to reduced flooding intensity experienced a greater effect of urbanization. The effects of urbanization and of past land uses on plant communities were greater for trees than for shrubs and herbs due to the high turnover rate of the latter. Finally, our results showed the importance of dispersal along rivers for biodiversity even in fragmented urban landscapes.

Plant trait composition as an indicator for the ecological memory of rehabilitated floodplains

Maintaining ecosystem functioning under global change requires resilient ecosystems to absorb disturbances, reorganize and maintain the adaptive capacity. Maintaining resilience is therefore a common objective for ecosystem management, but how this objective may be achieved remains largely unclear. The concept of ecological memory provides a perspective on how the adaptive capacity of ecosystems can be enhanced through management. It specifies how ecological processes in space and time assist in the reorganization of communities after disturbances. We present a trait-based approach that links environmental variables at site and patch level to plant traits. With a generalized linear mixed-effects model we test how environmental variation in management and floodplain dynamics, within and between sites, relates to plant traits that are considered relevant for ecological memory. The results show different mechanisms that intervene in ecological memory. Grazing enhances recruitment opportunities, both for internal reorganization and for colonization between sites. Dense vegetation structure selects for species survival via resprouting after disturbance and competitive species. Hydrodynamics interact with seed dispersal mechanisms and seed persistence. We show that at different spatial levels, plant trait composition can act as an indicator of ecological processes contributing to the ecological memory of a floodplain ecosystem. For ecosystem management to maintain and use as much of this memory as possible it should incorporate management measures at various levels of scale to enhance ecosystem resilience.

Wood density is a poor predictor of competitive ability among individuals of the same species

Competition between immediate neighbors has been regarded as one of the most important forces of natural selection that shapes the species composition, diversity and evolution of plant traits within a community. Here, I examined wood density (WD) variation in populations of two tree species, where individuals have contrasting access to resources. In five Nothofagus betuloides and Nothofagus pumilio even-aged, mixed second-growth forests in Patagonia (Chile), I sampled pairs of dominant (full access to resources) and the nearest-to-it suppressed individuals (constrained access to resources), with the following main objective: to assess whether WD is a good predictor of the competitive ability of individuals in tree populations. To accomplish this objective, I quantified, at the individual level, sapwood (WDsap) and heartwood densities (WDheart), sapwood proportion (Sapp), growth rates (BAI10) and growth efficiency (GE). Given that sapwood and heartwood differ in functionality, I used WDst, a standardized way of computing WD that considers both wood type proportions in the stem. In order to determine the relationship between growth rate (BAI10, a proxy of competitive ability) and WD at the intraspecific level, I analyzed the effect of contrasting access to resources (dominant versus suppressed individuals) and WD fitting mixed-effects correlation models (LMM). WDst showed very low variation (<6% of CV), and WDst did not differ between dominant and suppressed individuals for both species, nor did Sapp. Dominant individuals of both species had significantly higher BAI10 and GE values than suppressed individuals. I found a non-significant correlation between BAI10 and WDst. Independently of tree species and access to resources, WDheart was significantly higher than WDsap. In conclusion, my results are unequivocal in that WD is a poor predictor of competitive ability among individuals of the same species and thus interspecific trends found in the growth–WD relationship are not paralleled at the intraspecific level.

Community-Weighted Mean Plant Traits Predict Small Scale Distribution of Insect Root Herbivore Abundance.

Small scale distribution of insect root herbivores may promote plant species diversity by creating patches of different herbivore pressure. However, determinants of small scale distribution of insect root herbivores, and impact of land use intensity on their small scale distribution are largely unknown. We sampled insect root herbivores and measured vegetation parameters and soil water content along transects in grasslands of different management intensity in three regions in Germany. We calculated community-weighted mean plant traits to test whether the functional plant community composition determines the small scale distribution of insect root herbivores. To analyze spatial patterns in plant species and trait composition and insect root herbivore abundance we computed Mantel correlograms. Insect root herbivores mainly comprised click beetle (Coleoptera, Elateridae) larvae (43%) in the investigated grasslands. Total insect root herbivore numbers were positively related to community-weighted mean traits indicating high plant growth rates and biomass (specific leaf area, reproductive- and vegetative plant height), and negatively related to plant traits indicating poor tissue quality (leaf C/N ratio). Generalist Elaterid larvae, when analyzed independently, were also positively related to high plant growth rates and furthermore to root dry mass, but were not related to tissue quality. Insect root herbivore numbers were not related to plant cover, plant species richness and soil water content. Plant species composition and to a lesser extent plant trait composition displayed spatial autocorrelation, which was not influenced by land use intensity. Insect root herbivore abundance was not spatially autocorrelated. We conclude that in semi-natural grasslands with a high share of generalist insect root herbivores, insect root herbivores affiliate with large, fast growing plants, presumably because of availability of high quantities of food. Affiliation of insect root herbivores with large, fast growing plants may counteract dominance of those species, thus promoting plant diversity.

Variation in dry grassland communities along a heavy metals gradient.

The aim of this study was to investigate the variation in plant communities growing on metal-enriched sites created by historical Zn–Pb mining. The study sites were 65 small heaps of waste rock covered by grassland vegetation and scattered mostly over agricultural land of southern Poland. The sites were described in terms of plant coverage, species richness and composition, and the composition of plant traits. They were classified using phytosociological methods and detrended correspondence analysis. Identified plant communities were compared for vegetation parameters and habitat properties (soil characteristics, distance from the forest) by analysis of variance. The variation in plant community parameters was explained by multiple regression, in which the predictors were properties of the habitat selected on the basis of factor analysis. Grasslands that developed at low and high concentrations of heavy metals in soil were similar to some extent: they were composed on average of 17–20 species (per 4 m2), and their total coverage exceeded 90 %. The species composition changed substantially with increasing contamination with heavy metals; metal-sensitive species withdrew, while the metal-tolerant became more abundant. Other important predictors of community structure were: proximity to the forest (responsible for the encroachment of competitive forest species and ruderals), and the thickness of the surface soil (shallow soil favored the formation of the heavy metal grassland). The heavy metal grassland was closely related to the dry calcareous grasslands. The former was an earlier succession stage of the latter at low contamination with heavy metals.

Re‐growing a tropical dry forest: functional plant trait composition and community assembly during succession

SummaryA longstanding goal of ecology and conservation biology is to understand the environmental and biological controls of forest succession. However, the patterns and mechanisms that guide successional trajectories, especially within tropical forests, remain unclear.We collected leaf functional trait and abiotic data across a 110‐year chronosequence within a tropical dry forest in Costa Rica. Focusing on six key leaf functional traits related to resource acquisition and competition, along with measures of forest stand structure, we propose a mechanistic framework to link species composition, community trait distributions and forest structure. We quantified the community‐weighted trait distributions for specific leaf area, leaf dry matter concentration, leaf phosphorus concentration, leaf carbon to nitrogen ratio and leaf stable isotopic carbon and nitrogen. We assessed several prominent hypotheses for how these functional measures shift in response to changing environmental variables (soil water content, bulk density andpH) across the chronosequence.Increasingly, older forests differed significantly from younger forests in species composition, above‐ground biomass and shifted trait distributions. Early stages of succession were uniformly characterized by lower values of community‐weighted mean specific leaf area, leaf stable nitrogen isotope and leaf phosphorus concentration. Leaf dry matter concentration and leaf carbon to nitrogen ratio were lower during earlier stages of succession, and each trait reached an optimum during intermediate stages of succession. The leaf carbon isotope ratio was the only trait to decrease linearly with increasing stand age indicating reduced water use efficiency in older forests. However, in contrast with expectations, community‐weighted trait variances did not generally change through succession, and when compared to null expectations were lower than expected.The observed directional shift in community‐weighted mean trait values is consistent with the ‘productivity filtering’ hypothesis where a directional shift in water and light availability shifts physiological strategies from ‘slow’ to ‘fast’. In contrast with expectations arising from niche based ecology, none of the community trait distributions were over‐dispersed. Instead, patterns of trait dispersion are consistent with the abiotic filtering and/or competitive hierarchy hypotheses.

Structural and functional responses of floodplain vegetation to stream ecosystem restoration

Most river restoration projects have applied relatively small-scale measures focused on improving specific instream conditions, with only limited outcomes for biodiversity in rivers and their adjacent riparian habitats. Here, we investigate the effects of both small- and large-scale restoration projects on floodplain vegetation across 20 European catchments. We focused on the roles of different restoration parameters (i.e., the number, spatial extent and type of restoration measure applied and restoration age) and specific environmental characteristics in regulating changes in plant diversity and trait composition following restoration. Among restoration characteristics, restoration type was the only significant determinant of plant community responses, with stream channel widening having the strongest effects, particularly on the diversity and composition of species traits favoured by increases in physical disturbance (e.g. flooding) and open habitat patch availability (e.g. plant growth form, life strategy and life span). Of the environmental variables, altitude and discharge were positively and most strongly related to responses of both species and trait diversity. Our results emphasise the value of (i) choosing relevant restoration measures that affect environmental conditions of importance for the target organism group and (ii) conducting restoration projects in environmental settings where the likelihood of restoration “success” is maximised.

Hunting alters seedling functional trait composition in a Neotropical forest.

Defaunation alters trophic interactions between plants and vertebrates, whichmay disrupt trophic cascades, thereby favoring a subset of plant species and reducing diversity. If particular functional traits characterize the favored plant species,.then defaunation may alter community-wide patterns of functional trait composition. Changes in plant functional traits occurring with defaunation may help identify the species interactions affected by defaunation and the potential for other cascading effects of defaunation. We tested the hypotheses that defaunation would (1) disrupt seed dispersal, thereby favoring species whose dispersal agents are not affected (e.g., small birds, bats, and abiotic agents), (2) reduce seed predation, thereby favoring larger-seeded species, and (3) reduce herbivory, thereby favoring species with lower leaf mass per area (LMA), leaf toughness, and wood density. We examined how these six traits responded to vertebrate defaunation caused by hunters or by experimental exclosures among more than-30 000 woody seedlings in a lowland tropical moist forest. Exclosures reduced terrestrial frugivores, granivores, and herbivores, while hunters also reduced volant and arboreal frugivores and granivores. The comparison of exclosures and hunting allowed us to parse the impacts of arboreal and volant species (reduced by hunters only) and terrestrial species (reduced by both hunters and exclosures). The loss of terrestrial vertebrates alone had limited effects on plant trait composition. The additional loss of volant and arboreal vertebrates caused significant shifts in plant species composition towards communities with more species dispersed abiotically, including lianas and low wood-density tree species, and fewer species dispersed by large vertebrates. In contrast to previous studies, community seed mass did not decline significantly in hunted sites. Our exclosure results suggest this is because reducing seed predators disproportionately benefits large-seeded species,.partially compensating for the reduction of seed dispersers at hunted sites. Our result9sdemonstrate that decreased seed dispersal and seed predation are important determinants of seedling community compositional change as a consequence of defaunation. Defaunation may also negatively impact carbon storage in tropical forests, by favoring lianas and low wood density tree species.

How well is current plant trait composition predicted by modern and historical forest spatial configuration?

There is increasing evidence to suggest that a delayed response of many forest species to habitat loss and fragmentation leads to the development of extinction debts and immigration credits in affected forest habitat. These time lags result in plant communities which are not well predicted by present day landscape structure, reducing the accuracy of biodiversity assessments and predictions for future change. Here, species richness data and mean values for five life history characteristics within deciduous broadleaved forest habitat across Great Britain were used to quantify the degree to which aspects of present day forest plant composition are best explained by modern or historical forest patch area. Ancient forest specialist richness, mean rarity and mean seed terminal velocity were not well predicted by modern patch area, implying the existence of a degree of lag in British forest patches. Mean seedbank persistence values were more closely related to modern patch area than historical, particularly in larger patches. The variation in response for different mean trait values suggests that species respond to landscape change at different rates depending upon their combinations of different trait states. Current forest understorey communities are therefore likely to consist of a mixture of declining species whose extinction debt is still to be paid, and faster colonising immigrant species. These results indicate that without management action, rare and threatened species of plant are likely to be lost in the future as a result of changes in forest spatial configuration that have already taken place. The lag seen here for rare specialist plants suggests however that there may still be scope to protect such species before they are lost from forest patches.

Changes in species composition, diversity and biomass of herbaceous plant traits due to N amendment in a dry tropical environment of India

Changes in species composition, diversity and biomass of herbaceous plant traits due to N amendment in a dry tropical environment of India

Traits of plant communities in fragmented forests: the relative influence of habitat spatial configuration and local abiotic conditions

SummaryThe plant trait composition of forest fragments is thought to be partly determined by forest spatial properties, although the relative importance of habitat configuration and local abiotic drivers is poorly understood.To address this issue, large‐scale habitat extent data were combined with detailed field survey information for temperate broad‐leaved deciduous forest patches to quantify the relative effects of spatial and abiotic filters on plant community mean trait values.Local conditions such as shade and soil fertility had the largest effect on mean trait values, but aspects of habitat configuration also had significant partial effects on a number of traits.Mean trait values within older forest patches were more strongly influenced by forest spatial configuration than in younger patches.Synthesis. Results indicate that, in addition to the effects of greater light availability and competition in small patches and at forest edges, aspects of habitat configuration such as patch size and isolation are themselves important factors limiting the occurrence of forest specialist species. Large areas of core forest habitat contain a greater proportion of rare, poor dispersing species, although these effects were less visible in more recently established forest. This highlights the importance of maintaining existing large and old forest patches as a refuge for forest specialist plants. The results of this comparison of spatial and abiotic variables suggest that controlling the spatial properties of forest patches is likely to prove an effective way of managing plant species diversity, provided that sites with appropriate abiotic conditions are chosen.