Trait Composition Of Communities Research Articles

Equilibrium in plant functional trait responses to warming is stronger under higher climate variability during the Holocene

AbstractAimThe functional trait composition of plant communities is thought to be determined largely by climate, but relationships between contemporary trait distributions and climate are often weak. Spatial mismatches between trait and climatic conditions are commonly thought to arise from disequilibrium responses to past environmental changes. We aimed to investigate whether current trait–climate disequilibrium is likely to emerge during plant functional responses to Holocene climate warming.LocationNorth America.Time period14–0 ka.Major taxa studiedTerrestrial plants.MethodsWe joined global trait data with palaeoecological time series and climate simulations on 425 sites. We estimated plant community functional composition for three leaf traits involved in resource use. We then quantified disequilibrium in plant trait temporal responses to climate change during two contrasted periods: a period of high climate variability (14–7 ka) and a period of low climate variability (7–0 ka).ResultsFunctional trait composition showed consistent deviation from climatic equilibrium during both periods. The temporal dynamics of trait composition tends to be positively correlated with climate equilibrium expectations during Holocene climate warming (14–7 ka), but not during a subsequent period of low climate variability (7–0 ka).Main conclusionsLong‐term functional responses of plants to climate change showed mixed evidence for both equilibrium and disequilibrium responses. Temporal trait dynamics were closer to the expectations of spatial dynamics under high climate variability, indicating that the relevance of space‐for‐time substitution might be dependent, in part, on climate variability. Our results also suggest that current mismatches between trait and climatic conditions might arise because of a divergence of factors influencing trait dynamics during periods of low climate variability. These findings provide a counterpoint to the common assumption that contemporary trait–climate mismatches result from lagged responses to past climate warming. Our study also demonstrates the need for a deeper investigation of the potential influence of non‐climatic factors on functional plant community dynamics.

Unravelling the effects of multiple stressors on diatom and macroinvertebrate communities in European river basins using structural and functional approaches

Rivers suffer from more severe decreases in species diversity compared to other aquatic and terrestrial ecosystems due to a variety of pressures related to human activities. Species provide different roles in the functioning of the ecosystem, and their loss may reduce the capacity of the ecosystems to respond to multiple stressors. The effects on diversity will differ based on the type, combination and severity of stressors, as well as on the characteristics of the community composition and tolerance. Multiple trait-based approaches (MTBAs) can help to unravel the effects of multiple stressors on communities, providing a mechanistic interpretation, and, thus, complementing traditional biodiversity assessments using community structure. We studied the relationships between diversity indexes and trait composition of macroinvertebrate and diatom communities, as well as environmental variables that described the hydrological and geomorphological alterations and toxic pollution (pesticides and pharmaceuticals) of three different European river basins: the Adige, the Sava, and the Evrotas. These river basins can be considered representative cases of different situations in European freshwater systems. Hydrological variables were the main drivers determining the community structure and function in the rivers, for both diatoms and macroinvertebrates. For diatom communities, pharmaceutical active compound (PhAC) toxic units were also identified as a very important driver of diversity changes, explaining up to 57% of the variance in taxonomic richness. For macroinvertebrates, river geomorphology was an important driver of structural changes, particularly affecting Plecoptera richness. In addition, PhAC and pesticide toxic units were also identified as stressors for macroinvertebrate communities. MTBA provided a detailed picture of the effects of the stressors on the communities and confirmed the importance of hydrological variables in shaping the functional attributes of the communities.

Comparing taxon- and trait-environment relationships in stream communities

Abstract Traits define how organisms interact with their surrounding environment and with other organisms. Thus, trait composition of biological communities is expected to change predictably along environmental gradients. Because organisms’ traits, but not taxonomic identity, determine their fitness, trait-environment relationships should provide a better way to elucidate how biodiversity respond to environmental change. Here, we used data on tropical streams embedded in a landscape of intensive agriculture to investigate trait-environment and taxon-environment relationships in a set of 91 mayfly communities from southeastern Brazil. We expected that trait-environment relationships would be stronger than taxon-environment relationships and that the linkage between traits and environmental variables would provide mechanistic insights on environmental filtering. We found that variation in both species composition and traits were correlated to salinity, highlighting the influence of water salinization on mayfly communities due to agricultural practices. Surprisingly, using analogous statistical methods, in general, we found that the strengths of trait-environment relationships were lower than that of taxon-environment relationships. Further, (1) species responses to gradients were not correlated to similarity in their traits and (2) some species with different trait composition responded similarly to environmental variation, indicating that different suite of traits can cope with similar environmental contexts. Besides some cautionary results about trait-based approaches, results from taxon-based approaches indicated that variation in composition was more related to spatial variables, suggesting that dispersal limitation undermine its use for large scale assessments. Our results suggest that both taxon- and trait-based approaches have weakness and strengths and deciding between them for biomonitoring purposes will depend on spatial scales, trait interrelationships, and analytical methods.

Turnover or intraspecific trait variation: explaining functional variability in a neotropical anuran metacommunity

Trait variation across environmental gradients results from two processes: intraspecific variation (ITV) and turnover. Trait plasticity promotes intraspecific variation and can mediate, increasing or decreasing, interspecific variation. Here we evaluate patterns of ITV and trait-environment relationships in an anuran metacommunity from southern Brazil. We hypothesize that the contribution of ITV and turnover to trait variation and trait-environment relationships should vary between groups of habitats use and traits. To test this, we sampled anurans in 33 ponds and selected the eight most abundant species, which were grouped as arboreal or aquatic-terrestrial according to their use of space. We evaluated the following traits: head shape, eye size and position, limb length and body mass. We divided variation in community trait composition into ITV, variability due to turnover, and also the covariation between them. We modelled trait-environment relationships using linear mixed-effect models. ITV and turnover contributed similarly across traits, but differentially between sets of species. Trait variation seems to be mostly driven by ITV in arboreal anurans and by turnover in aquatic-terrestrial species. Depth, distance between ponds, area of Pinus surrounding the ponds, and types of pond vegetation and substrate strongly influenced trait variation, but their relative contribution depended on the analysed traits and species sets. The dominant contribution of ITV towards the variation of head shape and eye size and position suggests the existence of intraspecific adaptations to microhabitats, while turnover dominance in the variation of body mass and limb length suggests differences in dispersal and trophic segregation between species.

Functional diversity of chironomid communities in subarctic lakes across gradients in temperature and catchment characteristics

Northern ecosystems are experiencing rapid and large-scale changes driven by accelerated warming, which have profound effects on the terrestrial and freshwater biodiversity. A comprehensive understanding of the distribution of aquatic biodiversity of subarctic ecosystems is therefore needed to better predict future trajectories of their unique biodiversity. In this study, we examined the functional diversity of chironomid communities in subarctic lakes across a 1000 m-elevation gradient, reflecting gradual changes in temperature and landscape characteristics. Using fuzzy correspondence analyses, we investigated spatial variability in trait composition of chironomid communities from 100 lakes in northern Sweden, and tested the hypotheses that (1) climate directly and indirectly shapes chironomid trait composition across the studied gradient, and (2) that generalist taxa with smaller body size and broader food preferences are more able to persist in cold environments. Our results showed that complex interplays between direct (e.g. temperature) and indirect climate processes (e.g. elevation-driven changes in vegetation/habitats) affect the functional diversity of chironomid communities. Specifically, traits such as larval size, food preference and feeding habits were well separated along the gradient, and this pattern revealed that low elevation lakes with forested catchments tended to have more sediment-feeding taxa and larger larvae than those above the tree line. As expected, food resource availability in lakes is strongly linked to vegetation composition/cover, and traits related to resource exploitation in chironomid communities are therefore well constrained by landscape characteristics. Furthermore, our findings suggested that short life cycles could facilitate the development of viable population in northern and high-elevation lakes where the short ice-free period is a limiting factor, thus contradicting patterns showing smaller organisms in warmer environments reported for other invertebrates. As a consequence of climate warming, the highest elevation lakes in subarctic landscapes will likely lose their typical cold-adapted chironomid taxa along with their functional attributes leading to potential impacts on the food web structure and the overall functioning of northern lake ecosystems.

Plant traits as indicators of recovery of reclaimed wellsites in forested areas: Slow but directional succession trajectory

Trait-based approaches can provide a generalizable mechanistic understanding of complex post-disturbance succession dynamics of plant communities. Much of our knowledge regarding successional trajectories of functional trait composition come from observations of natural disturbances that leave physical and biological legacy on site for self regeneration. We lack, however, understanding of the long-term recovery in severely degraded lands following reclamation through active revegetation. To address this gap, we examined changes in trait composition of forest understory plant communities in reclaimed oil and gas wellsites using chronosequence data (7–48 years since reclamation) to assess recovery towards that of post-harvest and natural post-fire reference forest sites. We used multiple traits associated with resource acquisition (e.g., fast growth) and performance ability metrics (e.g., shade-tolerance) with putative environmental factors to evaluate the trait-environment relationships underlying plant community recovery in reclaimed sites. We found an overall directional change in functional composition with time since reclamation towards that observed in reference sites, but even older reclaimed sites remained significantly different from reference sites. This could be related to differential trajectory patterns among traits where some trait values progressed towards those of reference (long-distance dispersal by wind decreased with time since reclamation) whereas some fast-resource acquisition traits and exotic species showed no change and remained dominant in older reclaimed sites. The strong link between traits and environment suggests a significant influence of time and subsequent developing site conditions (e.g., canopy cover) as well as enduring legacies of wellsite operation/reclamation (e.g., high soil bulk density and exotic species) on functional composition. Knowledge of functional composition trajectories in severely degraded ecosystems, such as wellsites, could improve our understanding of recovery processes and inform more effective reclamation practices by identifying putative underlying environmental factors and specific ecological attributes that may delay successful recovery.

Changing taxonomic and functional β-diversity of cladoceran communities in Northeastern and South Brazil

Disturbances caused by both natural and anthropogenic forces can drive changes in alpha and beta taxonomic diversity and be accompanied by losses or gains in freshwater ecosystem function (e.g., secondary productivity and rate of decomposition). In this study, we tested the hypothesis that increases in cladoceran (microcrustaceans) taxonomic beta diversity in highly impacted environments lead to functional simplification and homogenization of community trait composition. This was accomplished by comparing a reference group of low-impact waterbodies (lakes and reservoirs) to high-impact waterbodies located in four regions of northeastern and south Brazil. Functional composition of cladoceran communities was inferred using a suite of morphological, physiological, behavioral, and life-history traits. Differences in taxonomic and functional community composition were tested using univariate and multivariate statistics. Taxonomic beta diversity and functional richness differed significantly between the reference (low-impact) and high-impact waterbodies, where high-impact environments showed higher taxonomic and functional beta diversity and lower functional richness. By contrast, we found functional homogenization of cladoceran communities in just one out of the four regions. Last, we propose that disturbances can affect traits locally in communities, making them rarer until they are lost, by promoting functional simplification. When disturbances are persistent, they lead to functional and taxonomic homogenization.

Direct and indirect effects of forest management on tree-hole inhabiting aquatic organisms and their functional traits

Ecological communities in forests have been shown to be strongly affected by forest management but a detailed understanding of how different components of management affect insect communities directly and indirectly via environmental variables, how management influences functional trait diversity and composition, and whether these results can be transferred to other functional groups besides insects (e.g. bacteria or nematodes) is still missing. To address these questions we used water-filled tree holes, which provide habitats for insect larvae and other aquatic organisms in forests, as a model system. We mapped all water-filled tree holes in 75 forest plots (1 ha) under different management intensity in three regions of Germany. We measured structural and climatic conditions at different spatial scales, sampled insect communities in 123 tree holes and bacterial and nematode communities in a subset of these. We found that forest management in terms of harvesting intensity and the proportion of non-natural tree species (species not part of the natural vegetation at the sites) negatively affected tree-hole abundance. An increased proportion of non-natural tree species had a positive direct effect on insect richness and functional diversity in the tree holes. However, a structural equation model showed that increasing management intensity had negative indirect effects on insect abundance and richness, operating via environmental variables at stand and tree-hole scale. Functional diversity and trait composition of insect communities similarly responded to changes in management-related variables. In contrast to insects, bacterial and nematode richness were not directly impacted by forest management but by other environmental variables. Our results suggest that forest management may strongly alter insect communities of tree holes, while nematodes and bacteria seem less affected. Most effects in our study were indirect and negative, indicating that management has often complex consequences for forest communities that should be taken into account in forest management schemes.

Catchment properties and the photosynthetic trait composition of freshwater plant communities.

Unlike in land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to carbon dioxide (CO2) to compensate for the low diffusivity and potential depletion of CO2 in water. Concentrations of bicarbonate and CO2 vary greatly with catchment geology. In this study, we investigate whether there is a link between these concentrations and the frequency of freshwater plants possessing the bicarbonate use trait. We show, globally, that the frequency of plant species with this trait increases with bicarbonate concentration. Regionally, however, the frequency of bicarbonate use is reduced at sites where the CO2 concentration is substantially above the air equilibrium, consistent with this trait being an adaptation to carbon limitation. Future anthropogenic changes of bicarbonate and CO2 concentrations may alter the species compositions of freshwater plant communities.

Biogeographic classification of streams using fish community– and trait–environment relationships

AbstractAimPresent a hybrid biogeographic and environmentally constrained clustering approach to classify ~853,000 stream reaches in the eastern United States. Examine the frequency of stream typologies in the landscape relative to anthropogenic stressors to identify potential stream conservation needs.LocationEastern United States.MethodsFish communities at 956 least‐disturbed sampling reaches were characterized using taxonomic and functional composition of native species. Environmental variables summarized within stream reaches included stream discharge, channel gradient, hydrologic regime, summer water temperature and boundaries of freshwater ecoregions. Multivariate regression trees were used to relate environmental variables to fish communities while simultaneously developing taxa‐ and trait‐specific biogeographic classifications. We then overlaid stream classifications with indices of anthropogenic disturbances to evaluate rarity and risk of complete loss of natural representation of stream types.ResultsTaxonomically based classes represented a combination of ecoregional boundaries and environmental gradients, whereas temperature gradients were most important in differentiating functional composition. An optimal taxonomy‐based classification contained 13 classes and explained 26.4% of community variation, and the optimal trait‐based classification contained 6 classes, explaining 25.2% of community variation. Overlaying class maps with an anthropogenic disturbance index revealed substantial variation in the severity of degradation among classes relative to their abundance in the landscape, especially rare classes (i.e., large rivers and cold headwater systems).Main conclusionsWe demonstrate the value of integrating local, regional and historical biogeographic factors with taxonomic and functional characteristics of freshwater biota to classify ecosystems based on mechanistic biota–environment relationships. This approach is important to addressing the challenge of developing stream classifications that reconcile the environmental drivers of community trait composition with the constraints of biogeographic regionality at large spatial scales. Furthermore, the spatially explicit and high‐resolution maps disseminated here can uniquely inform management decisions regarding anthropogenic threats to the biodiverse freshwaters of the eastern United States.

Impacts of dominant plant species on trait composition of communities: comparison between the native and invaded ranges

AbstractMost studies on the impacts of plant invasions focus on species richness or diversity of invaded communities, but much less attention has been paid to structural changes such as the representation of species with different traits. To bridge this knowledge gap, we assess the impact of dominant species on the trait composition of recipient communities (i.e., how species with certain height, seed mass, specific leaf area, clonality, and life form are represented in the vegetation plots sampled). We sampled vegetation that comprised three species native to Eurasia and invasive in North America (i.e., Agrostis capillaris, Bromus tectorum, and Cirsium arvense) and three species native to North America and invasive in Europe (i.e., Aster novi‐belgii, Lupinus polyphyllus, and Solidago canadensis), in both their native and invaded ranges. This study system based on reciprocal inter‐continental invasions allowed us to assess whether the impact on trait composition differed (1) between the native and invaded ranges and (2) between the two continents. The relationships between species’ dominance and trait composition were tested using linear mixed‐effect models and ordination methods. A general trend was that dominant species with an impact on species richness also had an impact on trait composition, especially in North America, where even the native dominants affected the trait composition of the community. Further, the impact of Eurasian dominants in North America was stronger than that associated with the opposite direction of invasion, due to a strong negative effect of Eurasian invaders on local tall clonal perennials. Our results show that (1) the traits of species in the invaded community co‐determine the impact of invasion and are related to the impacts on species richness and composition; (2) the impacts on trait composition differ between the native and invaded ranges; and (3) the direction of invasion affects the impact on trait composition.

Multiple-stressor effects of dicyandiamide (DCD) and agricultural stressors on trait-based responses of stream benthic algal communities.

Agricultural practices often result in multiple stressors affecting stream ecosystems, and interacting stressors complicate environmental assessment and management of impacted streams. The nitrification inhibitor dicyandiamide (DCD) is used for nitrogen management on farmland. Effects of leached DCD on stream ecosystems are still largely unstudied, even though it could be relevant as a stressor on its own or in combination with other agricultural stressors. We conducted two experiments in 128 outdoor stream-fed mesocosms to assess stressor effects on biomass, cell density, taxon richness, evenness and functional trait composition of benthic algal communities. First, we examined responses to a wide DCD gradient (eight concentrations, 0-31 mg L-1) and two additional stressors, deposited fine sediment (none, high) and nutrient enrichment (ambient, enriched). Second, we determined algal responses to four stressors: DCD, sediment, nutrients, and reduced flow velocity. Here DCD treatments included controls, constant application (1.4 mg L-1) and two pulsed treatments mimicking concentration patterns in real streams (peaks 3.5 mg L-1, 2.2 mg L-1). Sediment and nutrient enrichment were influential stressors in both experiments, with fine sediment having the most pervasive effects. In Experiment 2, reduced flow velocity had pervasive effects and stressor interactions were mainly restricted to two-way interactions. DCD had few, weak stressor main effects, especially at field-realistic concentrations (Experiment 2). At the highest concentrations in Experiment 1 (above levels observed in real streams), DCD effects were still rare but some significant stressor interactions occurred. Analyses of functional traits were helpful in identifying potential mechanisms driving changes in densities and community composition. These findings suggest that, while DCD on its own may be a minor stressor, it could have adverse effects on algal communities already exposed to other stressors, a scenario common in agricultural streams.

Quantifying the temperature dependence of growth rate in marine phytoplankton within and across species

AbstractModels of marine biogeochemistry capture the effects of temperature on phytoplankton growth via the monotonic, exponential Eppley coefficient, without considering the physiological or evolutionary processes that underpin this emergent, across‐species temperature response. Here, we investigated both the within‐ and across‐species temperature dependence of growth rate for 18 species of marine phytoplankton. We found that the temperature dependence of growth rate derived across species was lower than the average temperature response within species. This finding supports a “partial compensation” model of thermal adaptation and suggests that adaptation can partially compensate for the underlying thermodynamic effects of temperature on physiological rates observed within species. We also found that thermal tolerance traits (e.g. the optimum temperature for growth) systematically covaried with a host of key functional traits (e.g. cell size, elemental composition). Consequently, turnover in species composition in a warmer ocean, linked to interspecific variability in thermal tolerance traits, could be associated with major shifts in the functional trait composition of marine phytoplankton communities with far reaching implications for ecosystem functioning.

Carbon forms, nutrients and water velocity filter hydrophyte and riverbank species differently: A trait‐based study

AbstractQuestionsThe majority of theories of trait‐based plant community assembly have been developed and tested predominantly in terrestrial ecosystems. Studies investigating the functional trait composition of aquatic plant communities and their relation to environmental determinants remain scarce. Macrophytes are essential components of aquatic ecosystems, and a more detailed knowledge of their trait‐based assembly is crucial for their management. We identified how plant functional traits respond to environmental gradients in streams and rivers.LocationDanube River Catchment, Hungary.MethodsWe studied the processes governing community assembly along major environmental gradients related to carbon‐ and nutrient‐limiting factors as well as physical strain. We used six continuous traits (leaf area, specific leaf area, leaf dry matter content, seed weight, seed shape, woodiness) and calculated community‐weighted mean and standardised effect size of functional diversity for each community. We then used stepwise regression analyses for each trait along the environmental gradients to test which environmental factors explain the changes in community‐weighted mean and functional diversity. All analyses were conducted for aquatic (hydato‐helophyte) and riverbank species separately.ResultsWe found that the effect of environmental filtering significantly increased toward higher pH, indicating the response of functional traits to carbon limitation. Our results showed trait convergence among riverbank species in rivers with higher productivity. Larger functional diversity (i.e., trait divergence) among hydato‐helophyte species suggests an increase in the diversity of resource acquisition strategies under higher productivity.ConclusionsHere, we have shown that the functional trait distribution of aquatic and riverbank plant communities responds to major environmental drivers related to nutrient and carbon availability. The understanding of how community assembly mechanisms varied along environmental gradients might be useful when proposing future management and restoration plans and actions towards the conservation of the aquatic vegetation in streams and rivers.

Choices of sampling method bias functional components estimation and ability to discriminate assembly mechanisms

Abstract The understanding and prediction of species distributions have been advanced by the development of community assembly theories and functional trait‐based approaches. Coupled with null models, trait dispersion patterns are commonly used to gauge the relative importance of niche versus neutral‐based processes on shaping local communities. However, asymmetrical trait dispersion patterns of identical communities may artificially arise as a result of sampling methods choice. This non‐random filtering on traits is overlooked, and it may bias the estimation of functional components as well as the detection of underlying assembly mechanisms—especially for species‐rich arthropod communities. We sampled subtropical ground‐dwelling ant communities using a paired treatment design comprising pitfall traps and Winkler extractors (Winklers), two commonly used sampling techniques for terrestrial arthropods, in 17 shrublands and 33 secondary forest 400 m2 plots in Hong Kong to determine the effect of sampling filters on functional composition (community means of six morphological traits) and functional diversity (range and variance of individual traits; size and filling properties of multidimensional trait space) using a null model approach for each habitat. We found, as hypothesized, that sampling filters from different methods affected the trait composition and diversity of ant communities asymmetrically. In shrublands and forests, the trait compositions of communities sampled by pitfall traps were dominated by larger sized, slender‐shaped and long‐legged ants as compared to those sampled by Winklers. The latter method also underestimated the diversity of individual traits related to body size as well as the size and filling properties of multidimensional trait space. Our results highlight that the usage of particular sampling methods without prior knowledge on their potential filtering effects on traits can affect the detection of assembly processes, and interpretation of functional proxies, such as body size. Additional care should be taken when comparing trait components obtained from studies using different sampling methods, so as to distinguish the sampling artefacts from actual ecological phenomena. Hence, it is important to consider the potential biases that different sampling methods may introduce to functional trait‐based research.

Woody biomass removal in harvested boreal forest leads to a partial functional homogenization of soil mesofaunal communities relative to unharvested forest

Land-use intensification can lead to taxonomic and/or functional homogenization of biotic communities, with potential consequences for ecosystem functioning. In boreal forests, managers are increasingly considering intensifying woody biomass removal for bioenergy, but associated functional effects on soil fauna that use microhabitats associated with this biomass remain poorly understood. Two years after harvesting, we assessed the effects of an increasing intensity gradient of biomass removal in a northeastern Ontario jack pine (Pinus banksiana) stand on the functional structure of Collembola and Oribatida communities, two abundant soil taxa. The gradient ranged from (1) uncut forest to (2) stem-only harvesting to intense biomass removal through (3) whole-tree harvesting (stem, top and branches) with (4) stump removal and (5) additional removal of organic soil strata. Morphological and life-history response traits associated with hypothesized functions were measured to determine changes in the functional structure (species trait diversity and composition) of communities in response to the gradient and related environmental changes. We found that functional structure of communities of both taxa was overall significantly modified by biomass removal through a compositional shift in species traits in comparison to uncut forest. Functional homogenization was observed for Oribatida communities with a loss of species that were surface-dwelling, larger, predominantly sexually reproducing and mostly micro-detritivorous. In contrast, Collembola communities were less affected with only the most extreme treatment showing a more homogenized community than the uncut forest. These functional changes were mainly explained by fewer suitable microhabitats, characterized for example by a more stable microclimate as well as more abundant and diverse food resources, due to the disturbance of forest floor organic cover with harvesting. To improve sustainable management of boreal forests, long-term studies will be needed to assess if partial functional homogenization of soil mesofauna by intensive practices persists through time and may influence soil ecosystem function.

Effect of river restoration on life-history strategies in fish communities

Assessments of river restoration outcomes are mostly based on taxonomic identities of species, which may not be optimal because a direct relationship to river functions remains obscure and results are hardly comparable across biogeographic borders. The use of ecological species trait information instead of taxonomic units may help to overcome these challenges.Abundance data for fish communities were gathered from 134 river restoration projects conducted in Switzerland, Germany and Finland, monitored for up to 15 years. These data were related to a dataset of 22 categories of ecological traits describing fish life-history strategies to assess the outcome of the restoration projects.Restoration increased trait functional diversity and evenness in projects that were situated in the potamal zone of rivers. Restoration effect increased with the length of the restored river reaches. In areas with low levels of anthropogenic land use, the peak of the restoration effect was reached already within one to five years after the restoration and effect receded thereafter, while communities responded later in areas with higher levels of anthropogenic land use.In the lower potamal zone, a shift towards opportunistic life-history strategists was observed. In the upper rhithral zone, in contrast, species with an opportunistic life-history strategy increased only in the first five years of restoration, followed by a shift towards equilibrium strategists at restorations older than 5 years. This pattern was more pronounced in rivers with higher level of anthropogenic land use and longer restored river reaches. Restoration reduced the variability in community trait composition between river reaches suggesting that community trait composition within these zones converges when rivers are restored.This study showed how ecological traits are suitable to analyse restoration outcomes and how such an approach can be used for the evaluation and comparison of environmental management actions across geographical regions.

Short-term changes in plant functional traits and understory functional diversity after logging of different intensities: a temperate fir-beech forest experiment

The concept of plant functional traits has been demonstrated to be very effective in unravelling the ecological mechanisms governing plant community response to disturbance, especially when research is focused on short-term post-disturbance vegetation dynamics. In this study, we established an experiment to quantify how logging intensity affects the trait composition and functional diversity of understory communities in fir-beech forests in the Dinaric Mountains in Slovenia. Three different silvicultural treatments were implemented: control (no logging), 50% of the growing stock removed and 100% of the growing stock removed. Vegetation surveys of vascular plants were made before (in 2012) and two years after (in 2014) logging. Changes in species traits, C-S-R plant strategies (sensu Grime) and community-level functional diversity were analysed. The importance of traits such as small and light diaspores, short life span and anemochory increased with logging intensity. Moreover, species with the ability of both sexual and vegetative reproduction, longer flowering duration and overwintering green leaves increased in abundance after logging. C-S-R strategies mainly shifted from stress-tolerators in pre-logging conditions towards a more ruderal component in post-logging stands. Logging in the short term increased functional diversity, mainly due to newly colonized species being functionally dissimilar from persistent residents. Results suggest that logging intensity strongly influences the magnitude of change in both functional composition and diversity, which also has important implications for biodiversity conservation. At the landscape scale, increasing spatial heterogeneity by creating a mosaic of forest stands subjected to different logging intensities will likely contribute to the enhancement of plant functional diversity.

Effects of stand-level and landscape factors on understorey plant community traits in broad-leaved forest of the boreo-nemoral zone in Latvia

Knowledge of the limiting processes shaping the composition of plant communities of woodland is important in conservation of biological diversity. The aim of our study was to examine the effect of stand-level factors (soil and canopy composition, age and area) and landscape factors (fragmentation of broad-leaved forest, distance to a historical manor house, and past history) on plant community trait composition in broad-leaved forest. We hypothesized that the plant functional community is shaped by both dispersal filtering due to landscape factors and by environmental characteristics. We recorded all vascular plants, described canopy composition and estimated soil characteristics in 44 randomly chosen broad-leaved stands in Latvia. Relationships between plant community traits and potential factors were assessed using PCA and multivariate regression analysis. Interrelationship of richer topsoil fertility and admixture of broad-leaved tree species other than Q. robur was associated with greater abundance of nemoral species and hemicryptophytes. The invasion of Picea abies into the canopy was associated with poor topsoil fertility and acidified soil, likely due to poor litter quality, and with greater number of boreal species and geophytes in the herb layer. The results suggested a weak and contradictory effect of landscape structure and history on the forest plant community traits, maybe because the long-term history of afforestation around manors and spatio-temporal connectivity to ancient forests had resolved these effects.

Contrasting distribution patterns between aquatic and terrestrial Phytophthora species along a climatic gradient are linked to functional traits

Diversity of microbial organisms is linked to global climatic gradients. The genus Phytophthora includes both aquatic and terrestrial plant pathogenic species that display a large variation of functional traits. The extent to which the physical environment (water or soil) modulates the interaction of microorganisms with climate is unknown. Here, we explored the main environmental drivers of diversity and functional trait composition of Phytophthora communities. Communities were obtained by a novel metabarcoding setup based on PacBio sequencing of river filtrates in 96 river sites along a geographical gradient. Species were classified as terrestrial or aquatic based on their phylogenetic clade. Overall, terrestrial and aquatic species showed contrasting patterns of diversity. For terrestrial species, precipitation was a stronger driver than temperature, and diversity and functional diversity decreased with decreasing temperature and precipitation. In cold and dry areas, the dominant species formed resistant structures and had a low optimum temperature. By contrast, for aquatic species, temperature and water chemistry were the strongest drivers, and diversity increased with decreasing temperature and precipitation. Within the same area, environmental filtering affected terrestrial species more strongly than aquatic species (20% versus 3% of the studied communities, respectively). Our results highlight the importance of functional traits and the physical environment in which microorganisms develop their life cycle when predicting their distribution under changing climatic conditions. Temperature and rainfall may be buffered differently by water and soil, and thus pose contrasting constrains to microbial assemblies.