Trait Composition Of Plant Communities Research Articles

Giant root-rat engineering and livestock grazing activities regulate plant functional trait diversity of an Afroalpine vegetation community in the Bale Mountains, Ethiopia

Disturbances from rodent engineering and human activities profoundly impact ecosystem structure and functioning. Whilst we know that disturbances modulate plant communities, comprehending the mechanisms through which rodent and human disturbances influence the functional trait diversity and trait composition of plant communities is important to allow projecting future changes and to enable informed decisions in response to changing intensity of the disturbances. Here, we evaluated the changes in functional trait diversity and composition of Afroalpine plant communities in the Bale Mountains of Ethiopia along gradients of engineering disturbances of a subterranean endemic rodent, the giant root-rat (Tachyoryctes macrocephalus Rüppell 1842) and human activities (settlement establishment and livestock grazing). We conducted RLQ (co-inertia analysis) and fourth-corner analyses to test for trait-disturbance (rodent engineering/human activities) covariation. Overall, our results show an increase in plant functional trait diversity with increasing root-rat engineering and increasing human activities. We found disturbance specific association with traits. Specifically, we found strong positive association of larger seed mass with increasing root-rat fresh burrow density, rhizomatous vegetative propagation negatively associated with increasing root-rat old burrow, and stolonifereous vegetative propagation positively associated with presence of root-rat mima mound. Moreover, both leaf size and leaf nitrogen content were positively associated with livestock dung abundance but negatively with distance from settlement. Overall, our results suggest that disturbances by rodents filter plant traits related to survival and reproduction strategies, whereas human activities such as livestock grazing act as filters for traits related to leaf economics spectrum along acquisitive resource-use strategy.

The trait co-variation regulates the response of bryophytes to nitrogen deposition: A meta-analysis

The nitrogen deposition has the potential to alter the trait composition of plant communities by affecting the fitness and physiological adaptation of species, consequently exerting an influence on ecosystem processes. Despite the importance of bryophytes in nutrient and carbon dynamics across different ecosystems, there is a lack of research examining the relationship between nitrogen deposition and the co-variation of bryophyte traits. To address this gap, a meta-analysis was conducted using data from 27 independent studies to investigate potential associations between trait co-variation of bryophytes and nitrogen deposition. The results revealed that interspecific variability regulates the influence of nitrogen deposition on bryophytes by affecting trait co-variation. Multiple correspondence analysis identified six combinations of closely related traits. For example, species with unbranched main stems frequently exhibit robust leaf midribs, leading to leaf wrinkling and leaf clasping around the stem as a response to water loss. Some weft or mat species tend to obtain resources (nitrogen) through their scale hairs on the main stem. Some species with narrow leaves require leaf teeth to maintain a normal leaf shape. The subgroup analyses indicated that certain traits, including unbranched main stem, changes in leaf morphology, robust leaf midrib, main stem without scale hairs, narrow leaf, leaf margin with teeth, undeveloped apophysis, and erect capsule minimize interaction with pollutants and represent a resource strategy. Conversely, functional traits representing a resource acquisition strategy, such as branched main stem, no changes in leaf morphology, short and weak leaf midrib, main stem with scale hairs, broad leaf, leaf margin without teeth, developed apophysis, and non-erect capsule increase pollutant exposure. Overall, our results suggest that anthropogenic global change may significantly impact bryophytes due to changes in their individual physiology and colony ecological indicators caused by increased nitrogen deposition.

Intraspecific trait variation governs grazing-induced shifts in plant community above- and below-ground functional trait composition

In grasslands, grazing can regulate the functional trait composition of plant communities through intraspecific trait variation and species turnover. However, it is not well understood how these variables affect specific plant traits. Here, we partitioned the relative roles of intraspecific trait variation and species turnover to control grazing-induced shifts in community functional composition using a field manipulation experiment with seven levels of grazing intensity in the Inner Mongolia grassland. We concurrently measured six aboveground traits (i.e. plant height, plant aboveground biomass, plant density, leaf area, specific leaf area, SLA; and leaf density) and three root traits (average root diameter, ARD; specific root length, SRL; and root tissue density, RTD) of the first-, second- and third-order roots (1st-, 2nd-, and 3rd-). Our results showed that plant above-ground traits shifted towards grazing avoidance strategies (i.e. plant height and leaf area decreased) as grazing intensity increased, and below-ground traits shifted towards conservation strategies (i.e. 1st-SRL and 2nd-SRL decreased, 1st-RTD and 2nd-ARD increased). Additionally, functional tradeoffs were found between plant individual biomass and plant density, as well as between leaf area and leaf density under grazing. However, community-weighted mean SRL (SRLCWM) and ARD (ARDCWM) exhibited functional coordination under the grazing pressures. Altogether, shifts in community functional trait composition were predominantly governed by intraspecific variation in above- and below-ground traits, while changes in mean trait values among plant species with different resource strategies were mainly triggered by species turnover. Our results demonstrated that both above- and below-ground trait compositions in plant communities shifted towards conservation strategies under high levels of grazing intensity. Ultimately, this study highlights the important role of intraspecific trait variation in governing grazing-induced changes in the community above- and below-ground functional trait composition, which advances fundamental knowledge on the mechanisms of plant community assembly in semiarid grasslands.

Functional traits change but species diversity is not influenced by edge effects in an urban forest of Eastern China

Forest edges have significant effects on plant species and trait compositions. However, most current studies on edge effects are based on natural forests, and studies on edge effects in urban forests are still limited. Here, we set up 50 survey plots in Wuchao Mountain National Forest Park, an urban forest of Hangzhou, China. We tested how species composition changed with distance from the forest edge. Specifically, we investigated dispersal-related traits for 86 species, and analyzed trait composition changes with distance from the forest edge. The NMDS analysis revealed a significant difference in species composition between forest edge and interior, but species richness and functional diversity remain unchanged. However, single traits showed higher divergence than expected. The percentage of fleshy-fruited species declined with distance from the edge, but plant abundance of mammal-dispersed and animal-dispersal seed mass was increased. The different trend in seed size of different dispersal mode and seed mass from edge to the interior within the community may be related to the loss of mammal-dispersed plant species at the forest edge. This suggests that edge effects have a high influence on functional traits in urban forests, but not on species diversity. Edges had significant effects on animal-dispersed species and trait composition of plant communities. Our study highlights the importance of maintaining forest integrity by protecting interior habitats in urban regions. We also recommend reducing the creation of new edges and increasing the buffer area for biodiversity conservation.

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.

Cushion-plant protection determines guild-dependent plant strategies in high-elevation peatlands of the Cordillera Real, Bolivian Andes

The functional trait composition of plant communities reflects the influence of ecological constraints on their assembly. In high-elevation peatlands of the Andes, multiple abiotic and biotic stresses are exerted on herbaceous plant communities. We hypothesized that dominant cushion-plant species found in these ecosystems strongly influence the dynamics of their subordinate plants by providing protection against external stress. To test the hypothesis, we addressed the variation of functional traits reflecting how subordinate plants invest in durable tissues and develop below and above the canopy of two cushion-plant species dominating the ecosystem, with varying intensity of herbivore pressure. We expected different functional composition of plants living below (understory stratum) and above (emergent stratum) the canopy, related to cushion-plant protection. In addition, we considered the functional composition of basic morphological guilds, forbs and graminoids, as they invest differently in plant development and respond differently to herbivore pressure. We found contrasted functional compositions among morphological guilds and according to the position relatively to cushion-plant canopy. These variations support a protective influence of cushion-plants on subordinate plants for both strata, with investment into less costly leaves and a larger stature when protection is greater, depending on cushion-plant species and cushion-plant height. External stress mainly affected emergent plants and led to different responses according to the guild. Graminoids showed avoidant strategy, while forbs shifted from avoidant to tolerant strategy with increasing herbivore pressure. Both between-species and intraspecific trait variations contributed to explain functional changes of guilds, but the relative contributions depended on morphological guild and stratum. A basic trade-off in physiological and morphological variability determined different relative contribution in forbs and graminoids. While functional ecology classically focuses on the composition of spatially delimited communities, we here underline the need to address separately the functional composition and assembly dynamics of distinct guilds making a community. In addition, our survey is the first to investigate the functional ecology of high-elevation tropical peatlands and provides novel insights into vegetation ecology in this stressful ecosystem.

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.

A new paradigm for biomonitoring: an example building on the Danish Stream Plant Index

Summary Despite intensive efforts for more than a decade to develop Water Framework‐compliant assessment systems, shortcomings continue to appear. In particular, the lack of reference conditions has hindered the development of assessment systems capturing the heart of the Water Framework Directive (WFD) – that ecological status should be set as the deviation from the natural, undisturbed condition. Recently, the Danish Stream Plant Index (DSPI) was developed. This system contrasts existing systems in that it builds on an expert interpretation of the normative definitions of ecological status classes in the WFD without taking pressure–impact relationships into account. Here, we substantiate the approach taken in the development of DSPI and examine whether the DSPI class decreases with increasing level of anthropogenic stress and, additionally, whether the deviation from the natural undisturbed condition increases with decreasing DSPI class sensu WFD using trait composition of plant assemblages from Danish streams around year 1900 as a reference. We furthermore examine the trait composition of the vegetation in sites classified into different DSPI status classes to explore whether predictable patterns exist that can be used to identify the ultimate cause(s) of failure to meet ecological goals and help guide the selection of appropriate mitigation measures. We observed that DSPI declined with several parameters indicative of environmental stress in Danish streams and, furthermore, that the deviation from the natural undisturbed condition regarding the trait composition of plant communities declined with increasing DSPI, implying that the trait composition of plant communities in the high DSPI status class was most similar to those occurring in Danish streams around year 1900. We also found that trait characteristics capable of disentangling important stressors in Danish streams varied consistently among sites classified into different DSPI classes. Based on our findings, we call for new thinking. We suggest that more effort should be directed at describing reference conditions and interpreting the normative definitions of good, moderate, poor and bad instead of focusing solely on developing assessment systems using pressure–impact frameworks. We find this particularly important with respect to streams as these are seldom impacted by only a single stressor.

Functional traits composition predict macrophytes community productivity along a water depth gradient in a freshwater lake.

Functional trait composition of plant communities has been proposed as a helpful key for understanding the mechanisms of biodiversity effects on ecosystem functioning. In this study, we applied a step-wise modeling procedure to test the relative effects of taxonomic diversity, functional identity, and functional diversity on macrophytes community productivity along water depth gradient. We sampled 42 plots and 1513 individual plants and measured 16 functional traits and abundance of 17 macrophyte species. Results showed that there was a significant decrease in taxonomic diversity, functional identity (i.e., stem dry mass content, leaf [C] and leaf [N]), and functional diversity (i.e., floating leaf, mean Julian flowering date and rooting depth) with increasing water depth. For the multiple-trait functional diversity (FD) indices, functional richness decreased, while functional divergence increased with water depth gradient. Macrophyte community productivity was strongly determined by functional trait composition within community, but not significantly affected by taxonomic diversity. Community-weighted means (CWM) showed a two times higher explanatory power relative to FD indices in determining variations in community productivity. For nine of sixteen traits, CWM and FD showed significant correlations with community productivity, although the strength and direction of those relations depended on selected trait. Furthermore, functional composition in a community affected productivity through either additive or opposite effects of CWM and FD, depending on the particular traits being considered. Our results suggested both mechanisms of mass ratio and niche complementarity can operate simultaneously on variations in community productivity, and considering both CWM and FD would lead to a more profound understanding of traits–productivity relationships.

Mycorrhizal traits and plant communities: perspectives for integration

AbstractPlant functional type‐ and trait‐based approaches to understanding vegetation dynamics are gradually gaining popularity. However, plant mycorrhizal traits are rarely considered in plant trait databases and are almost totally neglected in trait‐based plant community studies, despite more than 90% of the land flora being mycorrhizal. In this paper I describe and define the mycorrhizal traits of plant species, notably mycorrhizal type, mycorrhizal status, mycorrhizal flexibility and mycorrhizal dependency, which potentially influence plant distribution and community structure. I propose ways of using these traits for large‐scale synthetic studies for understanding the role of mycorrhizal symbiosis in vegetation dynamics. I suggest considering plant community mycorrhization – community means of mycorrhizal traits weighted by plant species abundances – and suggest an index of mycorrhization to describe the mycorrhizal trait composition of plant communities.

Convergent effects of elevation on functional leaf traits within and among species

Summary Spatial variation in filters imposed by the abiotic environment causes variation in functional traits within and among plant species. This is abundantly clear for plant species along elevational gradients, where parallel abiotic selection pressures give rise to predictable variation in leaf phenotypes among ecosystems. Understanding the factors responsible for such patterns may provide insight into the current and future drivers of biodiversity, local community structure and ecosystem function. In order to explore patterns in trait variation along elevational gradients, we conducted a meta‐analysis of published observational studies that measured three key leaf functional traits that are associated with axes of variation in both resource competition and stress tolerance: leaf mass:area ratio (LMA), leaf nitrogen content per unit mass (Nmass) and N content per unit area (Narea). To examine whether there may be evidence for a genetic basis underlying the trait variation, we conducted a review of published results from common garden experiments that measured the same leaf traits. Within studies, LMA and Narea tended to decrease with mean annual temperature (MAT) along elevational gradients, while Nmass did not vary systematically with MAT. Correlations among pairs of traits varied significantly with MAT: LMA was most strongly correlated with Nmass and Narea at high‐elevation sites with relatively lower MAT. The strengths of the relationships were equal or greater within species relative to the relationships among species, suggesting parallel evolutionary dynamics along elevational gradients among disparate biomes. Evidence from common garden studies further suggests that there is an underlying genetic basis to the functional trait variation that we documented along elevational gradients. Taken together, these results indicate that environmental filtering both selects locally adapted genotypes within plant species and constrains species to elevational ranges based on their ranges of potential leaf trait values. If individual phenotypes are filtered from populations in the same way that species are filtered from regional species pools, changing climate may affect both the species and functional trait composition of plant communities.

Functional analysis of vegetation on alpine treeline ecotone in the Julian and Kamnik-Savinja Alps in Slovenia

Our study focused on the functional aspects of plant species and vegetation at the transition from larch (Larix decidua Mill.) forest to mountain pine (Pinus mugo Turra) stands on the alpine treeline ecotone. With increasing elevation, living conditions grow harsher, which is reflected in the plant species and functional trait composition of plant communities. At four different localities in the Slovenian Alps, releves along an altitudinal gradient and according to vegetation type were made (European larch forests, larch trees-mountain pine shrubs, mountain pine shrubs), using standard Central European phytocoenological method. In the upper mountain pine belt, few differential species were found, since most species represented in mountain pine stands also occurred in the lower two vegetation belts, while there were many differential species in the lower forest belt. Species with considerable competitive ability and moderate stress tolerance dominated the upper treeline ecotone, whereas ruderality is poorly expressed. The importance of stress tolerance in plant strategies increased slightly in the mountain pine belt. Changes in the representation of some functional traits attributes were detected by vegetation belts, but complete species turnover did not occur. Changes in dominant life form involved greater cover of chamaephytes and nanophanerophytes in the upper mountain pine belt. Species with evergreen leaves dominated mountain pine stands and deciduous forest stands. The share of species with scleromorphic leaves increased in the direction of the mountain pine belt while the share of species with mesomorphic and hygromorphic leaves declined. Mountain pine stands create good conditions for the regeneration of tree species and colonisation by ecologically more demanding forest species while species of alpine grasslands withdraw on open areas. Since today’s treeline is lowered due to past human activity, an upward shift is expected. Also, considering the great importance of competition strategy, current conditions in mountain pine stands are favourable for future forest succession.

Plant trait responses to the environment and effects on ecosystem properties

A combined analysis of plant trait responses to the environment, and their effects on ecosystem properties has recently been proposed. In this study, we related the trait composition of plant communities to soil nutrients and disturbance as environmental drivers and to productivity, decomposition and soil carbon as ecosystem properties. We surveyed two sites, one comprising intensively grazed and fertilized grasslands, the other consisting of semi-natural grassland and open heathland. Species abundance and trait values of 49 species were recorded in 69 plots, as well as parameters describing soil resources, land-use disturbances, and ecosystem properties. Our main goal was to test whether the average or the diversity of the trait values of the vegetation had stronger effects on ecosystem properties (mass ratio vs. diversity hypothesis). Structural equation modeling was used to perform a simultaneous analysis of trait responses and effects. Specific leaf area and leaf nutrient contents were always negatively correlated with stem dry matter content and canopy height, indicating greater investments in supportive and nutrient-conserving tissue as plants increased in size. In the agricultural site, disturbance was the single most important factor decreasing plant height, while leaf traits such as specific leaf area and leaf nutrient contents increased with soil resources in heathlands. Productivity was directly or indirectly driven by leaf traits, and investments in structural tissue increased standing biomass and soil carbon. Different environmental drivers in the two sites produced opposing leaf trait effects on litter decomposition. Ecosystem properties were explained by the community mean trait value as predicted by the mass ratio hypothesis. Evidence for effects of functional diversity on productivity and other ecosystem properties was not detected, suggesting that diversity–productivity relationships depend on the length of the investigated environmental gradients. We conclude that changes in community composition and dominance hierarchies deserve the most attention when ecosystem properties must be maintained.