Community Functional Responses Research Articles

Identifying ‘climate keystone species’ as a tool for conserving ecological communities under climate change

AbstractAimClimate change affects ecological communities via impacts on species. The community's response to climate change can be represented as the temporal trend in a climate‐related functional property that is quantified using a relevant functional trait. Noteworthy, some species influence this response in the community more strongly than others.InnovationLeveraging on the concept of keystone species, we propose that species with a strong effect on the community's functional response to climate change beyond their relative abundance can be considered as ‘climate keystone species’. We develop a stepwise tool to determine species' effects on a community's climate response and identify climate keystone species. We quantify the species‐specific effect by measuring the difference in the community's climate response with and without the species. Next, we identify climate keystone species as those with a strong residual effect after weighting with their relative abundances in the community.Main ConclusionsTo illustrate the use of the stepwise tool with empirical data, we identify climate keystone species that have a strong effect on the change in the average temperature niche in North American bird communities over time and find the identification tool ecologically relevant. Identification of climate keystone species can serve as an additional conservation method to efficiently protect ecological communities and, in turn, the ecosystem functions they provide.

Re-inoculated Bacteria Driving Microbial Community Functional Response to Bioleaching of Low-Grade Copper Sulfide Ores: Potential to Improve Copper Recovery

Re-inoculated Bacteria Driving Microbial Community Functional Response to Bioleaching of Low-Grade Copper Sulfide Ores: Potential to Improve Copper Recovery

Response-effect trait overlap and correlation in riparian plant communities suggests sensitivity of ecosystem functioning and services to environmental change

Environmental changes and biodiversity loss have emphasized the need to understand how communities affect ecosystem functioning and services. In riparian ecosystems, integrative, generalizable, broad-scale models of ecosystem functioning are still required to fulfill this need. However, few studies have explored the links between functional traits, ecosystem functions, and the services of riparian vegetation. Here we adapt the response-effect trait framework to link drivers, traits, ecosystem functions, and services in riparian ecosystems and assess ecosystem functioning sensitivity to environmental changes. The response-effect trait framework distinguishes between traits related to responses to the environment (response traits) and effects on ecosystem functioning (effect traits). The framework predicts that if response and effect traits are tightly linked, shifts in environmental drivers may alter communities' traits and ecosystem functioning.We adapted the response-effect trait framework for riparian plant communities and used it to assess the overlap between response and effect traits. We tested for correlation among traits identified in the framework and for community functional responses to climatic, topographic, soil, and land cover factors using riparian plant communities along a Temperate-Mediterranean climate gradient in North Portugal.We found a high overlap between response and effect traits, with seven out of thirteen traits identified as both response and effect. Additionally, we found trait linkages in four groups of positively correlated community mean traits. Precipitation and aridity were the most predictive drivers of community functional structure, and life form and leaf area were the most responsive traits.Overall, our findings suggest riparian plant communities are likely to propagate the effects of environmental changes to ecosystem functioning and services, affecting several regulation ecosystem services.This work highlights the sensitivity of riparian ecosystems to environmental changes and how it can affect ecosystem services. Similar functional approaches can be useful for adaptive ecosystem management to sustain biodiversity and ecosystem services.

Different functional feeding groups of mangrove soil molluscs invoke unique co‐occurrence patterns in response to a climate extreme

AbstractAimDue to differences in community functional traits and composition, the response of communities to environmental changes can be variable, and thus an understanding of the mechanisms underlying differential functional group responses is necessary. We investigated a mangrove soil mollusc community before (in 2007) and after (in 2008 and 2009) an extreme cold event (ECE) to determine the effects of the ECE on co‐occurrence patterns, spatiotemporal turnover and ecological processes in different functional groups (i.e. in‐faunal shelled deposit feeders [ISDFs] and hard‐bodied, mobile scavenger/predators [MS/Ps]).LocationSoutheast coasts of China.MethodWe used network analysis and null models to test the co‐occurrence patterns of the soil mollusc community. We used the analysis of distance and time decay to characterize the spatial turnover and temporal succession of the mollusc community based on presence/absence, relative abundance and biomass data. We performed random forest (RF), variation partitioning analysis (VPA) and Mantel tests to detect the effects of local environmental filtering and dispersal limitations on the soil mollusc community.ResultsWe found a decrease in species richness and biomass and an increase in abundance after an ECE, reflecting a significant change in mangrove soil mollusc communities. The network modularization, divergent succession and geographical differentiation of the ISDFs increased from 2008 to 2009, but environmental filtering and regional dispersal limitations decreased. The temporal trends of the network modules, geographical differentiation and dispersal limitations of MS/Ps followed a hump‐shaped pattern from 2008 to 2009, whereas the temporal trends of environmental filtering and temporal divergence exhibited an inverted hump‐shape pattern. The ECE changed the main environmental drivers of ISDFs and MS/Ps from water salinity to meteorology and vegetation factors.Main conclusionsMangrove soil mollusc communities in different functional groups invoked different spatiotemporal turnover models and ecological processes to shape unique co‐occurrence patterns in response to an ECE. We highlight the value of dividing different functional groups in developing predictive frameworks for a better understanding of community functional responses to global change.

The interaction of acidophiles driving community functional responses to the re-inoculated chalcopyrite bioleaching process

Re-inoculation was an effective way to improve bioleaching efficiency by enhancing the synergetic effects of biogenic Fe3+ coupling with S0 oxidation. However, the complex microbial interactions after re-inoculation have received far less attention, which was crucial to the bioleaching performances. Herein, the enriched ferrous oxidizers (FeO) or sulfur oxidizers (SO) were inoculated to chalcopyrite microcosm, then they were crossly re-inoculated again to characterize the interspecific interaction patterns. The results showed that the dominant species in Fe groups were Acidithiobacillus ferrooxidans, while A. thiooxidans predominated in S groups. Introducing FeO resulted in a great disturbance by shifting the community diversity and evenness significantly (p < 0.05). In comparison, the communities intensified by SO maintained the original composition and structures. Microbial networks were constructed positively and modularly. The networks intensified by FeO were less connected and complex with less nodes and edges, but showed faster responses to the re-inoculation disturbance reflected by shorter average path length. Interestingly, the genus Leptospirillum were identified as keystones in S groups, playing critical roles in iron-oxidizing with lots of sulfur oxidizers. The introduced sulfur oxidizers enhanced microbial cooperation, formed robust community with strong bio-dissolution capability, and harbored the highest bioleaching efficiency. These findings improved our understanding about the acidophiles interactions, which drive community functional responses to the re-inoculated bioleaching process.

Distinct temporal diversity profiles for nitrogen cycling genes in a hyporheic microbiome.

Biodiversity is thought to prevent decline in community function in response to changing environmental conditions through replacement of organisms with similar functional capacity but different optimal growth characteristics. We examined how this concept translates to the within-gene level by exploring seasonal dynamics of within-gene diversity for genes involved in nitrogen cycling in hyporheic zone communities. Nitrification genes displayed low richness-defined as the number of unique within-gene phylotypes-across seasons. Conversely, denitrification genes varied in both richness and the degree to which phylotypes were recruited or lost. These results demonstrate that there is not a universal mechanism for maintaining community functional potential for nitrogen cycling activities, even across seasonal environmental shifts to which communities would be expected to be well adapted. As such, extreme environmental changes could have very different effects on the stability of the different nitrogen cycle activities. These outcomes suggest a need to modify existing conceptual models that link biodiversity to microbiome function to incorporate within-gene diversity. Specifically, we suggest an expanded conceptualization that 1) recognizes component steps (genes) with low diversity as potential bottlenecks influencing pathway-level function, and 2) includes variation in both the number of entities (e.g. species, phylotypes) that can contribute to a given process and the turnover of those entities in response to shifting conditions. Building these concepts into process-based ecosystem models represents an exciting opportunity to connect within-gene-scale ecological dynamics to ecosystem-scale services.

Soil chemistry and microbial community functional responses to invasive shrub removal in mixed hardwood forests

Invasive woody plant species are a threat to biodiversity and ecosystem function in forests of the eastern U.S., due in part to their effects on soil properties and nutrient cycling. Controlling invasive shrubs can benefit the ecosystem at multiple scales, but these species tend to resprout when cut, and post-cutting flushes of root exudates have been linked to accelerated decomposition of soil organic matter (SOM), a rhizosphere priming effect. We removed the invasive shrub Lonicera maackii (Rupr.) Herder (Amur honeysuckle) from forested sites in central Indiana, USA, using cut-stump and forestry mulching head treatments. For two growing seasons after the initial removal treatments, we compared the soil chemistry and microbial community function of bulk and honeysuckle rhizosphere soils in shrub removal areas to those in invaded reference areas. Microbial activity measured using multiple substrate induced respiration (MSIR) in bulk soils was generally lower in removal areas than reference areas the first year, coinciding with relatively elevated responses in the rhizosphere soils of resprouting shrubs. Elevated SOM and organic C in rhizosphere soils of resprouting shrubs suggested a flush of rhizodeposits from cutting and regrowth. However, bulk soil chemistry responses to shrub removal did not show any evidence of a rhizosphere priming effect, but instead reflected the reduced effects of honeysuckle on throughfall precipitation chemistry—higher ammonium and lower magnesium. Nonetheless, changes in bulk soil chemistry between years were driven by the chemical characteristics of rhizosphere soil associated with resprouting honeysuckle. This study is the first to document the potential for invasive shrub control to affect soil properties through rhizodeposition by the target species.

Urban stream microbial communities show resistance to pharmaceutical exposure

AbstractResidues of pharmaceuticals are increasingly detected in surface waters throughout the world. In four streams in Baltimore, Maryland, USA, we detected analgesics, stimulants, antihistamines, and antibiotics using passive organic samplers. We exposed biofilm communities in these streams to the common drugs caffeine, cimetidine, ciprofloxacin, and diphenhydramine. Respiration rates in the least urban stream were suppressed when exposed to these drugs, but biofilm functioning in the most urban stream was resistant to drug exposure. Exposure to the antibiotic ciprofloxacin altered bacterial community composition at all sites, with the greatest change occurring in the most urban stream. These results indicated that continuous exposure to drugs in urban streams may select for sub‐populations of highly resistant bacteria that maintain community function in response to urban contaminants.

Harvesting Douglas-fir Stands Shifts Soil Microbial Activity and Biogeochemical Cycling

Clear-cutting is a common timber extraction method used across the Pacific Northwest, but the variability in soil microbial community functional response across the range of soil types and stand ages in the region is largely unknown. Our objective was to determine if shifts in soil microbial carbon (C) and nitrogen (N) pools and activities shortly following harvest are similar among similarly treated, but environmentally diverse sites. At nine second-growth Douglas-fir forests, paired soil samples were collected one year before and after clear-cutting. Samples were analyzed for total, extractable, and microbial biomass C and N, and seven extracellular enzyme activities. Total C and N did not change following harvest, but extractable organic C decreased and total extractable N increased. Microbial biomass C generally increased, as did microbial C/N. Activities of β-glucosidase and cellobiohydrolase increased significantly, whereas activities of phenol oxidase and peroxidase decreased. N-acetylglucosaminidase, leucine aminopeptidase, and phosphatase showed site-specific responses. Cumulative respiration during a 3-mo incubation was lower in post-harvest soils. Although the total N leached during the incubation was similar in soils sampled before and after harvest, it was dominated by dissolved organic N pre-harvest and NO₃⁻ post-harvest. Collectively, the changes in soils following harvest were related to shifts in available C and N. Pre-harvest measurements suggested that soil microbial communities may be co-limited by C and N, whereas C limitation was suggested post-harvest. Analyzing short-term microbial responses following harvest may bolster understanding of post-harvest successional processes, which is essential for determining the long-term sustainability of these practices.

Grazing‐induced shifts in community functional composition and soil nutrient availability in Tibetan alpine meadows

SummaryThe functional structure of plant communities can be altered by grazing through two main mechanisms: species turnover (i.e. changes in species occurrence and relative abundance) and intraspecific trait variability (ITV), which is driven by phenotypic responses of individual plants and shifts in the relative abundance of genotypic variants within species. Studies of grassland ecosystem function under grazing often focus on community changes induced by species turnover, which ignores the effects ofITVon biomass productivity, soil carbon or nutrient availability. By quantifying the relative contribution of both effects on shifts in community‐wide traits, we highlight the role ofITVin community functional response to grazing and its implications for ecosystem function in Tibetan alpine meadows.We measured three chemical traits (LC: leaf carbon,LN: leaf nitrogen andLP: leaf phosphorus concentrations) and two morphological traits (SLA: specific leaf area,LDMC: leaf dry matter content) that are critical components of plant production and forage quality in grazed and ungrazed plots. Using variance decomposition of community‐weighted means (CWM) for these foliar traits, we distinguished the relative importance ofITVvs. change in species occurrence and abundance in response to grazing and the associated changes in soil carbon and nutrient availability.TheCWMfor foliar nutrients andSLACWMincreased in response to grazing together with decreases in soil carbon and nutrient stores, especiallyLPCWMenrichment and loss of available soil P. TheLPCWMwas strongly negatively correlated withLDMCCWM, which was significantly higher in ungrazed plots. These community‐wide trait responses to grazing were generally best captured byITVand not changes in species occurrence and abundance, althoughITVwas consistently correlated with species turnover for all traits.Synthesis and applications. In response to continuous grazing, plants in Tibetan alpine meadows increase specific leaf area and foliar nutrients but tend to have lower leaf dry matter content, a response consistent with faster growth and regrowth under grazing. This intraspecific trait variability response drives a shift in community function from conservative, slow‐growing resource use in ungrazed meadows to exploitative resource use under grazing. This community‐wide functional response enhances forage quality, in turn favouring the secondary productivity of small herbivorous mammal communities, but also contributes to accelerated depletion of soil available phosphorus. We discuss the implications of these results for biodiversity conservation, ecosystem function and rangeland sustainability in the Qinghai–Tibetan Plateau, especially with regard to managing grazing rotation to strike a balance between favouring secondary productivity of domesticated stock vs. small herbivorous mammals.

Intraspecific trait variation drives functional responses of old-field plant communities to nutrient enrichment.

Environmental changes are expected to shift the distribution of functional trait values in plant communities through a combination of species turnover and intraspecific variation. The strength of these shifts may depend on the availability of individuals with trait values adapted to new environmental conditions, represented by the functional diversity (FD) of existing community residents or dispersal from the regional species pool. We conducted a 3-year nutrient- and seed-addition experiment in old-field plant communities to examine the contributions of species turnover and intraspecific variation to community trait shifts, focusing on four key plant functional traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We further examined the influence of initial FD and seed availability on the strength of these shifts. Community mean height, leaf area, and SLA increased in response to fertilization, and these shifts were driven almost entirely by intraspecific variation. The strength of intraspecific shifts in height and leaf area was positively related to initial intraspecific FD in these traits. Intraspecific trait responses to fertilization varied among species, with species of short stature displaying stronger shifts in SLA and LDMC but weaker shifts in leaf area. Trait shifts due to species turnover were generally weak and opposed intraspecific responses. Seed addition altered community taxonomic composition but had little effect on community trait shifts. These results highlight the importance of intraspecific variation for short-term community functional responses and demonstrate that the strength of these responses may be mediated by community FD.

Integrating Ecological and Engineering Concepts of Resilience in Microbial Communities.

Many definitions of resilience have been proffered for natural and engineered ecosystems, but a conceptual consensus on resilience in microbial communities is still lacking. We argue that the disconnect largely results from the wide variance in microbial community complexity, which range from compositionally simple synthetic consortia to complex natural communities, and divergence between the typical practical outcomes emphasized by ecologists and engineers. Viewing microbial communities as elasto-plastic systems that undergo both recoverable and unrecoverable transitions, we argue that this gap between the engineering and ecological definitions of resilience stems from their respective emphases on elastic and plastic deformation, respectively. We propose that the two concepts may be fundamentally united around the resilience of function rather than state in microbial communities and the regularity in the relationship between environmental variation and a community's functional response. Furthermore, we posit that functional resilience is an intrinsic property of microbial communities and suggest that state changes in response to environmental variation may be a key mechanism driving functional resilience in microbial communities.

Plant trait variation along an altitudinal gradient in mediterranean high mountain grasslands: controlling the species turnover effect.

Assessing changes in plant functional traits along gradients is useful for understanding the assembly of communities and their response to global and local environmental drivers. However, these changes may reflect the effects of species composition (i.e. composition turnover), species abundance (i.e. species interaction), and intra-specific trait variability (i.e. species plasticity). In order to determine the relevance of the latter, trait variation can be assessed under minimal effects of composition turnover. Nine sampling sites were established along an altitudinal gradient in a Mediterranean high mountain grassland community with low composition turnover (Madrid, Spain; 1940 m–2419 m). Nine functional traits were also measured for ten individuals of around ten plant species at each site, for a total of eleven species across all sites. The relative importance of different sources of variability (within/between site and intra-/inter-specific functional diversity) and trait variation at species and community level along the considered gradients were explored. We found a weak individual species response to altitude and other environmental variables although in some cases, individuals were smaller and leaves were thicker at higher elevations. This lack of species response was most likely due to greater within- than between-site species variation. At the community level, inter-specific functional diversity was generally greater than the intra-specific component except for traits linked to leaf element content (leaf carbon content, leaf nitrogen content, δ13C and δ15N). Inter-specific functional diversity decreased with lower altitude for four leaf traits (specific leaf area, leaf dry matter content, δ13C and δ15N), suggesting trait convergence between species at lower elevations, where water shortage may have a stronger environmental filtering effect than colder temperatures at higher altitudes. Our results suggest that, within a vegetation type encompassing various environmental gradients, both, changes in species abundance and intra-specific trait variability adjust for the community functional response to environmental changes.

Phenotypic plasticity in heterotrophic marine microbial communities in continuous cultures.

Phenotypic plasticity (PP) is the development of alternate phenotypes of a given taxon as an adaptation to environmental conditions. Methodological limitations have restricted the quantification of PP to the measurement of a few traits in single organisms. We used metatranscriptomic libraries to overcome these challenges and estimate PP using the expressed genes of multiple heterotrophic organisms as a proxy for traits in a microbial community. The metatranscriptomes captured the expression response of natural marine bacterial communities grown on differing carbon resource regimes in continuous cultures. We found that taxa with different magnitudes of PP coexisted in the same cultures, and that members of the order Rhodobacterales had the highest levels of PP. In agreement with previous studies, our results suggest that continuous culturing may have specifically selected for taxa featuring a rather high range of PP. On average, PP and abundance changes within a taxon contributed equally to the organism's change in functional gene abundance, implying that both PP and abundance mediated observed differences in community function. However, not all functional changes due to PP were directly reflected in the bulk community functional response: gene expression changes in individual taxa due to PP were partly masked by counterbalanced expression of the same gene in other taxa. This observation demonstrates that PP had a stabilizing effect on a community's functional response to environmental change.

Community functional responses to soil and climate at multiple spatial scales: when does intraspecific variation matter?

Despite increasing evidence of the importance of intraspecific trait variation in plant communities, its role in community trait responses to environmental variation, particularly along broad-scale climatic gradients, is poorly understood. We analyzed functional trait variation among early-successional herbaceous plant communities (old fields) across a 1200-km latitudinal extent in eastern North America, focusing on four traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We determined the contributions of species turnover and intraspecific variation to between-site functional dissimilarity at multiple spatial scales and community trait responses to edaphic and climatic factors. Among-site variation in community mean trait values and community trait responses to the environment were generated by a combination of species turnover and intraspecific variation, with species turnover making a greater contribution for all traits. The relative importance of intraspecific variation decreased with increasing geographic and environmental distance between sites for SLA and leaf area. Intraspecific variation was most important for responses of vegetative height and responses to edaphic compared to climatic factors. Individual species displayed strong trait responses to environmental factors in many cases, but these responses were highly variable among species and did not usually scale up to the community level. These findings provide new insights into the role of intraspecific trait variation in plant communities and the factors controlling its relative importance. The contribution of intraspecific variation to community trait responses was greatest at fine spatial scales and along edaphic gradients, while species turnover dominated at broad spatial scales and along climatic gradients.

Long-Term Functional Dynamics of an Aphidophagous Coccinellid Community Remain Unchanged despite Repeated Invasions

Aphidophagous coccinellids (ladybeetles) are important providers of herbivore suppression ecosystem services. In the last 30 years, the invasion of exotic coccinellid species, coupled with observed declines in native species, has led to considerable interest in the community dynamics and ecosystem function of this guild. Here we examined a 24-year dataset of coccinellid communities in nine habitats in southwestern Michigan for changes in community function in response to invasion. Specifically we analyzed their temporal population dynamics and species diversity, and we modeled the community’s potential to suppress pests. Abundance of coccinellids varied widely between 1989 and 2012 and became increasingly exotic-dominated. More than 71% of 57,813 adult coccinellids captured over the 24-year study were exotic species. Shannon diversity increased slightly over time, but herbivore suppression potential of the community remained roughly constant over the course of the study. However, both Shannon diversity and herbivore suppression potential due to native species declined over time in all habitats. The relationship between Shannon diversity and herbivore suppression potential varied with habitat type: a positive relationship in forest and perennial habitats, but was uncorrelated in annual habitats. This trend may have been because annual habitats were dominated by a few, highly voracious exotic species. Our results indicated that although the composition of the coccinellid community in southwestern Michigan has changed dramatically in the past several decades, its function has remained relatively unchanged in both agricultural and natural habitats. While this is encouraging from the perspective of pest management, it should be noted that losses of one of the dominant exotic coccinellids could result in a rapid decline in pest suppression services if the remaining community is unable to respond.

Intraspecific trait variability mediates the response of subalpine grassland communities to extreme drought events

Summary Climate change is expected to increase the magnitude and the frequency of extreme climatic events such as droughts. Better understanding how plant communities will respond to these droughts is a major challenge. We expect the response to be a shift in functional trait values resulting from both species turnover and intraspecific trait variability, but little research has addressed the relative contribution of both components. We analysed the short‐term functional response of subalpine grassland communities to a simulated drought by focusing on four leaf traits (LDMC: leaf dry matter content, SLA: specific leaf area, LNC: leaf nitrogen concentration and LCC: leaf carbon concentration). After evaluating species turnover and intraspecific variability separately, we determined their relative contribution in the community functional response to drought, reflected by changes in community‐weighted mean traits. We found significant species turnover and intraspecific variability, as well as significant changes in community‐weighted mean for most of the traits. The relative contribution of intraspecific variability to the changes in community mean traits was more important (42–99%) than the relative contribution of species turnover (1–58%). Intraspecific variability either amplified (for LDMC, SLA and LCC) or dampened (for LNC) the community functional response mediated by species turnover. We demonstrated that the small contribution of species turnover to the changes in community mean LDMC and LCC was explained by a lack of covariation between species turnover and interspecific trait differences. Synthesis. These results highlight the need for a better consideration of intraspecific variability to understand and predict the effect of climate change on plant communities. While both species turnover and intraspecific variability can be expected following an extreme drought, we report new evidence that intraspecific variability can be a more important driver of the short‐term functional response of plant communities.

Structural and functional vulnerability to elevated pCO2 in marine benthic communities

The effect of elevated pCO2/low pH on marine invertebrate benthic biodiversity, community structure and selected functional responses which underpin ecosystem services (such as community production and calcification) was tested in a medium-term (30 days) mesocosm experiment in June 2010. Standardised intertidal macrobenthic communities, collected (50.3567°N, 4.1277°W) using artificial substrate units (ASUs), were exposed to one of seven pH treatments (8.05, 7.8. 7.6, 7.4, 7.2, 6.8 and 6.0). Community net calcification/dissolution rates, as well as changes in biomass, community structure and diversity, were measured at the end of the experimental period. Communities showed significant changes in structure and reduced diversity in response to reduced pH: shifting from a community dominated by calcareous organisms to one dominated by non-calcareous organisms around either pH 7.2 (number of individuals and species) or pH 7.8 (biomass). These results were supported by a reduced total weight of CaCO3 structures in all major taxa at lowered pH and a switch from net calcification to net dissolution around pH 7.4 (Ωcalc = 0.78, Ωara = 0.5). Overall community soft tissue biomass did not change with pH and high mortality was observed only at pH 6.0, although molluscs and arthropods showed significant decreases in soft tissue. This study supports and refines previous findings on how elevated pCO2 can induce changes in marine biodiversity, underlined by differential vulnerability of different phyla. In addition, it shows significant elevated pCO2-/low pH-dependent changes in fundamental community functional responses underpinning changes in ecosystem services.

Assessing species and community functional responses to environmental gradients: which multivariate methods?

AbstractQuestionHow do multivariate methods perform in relating species‐ and community‐level trait responses to the environment?Location(1) Field data from grazed semi‐natural grasslands, NE Germany; (2) artificial data.MethodsResearch questions associated with trait–environment relationships were briefly reviewed and seven available methods evaluated. The main distinction between research questions is whether trait–environment relationships should be addressed at community or species level. A redundancy analysis (RDA) of mean trait values of species in a plot weighted by their abundances (CWM‐RDA) is exclusively suitable for the community level. The other six methods address the species level. A double inertia analysis of two arrays (RLQ) and double canonical correspondence analysis (doubleCCA) use combinations of ordinations to simultaneously analyse species and trait responses to the environment. A combination of the outlying mean index with generalized additive models (OMI‐GAM) predicts the response of species to environmental variables on trait gradients.RDA‐RegTree first analyses species responses to the environment withRDAand then uses a regression tree to classify trait expressions according to scores of species responses on the ordination axes. Cluster regression uses cluster analyses and logistic regression to search for trait combinations with the best response to the environmental variables. This method models the distribution of functional groups on environmental gradients. All methods and data are available as R scripts.ResultsAll methods consistently revealed the main trait responses to environment in the field data set, namely that life history was associated with available phosphorus while grazing intensity was related to leafC:Nratio and canopy height. At community level,CWM‐RDAgave a good overview of trait–environment relationships, as also provided by the species‐based methodsRLQand doubleCCA.OMI‐GAMrevealed non‐linear relationships in the field data set. Field and artificial data gave that the number and stability of functional groups produced byCluster regression andRDA‐RegTree varied more strongly thanRLQ, doubleCCAandOMI‐GAM.ConclusionsEach method addresses particular ecological concepts and research questions. If a user asks for the response of average trait expressions of communities to environmental gradients,CWM‐RDAmay be the first choice. However, species‐based methods should be applied to address questions regarding co‐existence of different life histories or to assess how groups of species respond to environmental changes. The artificial data set revealed that the methods differed in sensitivity to gradient lengths and random data.

Combining plant and animal traits to assess community functional responses to disturbance

There is a general consensus that functional traits are reliable indicators of adaptation of organisms to particular environmental characteristics. In this study we relate the combined distributions of species traits of plants and animals to disturbance regimes in chestnut forests of southern Switzerland affected by regular winter fires. We used co‐inertia analysis for combining the trait response of 471 invertebrate species (117 001 individuals) and 81 plant species at 23 sites with different fire and cutting histories. Trait response was assessed by calculating the variation in weighted mean traits averaged over the communities and by using mean traits in multivariate analyses. The analysis showed a strong association between plant and animal traits under fire constraints (Monte‐Carlo test, p=0.0045). Plants and animal distributions show parallel trends in responses to fire which selects traits relating to persistence (ability to survive), resilience (ability to recover) and mobility. Warmth‐demanding insects, herbivores, flying carnivores and pollinators were associated with recent fires, as were annual, ruderal and light‐demanding plant species with long flowering duration. Small arthropods feeding on dead wood and those with narrow habitat requirements were associated with low fire frequency and unburnt sites, as were competitive plants with large seeds favoring moist sites. The spatial association between plant and animal traits reflected adaptations that promote survival in the disturbance regime, while the disturbance acts as an environmental filter on the distribution and assemblage of the trait values within communities.This combined analysis of plant and invertebrate traits distributions illustrates how community and ecosystem responses can be monitored and the results generalized across localities and disturbance types. Analyses of traits that cross trophic levels provide powerful and promising tools for validating management procedures and controlling ecosystem functions.