Long-term and year-to-year stability and its drivers in a Mediterranean grassland

Understanding the mechanisms underlying community stability has become an urgent need to protect ecosystems from global change and resulting biodiversity loss. While community stability can be influenced by species richness, synchrony in annual fluctuations of species, species stability and functional traits, the relative contributions of these drivers to stability are still unclear. In semi-natural grasslands, land-use changes such as fertilization might affect stability by decreasing richness and influencing year-to-year fluctuations. In addition, they can promote long-term directional trends, shifting community composition and influencing grassland maintenance. Thus, it is important to consider how species and community stability vary year-to-year but also in the long term. Using a 14-year vegetation time series of a species-rich semi-natural Mediterranean grassland, we studied the relative importance of richness, synchrony, species stability and functional traits on community stability. To assess land-use change effects on stability, we applied a fertilization treatment. To distinguish stability patterns produced by year-to-year fluctuations from those caused by long-term trends, we compared the results obtained using a detrending approach from those without detrending. Independently of the treatment and approach applied, the most stable communities were those composed of asynchronous species with low specific leaf area. Fertilization decreased year-to-year and long-term community stability by increasing community-weighted mean of specific leaf area, decreasing species stability or also reducing richness in the case of year-to-year stability. Additionally, traits such as seed mass had an indirect effect on stability through synchrony. Long-term trends appeared in control and fertilized plots (due to fertilization), decreasing community and species stability and leading to differences in the relationships found between community stability and some of its drivers. This reflects the importance of accounting for the effect of temporal trends on community and species stability using both a long-term and a year-to-year approach. Synthesis. Stability is influenced by richness, synchrony and functional traits. Fertilization decreases species and community stability by promoting long-term trends in species composition, favouring competitive species and decreasing richness. Studying stability at the community level and species level, and accounting for the effect of trends is essential to understand stability and its drivers more comprehensively

Long-term and year-to-year stability and its drivers in a Mediterranean grassland

Understanding the mechanisms underlying community stability has become an urgent need to protect ecosystems from global change and resulting biodiversity loss. While community stability can be influenced by species richness, synchrony in annual fluctuations of species, species stability and functional traits, the relative contributions of these drivers to stability are still unclear. In semi-natural grasslands, land-use changes such as fertilization might affect stability by decreasing richness and influencing year-to-year fluctuations. In addition, they can promote long-term directional trends, shifting community composition and influencing grassland maintenance. Thus, it is important to consider how species and community stability vary year-to-year but also in the long term. Using a 14-year vegetation time series of a species-rich semi-natural Mediterranean grassland, we studied the relative importance of richness, synchrony, species stability and functional traits on community stability. To assess land-use change effects on stability, we applied a fertilization treatment. To distinguish stability patterns produced by year-to-year fluctuations from those caused by long-term trends, we compared the results obtained using a detrending approach from those without detrending. Independently of the treatment and approach applied, the most stable communities were those composed of asynchronous species with low specific leaf area. Fertilization decreased year-to-year and long-term community stability by increasing community-weighted mean of specific leaf area, decreasing species stability or also reducing richness in the case of year-to-year stability. Additionally, traits such as seed mass had an indirect effect on stability through synchrony. Long-term trends appeared in control and fertilized plots (due to fertilization), decreasing community and species stability and leading to differences in the relationships found between community stability and some of its drivers. This reflects the importance of accounting for the effect of temporal trends on community and species stability using both a long-term and a year-to-year approach. Synthesis. Stability is influenced by richness, synchrony and functional traits. Fertilization decreases species and community stability by promoting long-term trends in species composition, favouring competitive species and decreasing richness. Studying stability at the community level and species level, and accounting for the effect of trends is essential to understand stability and its drivers more comprehensively

On the biogeography of seed mass in Germany - distribution patterns and environmental correlates

With environmental factors being spatially structured, plant traits that are related to these factors should exhibit a corresponding spatial pattern. We analyzed the distribution pattern of seed mass in Germany. We calculated the median seed mass for 10' longitude by 6' latitude grid cells across Germany using the trait databases BIOLFLOR and the plant distribution database FLORKART. To explain these distribution patterns of median seed mass, we applied multiple regression analyses on twelve selected environmental variables, accounting for spatial autocorrelation. To deal with collinearities of the predictors, we used hierarchical partitioning to analyze the independent and joint explanatory power of the environmental variables. To test whether statistical relationships are due to hidden correlations between seed mass and plant growth form, we conducted seperate analyses for annual, perennial herbs, shrubs and trees. Low median seed mass was found in the lowlands and river valleys whereas high median seed mass was typical for the rich loess regions and the calcareous mountain ranges. Seed mass exhibited a strong positive correlation with soil pH (62% of variance explained) and a negative correlation with soil moisture (25%). Light was less important as a predictor of seed mass. Within the growth forms we observed similar distribution and correlation patterns pointing to a direct link between seed mass and the environmental variables soil pH and moisture. We argue that this striking relationship with soil pH is caused by the high stress from competition on fertile calcareous sites. The negative moisture effect may be due to drought stress. Both relationships are particulary interesting for the prediction of ecosystem responses to climate and land use changes. [References: 65

A multifaceted approach for beech forest conservation: Environmental drivers of understory plant diversity

Studies addressing multiple aspects of biodiversity simultaneously (i.e., multifaceted approaches) can quantify plant diversity-environment links comprehensively - this is because of the multidimensional nature of plant diversity. However, multifaceted studies are scant in forests. Here, we examined taxonomic, functional and phylogenetic diversity patterns in 19 beech forest understory plots in two areas belonging to a biodiversity monitoring plan in Tuscany, Italy. We performed linear mixed effect models to quantify the influence of elevation (proxy for macroclimate), aspect (affecting microclimate), and basal area (related to microclimate and stand maturity) on diversity facets of vascular plants. Elevation played a major role in shaping diversity: high-elevation plots were less rich in species and had a reduced functional diversity of storage organs that may promote cold-tolerance. Conversely, the diversity of flowering phenology increased with elevation, thus low-elevation vegetation converged functionally towards a common, short blooming period. This strategy may be advantageous for understory plants in the deciduous beech forests experiencing longer growing seasons, hence more extended canopy closure at lower elevations. Basal area negatively affected foliar and multiple traits functional diversity which may be associated with highly selective and competitive environment for light capture in closed canopy, mature stands. Slope aspect did not exert any significant effect on diversity facets, neither did interactions among predictors. Overall, these results confirm the usefulness of implementing multifaceted approaches to i) better understand the influence of environmental drivers on different aspects of plant diversity, and ii) inform the biodiversity monitoring plan that is in place in the study forests by systematically including functional diversity instead of taxonomic metrics only

Invaders among locals: Alien species decrease phylogenetic and functional diversity while increasing dissimilarity among native community members

1. Plant invasions can drastically change the structure of native communities, but it is not fully understood whether alien species occupy phylogenetic and functional space within the range occupied by natives, or provide a novel set of evolutionary origins and traits to the invaded communities. 2. Here, we evaluated this open question with data on a large number of plant communities from different terrestrial habitats. We used ~27,000 vegetation plots from 26 terrestrial habitats in the Czech Republic and compared phylogenetic and functional diversity (PD and FD, respectively) and community trait means in invaded and non‐invaded plots. We tested for differences (1) between invaded vs. non‐invaded plots, (2) among natives in invaded vs. non‐invaded plots, and (3) in invaded plots only, with and without aliens. To minimize habitat filtering effects on PD and FD, we ran these tests within the habitat‐specific species pools of the 26 vegetation types. 3. In general, PD, FD and trait mean values changed with invasion, with changes being rather consistent across the habitats considered. Invaded plots were less phylogenetically, but more functionally diverse than non‐invaded plots. The greater FD in invaded plots, compared to non‐invaded ones, was due to greater dissimilarity between natives. In fact, native species in invaded plots showed higher PD and FD than native species in non‐invaded plots, while alien species reduced PD and FD in invaded plots. Changes in the trait means with invasion were due to differences in native species in invaded and non‐invaded plots, rather than to an effect of alien species. Within most habitats, the trait means and variance of all aliens were similar to those of all natives, while in some habitats, the variability in traits was greater between aliens that belonged to phylogenetically closer clades. 4. Synthesis. Our results suggest that alien species more often occupy a phylogenetic and functional space within the range formed by the native species in a community. They do so either by filling empty gaps or by excluding natives from the existing phylogenetic and functional space, rather than occupying or creating a phylogenetic and trait space outside of it

Multidimensional ecological analyses demonstrate how interactions between functional traits shape fitness and life history strategies

Traditionally, trait‐based studies have explored single‐trait‐fitness relationships. However, this approximation in the study of fitness components is often too simplistic, given that fitness is determined by the interplay of multiple traits, which could even lead to multiple functional strategies with comparable fitness (i.e. alternative designs). Here we suggest that an analytical framework using boosted regression trees (BRT) can prove more informative to test hypotheses on trait combinations compared to standard linear models. We use two published datasets for comparisons: a botanical garden dataset with 557 plant species (Herben, 2012, Journal of Ecology, 100, 1522) and an observational dataset with 83 plant species (Adler, 2014, Proceedings of the National Academy of Sciences, 111, 740). Using the observational dataset, we found that BRTs predict the role of traits on the relative importance of survival, growth and reproduction for population growth rate better than linear models do. Moreover, we split species cultivated in different habitats within the botanical garden and observed that seed and vegetative reproduction depended on trait combinations in most habitats. Our analyses suggest that, while not all traits impact fitness components to the same degree, it is crucial to consider traits that represent different ecological dimensions. Synthesis. The analysis of trait combinations, and corresponding alternative designs via BRTs, represent a promising approach for understanding and managing functional changes in vegetation composition through measurement of suites of relatively easily measurable traits

LOTVS: A Global Collection of Permanent Vegetation Plots

Analysing temporal patterns in plant communities is extremely important to quantify the extent and the consequences of ecological changes, especially considering the current biodiversity crisis. Long-term data collected through the regular sampling of permanent plots represent the most accurate resource to study ecological succession, analyse the stability of a community over time and understand the mechanisms driving vegetation change. We hereby present the LOng-Term Vegetation Sampling (LOTVS) initiative, a global collection of vegetation time-series derived from the regular monitoring of plant species in permanent plots. With 79 data sets from five continents and 7,789 vegetation time-series monitored for at least 6 years and mostly on an annual basis, LOTVS possibly represents the largest collection of temporally fine-grained vegetation time-series derived from permanent plots and made accessible to the research community. As such, it has an outstanding potential to support innovative research in the fields of vegetation science, plant ecology and temporal ecology.Czech Science Foundation 19-28491XCzech Academy of Sciences RVO 67985939Gobierno de España PGC2018-099027-B-I00, PID2019-110521GB-I00German Federal Ministry of Education and Research 031B0516C, 01LG1201N, 01LC0024, 01LC0024A, 01LC0624A2, 01LG1201A, 01LG1201NComunidad Autónoma de Madrid 2017-T2/AMB-5406, M216

Functional species pool framework to test for biotic effects on community assembly

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