Search

Recent losses in the abundance and diversity of arthropods have been documented in many regions and ecosystems. In grasslands, such insect declines are largely attributed to land use, including modern machinery and mowing regimes. However, the effects of different mowing techniques on arthropods remain poorly understood. Using 11 years of data from 111 agricultural grassland plots across Germany, we analyzed the influence of various grassland management variables on the abundance and abundance‐accounted species richness of four arthropod orders: Araneae, Coleoptera, Hemiptera, and Orthoptera. The analysis focused on detailed mowing information, for example, days after mowing and mower type, and compared their effect with other aspects of grassland management, that is, rolling, leveling, fertilization, and grazing. We found strong negative effects of mowing on all four arthropod orders, with arthropod abundance being lowest directly after mowing and steadily increasing to three to seven times the abundance after 100 days post‐mowing. Likewise, Hemiptera and Coleoptera species richness was 30% higher 100 days after mowing. Mower width showed a positive effect on Orthoptera abundance, but not on the other arthropods. Arthropod abundance and Coleoptera species richness were lowest when a mulcher was used compared to rotary or bar mowers. In addition to mowing, intensive grazing negatively affected Orthoptera abundance but not the other orders. Mowing represents a highly disturbing and iterative stressor with negative effects on arthropod abundance and diversity, likely contributed by mowing‐induced mortality and habitat alteration. While modifications of mowing techniques such as mower type or mowing height and width may help to reduce the negative impact of mowing on arthropods, our results show that mowing itself has the most substantial negative effect. Based on our results, we suggest that reduced mowing frequency, omission of mowing in parts of the grassland (refuges), or extensive grazing instead of mowing have the greatest potential to promote arthropod populations. [ABSTRACT FROM AUTHOR]

In modified production landscapes, biodiversity faces unprecedented pressures from human actions, resulting in significant species declines of plant and animal taxa, including birds. Understanding the underlying mechanisms responsible for such declines is essential to counteract further loss and support practitioners in conserving biodiversity and associated ecosystem function. In this study, we used standardized bird monitoring data collected over 6 years in managed forest and grassland areas across different regions in Germany, Central Europe. We combined these data with morphometric, ecological, behavioral, and acoustic trait data and detailed information on local land use management practices to understand how management decisions affect species and functional diversity, as well as ecological processes shaping local species composition. Our results reveal that the ecosystem and regional context must be considered to understand how management practices affect bird diversity aspects and composition. In forests, regional management decisions related to tree species and stand age affected bird diversity, as well as community and functional composition, and indicated environmental sorting due to ecological and behavioral requirements, biotic interactions, and morphometric constraints. In grasslands, independent of local management practices, increased intensity of land use resulted in an overall loss in bird species richness and functional diversity. Predominantly, constraints due to ecological or behavioral requirements affected bird species assemblage composition. In addition, our results indicated the importance of woody vegetation near managed grasslands and of considering environmental conditions beyond the local scale to support bird diversity and associated ecosystem functions. Our results highlighted that local management decisions can support bird diversity and maintain ecological function. However, this needs a view beyond the local scale of management units. It also demands a joint effort of biologists and land managers to integrate targeted conservation actions into regional management practices and create a network of habitats within production landscapes to protect nature, guard against biotic and functional homogenization, and prevent further degradation of ecosystems in production landscapes. [ABSTRACT FROM AUTHOR]

Ecosystem management aims at providing many ecosystem services simultaneously. Such ecosystem service multifunctionality can be limited by tradeoffs and increased by synergies among the underlying ecosystem functions (EF), which need to be understood to develop targeted management. Previous studies found differences in the correlation between EFs. We hypothesised that correlations between EFs are variable even under the controlled conditions of a field experiment and that seasonal and annual variation, plant species richness, and plot identity (identity effects of plots, such as the presence and proportion of functional groups) are drivers of these correlations. We used data on 31 EFs related to plants, consumers, and physical soil properties that were measured over 5 to 19 years, up to three times per year, in a temperate grassland experiment with 80 different plots, constituting six sown plant species richness levels (1, 2, 4, 8, 16, 60 species). We found that correlations between pairs of EFs were variable, and correlations between two particular EFs could range from weak to strong or negative to positive correlations among the repeated measurements. To determine the drivers of pairwise EF correlations, the covariance between EFs was partitioned into contributions from species richness, plot identity, and time (including years and seasons). We found that most of the covariance for synergies was explained by species richness (26.5%), whereas for tradeoffs, most covariance was explained by plot identity (29.5%). Additionally, some EF pairs were more affected by differences among years and seasons, showing a higher temporal variation. Therefore, correlations between two EFs from single measurements are insufficient to draw conclusions on tradeoffs and synergies. Consequently, pairs of EFs need to be measured repeatedly under different conditions to describe their relationships with more certainty and be able to derive recommendations for the management of grasslands. [ABSTRACT FROM AUTHOR]

Insects are declining, but the underlying drivers and differences in responses between species are still largely unclear. Despite the importance of forests, insect trends therein have received little attention. Using 10 years of standardized data (120,996 individuals; 1,805 species) from 140 sites in Germany, we show that declines occurred in most sites and species across trophic groups. In particular, declines (quantified as the correlation between year and the respective community response) were more consistent in sites with many non-native trees or a large amount of timber harvested before the onset of sampling. Correlations at the species level depended on species' life-history. Larger species, more abundant species, and species of higher trophic level declined most, while herbivores increased. This suggests potential shifts in food webs possibly affecting ecosystem functioning. A targeted management, including promoting more natural tree species composition and partially reduced harvesting, can contribute to mitigating declines. Species richness and biomass of insects has declined on average across 140 forest sites sampled over a decade in Germany, with larger, more abundant, and carnivorous species found to be more susceptible to decline. [ABSTRACT FROM AUTHOR]

Numerous studies have demonstrated that biodiversity drives ecosystem functioning, yet how biodiversity loss alters ecosystems functioning and stability in the long-term lacks experimental evidence. We report temporal effects of species richness on community productivity, stability, species asynchrony, and complementarity, and how the relationships among them change over 17 years in a grassland biodiversity experiment. Productivity declined more rapidly in less diverse communities resulting in temporally strengthening positive effects of richness on productivity, complementarity, and stability. In later years asynchrony played a more important role in increasing community stability as the negative effect of richness on population stability diminished. Only during later years did species complementarity relate to species asynchrony. These results show that species complementarity and asynchrony can take more than a decade to develop strong stabilizing effects on ecosystem functioning in diverse plant communities. Thus, the mechanisms stabilizing ecosystem functioning change with community age. Biodiversity-ecosystem functioning relationships may change over time. Here, Wagg et al. show that richness-productivity and richness stability relationships grow stronger over time in an experimental grassland community, and shed light on the ecological mechanisms. [ABSTRACT FROM AUTHOR]

Increasing plant species richness has been shown to positively affect the diversity of a range of other organisms, both above‐ and belowground. Although ants have a multitude of interactions with other organisms through their role as predators and mutualists, ants are a taxon that has rarely been investigated in studies of biodiversity effects. Ants are known to respond to changes in microclimatic conditions such as temperature and humidity, and these microclimatic conditions are known to be affected by vegetation characteristics such as standing biomass, which in turn can be affected by plant diversity. We investigated the effects of plant species richness (1–60), the number of plant functional groups (FGs; 1–4), and the presence of particular FGs on the occurrence and activity of ants, in the context of a grassland biodiversity experiment. Ant abundance, estimated as the mean number of workers in pitfall traps, and the number of colonies within plots, but not ant species richness, were negatively affected by plant species richness, and also by the identity of plant FGs, particularly legumes (negative effects) and grasses (positive effects). Statistical approaches showed that these effects were largely mediated by biotic (aboveground plant biomass: negative effect) and abiotic variables (soil temperature: positive effect). Notably, ant activity, measured as the mean number of workers foraging on baits and with a disproportionate dominance of a single species (Lasius niger), showed a more complex pattern, where plant species richness and number of FGs interacted to explain differential attractiveness to different resources (represented by sugar and tuna baits), likely representing current nutritional requirements for ants. Similarly, increasing soil temperature increased the level of ant activity, indicating that abiotic factors might impose thermal constraints on ectotherms inhabiting temperate grasslands. Our results indicate that a higher number of plant species and higher plant biomass had a negative effect on ants in experimental grasslands. Understanding the responses of an ecologically important group such as ants will allow us to infer the effects that biodiversity loss could have on animal‐mediated ecosystem processes. [ABSTRACT FROM AUTHOR]

Context: Current diversity and species composition of ecological communities can often not exclusively be explained by present land use and landscape structure. Historical land use may have considerably influenced ecosystems and their properties for decades and centuries. Objectives: We analysed the effects of present and historical landscape structure on plant and arthropod species richness in temperate grasslands, using data from comprehensive plant and arthropod assessments across three regions in Germany and maps of current and historical land cover from three time periods between 1820 and 2016. Methods: We calculated local, grassland class and landscape scale metrics for 150 grassland plots. Class and landscape scale metrics were calculated in buffer zones of 100 to 2000 m around the plots. We considered effects on total species richness as well as on the richness of species subsets determined by taxonomy and functional traits related to habitat use, dispersal and feeding. Results: Overall, models containing a combination of present and historical landscape metrics showed the best fit for several functional groups. Comparing three historical time periods, data from the 1820/50s was among the most frequent significant time periods in our models (29.7% of all significant variables). Conclusions: Our results suggest that the historical landscape structure is an important predictor of current species richness across different taxa and functional groups. This needs to be considered to better identify priority sites for conservation and to design biodiversity-friendly land use practices that will affect landscape structure in the future. [ABSTRACT FROM AUTHOR]

Agricultural intensification is one of the main drivers of species loss worldwide, but there is still a lack of information about its effect on functional diversity of arable weed communities.Using a large‐scale pan European study including 786 fields within 261 farms from eight countries, we analysed differences in the taxonomic and functional diversity of arable weeds assemblages across different levels of agricultural intensification. We estimated weed species frequency in each field, and collected species' traits (vegetative height, SLA and seed mass) from the TRY plant trait database. With this information, we estimated taxonomic (species richness), functional composition (community weighted means) and functional diversity (functional richness, evenness, divergence and redundancy). We used indicators of agricultural management intensity at the individual field scale (e.g. yield, inputs of nitrogen fertilizer and herbicides, frequency of mechanical weed control practices) and at the landscape scale surrounding the field (i.e. number of crop types, mean field size and proportion of arable land cover within a radius of 500 m from the sampling points).The effects of agricultural intensification on species and functional richness at the field scale were stronger than those of intensification at the landscape scale, and we did not observe evidence of interacting effects between the two scales. Overall, assemblages in more intensified areas had fewer species, a higher prevalence of species with ruderal strategies (low stature, high leaf area, light seeds), and lower functional redundancy.Maintaining the diversity of Europe's arable weed communities requires some simple management interventions, for example, reducing the high intensity of field‐level agricultural management across Europe, which could be complemented by interventions that increase landscape complexity. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

Despite the important role of wood-inhabiting fungi (WIF) in deadwood decomposition, our knowledge of the factors shaping the dynamics of their species richness and community composition is scarce. This is due to limitations regarding the resolution of classical methods used for characterizing WIF communities and to a lack of well-replicated long-term experiments with sufficient numbers of tree species. Here, we used a large scale experiment with logs of 11 tree species at an early stage of decomposition, distributed across three regions of Germany, to identify the factors shaping WIF community composition and Operational Taxonomic Unit (OTU) richness using next generation sequencing. We found that tree species identity was the most significant factor, corresponding to (P < 0.001) and explaining 10% (representing 48% of the explainable variance) of the overall WIF community composition. The next important group of variables were wood-physicochemical properties, of which wood pH was the only factor that consistently corresponded to WIF community composition. For overall WIF richness patterns, we found that approximately 20% of the total variance was explained by wood N content, location, tree species identity and wood density. It is noteworthy that the importance of determinants of WIF community composition and richness appeared to depend greatly on tree species group (broadleaved vs. coniferous) and it differed between the fungal phyla Ascomycota and Basidiomycota. [ABSTRACT FROM AUTHOR]

Biodiversity-ecosystem function experiments test how species diversity influences fundamental ecosystem processes. Historically, arthropod driven functions, such as herbivory and pest-control, have been thought to be influenced by direct and indirect associations among species. Although a number of studies have evaluated how plant diversity affects arthropod communities and arthropod-mediated ecosystem processes, it remains unclear whether diversity effects on arthropods are sufficiently consistent over time such that observed responses can be adequately predicted by classical hypotheses based on associational effects. By combining existing results from a long-term grassland biodiversity experiment (Jena Experiment) with new analyses, we evaluate the consistency of consumer responses within and across taxonomic, trophic, and trait-based (i.e. vertical stratification) groupings, and we consider which changes in arthropod community composition are associated with changes in consumer-mediated ecosystem functions. Overall, higher plant species richness supported more diverse and complex arthropod communities and this pattern was consistent across multiple years. Vegetation-associated arthropods responded more strongly to changes in plant species richness than ground-dwelling arthropods. Additionally, increases in plant species richness were associated with shifts in the species-abundance distributions for many, but not all taxa. For example, highly specialized consumers showed a decrease in dominance and an increase in the number of rare species with increasing plant species richness. Most ecosystem processes investigated responded to increases in plant species richness in the same way as the trophic group mediating the process, e.g. both herbivory and herbivore diversity increase with increasing plant species richness. In the Jena Experiment and other studies, inconsistencies between predictions based on classic hypotheses of associational effects and observed relationships between plant species richness and arthropod diversity likely reflect the influence of multi-trophic community dynamics and species functional trait distributions. Future research should focus on testing a broader array of mechanisms to unravel the biological processes underlying the biodiversity-ecosystem functioning relationships. [ABSTRACT FROM AUTHOR]

Changes to primary producer diversity can cascade up to consumers and affect ecosystem processes. Although the effect of producer diversity on higher trophic groups have been studied, these studies often quantify taxonomy‐based measures of biodiversity, like species richness, which do not necessarily reflect the functioning of these communities. In this study, we assess how plant species richness affects the functional composition and diversity of higher trophic levels and discuss how this might affect ecosystem processes, such as herbivory, predation and decomposition. Based on six different consumer traits, we examined the functional composition of arthropod communities sampled in experimental plots that differed in plant species richness. The two components we focused on were functional variation in the consumer community structure (functional structure) and functional diversity, expressed as functional richness, evenness and divergence. We found a consistent positive effect of plant species richness on the functional richness of herbivores, carnivores, and omnivores, but not decomposers, and contrasting patterns for functional evenness and divergence. Increasing plant species richness shifted the omnivore community to more predatory and less mobile species, and the herbivore community to more specialized and smaller species. This was accompanied by a shift towards more species occurring in the vegetation than in the ground layer. Our study shows that plant species richness strongly affects the functional structure and diversity of aboveground arthropod communities. The observed shifts in body size (herbivores), specialization (herbivores), and feeding mode (omnivores) together with changes in the functional diversity may underlie previously observed increases in herbivory and predation in plant communities of higher diversity. [ABSTRACT FROM AUTHOR]

Niche complementarity and competitive disparity are driving mechanisms behind plant community assembly and productivity. Consequently, there is great interest in predicting species complementarity and their competitive differences from their functional traits as dissimilar species may compete less and result in more complete use of resources., Here we assessed the role of trait dissimilarities for species complementarity and competitive disparities within an experimental gradient of plant species richness and functional trait dissimilarity. Communities were assembled using three pools of grass and forb species based on a priori knowledge of traits related to (1) above- and below-ground spatial differences in resource acquisition, (2) phenological differences or (3) both. Complementarity and competitive disparities were assessed by partitioning the overyielding in mixed species communities into species complementarity and dominance effects., Community overyielding and the underlying complementarity and competitive dominance varied strongly among the three plant species pools. Overyielding and complementarity were greatest among species that were assembled based on their variation in both spatial and phenological traits. Competitive dominance was greatest when species were assembled based on spatial resource acquisition traits alone., In communities that were assembled based on species variation in only spatial or phenological traits, greater competitive dominance was predicted by greater differences in SLA and flowering initiation respectively, while greater complementarity was predicted by greater dissimilarity in leaf area and flowering senescence respectively. Greater differences in leaf area could also be linked to greater species complementarity in communities assembled based on variation in both phenological and spatial traits, but trait dissimilarity was unrelated to competitive dominance in these communities., Our results indicate that complementarity and competitive disparity among species are both driven by trait dissimilarities. However, the identity of the traits that drives the complementarity and competitive disparity depends on the trait variation among species that comprise the community. Moreover, we demonstrate that communities assembled with the greater variation in both spatial and phenological traits show the greatest complementarity among species., A is available for this article. [ABSTRACT FROM AUTHOR]

In the past two decades, a large number of studies have investigated the relationship between biodiversity and ecosystem functioning, most of which focussed on a limited set of ecosystem variables. The Jena Experiment was set up in 2002 to investigate the effects of plant diversity on element cycling and trophic interactions, using a multi-disciplinary approach. Here, we review the results of 15 years of research in the Jena Experiment, focussing on the effects of manipulating plant species richness and plant functional richness. With more than 85,000 measures taken from the plant diversity plots, the Jena Experiment has allowed answering fundamental questions important for functional biodiversity research. First, the question was how general the effect of plant species richness is, regarding the many different processes that take place in an ecosystem. About 45% of different types of ecosystem processes measured in the ‘main experiment’, where plant species richness ranged from 1 to 60 species, were significantly affected by plant species richness, providing strong support for the view that biodiversity is a significant driver of ecosystem functioning. Many measures were not saturating at the 60-species level, but increased linearly with the logarithm of species richness. There was, however, great variability in the strength of response among different processes. One striking pattern was that many processes, in particular belowground processes, took several years to respond to the manipulation of plant species richness, showing that biodiversity experiments have to be long-term, to distinguish trends from transitory patterns. In addition, the results from the Jena Experiment provide further evidence that diversity begets stability, for example stability against invasion of plant species, but unexpectedly some results also suggested the opposite, e.g. when plant communities experience severe perturbations or elevated resource availability. This highlights the need to revisit diversity–stability theory. Second, we explored whether individual plant species or individual plant functional groups, or biodiversity itself is more important for ecosystem functioning, in particular biomass production. We found strong effects of individual species and plant functional groups on biomass production, yet these effects mostly occurred in addition to, but not instead of, effects of plant species richness. Third, the Jena Experiment assessed the effect of diversity on multitrophic interactions. The diversity of most organisms responded positively to increases in plant species richness, and the effect was stronger for above- than for belowground organisms, and stronger for herbivores than for carnivores or detritivores. Thus, diversity begets diversity. In addition, the effect on organismic diversity was stronger than the effect on species abundances. Fourth, the Jena Experiment aimed to assess the effect of diversity on N, P and C cycling and the water balance of the plots, separating between element input into the ecosystem, element turnover, element stocks, and output from the ecosystem. While inputs were generally less affected by plant species richness, measures of element stocks, turnover and output were often positively affected by plant diversity, e.g. carbon storage strongly increased with increasing plant species richness. Variables of the N cycle responded less strongly to plant species richness than variables of the C cycle. Fifth, plant traits are often used to unravel mechanisms underlying the biodiversity–ecosystem functioning relationship. In the Jena Experiment, most investigated plant traits, both above- and belowground, were plastic and trait expression depended on plant diversity in a complex way, suggesting limitation to using database traits for linking plant traits to particular functions. Sixth, plant diversity effects on ecosystem processes are often caused by plant diversity effects on species interactions. Analyses in the Jena Experiment including structural equation modelling suggest complex interactions that changed with diversity, e.g. soil carbon storage and greenhouse gas emission were affected by changes in the composition and activity of the belowground microbial community. Manipulation experiments, in which particular organisms, e.g. belowground invertebrates, were excluded from plots in split-plot experiments, supported the important role of the biotic component for element and water fluxes. Seventh, the Jena Experiment aimed to put the results into the context of agricultural practices in managed grasslands. The effect of increasing plant species richness from 1 to 16 species on plant biomass was, in absolute terms, as strong as the effect of a more intensive grassland management, using fertiliser and increasing mowing frequency. Potential bioenergy production from high-diversity plots was similar to that of conventionally used energy crops. These results suggest that diverse ‘High Nature Value Grasslands’ are multifunctional and can deliver a range of ecosystem services including production-related services. A final task was to assess the importance of potential artefacts in biodiversity–ecosystem functioning relationships, caused by the weeding of the plant community to maintain plant species composition. While the effort (in hours) needed to weed a plot was often negatively related to plant species richness, species richness still affected the majority of ecosystem variables. Weeding also did not negatively affect monoculture performance; rather, monocultures deteriorated over time for a number of biological reasons, as shown in plant-soil feedback experiments. To summarize, the Jena Experiment has allowed for a comprehensive analysis of the functional role of biodiversity in an ecosystem. A main challenge for future biodiversity research is to increase our mechanistic understanding of why the magnitude of biodiversity effects differs among processes and contexts. It is likely that there will be no simple answer. For example, among the multitude of mechanisms suggested to underlie the positive plant species richness effect on biomass, some have received limited support in the Jena Experiment, such as vertical root niche partitioning. However, others could not be rejected in targeted analyses. Thus, from the current results in the Jena Experiment, it seems likely that the positive biodiversity effect results from several mechanisms acting simultaneously in more diverse communities, such as reduced pathogen attack, the presence of more plant growth promoting organisms, less seed limitation, and increased trait differences leading to complementarity in resource uptake. Distinguishing between different mechanisms requires careful testing of competing hypotheses. Biodiversity research has matured such that predictive approaches testing particular mechanisms are now possible. [ABSTRACT FROM AUTHOR]

Climate change is projected to increase the frequency of extreme events, such as flooding and droughts, which are anticipated to have negative effects on the biodiversity of primary producers and consequently the associated consumer communities. Here we assessed the effects of an extreme early summer flooding event in 2013 on ant colonies along an experimental gradient of plant species richness in a temperate grassland. We tested the effects of flood duration, plant species richness, plant cover, soil temperature, and soil porosity on ant occurrence and abundance. We found that the ant community was dominated by Lasius niger, whose presence and abundance after the flood was not significantly affected by any of the tested variables, including plant species richness. We found the same level of occupation by L. niger at the field site after the flood (surveyed in 2013) as before the flood (surveyed in 2006). Thus, there were no negative effects of the flood on the presence of L. niger in the plots. We can exclude recolonisation as a possible explanation of ant presence in the field site due to the short time period between the end of the flood and survey as well as to the absence of a spatial pattern in the occupancy data. Thus, the omnipresence of this dominant ant species 1 month after the flood indicates that the colonies were able to survive a 3-week summer flood. The observed ant species proved to be flood resistant despite experiencing such extreme climatic events very rarely. [ABSTRACT FROM AUTHOR]

The impact of species richness and functional diversity of plants on ecosystem water vapor fluxes has been little investigated. To address this knowledge gap, we combined a lysimeter setup in a controlled environment facility (Ecotron) with large ecosystem samples/monoliths originating from a long-term biodiversity experiment (The Jena Experiment) and a modeling approach. Our goals were (1) quantifying the impact of plant species richness (four vs. 16 species) on day- and nighttime ecosystem water vapor fluxes; (2) partitioning ecosystem evapotranspiration into evaporation and plant transpiration using the Shuttleworth and Wallace ( SW) energy partitioning model; and (3) identifying the most parsimonious predictors of water vapor fluxes using plant functional-trait-based metrics such as functional diversity and community weighted means. Daytime measured and modeled evapotranspiration were significantly higher in the higher plant diversity treatment, suggesting increased water acquisition. The SW model suggests that, at low plant species richness, a higher proportion of the available energy was diverted to evaporation (a non-productive flux), while, at higher species richness, the proportion of ecosystem transpiration (a productivity-related water flux) increased. While it is well established that LAI controls ecosystem transpiration, here we also identified that the diversity of leaf nitrogen concentration among species in a community is a consistent predictor of ecosystem water vapor fluxes during daytime. The results provide evidence that, at the peak of the growing season, higher leaf area index ( LAI) and lower percentage of bare ground at high plant diversity diverts more of the available water to transpiration, a flux closely coupled with photosynthesis and productivity. Higher rates of transpiration presumably contribute to the positive effect of diversity on productivity. [ABSTRACT FROM AUTHOR]

Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2°C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and functioning. We furthermore conclude that artificial tree-hole analogues represent a useful experimental alternative to test effects of changes in forest management on natural communities. [ABSTRACT FROM AUTHOR]

Changes in producer diversity cause multiple changes in consumer communities through various mechanisms. However, past analyses investigating the relationship between plant diversity and arthropod consumers focused only on few aspects of arthropod diversity, e.g. species richness and abundance. Yet, shifts in understudied facets of arthropod diversity like relative abundances or species dominance may have strong effects on arthropod-mediated ecosystem functions. Here we analyze the relationship between plant species richness and arthropod diversity using four complementary diversity indices, namely: abundance, species richness, evenness (equitability of the abundance distribution) and dominance (relative abundance of the dominant species). Along an experimental gradient of plant species richness (1, 2, 4, 8, 16 and 60 plant species), we sampled herbivorous and carnivorous arthropods using pitfall traps and suction sampling during a whole vegetation period. We tested whether plant species richness affects consumer diversity directly (i), or indirectly through increased productivity (ii). Further, we tested the impact of plant community composition on arthropod diversity by testing for the effects of plant functional groups (iii). Abundance and species richness of both herbivores and carnivores increased with increasing plant species richness, but the underlying mechanisms differed between the two trophic groups. While higher species richness in herbivores was caused by an increase in resource diversity, carnivore richness was driven by plant productivity. Evenness of herbivore communities did not change along the gradient in plant species richness, whereas evenness of carnivores declined. The abundance of dominant herbivore species showed no response to changes in plant species richness, but the dominant carnivores were more abundant in species-rich plant communities. The functional composition of plant communities had small impacts on herbivore communities, whereas carnivore communities were affected by forbs of small stature, grasses and legumes. Contrasting patterns in the abundance of dominant species imply different levels of resource specialization for dominant herbivores (narrow food spectrum) and carnivores (broad food spectrum). That in turn could heavily affect ecosystem functions mediated by herbivorous and carnivorous arthropods, such as herbivory or biological pest control. [ABSTRACT FROM AUTHOR]

Land-use change is a major driver of the global loss of biodiversity, but it is unclear to what extent this also results in a loss of ecological traits. Therefore, a better understanding of how land-use change affects ecological traits is crucial for efforts to sustain functional diversity. To this end we tested whether higher species richness or taxonomic distinctness generally leads to increased functional distinctness and whether intensive land use leads to functionally more narrow arthropod communities. We compiled species composition and trait data for 350 species of terrestrial arthropods (Araneae, Carabidae and Heteroptera) in different land-use types (forests, grasslands and arable fields) of low and high land-use intensity. We calculated the average functional and taxonomic distinctness and the rarified trait richness for each community. These measures reflect the range of traits, taxonomic relatedness and number of traits that are observed in local communities. Average functional distinctness only increased significantly with species richness in Carabidae communities. Functional distinctness increased significantly with taxonomic distinctness in communities of all analyzed taxa suggesting a high functional redundancy of taxonomically closely related species. Araneae and Heteroptera communities had the expected lower functional distinctness at sites with higher land-use intensity. More frequently disturbed land-use types such as managed grasslands or arable fields were characterized by species with smaller body sizes and higher dispersal abilities and communities with lower functional distinctness or trait richness. Simple recommendations about the conservation of functional distinctness of arthropod communities in the face of future land-use intensification and species loss are not possible. Our study shows that these relationships depend on the studied taxa and land-use type. However, for some arthropod groups functional distinctness is threatened by intensification and conversion from less to more frequently disturbed land-uses. [ABSTRACT FROM AUTHOR]

Forest management is known to influence species diversity of various taxa but inconsistent or even contrasting effects are reported for arthropods. Regional differences in management as well as differences in regional species pools might be responsible for these inconsistencies, but, inter-regional replicated studies that account for regional variability are rare. We investigated the effect of forest type on the abundance, diversity, community structure and composition of two important ground-dwelling beetle families, Carabidae and Staphylinidae, in 149 forest stands distributed over three regions in Germany. In particular we focused on recent forestry history, stand age and dominant tree species, in addition to a number of environmental descriptors. Overall management effects on beetle communities were small and mainly mediated by structural habitat parameters such as the cover of forest canopy or the plant diversity on forest stands. The general response of both beetle taxa to forest management was similar in all regions: abundance and species richness of beetles was higher in older than in younger stands and species richness was lower in unmanaged than in managed stands. The abundance ratio of forest species-to-open habitat species differed between regions, but generally increased from young to old stands, from coniferous to deciduous stands and from managed to unmanaged stands. The response of both beetle families to dominant tree species was variable among regions and staphylinid richness varied in the response to recent forestry history. Our results suggest that current forest management practices change the composition of ground-dwelling beetle communities mainly by favoring generalists and open habitat species. To protect important forest beetle communities and thus the ecosystem functions and services provided by them, we suggest to shelter remaining ancient forests and to develop near-to-nature management strategies by prolonging rotation periods and increasing structural diversity of managed forests. Possible geographic variations in the response of beetle communities need to be considered in conservation-orientated forest management strategies. [ABSTRACT FROM AUTHOR]

Intensive land use is a driving force for biodiversity decline in many ecosystems. In semi-natural grasslands, land-use activities such as mowing, grazing and fertilization affect the diversity of plants and arthropods, but the combined effects of different drivers and the chain of effects are largely unknown. In this study we used structural equation modelling to analyse how the arthropod communities in managed grasslands respond to land use and whether these responses are mediated through changes in resource diversity or resource quantity (biomass). Plants were considered resources for herbivores which themselves were considered resources for predators. Plant and arthropod (herbivores and predators) communities were sampled on 141 meadows, pastures and mown pastures within three regions in Germany in 2008 and 2009. Increasing land-use intensity generally increased plant biomass and decreased plant diversity, mainly through increasing fertilization. Herbivore diversity decreased together with plant diversity but showed no response to changes in plant biomass. Hence, land-use effects on herbivore diversity were mediated through resource diversity rather than quantity. Land-use effects on predator diversity were mediated by both herbivore diversity (resource diversity) and herbivore quantity (herbivore biomass), but indirect effects through resource quantity were stronger. Our findings highlight the importance of assessing both direct and indirect effects of land-use intensity and mode on different trophic levels. In addition to the overall effects, there were subtle differences between the different regions, pointing to the importance of regional land-use specificities. Our study underlines the commonly observed strong effect of grassland land use on biodiversity. It also highlights that mechanistic approaches help us to understand how different land-use modes affect biodiversity. [ABSTRACT FROM AUTHOR]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Numerous studies have reported positive effects of species richness on plant community productivity. Such biodiversity effects are usually quantified by comparing the performance of plant mixtures with reference monocultures. However, several mechanisms, such as the lack of resource complementarity and facilitation or the accumulation of detrimental agents, suggest that monocultures are more likely than mixtures to deteriorate over time. Increasing biodiversity effects over time could therefore result from declining monocultures instead of reflecting increases in the functioning of mixtures. Commonly, the latter is assumed when positive trends in biodiversity effects occur. Here, we analysed the performance of 60 grassland species growing in monocultures and mixtures over 9 years in a biodiversity experiment to clarify whether their temporal biomass dynamics differed and whether a potential decline of monocultures contributed significantly to the positive net biodiversity effect observed. Surprisingly, individual species’ populations produced, on average, significantly more biomass per unit area when growing in monoculture than when growing in mixture. Over time, productivity of species decreased at a rate that was, on average, slightly more negative in monocultures than in mixtures. The mean net biodiversity effect across all mixtures was continuously positive and ranged between 64–217 g per m2. Short-term increases in the mean net biodiversity effect were only partly due to deteriorating monocultures and were strongly affected by particular species gaining dominance in mixtures in the respective years. We conclude that our species performed, on average, comparably in monocultures and mixtures; monoculture populations being slightly more productive than mixture populations but this trend decreased over time. This suggested that negative feedbacks had not yet affected monocultures strongly but could potentially become more evident in the future. Positive biodiversity effects on aboveground productivity were heavily driven by a small, but changing, set of species that behaved differently from the average species. [ABSTRACT FROM AUTHOR]

Copyright of Basic & Applied Ecology is the property of Urban & Fischer Verlag and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Environmental factors can lead individuals down different developmental pathways giving rise to distinct phenotypes (phenotypic plasticity). The production of winged or unwinged morphs in aphids is an example of two alternative developmental pathways. Dispersal is paramount in aphids that often have a metapopulation structure, where local subpopulations frequently go extinct, such as the specialized aphids on tansy (Tanacetum vulgare). We conducted various experiments to further understand the cues involved in the production of winged dispersal morphs by the two dominant species of the tansy aphid metacommunity, Metopeurum fuscoviride and Macrosiphoniella tanacetaria. We found that the ant-tended M. fuscoviride produced winged individuals predominantly at the beginning of the season while the untended M. tanacetaria produced winged individuals throughout the season. Winged mothers of both species produced winged offspring, although in both species winged offspring were mainly produced by unwinged females. Crowding and the presence of predators, effects already known to influence wing production in other aphid species, increased the percentage of winged offspring in M. tanacetaria, but not in M. fuscoviride. We find there are also other factors (i.e. temporal effects) inducing the production of winged offspring for natural aphid populations. Our results show that the responses of each aphid species are due to multiple wing induction cues. [ABSTRACT FROM AUTHOR]