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The capacity of forests to sequester carbon in both above‐ and belowground compartments is a crucial tool to mitigate rising atmospheric carbon concentrations. Belowground carbon storage in forests is strongly linked to soil microbial communities that are the key drivers of soil heterotrophic respiration, organic matter decomposition and thus nutrient cycling. However, the relationships between tree diversity and soil microbial properties such as biomass and respiration remain unclear with inconsistent findings among studies. It is unknown so far how the spatial configuration and soil depth affect the relationship between tree richness and microbial properties. Here, we studied the spatial distribution of soil microbial properties in the context of a tree diversity experiment by measuring soil microbial biomass and respiration in subtropical forests (BEF‐China experiment). We sampled soil cores at two depths at five locations along a spatial transect between the trees in mono‐ and hetero‐specific tree pairs of the native deciduous species Liquidambar formosana and Sapindus saponaria. Our analyses showed decreasing soil microbial biomass and respiration with increasing soil depth and distance from the tree in mono‐specific tree pairs. We calculated belowground overyielding of soil microbial biomass and respiration – which is higher microbial biomass or respiration than expected from the monocultures – and analysed the distribution patterns along the transect. We found no general overyielding across all sampling positions and depths. Yet, we encountered a spatial pattern of microbial overyielding with a significant microbial overyielding close to L. formosana trees and microbial underyielding close to S. saponaria trees. We found similar spatial patterns across microbial properties and depths that only differed in the strength of their effects. Our results highlight the importance of small‐scale variations of tree–tree interaction effects on soil microbial communities and functions and are calling for better integration of within‐plot variability to understand biodiversity–ecosystem functioning relationships. [ABSTRACT FROM AUTHOR]

Aim: Theoretical, experimental and observational studies have shown that biodiversity–ecosystem functioning (BEF) relationships are influenced by functional community structure through two mutually non‐exclusive mechanisms: (1) the dominance effect (which relates to the traits of the dominant species); and (2) the niche partitioning effect [which relates to functional diversity (FD)]. Although both mechanisms have been studied in plant communities and experiments at small spatial extents, it remains unclear whether evidence from small‐extent case studies translates into a generalizable macroecological pattern. Here, we evaluate dominance and niche partitioning effects simultaneously in grassland systems world‐wide. Location: Two thousand nine hundred and forty‐one grassland plots globally. Time period: 2000–2014. Major taxa studied: Vascular plants. Methods: We obtained plot‐based data on functional community structure from the global vegetation plot database "sPlot", which combines species composition with plant trait data from the "TRY" database. We used data on the community‐weighted mean (CWM) and FD for 18 ecologically relevant plant traits. As an indicator of primary productivity, we extracted the satellite‐derived normalized difference vegetation index (NDVI) from MODIS. Using generalized additive models and deviation partitioning, we estimated the contributions of trait CWM and FD to the variation in annual maximum NDVI, while controlling for climatic variables and spatial structure. Results: Grassland communities dominated by relatively tall species with acquisitive traits had higher NDVI values, suggesting the prevalence of dominance effects for BEF relationships. We found no support for niche partitioning for the functional traits analysed, because NDVI remained unaffected by FD. Most of the predictive power of traits was shared by climatic predictors and spatial coordinates. This highlights the importance of community assembly processes for BEF relationships in natural communities. Main conclusions: Our analysis provides empirical evidence that plant functional community structure and global patterns in primary productivity are linked through the resource economics and size traits of the dominant species. This is an important test of the hypotheses underlying BEF relationships at the global scale. [ABSTRACT FROM AUTHOR]

Ernst-Gerhard Mahn was a renowned geobotanist who specialized in the vegetation of steppes and dry grasslands in central Germany. He researched microclimatic and soil-related causes for differences in species composition. Later, he focused on agroecological work and studied the interaction between weeds and cultivated plants. Mahn made a significant contribution to geobotany and was a member of various national and international committees. After his retirement, he remained active and engaged, including serving as an editor for a journal. [Extracted from the article]

Reversing the decline of biodiversity in European agricultural landscapes is urgent. We suggest eight measures addressing politics, economics, and civil society to instigate transformative changes in agricultural landscapes. We emphasize the need for a well-informed society and political measures promoting sustainable farming by combining food production and biodiversity conservation [ABSTRACT FROM AUTHOR]

Christensen et al. criticized the application of Beals' index of sociological favourability to adjust for incomplete species lists when comparing repeated surveys. Their main argument was that using Beals' conditional occurrence probabilities would systematically underestimate biodiversity change compared to using observed frequencies. Although this might be the case for rare species, as we explicitly stated in our original publication, we here use a worked‐out example to show that this criticism is unjustified for species that are sufficiently represented in the reference data set. In our opinion, the misconception derives from ignoring one of the key requirements for applying Beal's index, which is the use of a sufficiently large reference data set to derive a reliable co‐occurrence matrix. We here show how the predicted probability for the occurrence of a species depends on the size of the reference data set and give recommendations on the premises for applying Beals' approach for monitoring purposes. [ABSTRACT FROM AUTHOR]

As woody plants provide much of the trophic basis for food webs in forests their species richness, but also stand age and numerous further variables such as vegetation structure, soil properties and elevation can shape assemblages of ground beetles (Coleoptera: Carabidae). However, the combined impact of these numerous variables on ground beetle diversity and community structure has rarely been studied simultaneously. Therefore, ground beetles were studied in 27 plots in a highly diverse and structurally heterogeneous subtropical forest ecosystem, the Gutianshan National Park (southeast China) using pitfall traps and flight interception traps. Both trapping methods collected partly overlapping species spectra. The arboreal fauna was dominated by lebiines and to a smaller extent by tiger beetles and platynines; the epigeic fauna comprised mostly representatives of the genus Carabus and numerous tribes, especially anisodactylines, pterostichines, and sphodrines. Ground beetle species richness, abundance, and biomass of the pitfall trap catches were analyzed with generalized linear mixed models (GLMMs), fitted with seven environmental variables. Four of these variables influenced the ground beetle assemblages: Canopy cover, herb cover, pHvalue of the topsoil and elevation. Contrary to our expectations, woody plant species richness and stand age did not significantly affect ground beetle assemblages. Thus, ground beetles seem to respond differently to environmental variables than ants and spiders, two other predominantly predatory arthropod groups that were studied on the same plots in our study area and which showed distinct relationships with woody plant richness. Our results highlight the need to study a wider range of taxa to achieve a better understanding of how environmental changes affect species assemblages and their functioning in forest ecosystems. [ABSTRACT FROM AUTHOR]

Aim: Bogs and transition mires in Central Europe have undergone tremendous changes in the last decades, declining in spatial extent and favourable conservation status. However, species extinctions have been documented only rarely because of a lack of reliable floristic data. Here, we assessed species losses of bog complexes and analysed their potential drivers. Location: Black Forest, Germany. Methods: We made use of the unique situation that the majority of bogs in the Black Forest (124 sites) had been systematically surveyed from 1972 to 1980 and resurveyed the flora of the same sites between 2017 and 2020. In addition, we included further data from the preceding decades. Results: Out of 88 species for which we compiled site occupancy data, two species went extinct in the whole study area and 37 decreased from 1972 to 2020, losing on average 33% of their initial frequency. In contrast, 46 species displayed a positive trend. While decreasing species were characteristic of raised bogs, moorland ponds and base‐rich mires, increasing species were typical of poor mires, fens and wet meadows. Species losses were higher at low elevation, pointing to increasing temperature increase and decreasing precipitation as main drivers of extinction, while habitat area, distance to the nearest site and land use played no significant role. The mean altitude at which extinctions of populations occurred increased with time. Assuming a continuation of the observed negative trends for declining bog species, our models predict the extinction of further ten species by 2045. Main Conclusion: Our study highlights the value of systematic and comprehensive past biodiversity surveys to assess biodiversity change. We demonstrated that low‐mountain habitats have already suffered biodiversity loss as a result of climate change. There are only limited management options against rising temperatures and decreasing precipitation. [ABSTRACT FROM AUTHOR]

Aims: The machine‐readable formal language of classification expert systems has become a standard for applying plot assignment rules in vegetation classification. Here we present an efficient algorithm implementing the vegetation classification expert system in the statistical programming language R. Methods: The principal idea of the R implementation is to solve the assignments to vegetation types not sequentially plot by plot but to parse the assignment rules into (nested) components that each can be evaluated by simultaneous vector‐based processing of all plots in a database. Results and conclusions: We demonstrate the algorithm taking the EUNIS classification expert system of European habitat types (EUNIS‐ESy) as an example. The R code version of the vegetation classification expert system is particularly useful in large vegetation‐plot databases because it solves all logical operations vector‐wise across all plots, allowing for efficient evaluation of membership expressions and formulas. Another advantage of the R implementation is that membership formulas are not only readable but can also be produced as a machine‐written result, for example as the output of classification algorithms run in R. [ABSTRACT FROM AUTHOR]

Exotic plant species can evolve adaptations to environmental conditions in the exotic range. Furthermore, soil biota can foster exotic spread in the absence of negative soil pathogen–plant interactions or because of increased positive soil biota–plant feedbacks in the exotic range. Little is known, however, about the evolutionary dimension of plant–soil biota interactions when comparing native and introduced ranges.To assess the role of soil microbes for rapid evolution in plant invasion, we subjected Verbascum thapsus, a species native to Europe, to a reciprocal transplant experiment with soil and seed material originating from Germany (native) and New Zealand (exotic). Soil samples were treated with biocides to distinguish between effects of soil fungi and bacteria. Seedlings from each of five native and exotic populations were transplanted into soil biota communities originating from all populations and subjected to treatments of soil biota reduction: application of (a) fungicide, (b) biocide, (c) a combination of the two, and (d) control.For most of the investigated traits, native populations showed higher performance than exotic populations; there was no effect of soil biota origin. However, plants developed longer leaves and larger rosettes when treated with their respective home soil communities, indicating that native and exotic plant populations differed in their interaction with soil biota origin. The absence of fungi and bacteria resulted in a higher specific root length, suggesting that V. thapsus may compensate the absence of mutualistic microbes by increasing its root–soil surface contact.Synthesis. Introduced plants can evolve adaptations to soil biota in their new distribution range. This demonstrates the importance of biogeographic differences in plant–soil biota relationships and suggests that future studies addressing evolutionary divergence should account for differential effects of soil biota from the home and exotic range on native and exotic populations of successful plant invaders. [ABSTRACT FROM AUTHOR]

Meta‐analyses often encounter studies with incompletely reported variance measures (e.g., standard deviation values) or sample sizes, both needed to conduct weighted meta‐analyses. Here, we first present a systematic literature survey on the frequency and treatment of missing data in published ecological meta‐analyses showing that the majority of meta‐analyses encountered incompletely reported studies. We then simulated meta‐analysis data sets to investigate the performance of 14 options to treat or impute missing SDs and/or SSs. Performance was thereby assessed using results from fully informed weighted analyses on (hypothetically) complete data sets. We show that the omission of incompletely reported studies is not a viable solution. Unweighted and sample size‐based variance approximation can yield unbiased grand means if effect sizes are independent of their corresponding SDs and SSs. The performance of different imputation methods depends on the structure of the meta‐analysis data set, especially in the case of correlated effect sizes and standard deviations or sample sizes. In a best‐case scenario, which assumes that SDs and/or SSs are both missing at random and are unrelated to effect sizes, our simulations show that the imputation of up to 90% of missing data still yields grand means and confidence intervals that are similar to those obtained with fully informed weighted analyses. We conclude that multiple imputation of missing variance measures and sample sizes could help overcome the problem of incompletely reported primary studies, not only in the field of ecological meta‐analyses. Still, caution must be exercised in consideration of potential correlations and pattern of missingness. [ABSTRACT FROM AUTHOR]

Defining the species pool of a community is crucial for many types of ecological analyses, providing a foundation to metacommunity, null modelling or dark diversity frameworks. It is a challenge to derive the species pool empirically from large and heterogeneous databases. Here, we propose a method to define a site‐specific species pool (SSSP), i.e. the probabilistic set of species that may co‐occur with the species of a target community. Using large databases with geo‐referenced records that comprise full plant community surveys, our approach characterizes each site by its own species pool without requiring a pre‐defined habitat classification. We calculate the probabilities of each species in the database to occur in the target community using Beals' index of sociological favourability, and then build sample‐based rarefaction curves from neighbouring records with similar species composition to estimate the asymptotic species pool size. A corresponding number of species is then selected among the species having the highest occurrence probability, thus defining both size and composition of the species pool. We tested the robustness of this approach by comparing SSSPs obtained with different spatial extents and dissimilarity thresholds, fitting different models to the rarefaction curves, and comparing the results obtained when using Beals co‐occurrence probabilities or presence/absence data. As an example application, we calculated the SSSPs for all calcareous grassland records in the German Vegetation Reference Database, and show how our method could be used to 1) produce grain‐dependent estimations of species richness across plots, 2) derive scalable maps of species richness and 3) define the full list of species composing the SSSP of each target site. By deriving the species pool exclusively from community characteristics, the SSSP framework presented here provides a robust approach to bridge biodiversity estimations across spatial scales. [ABSTRACT FROM AUTHOR]

Aim: The loss of biodiversity has raised serious concerns about the entailing losses of ecosystem services. Here, we explore the potential of repeated habitat mapping data to identify floristic changes over time. Using one German federal state as a case study, we assessed floristic changes between the 1980s and 2010s. These habitat data have great potential for analysis because of their high spatial coverage while also posing methodological challenges such as incomplete observation data. We developed a modelling approach that accounts for incomplete observations and explored the ability to detect temporal trends. Location: The Federal State of Schleswig‐Holstein (Germany) Methods: We compiled plant species lists from the earliest (1980s) and most recent (2010s) habitat mapping survey and aligned differing habitat definitions across mapping campaigns. A total of 5,503 mapped polygons, each with a list of species records, intersected the two surveys. We accounted for underrecorded species by assigning occurrence probabilities, based on species co‐occurrence information across all surveys, using Beals' index and tested the robustness of this approach by simulation experiments. For those species with significant increases and decreases in occurrence probability, we linked these trends to the species' functional characteristics. Results: We found a systematic loss of species that are moderately threatened. Species that indicate low nitrogen supply and high soil moisture declined, suggesting a shift towards a more eutrophic and drier landscape. Importantly, assessing specific plant traits associated with losses, we also detected a decrease in species with reddish and blueish flowers and species providing nectar, pointing to a decrease of insect‐pollinated taxa. Main conclusions: The identified changes raise concerns that plant biodiversity has fundamentally changed over the last three decades, with concomitant consequences for ecosystem services, especially pollination. Given the general lack of historical standardized data, our approach for trend analyses using incomplete observation data may be widely applicable to assess long‐term biodiversity change. [ABSTRACT FROM AUTHOR]

Biodiversity is a major driver of numerous ecosystem functions. However, consequences of changes in forest biodiversity remain difficult to predict because of limited knowledge about how tree diversity influences ecosystem functions. Litter decomposition is a key process affecting nutrient cycling, productivity, and carbon storage and can be influenced by plant biodiversity. Leaf litter species composition, environmental conditions, and the detritivore community are main components of the decomposition process, but their complex interactions are poorly understood. In this study, we tested the effect of tree functional diversity (FD) on litter decomposition in a field experiment manipulating tree diversity and partitioned the effects of litter physiochemical diversity and the detritivore community. We used litterbags with different mesh sizes to separate the effects of microorganisms and microfauna, mesofauna, and macrofauna and monitored soil fauna using pitfall traps and earthworm extractions. We hypothesized that higher tree litter FD accelerates litter decomposition due to the availability of complementary food components and higher activity of detritivores. Although we did not find direct effects of tree FD on litter decomposition, we identified key litter traits and macrodetritivores that explained part of the process. Litter mass loss was found to decrease with an increase in leaf litter carbon:nitrogen ratio. Moreover, litter mass loss increased with an increasing density of epigeic earthworms, with most pronounced effects in litterbags with a smaller mesh size, indicating indirect effects. Higher litter FD and litter nutrient content were found to increase the density of surface‐dwelling macrofauna and epigeic earthworm biomass. Based on structural equation modeling, we conclude that tree FD has a weak positive effect on soil surface litter decomposition by increasing the density of epigeic earthworms and that litter nitrogen‐related traits play a central role in tree composition effects on soil fauna and decomposition. [ABSTRACT FROM AUTHOR]

Aim: Alien plant species can cause severe ecological and economic problems, and therefore attract a lot of research interest in biogeography and related fields. To identify potential future invasive species, we need to better understand the mechanisms underlying the abundances of invasive tree species in their new ranges, and whether these mechanisms differ between their native and alien ranges. Here, we test two hypotheses: that greater relative abundance is promoted by (a) functional difference from locally co‐occurring trees, and (b) higher values than locally co‐occurring trees for traits linked to competitive ability. Location: Global. Time period: Recent. Major taxa studied: Trees. Methods: We combined three global plant databases: sPlot vegetation‐plot database, TRY plant trait database and Global Naturalized Alien Flora (GloNAF) database. We used a hierarchical Bayesian linear regression model to assess the factors associated with variation in local abundance, and how these relationships vary between native and alien ranges and depend on species' traits. Results: In both ranges, species reach highest abundance if they are functionally similar to co‐occurring species, yet are taller and have higher seed mass and wood density than co‐occurring species. Main conclusions: Our results suggest that light limitation leads to strong environmental and biotic filtering, and that it is advantageous to be taller and have denser wood. The striking similarities in abundance between native and alien ranges imply that information from tree species' native ranges can be used to predict in which habitats introduced species may become dominant. [ABSTRACT FROM AUTHOR]

Aims: We introduce ReSurveyEurope — a new data source of resurveyed vegetation plots in Europe, compiled by a collaborative network of vegetation scientists. We describe the scope of this initiative, provide an overview of currently available data, governance, data contribution rules, and accessibility. In addition, we outline further steps, including potential research questions. Results: ReSurveyEurope includes resurveyed vegetation plots from all habitats. Version 1.0 of ReSurveyEurope contains 283,135 observations (i.e., individual surveys of each plot) from 79,190 plots sampled in 449 independent resurvey projects. Of these, 62,139 (78%) are permanent plots, that is, marked in situ, or located with GPS, which allow for high spatial accuracy in resurvey. The remaining 17,051 (22%) plots are from studies in which plots from the initial survey could not be exactly relocated. Four data sets, which together account for 28,470 (36%) plots, provide only presence/absence information on plant species, while the remaining 50,720 (64%) plots contain abundance information (e.g., percentage cover or cover–abundance classes such as variants of the Braun‐Blanquet scale). The oldest plots were sampled in 1911 in the Swiss Alps, while most plots were sampled between 1950 and 2020. Conclusions: ReSurveyEurope is a new resource to address a wide range of research questions on fine‐scale changes in European vegetation. The initiative is devoted to an inclusive and transparent governance and data usage approach, based on slightly adapted rules of the well‐established European Vegetation Archive (EVA). ReSurveyEurope data are ready for use, and proposals for analyses of the data set can be submitted at any time to the coordinators. Still, further data contributions are highly welcome. [ABSTRACT FROM AUTHOR]

Aim: Biodiversity databases are valuable resources for understanding plant species distributions and dynamics, but they may insufficiently represent the actual geographic distribution and climatic niches of species. Here we propose and test a method to assess sampling coverage of species distribution in biodiversity databases in geographic and climatic space. Location: Europe. Methods: Using a test selection of 808,794 vegetation plots from the European Vegetation Archive (EVA), we assessed the sampling coverage of 564 European vascular plant species across both their geographic ranges and realized climatic niches. Range maps from the Chorological Database Halle (CDH) were used as background reference data to capture species geographic ranges and to derive species climatic niches. To quantify sampling coverage, we developed a box‐counting method, the Dynamic Match Coefficient (DMC), which quantifies how much a set of occurrences of a given species matches with its geographic range or climatic niche. DMC is the area under the curve measuring the match between occurrence data and background reference (geographic range or climatic niche) across grids with variable resolution. High DMC values indicate good sampling coverage. We applied null models to compare observed DMC values with expectations from random distributions across species ranges and niches. Results: Comparisons with null models showed that, for most species, actual distributions within EVA are deviating from null model expectations and are more clumped than expected in both geographic and climatic space. Despite high interspecific variation, we found a positive relationship in DMC values between geographic and climatic space, but sampling coverage was in general more random across geographic space. Conclusion: Because DMC values are species‐specific and most biodiversity databases are clearly biased in terms of sampling coverage of species occurrences, we recommend using DMC values as covariates in macro‐ecological models that use species as the observation unit. [ABSTRACT FROM AUTHOR]

Aims: Vegetation‐plot records provide information on the presence and cover or abundance of plants co‐occurring in the same community. Vegetation‐plot data are spread across research groups, environmental agencies and biodiversity research centers and, thus, are rarely accessible at continental or global scales. Here we present the sPlot database, which collates vegetation plots worldwide to allow for the exploration of global patterns in taxonomic, functional and phylogenetic diversity at the plant community level. Results: sPlot version 2.1 contains records from 1,121,244 vegetation plots, which comprise 23,586,216 records of plant species and their relative cover or abundance in plots collected worldwide between 1885 and 2015. We complemented the information for each plot by retrieving climate and soil conditions and the biogeographic context (e.g., biomes) from external sources, and by calculating community‐weighted means and variances of traits using gap‐filled data from the global plant trait database TRY. Moreover, we created a phylogenetic tree for 50,167 out of the 54,519 species identified in the plots. We present the first maps of global patterns of community richness and community‐weighted means of key traits. Conclusions: The availability of vegetation plot data in sPlot offers new avenues for vegetation analysis at the global scale. We describe sPlot, the first global vegetation‐plot database, containing 1,121,244 plots with plant species lists combined with traits from the TRY database and a global phylogeny. The potential of sPlot is illustrated with the first maps of global patterns of community richness and community‐weighted means of key traits. Rules for data usage, expected impact and limitations of sPlot are discussed. [ABSTRACT FROM AUTHOR]

Yang et al. have raised criticism that the results reported by us would not be relevant for natural forests. We argue that productivity is positively related to species richness also in subtropical natural forests, and that both the species pools and the range of tree species richness used in our experiment are representative of many natural forests of this biome. [ABSTRACT FROM AUTHOR]

Given the key role of belowground biota on forest ecosystem functioning, it is important to identify the factors that influence their abundance and composition. However, the understanding of the ecological linkage between tree diversity and belowground biota is still insufficient. Here we investigated the influence of tree diversity (richness, True Shannon diversity index, functional diversity) and identity (proportion of evergreen leaf litter and leaf litter quality) on earthworm species richness and biomass at a continental and regional scale, using data from a Europe-wide forest research platform (FunDivEUROPE) spanning six major forest types. We found a marked tree identity effect at the continental scale, with proportion of evergreen leaf litter negatively affecting total earthworm biomass and species richness, as well as their biomass per functional group. Furthermore, there were clear litter quality effects with a latitudinal variation in trait-specific responses. In north and central Europe, earthworm biomass and species richness clearly increased with increasing litter nutrient concentrations (decreasing C:N ratio and increasing calcium concentration), whereas this influence of litter nutrients was absent or even reversed in southern Europe. In addition, although earthworms were unaffected by the number of tree species, tree diversity positively affected earthworm biomass at the continental scale through functional diversity of the leaf litter. By focusing on tree leaf litter traits, this study advanced our understanding of the mechanisms driving tree identity effects and supported previous findings that litter quality, as a proxy of tree identity, was a stronger driver of earthworm species richness and biomass than tree diversity. [ABSTRACT FROM AUTHOR]

Forest ecosystems are critical for their carbon sequestration potential. Increasing tree diversity has been shown to enhance both forest productivity and litter decomposition. Litter diversity increases litter decomposability by increasing the diversity of substrates offered to decomposers. However, the relative importance of litter decomposability and decomposer community in mediating tree diversity effects on decomposition remains unknown. Moreover, tree diversity modulation of litterfall spatial distribution, and consequently litter decomposition, has rarely been tested. We studied tree diversity effects on leaf litter decomposition and its mediation by the amount of litterfall, litter species richness and decomposability, and soil microorganisms in a large‐scale tree diversity experiment in subtropical China. Furthermore, we examined how litter functional identity and diversity affect leaf litter decomposability. Finally, we tested how leaf functional traits, tree biomass, and forest spatial structure drive the litterfall spatial distribution. We found evidence that tree species richness increased litter decomposition by increasing litter species richness and the amount of litterfall. We showed that soil microorganisms in this subtropical forest perform 84–87% of litter decomposition. Moreover, changes in the amount of litterfall and microbial decomposition explained 19–37% of the decomposition variance. Additionally, up to 20% of the microbial decomposition variance was explained by litter decomposability, while litter decomposability itself was determined by litter functional identity, diversity, and species richness. Tree species richness increased litter species richness and the amount of litterfall (+200% from monoculture to eight‐species neighborhood). We further demonstrated that the amount of species‐specific litterfall increased with increasing tree proximity and biomass, and was modulated by leaf functional traits. These litterfall drivers increased the spatial heterogeneity of litter distribution, and thus litter decomposition. We highlighted multiple biomass‐ and diversity‐mediated effects of tree diversity on ecosystem properties driving forest nutrient cycling. We conclude that considering spatial variability in biotic properties will improve our mechanistic understanding of ecosystem functioning. [ABSTRACT FROM AUTHOR]

Human activities affect both tree species composition and diversity in forested ecosystems. This in turn alters the species diversity of plant litter and litter quality, which may have cascading effects on soil microbial communities and their functions for decomposition and nutrient cycling. We tested microbial responses to litter species diversity in a leaf litter decomposition experiment including monocultures, 2-, and 4-species mixtures in the subtropical climate zone of southeastern China. Soil microbial community composition was assessed by lipid analysis, and microbial functions were measured using extracellular enzyme activity and gross rates of nitrogen mineralization. We observed a positive relationship between litter species diversity and abundances of mycorrhizal fungi and actinomycetes. Alternatively, enzyme activities involved in carbon and phosphorus acquisition, and enzyme indices of relative carbon limitation, were higher only in the 4-species mixtures. This suggests that the minimum basal substrate level for enzyme production was reached, or that limitation was higher, at the highest diversity level only. Responses to litter diversity also changed over time, where phosphatase responses to litter diversity were strongest early in decomposition and the indices of carbon limitation relative to other nutrients showed stronger responses later in decomposition. Enzyme activities were related to lipid biomarker data and the mass of litter remaining at the third time point, but relationships between enzyme activity and the mass of litter remaining were not consistent across other time points. We conclude that litter species richness will likely only reduce microbial functions at key intervals of diversity loss while microbial growth is more sensitive to incremental diversity loss, with no clear relationships between them or to ecosystem functions. The observed litter diversity effects on soil microbial biomass and enzyme activity indicate interactions of aboveground and belowground communities, and together with environmental conditions they are important for maintaining ecosystem functions. [ABSTRACT FROM AUTHOR]

Stand diversification is considered a promising management approach to increasing the multifunctionality and ecological stability of forests. However, how tree diversity affects higher trophic levels and their role in regulating forest functioning is not well explored particularly for (sub)tropical regions. We analyzed the effects of tree species richness, community composition, and functional diversity on the abundance, species richness, and beta diversity of important functional groups of herbivores and predators in a large-scale forest biodiversity experiment in south-east China. Tree species richness promoted the abundance, but not the species richness, of the dominant, generalist herbivores (especially, adult leaf chewers), probably through diet mixing effects. In contrast, tree richness did not affect the abundance of more specialized herbivores (larval leaf chewers, sap suckers) or predators (web and hunting spiders), and only increased the species richness of larval chewers. Leaf chemical diversity was unrelated to the arthropod data, and leaf morphological diversity only positively affected oligophagous herbivore and hunting spider abundance. However, richness and abundance of all arthropods showed relationships with community-weighted leaf trait means (CWM). The effects of trait diversity and CWMs probably reflect specific nutritional or habitat requirements. This is supported by the strong effects of tree species composition and CWMs on herbivore and spider beta diversity. Although specialized herbivores are generally assumed to determine herbivore effects in species-rich forests, our study suggests that generalist herbivores can be crucial for trophic interactions. Our results indicate that promoting pest control through stand diversification might require a stronger focus on identifying the best-performing tree species mixtures. [ABSTRACT FROM AUTHOR]

Aims In one approach of formalized vegetation classification, species groups define a vegetation unit as a set of relevés, each of which possesses a minimum number of species from that group. Thus, species groups provide unequivocal rules for the assignment of individual vegetation records to vegetation units and can be applied beyond the set of records used for defining them. Here, I present a new method that subjects all species in a vegetation database to clustering that produces such clear membership rules of vegetation records to clusters. More specifically, the algorithm obtains species groups from a species × relevé matrix which consist of species that show the highest probability of co-occurring with each other and delivers unequivocal rules to assign relevés to these groups. Methods A hierarchical agglomerative clustering algorithm for species is presented that starts with a species × species matrix of the Ф coefficient of association. After fusing the species with the highest Ф coefficient, the Ф association matrix is recalculated for the new group of species. For calculating Ф association for groups to other species or to the nodes formed by groups of species, the observed frequency distribution of co-occurrences of the species in that group is compared to the expected frequency distribution of co-occurrence, derived the from the observed number of species occurrences. As a result, for each species group a minimum number of species is obtained that is required to assign a relevé to this species group. The resulting Cocktail species groups are partially nested, and with increasing node hierarchy show a tendency of decreasing Ф correlation to the last-joining species to that group. Results and Conclusion As the clustering algorithm assigns all of the n species in a data set to groups, the result are n − 1 partly nested species groups. These groups correspond to species groups that have been extracted from the same data sets using preconceived start groups. Subsequently, the species groups can be used separately or in logical combinations to classify vegetation relevés either by expert systems, Twinspan-like classification algorithms or by redefining existing vegetation units with automated brute-force match algorithms. Used in this way, Cocktail clustering is able to form the backbone of a consistent large-scale vegetation classification system. [ABSTRACT FROM AUTHOR]

Evidence from grassland experiments suggests that a plant community's phylogenetic diversity (PD) is a strong predictor of ecosystem processes, even stronger than species richness per se. This has, however, never been extended to species-rich forests and host-parasitoid interactions. We used cavitynesting Hymenoptera and their parasitoids collected in a subtropical forest as a model system to test whether hosts, parasitoids, and their interactions are influenced by tree PD and a comprehensive set of environmental variables, including tree species richness. Parasitism rate and parasitoid abundance were positively correlated with tree PD. All variables describing parasitoids decreased with elevation, and were, except parasitism rate, dependent on host abundance. Quantitative descriptors of host-parasitoid networks were independent of the environment. Our study indicates that host-parasitoid interactions in species-rich forests are related to the PD of the tree community, which influences parasitism rates through parasitoid abundance. We show that effects of tree community PD are much stronger than effects of tree species richness, can cascade to high trophic levels, and promote trophic interactions. As during habitat modification phylogenetic information is usually lost nonrandomly, even species-rich habitats may not be able to continuously provide the ecosystem process parasitism if the evolutionarily most distinct plant lineages vanish. [ABSTRACT FROM AUTHOR]

Forests are ecosystems critical to understanding the global carbon budget, due to their carbon sequestration potential in both aboveground and belowground compartments, especially in species‐rich forests. Soil carbon sequestration is strongly linked to soil microbial communities, and this link is mediated by the tree community, likely due to modifications of microenvironmental conditions (i.e., biotic conditions, soil properties, and microclimate). We studied soil carbon concentration and the soil microbial biomass of 180 local neighborhoods along a gradient of tree species richness ranging from 1 to 16 tree species per plot in a Chinese subtropical forest experiment (BEF‐China). Tree productivity and different tree functional traits were measured at the neighborhood level. We tested the effects of tree productivity, functional trait identity, and dissimilarity on soil carbon concentrations, and their mediation by the soil microbial biomass and microenvironmental conditions. Our analyses showed a strong positive correlation between soil microbial biomass and soil carbon concentrations. In addition, soil carbon concentration increased with tree productivity and tree root diameter, while it decreased with litterfall C:N content. Moreover, tree productivity and tree functional traits (e.g., fungal root association and litterfall C:N ratio) modulated microenvironmental conditions with substantial consequences for soil microbial biomass. We also showed that soil history and topography should be considered in future experiments and tree plantations, as soil carbon concentrations were higher at sites where historical (i.e., at the beginning of the experiment) carbon concentrations were high, themselves being strongly affected by the topography. Altogether, these results implied that the quantification of the different soil carbon pools is critical for understanding microbial community–soil carbon stock relationships and their dependence on tree diversity and microenvironmental conditions. [ABSTRACT FROM AUTHOR]

Soil erosion is a key threat to many ecosystems, especially in subtropical China where high erosion rates occur. While the mechanisms that induce soil erosion on agricultural land are well understood, soil erosion processes in forests have rarely been studied. Throughfall kinetic energy (TKE) is influenced in manifold ways and often determined by the tree’s leaf and architectural traits. We investigated the role of species identity in mono-specific stands on TKE by asking to what extent TKE is species-specific and which leaf and architectural traits account for variation in TKE. We measured TKE of 11 different tree species planted in monocultures in a biodiversity-ecosystem-functioning experiment in subtropical China, using sand-filled splash cups during five natural rainfall events in summer 2013. In addition, 14 leaf and tree architectural traits were measured and linked to TKE. Our results showed that TKE was highly species-specific. Highest TKE was found below Choerospondias axillaris and Sapindus saponaria, while Schima superba showed lowest TKE. These species-specific effects were mediated by leaf habit, leaf area (LA), leaf pinnation, leaf margin, stem diameter at ground level (GD), crown base height (CBH), tree height, number of branches and leaf area index (LAI) as biotic factors and throughfall as abiotic factor. Among these, leaf habit, tree height and LA showed the highest effect sizes on TKE and can be considered as major drivers of TKE. TKE was positively influenced by LA, GD, CBH, tree height, LAI, and throughfall amount while it was negatively influenced by the number of branches. TKE was lower in evergreen, simple leaved and dentate leaved than in deciduous, pinnated or entire leaved species. Our results clearly showed that soil erosion in forest plantations can be mitigated by the appropriate choice of tree species. [ABSTRACT FROM AUTHOR]

Despite the importance of herbivory for the structure and functioning of species-rich forests, little is known about how herbivory is affected by tree species richness, and more specifically by random vs. non-random species loss., We assessed herbivore damage and its effects on tree growth in the early stage of a large-scale forest biodiversity experiment in subtropical China that features random and non-random extinction scenarios of tree mixtures numbering between one and 24 species. In contrast to random species loss, the non-random extinction scenarios were based on the tree species' local rarity and specific leaf area - traits that may strongly influence the way herbivory is affected by plant species richness., Herbivory increased with tree species richness across all scenarios and was unaffected by the different species compositions in the random and non-random extinction scenarios. Whereas tree growth rates were positively related to herbivory on plots with smaller trees, growth rates significantly declined with increasing herbivory on plots with larger trees. Our results suggest that the effects of herbivory on growth rates increase from monocultures to the most species-rich plant communities and that negative effects with increasing tree species richness become more pronounced with time as trees grow larger., Synthesis. Our results indicate that key trophic interactions can be quick to become established in forest plantations (i.e. already 2.5 years after tree planting). Stronger herbivory effects on tree growth with increasing tree species richness suggest a potentially important role of herbivory in regulating ecosystem functions and the structural development of species-rich forests from the very start of secondary forest succession. The lack of significant differences between the extinction scenarios, however, contrasts with findings from natural forests of higher successional age, where rarity had negative effects on herbivory. This indicates that the effects of non-random species loss could change with forest succession. [ABSTRACT FROM AUTHOR]

Exotic plant invasions are widely observed to have strong biogeographic patterns with invasive species occurring at higher abundances in their introduced range when compared with their native range. However, only few field studies have validated this assumption by comparing plant populations of multiple species in their native and introduced ranges and have evaluated to what extent changes in sexual and clonal reproduction potentially have contributed to the success of plant invasions. Here, we present the results of a comparative field study in both the native ( Germany) and the introduced ( New Zealand, NZ) ranges of six clonal plant species with different invasive status: Achillea millefolium L., Pilosella officinarum Vaill., Hypericum perforatum L., Prunella vulgaris L., Leucanthemum vulgare Lam. and Lotus pedunculatus Cav. We hypothesized that all six species show better performance in introduced NZ than in native German populations and tested if population structures investigated at different scales provide a useful tool to identify differences between native and introduced occurrences. In 10 populations per species and country we assessed plant density and flowering proportion at the population scale and around individual plants, thereby identifying the 'crowdedness' of the populations. Furthermore, we collected individual plants and determined the number of attached clonal organs and plant biomass. For all six species crowdedness in NZ populations was higher than in German populations. Additionally, overall population density of four species and the production of clonal organs (expressed as total number or per biomass ratio) of three species were higher in NZ than in Germany. When measured around individual plants, the flowering proportion was higher in native German populations of Pilosella officinarum, Hypericum perforatum and Leucanthemum vulgare. Although the study species differed in their invasive status, our findings show that for all six species performance was better in introduced than in native populations. Furthermore, this study emphasizes that multiple measures of plant performance, different spatial scales and differences among species should be taken into account when trying to identify biogeographic differences in the performance of weed species. [ABSTRACT FROM AUTHOR]

The effects of species loss on ecosystems depend on the community's functional diversity (FD). However, how FD responds to environmental changes is poorly understood. This applies particularly to higher trophic levels, which regulate many ecosystem processes and are strongly affected by human-induced environmental changes. We analyzed how functional richness (FRic), evenness (FEve), and divergence (FDiv) of important generalist predators-epigeic spiders-are affected by changes in woody plant species richness, plant phylogenetic diversity, and stand age in highly diverse subtropical forests in China. FEve and FDiv of spiders increased with plant richness and stand age. FRic remained on a constant level despite decreasing spider species richness with increasing plant species richness. Plant phylogenetic diversity had no consistent effect on spider FD. The results contrast with the negative effect of diversity on spider species richness and suggest that functional redundancy among spiders decreased with increasing plant richness through non-random species loss. Moreover, increasing functional dissimilarity within spider assemblages with increasing plant richness indicates that the abundance distribution of predators in functional trait space affects ecological functions independent of predator species richness or the available trait space. While plant diversity is generally hypothesized to positively affect predators, our results only support this hypothesis for FD-and here particularly for trait distributions within the overall functional trait space-and not for patterns in species richness. Understanding the way predator assemblages affect ecosystem functions in such highly diverse, natural ecosystems thus requires explicit consideration of FD and its relationship with species richness. [ABSTRACT FROM AUTHOR]

Abstract: Global warming presents a threat to plant species distributed at montane or alpine altitudes if the topography does not allow upward shifts in distribution ranges. Nevertheless, the species might also benefit from increasing temperatures and secondary effects on dominant species (e.g. bark beetle outbreaks or summer drought affecting the canopy species). As a consequence, disturbance frequency in montane forests might increase and light availability for herb layer species will increase. We addressed these interactions in a common garden experiment in Central Germany at different altitudes, representing cold and moist vs. warm and dry conditions. We investigated three montane species with different life forms, including a herb (Trientalis europaea), a grass (Calamagrostis villosa) and a dwarf shrub (Vaccinium myrtillus) under three shading treatments (3%, 28% and 86% of full sunlight). We hypothesized that montane species are at a disadvantage in the lowland, with the dwarf shrub suffering more than the grass. Furthermore, we hypothesized an antagonistic interaction of increased temperature and increased light conditions. While T. europaea and V. myrtillus showed only slightly responses to low altitude conditions, C. villosa displayed a nearly fifteen fold increase in biomass production, despite higher observed herbivory levels in the lowland. We failed to show an antagonistic effect of increased temperature and increased light availability, as all study species suffered from deep shade conditions and grew best under full light conditions at both sites. In conclusion, both improved temperature and light conditions might be principally beneficial for the investigated boreal species, in particular for the grass species C. villosa. [Copyright &y& Elsevier]

Abstract: Different plant species make use of resource gradients such as light in different ways. First, plant species specialize in using different parts of the gradient, resulting in niche partitioning, Second, within the section of the gradient used by a species, plants respond to a different resource supply by plasticity. Our study addressed both of these strategies, with the main objective to relate mean responses and plasticity indices of seedlings of woody species to species characteristics such as leaf habit and to variation in branch lengths and local frequency of adult trees in forest communities. A greenhouse experiment with 36 deciduous and 35 evergreen subtropical tree and shrub species was carried out to test the influence of light and nutrient availability on trait expression and plasticity of the species. The greenhouse responses of seedlings were compared with adult individuals in the field, based on a set of 46 species that occurred also in the 27 permanent plots in a secondary subtropical broadleaved forest in Zhejiang Province (SE-China). In the greenhouse experiment, most variables showed significant differences between unshaded (250μEm−2 s−1) and shaded (10μEm−2 s−1) treatments as well as between high and low nutrient supply. Deciduous species were more plastic than evergreen species in their response to light. No significant correlations were detected in mean responses and plasticity between juvenile plants in the greenhouse and adult trees in the field. However, some trait values such as biomass and node density as well as plasticity of several traits were positively related to the species’ abundance in the field, suggesting that locally abundant species tend to be less “plastic” than locally rare species. [Copyright &y& Elsevier]

Both phenotypic and genetic variation can affect the establishment success of exotic species. Using the weed Senecio vernalis Waldst. & Kit. with a continuous westward expansion of the native geographic range, we asked to what degree seed traits and germination patterns differ among different habitat disturbance types in the introduced region. We hypothesized that seed traits and germination pattern differ between different disturbance types, with lighter seeds and enhanced germination speed in highly disturbed habitats. Since S. vernalis colonizes successfully various disturbed habitats, we expected to find a high phenotypic genetic variation. Individuals from 19 populations were sampled from one region in Eastern Germany to study seed trait variation and germination success by means of a germination experiment and to assess genetic patterns using amplified fragment length polymorphism (AFLP) markers. Contrary to our expectation, habitat disturbance types did not differ in seed traits, germination characteristics or genetic variation. Instead, we found highest phenotypic and genetic variation within populations. Maximum percentage of germination was positively affected by seed mass. In addition, there was a weak but significant association between AFLP band patterns and population size and seed width, indicating that some variation in seed traits has a genetic component. In conclusion, the absence of a population differentiation at this geographic scale makes it unlikely that adaptation to different disturbance regimes is involved. Instead, a high variation in seed traits, overall high germination and genetic variation within populations under a wide range of habitat disturbance conditions seems to enable the offspring to colonize various habitat disturbance types. [ABSTRACT FROM PUBLISHER]

Differences in herbivory among woody species can greatly affect the functioning of forest ecosystems, particularly in species-rich (sub)tropical regions. However, the relative importance of the different plant traits which determine herbivore damage remains unclear. Defence traits can have strong effects on herbivory, but rarely studied geographical range characteristics could complement these effects through evolutionary associations with herbivores. Herein, we use a large number of morphological, chemical, phylogenetic and biogeographical characteristics to analyse interspecific differences in herbivory on tree saplings in subtropical China. Unexpectedly, we found no significant effects of chemical defence traits. Rather, herbivory was related to the plants' leaf morphology, local abundance and climatic niche characteristics, which together explained 70% of the interspecific variation in herbivory in phylogenetic regression. Our study indicates that besides defence traits and apparency to herbivores, previously neglected measures of large-scale geographical host distribution are important factors influencing local herbivory patterns among plant species. [ABSTRACT FROM AUTHOR]

Adaptive processes in invasive plant populations may explain exotic range expansions and ecotypic shifts between native and invasive populations of the same species. Sufficient genetic variation in invasive populations occurring within the new range is a precondition for selection. While genetic diversity can be considerably reduced during invasions following founder effects and genetic drift, it can also be maintained via mechanisms of effective gene flow. Rhododendron ponticum L., an aggressive invader in the British Isles, is an appropriate test species for investigating changes in genetic diversity and differentiation. Six native populations in Georgia and Spain each and six invasive populations in Ireland were analyzed with amplified fragment length polymorphism markers to calculate genetic distances, genetic diversity, and differentiation within and among populations. While the highest level of genetic diversity was found within native Georgian populations, thus indicating a refugium, native Spanish and invasive Irish populations showed reduced levels of genetic diversity but displayed no further reduction in the invasive range. Genetic differentiation within countries was weak. Spanish and Irish populations showed close relationships supporting a probable Spanish provenance for the invasive Rhododendron. We suggest that the preservation of sufficient genetic variation in invasive R. ponticum populations in Ireland has been vital to the species' adaptation to new environmental conditions. [ABSTRACT FROM AUTHOR]

The germination stage is critical in plant life-history and is also a key process during the expansion of species' ranges into new environments. In this study we investigated the germination patterns of three plant species ( Achillea millefolium, Hieracium pilosella and Hypericum perforatum) that are invasive to New Zealand (NZ) and native to Central Europe. We asked whether the species show differences in germination temperature requirements, germination speed and maximum germination rates, and thus, whether they display evidence of adaptation to different conditions in the invasive range. Seeds from three populations per species and region were subjected to three different temperature regimes to compare germination rates among origins and across temperature conditions. For Achillea millefolium and Hypericum perforatum, germination rates were significantly higher for invasive NZ provenances than for native German ones. Seeds from invasive populations of all three species displayed increased maximum germination at medium temperature conditions when compared to native populations, which indicates altered germination strategies in the invaded range. Changes in temporal development patterns were most conspicuous for invasive Hieracium pilosella and Hypericum perforatum populations. These findings imply that adaptation in germination patterns towards different climatic conditions in invasive populations has occurred. Our study emphasises the importance of the germination stage during plant invasion and its role in explaining range expansion of these species. [ABSTRACT FROM AUTHOR]

Subtropical broad-leaved forests in southeastern China support a high diversity of woody plants. Using a comparative study design with 30 × 30 m plots (n = 27) from five successional stages (<20, <40, <60, <80, and =80 yr), we investigated how the gradient in species composition reflects underlying processes of community assembly. In particular, we tested whether species richness of adult trees and shrubs decreased or increased and assessed to which degree this pattern was caused by negative density dependence or continuous immigration over time. Furthermore, we tested whether rare species were increasingly enriched and the species composition of adult trees and shrubs became more similar to species composition of seedlings during the course of succession. We counted the individuals of all adult species and shrubs >1 m in height in each plot and counted all woody recruits (bank of all seedlings =1 m in height) in each central 10 × 10 m quadrant of each plot. In addition, we measured a number of environmental variables (elevation, slope, aspect, soil moisture, pH, C, N, and C/N ratio) and biotic structural variables (height and cover of layers). Adult species richness varied from 25 to 69 species per plot, and in total 148 woody species from 46 families were recorded. There was a clear successional gradient in species composition as revealed by nonmetric multidimensional scaling (NMDS), but only a poor differentiation of different successional stages with respect to particular species. Adult richness per 100 individuals (rarefaction method) increased with successional stage. None of the measured abiotic variables were significantly correlated with adult species richness. We found no evidence that rare species were responsible for the increasing adult species richness, as richness of rare species among both adults and recruits was independent of the successional stage. Furthermore, the similarity between established adults and recruits did not increase with successional stage. There was a constant number of recruit species and also of exclusive recruit species, i.e., those that had not been present as adult individuals, across all successional stages, suggesting a continuous random immigration over time. [ABSTRACT FROM AUTHOR]

Abstract: Norway spruce (Picea abies (L.) Karst.) exhibits strong ecotypic variation along altitudinal gradients in morphological traits, e.g. slenderness of crowns or arrangement of second-order branches. We were interested whether montane and lowland morphotypes differ in a key trait for the survival in cold environments, i.e. frost hardiness, and asked: (i) are montane morphotypes more resistant to frost damage and (ii) do they have a lower risk of frost damage by late frosts in spring than lowland morphotypes? We used the electrolyte leakage-method to measure frost hardiness on a monthly basis from October 2006 to May 2007 in stands of the montane and lowland morphotypes at Mt. Brocken in the Harz Mountains, Germany. LT50 (i.e. the temperature that results in 50% of maximum electrolyte leakage) was assessed by freezing treatments in a frost chamber and was significantly influenced by morphotype, month and minimum ambient temperatures. LT50 was significantly lower in the montane than in the lowland morphotype, with −107°C and −49°C, respectively. However, the interactions between morphotype with minimum ambient temperature or month were not significant. Thus, as frost hardiness of the two morphotypes responded to temperature in the same way, both morphotypes can be supposed to be exposed to the same risk of frost damage during hardening in autumn and dehardening in spring. [Copyright &y& Elsevier]

Questions: Do the vegetation-specific patterns in the forelands of river oases of the Taklamakan Desert provide clues to the degree to which a vegetation type depends on unsaturated soil moisture, brought about by extensive floodings, or phreatic water? Location: Foreland of the Qira oasis on the southern rim of the Taklamakan Desert, Xinjiang Uygur Autonomous Region, China. Methods: A vegetation map was prepared using a SPOT satellite image and ground truthing. Measurements of soil water contents were obtained from a flooding experiment and transformed into water potentials. Sum excedance values were calculated as the percentage of days on which different thresholds of soil water potentials were transgressed. Groundwater depth was mapped by drilling 30 groundwater holes and extrapolating the distances to the whole study area. Results: The vegetation was characterized by only six dominant or codominant species: Alhagi sparsifolia, Karelinia caspia, Populus euphratica, Tamarix ramosissima, Calligonum caput-medusae and Phragmites australis. The vegetation patterns encountered lacked any linear features typical of phreatophytes, thus not allowing direct conclusions on the type of the sustaining water sources. Soil water potentials never transgressed a threshold of pF 5 (−10 MPa) in horizons above the capillary fringe during periods without inundation, thus representing water not accessible for plants. Depth to the groundwater ranged between 2.3 and 17.5 m among plots and varied between 1.7 and 8.0 m within a plot owing to dune relief. The seven main vegetation types showed distinct niches of groundwater depths, corresponding to the observed concentric arrangement of vegetation types around the oasis. Conclusions: Inundation by flooding and unsaturated soil moisture are irrelevant for the foreland vegetation water supply. Although distances to the groundwater table can reach about 20 m, which is exceptionally large for phreatophytes, groundwater is the only water source for all vegetation types in the oasis foreland. In consequence, successful maintenance of oasis foreland vegetation will crucially depend on providing non-declining ground water tables. [ABSTRACT FROM AUTHOR]

To determine which factors contribute most to the stability of species composition in a beech forest after profound disturbance, we made use of a natural experiment caused by a severe windthrow that occurred at a permanent monitoring site in an old beech forest in Lower Saxony (Germany). The floristic composition was recorded for the succeeding five years after the disturbance and used to derive measures of resistance and resilience for plots as well as for individual species. Due to the existence of previously established randomly distributed permanent plots, we had precise information of the pre-disturbance state, including initial cover of the herb layer, species richness, and species composition. Variables describing the floristic change, resistance, and resilience were derived from correspondence analysis allowing for partitioning the effects of variation among plots from those of temporal change. We asked to which degree these variables could be predicted by pre-disturbance state and disturbance intensity. We found that both the pre-disturbance state and the disturbance intensity were good predictors for floristic change and resistance, while they failed to predict resilience. Among the descriptors of the pre-disturbance state the initial cover of the herb layer turned out to be a useful predictor, which is explained by a high vegetation cover buffering against losses and preventing establishment of newcomers. In contrast, species number neither showed a relationship to floristic change nor to resistance. Putative positive effects of species number on stability according to the insurance hypothesis might have been counterbalanced by a disruption of niche complementarity in species-rich communities. Among the descriptors of disturbance intensity, the loss in canopy cover and the change in photosynthetically active radiation after the storm were equally good predictors for the change in floristic composition and resistance. The analysis of the responses of single species on initial vegetation cover and disturbance intensity revealed that a wide range of different mechanisms were involved. Resistance and resilience did not depend on the presence of particular species or on specific traits. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented on "The bioclimatic species distribution models," by J. C. Svenning and F. Skov..

Aim To test whether species groups (i.e. assemblages of species co-occurring in nature) that are statistically derived at one scale (broad, medium, or fine scale) can be transferred to another scale, and to identify the driving forces that determine species groups at the various scales. Location Northern Bohemia (Czech Republic, central Europe) in the Ještědský hřbet mountain range and its neighbourhood. Methods Three data sets were sampled: a floristic data set at the broad scale, another floristic data set at the intermediate scale, and a vegetation data set at the habitat scale. First, in each data set, species groups were produced by the COCKTAIL algorithm, which ensures maximized joint occurrence in the data set using a fidelity coefficient. Corresponding species groups were produced in the individual data sets by employing the same species for starting the algorithm. Second, the species groups formed in one data set, i.e. at a particular scale, were applied crosswise to the other data sets, i.e. to the other scales. Correspondence of a species group formed at a particular scale with a species group at another scale was determined. Third, to highlight the driving factors for the distribution of the plant species groups at each scale, canonical correspondence analysis was carried out. Results Twelve species groups were used to analyse the transferability of the groups across the three scales, but only six of them were found to be common to all scales. Correspondence of species groups derived from the finest scale with those derived at the broadest scale was, on average, higher than in the opposite direction. Forest (tree layer) cover, altitude and bedrock type explained most of the variability in canonical correspondence analysis across all scales. Main conclusions Transferability of species groups distinguished at a fine scale to broader scales is better than it is in the opposite direction. Therefore, a possible application of the results is to use species groups to predict the potential occurrence of missing species in broad-scale floristic surveys from fine-scale vegetation-plot data. [ABSTRACT FROM AUTHOR]

The central-marginal model assumes unfavourable and more variable environmental conditions at the periphery of a species’ distribution range to negatively affect demographic transition rates, finally resulting in reduced population sizes and densities. Previous studies on density-dependence as a crucial factor regulating plant population growth have mainly focussed on fecundity and survival. Our objective is to analyse density-dependence in combination with the effect of inter-annual variation and range position on all life stages of an annual plant species, Hornungia petraea, including germination and seed incorporation into the seed bank. As previous studies on H. petraea had revealed a pattern opposite to existing theory with lower population densities at the distribution centre in Italy than at the periphery in Germany, we hypothesised that (1) demographic transition rates are lower, (2) the inter-annual variation in demographic transition rates is higher and (3) the intensity of density-dependence is weaker in Italy than in Germany. To analyse demographic transition rates, we used an autoregressive covariance strategy for repeated measures including density and inter-annual variation. All the three hypotheses were confirmed, but the impact of range position, density-dependence and inter-annual variation differed among the transition steps. All transition rates except fecundity were higher in the German populations than in the Italian populations. Germination rate and incorporation rate into the seed bank were strongly density-dependent. Central populations showed a larger inter-annual variation in fecundity and winter survival rate. Winter survival rate was the only transition step with a stronger density-dependence in peripheral populations. In most cases, these differences between distribution centre and periphery would not have emerged without taking density-dependence and inter-annual variation into account. We conclude that including range position, inter-annual variation and density-dependence in one single statistical model is an important tool for the interpretation of demographic patterns regarding the central-marginal model. [ABSTRACT FROM AUTHOR]

Previous studies have shown that the invasive spread of Rhododendron ponticum in the British Isles is influenced by the more favourable environmental conditions in the new territory than in the species’ home range. In this study, we asked whether the species’ invasion success might also involve a genotypic background for higher growth and germination rates in invasive populations. We tested the hypotheses that invasive populations have higher absolute germination rates, germinate faster and exhibit higher growth rates. We present data from greenhouse and climate chamber experiments with seed material and Rhododendron cuttings from six populations each of native Georgian, native Spanish and invasive Irish populations subjected to different temperature environments. There were no differences in the maximum germination rate and optimum germination temperature between native and invasive origins. We found significant differences in germination velocity with the Irish seeds responding most rapidly to all germination treatments. Accordingly, in the growth experiment the invasive Irish origins had the highest relative growth rates in all environments tested. Our results provide evidence for a genetic shift in invasive populations towards an increased investment in growth and towards a faster germination rate. Both traits would contribute to explaining this species’ range expansion. The underlying evolutionary mechanisms for this shift are discussed, including the possibility of hybridisation or of an ecological release from hitherto experienced constraints in the native area. [ABSTRACT FROM AUTHOR]

Abstract: Seedling establishment as the life stage transition most sensitive to herbivory might be impossible even if the herbivory losses suffered by adult plants of the same species are tolerable. We tested the hypothesis that herbivory impedes seedling establishment of two montane Asteraceae species on their lower altitudinal distribution border. In a submontane meadow in the Harz Mountains, Germany, the montane grassland perennials Arnica montana and Centaurea pseudophrygia (Asteraceae) were sown into artificially created gaps of two different sizes, half of which were protected from slug grazing by molluscicide application in the initial phase of the experiments. The Arnica experiments started in spring and late summer of 1999 and in spring of 2000; whereas Centaurea was only sown in the spring of 2000. Seedling survival was monitored until the autumn of 2000. Ten weeks after sowing, mollusc exclusion resulted in significantly higher Arnica or Centaurea seedling numbers in all experiments; whereas grasses and dicotyledons that emerged from the seedbank were promoted by slug exclosure in only one experiment. Species diversity was not affected by molluscicide application. By the end of the second growing season, the survivorship of Arnica sown in the spring of 1999 was reduced to less than 1% of the number of sown seeds in the gaps with natural slug grazing, compared to 7–15% in the gaps with molluscicide treatment. Plant density of most species was higher in the small than in the large gaps, indicating a microclimatic shelter effect of the surrounding vegetation. The results show that slug herbivory might exert large effects on species composition in grassland; it does strongly influence the seedling establishment of the highly palatable, slow-growing A. montana, while the seedlings of C. pseudophrygia, although of similar palatability, are more able to tolerate slug feeding because of their higher growth rate. [Copyright &y& Elsevier]

1 More or less continuous distributions tend to become fragmented towards species’ distribution limits. Peripheral or isolated populations of a species are predicted to have lower population sizes and densities than central populations, as a result of environmental and/or genetic stress. Population densities at the periphery may be reduced by decreased reproduction or higher interannual variation in reproduction. In particular, fecundity and survival are likely to be reduced by less favourable growing conditions.2 We compared populations of the annual speciesHornungia petraea(Brassicaceae) in two contrasting regions of the species’ range and at the population scale within regions. Ten populations in Italy (central to the species range) and 10 German populations (peripheral) were monitored for three growing periods from spring 1999 to spring 2001.3 All life-cycle stages, adult plant density, seed production and pre- and post-dispersal seed bank density were studied in a nested sampling design and variation in various demographic factors was attributed to the effects of the two countries, of populations nested within country and to temporal effects.4 Peripheral populations had higher densities than populations in the centre of the species distribution, both as adult plants and in the seed bank.5 Fecundity was strongly influenced by temporal effects, but only affected to a minor degree by the study region. High interannual variation in fecundity was not reflected in high interannual variation of either adult plant density in spring or of the seed bank. Significant regional differences were, however, found in seasonal seed bank dynamics, which were more pronounced in peripheral German populations than in central Italian populations.6 We conclude that seasonal seed bank dynamics are a key factor in explaining differences inH.petraeadensity patterns, particularly in central populations, where fewer seeds are incorporated into the seed bank.Journal of Ecology(2005)doi: 10.1111/j.1365-2745.2005.00997.x [ABSTRACT FROM AUTHOR]

The analysis of diversity across multiple scales is hampered by methodological difficulties resulting from the use of different sampling methods at different scales and by the application of different definitions of the communities to be sampled at different scales. It is our aim to analyse diversity in a nested hierarchy of scales by applying a formalized sampling concept used in population ecology when analysing population structure. This concept involved a precise definition of the sampled vegetation type by the presence of a target species, in our case Hornungia petraea. We compared separate indices of inventory diversity (i.e. number of species) and differentiation diversity (i.e. extent of change in species composition or dissimilarity) with indices derived from species accumulation curves and related diversity patterns to topographical plot characteristics such as area and distance. Ten plots were established systematically over a distance of 100 km each in the distribution centre of H. petraea in Italy (i.e. Marche and Umbria) and in a peripheral exclave in Germany (i.e. Thuringia and Saxony-Anhalt). We used a nested sampling design of 10 random subplots within plots and 10 systematically placed plots within regions. Internal α-diversity (species richness) and internal β-diversity (dissimilarity) were calculated on the basis of subplots, α-, β- and γ-diversity on the basis of plots in Italy and Germany. In addition, indices of inventory diversity and differentiation diversity were derived by fitting species accumulation curves to the Michaelis–Menten equation. There was no significant difference in the internal α-diversity between German and Italian plots but the α- and γ-diversity were higher in Italy than in Germany. In Germany, the internal β-diversity and β-diversity were lower than in Italy. The differentiation diversity increased with increasing scale from subplots over plots to regions. The same results were obtained by calculating species accumulation curves. Significant positive correlations were encountered between the internal α-diversity and α-diversity in both countries, while the internal β-diversity and internal α-diversity showed a correlation only for the Italian plots. Similarity decay was found for German plots with respect to inter-plot distance and for Italian plots with respect to altitudinal difference and to a smaller degree to distance between plots. The design chosen and the consistent analysis of species accumulation curves by the Michaelis–Menten equation yielded consistent results over different scales. The specific therophyte vegetation type in this study reflected diversity patterns also observed in other studies, e.g. a greater differentiation diversity in central than in peripheral habitats and a trend of increasing species richness towards lower altitudes. No asymptotic saturation of species richness between different scales was observed. Indications were found that the absolute level of inventory diversity at a particular scale and the completeness of the sampling procedure are the main clues for explaining the relationship between inventory and differentiation diversity at this particular scale. [ABSTRACT FROM AUTHOR]

The effects of warming on a montane meadow was simulated by a translocation experiment. A coherent piece of turf and soil was transferred from 600 m to 170 m a.s.l., corresponding to an increase in temperature of ca .2.8 K. The vegetation was monitored by recording cover and counting individuals one year before the translocation and continued for the subsequent seven years. For comparison, a control plot that had also been translocated but remained at 600 m was monitored. Four of eight species with a montane distribution in Europe showed a constant degree of cover during the investigation period (Nardus stricta, Poa chaixii, Polygonatum verticillatum, Potentilla erecta ). In contrast, another four montane species declined in cover or died out (Arnica montana, Meum athamanticum, Hypericum maculatum, Galium harcynicum). None of these species declined on the control plot. It is argued that the species' responded individualistically to the site factors that had changed with the translocation to low altitude. A direct effect of enhanced temperature was probably the reason for the decline of only one species (Meum athamanticum). Reduced humidity might be the reason for the extinction of two moisture demanding species (Viola palustris, Succisa pratensis ). The biomass of the plot increased by increased growth of one of the matrix species (Festuca rubra), probably due to elevated nutrient mineralization. Many low growing species responded indirectly to the reduced light availability, caused by an increased level of competition for light (e.g. Galium harcynicum). Increased slug herbivory at low altitude resulted in the extinction of Arnica montana. At the end of the investigation period, the similarity in species composition to the initial state was only 45%, indicating that the community had changed into a different plant association. The importance of considering biotic interactions when predicting the impacts of climate change is discussed. [ABSTRACT FROM AUTHOR]

Summary: There is limited knowledge on how the association of trees with different mycorrhizal types shapes soil microbial communities in the context of changing tree diversity levels. We used arbuscular (AM) and ectomycorrhizal (EcM) tree species as con‐ and heterospecific tree species pairs (TSPs), which were established in plots of three tree diversity levels including monocultures, two‐species mixtures and multi‐tree species mixtures in a tree diversity experiment in subtropical China. We found that the tree mycorrhizal type had a significant effect on fungal but not bacterial alpha diversity. Furthermore, only EcM but not AM TSPs fungal alpha diversity increased with tree diversity, and the differences between AM and EcM TSPs disappeared in multi‐species mixtures. Tree mycorrhizal type, tree diversity and their interaction had significant effects on fungal community composition. Neither fungi nor bacteria showed any significant compositional variation in TSPs located in multi‐species mixtures. Accordingly, the most influential taxa driving the tree mycorrhizal differences at low tree diversity were not significant in multi‐tree species mixtures. Collectively, our results indicate that tree mycorrhizal type is an important factor determining the diversity and community composition of soil microbes, and higher tree diversity levels promote convergence of the soil microbial communities. Significance statement: More than 90% of terrestrial plants have symbiotic associations with mycorrhizal fungi which could influence the coexisting microbiota. Systematic understanding of the individual and interactive effects of tree mycorrhizal type and tree species diversity on the soil microbiota is crucial for the mechanistic comprehension of the role of microbes in forest soil ecological processes. Our tree species pair (TSP) concept coupled with random sampling within and across the plots, allowed us the unbiased assessment of tree mycorrhizal type and tree diversity effects on the tree‐tree interaction zone soil microbiota. Unlike in monocultures and two‐species mixtures, we identified species‐rich and converging fungal and bacterial communities in multi‐tree species mixtures. Consequently, we recommend planting species‐rich mixtures of EcM and AM trees, for afforestation and reforestation regimes. Specifically, our findings highlight the significance of tree mycorrhizal type in studying 'tree diversity – microbial diversity – ecosystem function' relationships. [ABSTRACT FROM AUTHOR]

The functioning of a tree is shaped by the neighbouring species through the interspecific interaction and local environments. The functional trait composition of the neighbourhood could provide mechanistic insights into the effects of neighbours on the resource strategies of focal trees. In this study, we deployed an automated high‐frequency measurement of the sap flow density (SFD) and the radial growth of 48 trees of 12 species at BEF‐China, a large‐scale forest biodiversity manipulation experiment, to investigate the consequences and underlying mechanisms of the functional trait composition of the neighbourhood on the sap flow and radial growth of focal trees. We found a positive relationship between SFD and growth, reflecting the important supportive role of sap flow in tree growth. High functional diversity (FD) of the neighbourhood depressed SFD but promoted growth when considering all species, and thus promoted water‐use efficiency. Acquisitiveness of neighbouring trees positively affected growth, suggesting interspecific facilitation. Furthermore, neighbourhood FD benefits evergreen focal trees by promoting growth. However, in deciduous focal trees, neighbourhood FD reduced SFD but had no significant effects on growth. Our findings suggest that considering the functional trait composition of neighbourhood communities will support effective afforestation and forest management. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

To achieve the goals of the 2030 Global Biodiversity Framework, the European Biodiversity Strategy, and the EU Green Deal, biodiversity monitoring is critical. Monitoring efforts in Europe, however, suffer from gaps and biases in taxonomy, spatial coverage, and temporal resolution, resulting in fragmented and disconnected data. To assess user and policy needs in biodiversity monitoring, we employed a four‐step user‐centered stakeholder engagement process with over 300 stakeholders including a public stakeholder workshop, online survey, interviews, and a meeting with experts from 18 EU member states, the European Commission, and the European Environment Agency. The stakeholders identified policy needs, current challenges, and potential solutions. Based on the policy and stakeholder assessment, we recommend establishing a European Biodiversity Observation Coordinating Centre to optimize existing observation efforts, harmonize data, and enhance our ability to predict and respond to key challenges related to biodiversity loss in Europe. [ABSTRACT FROM AUTHOR]