Showing papers by "Volkmar Wolters published in 2016"

Biodiversity at multiple trophic levels is needed for ecosystem multifunctionality

Abstract: Many experiments have shown that loss of biodiversity reduces the capacity of ecosystems to provide the multiple services on which humans depend. However, experiments necessarily simplify the complexity of natural ecosystems and will normally control for other important drivers of ecosystem functioning, such as the environment or land use. In addition, existing studies typically focus on the diversity of single trophic groups, neglecting the fact that biodiversity loss occurs across many taxa and that the functional effects of any trophic group may depend on the abundance and diversity of others. Here we report analysis of the relationships between the species richness and abundance of nine trophic groups, including 4,600 above- and below-ground taxa, and 14 ecosystem services and functions and with their simultaneous provision (or multifunctionality) in 150 grasslands. We show that high species richness in multiple trophic groups (multitrophic richness) had stronger positive effects on ecosystem services than richness in any individual trophic group; this includes plant species richness, the most widely used measure of biodiversity. On average, three trophic groups influenced each ecosystem service, with each trophic group influencing at least one service. Multitrophic richness was particularly beneficial for 'regulating' and 'cultural' services, and for multifunctionality, whereas a change in the total abundance of species or biomass in multiple trophic groups (the multitrophic abundance) positively affected supporting services. Multitrophic richness and abundance drove ecosystem functioning as strongly as abiotic conditions and land-use intensity, extending previous experimental results to real-world ecosystems. Primary producers, herbivorous insects and microbial decomposers seem to be particularly important drivers of ecosystem functioning, as shown by the strong and frequent positive associations of their richness or abundance with multiple ecosystem services. Our results show that multitrophic richness and abundance support ecosystem functioning, and demonstrate that a focus on single groups has led to researchers to greatly underestimate the functional importance of biodiversity.

Land-use intensification causes multitrophic homogenization of grassland communities

Abstract: Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in β-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (α)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing β-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in α-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on β-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in β-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local α-diversity in aboveground groups, whereas the α-diversity increased in belowground groups. Correlations between the β-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.

Locally rare species influence grassland ecosystem multifunctionality

Abstract: Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity-multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land-use intensity (LUI) gradient. The diversity of above- and below-ground rare species had opposite effects, with rare above-ground species being associated with high levels of multifunctionality, probably because their effects on different functions did not trade off against each other. Conversely, common species were only related to average, not high, levels of multifunctionality, and their functional effects declined with LUI. Apart from the community-level effects of diversity, we found significant positive associations between the abundance of individual species and multifunctionality in 6% of the species tested. Species-specific functional effects were best predicted by their response to LUI: species that declined in abundance with land use intensification were those associated with higher levels of multifunctionality. Our results highlight the importance of rare species for ecosystem multifunctionality and help guiding future conservation priorities.

Intraspecific body size increases with habitat fragmentation in wild bee pollinators

Abstract: In modern agricultural landscapes, fragmentation of partial habitats is a significant filter for multi-habitat users, reducing local taxonomic and functional diversity. There is compelling evidence that small species are more susceptible than large species. The impact of habitat fragmentation on intraspecific body-size distribution, however, is yet unexplored. We tested habitat fragmentation, a major driver of pollinator loss, for its impact on intraspecific body-size distributions of solitary wild-bee species. Subsequently, we tested individual body size for its impact on pollination services. We sampled 1272 individuals of the four most common Andrena wild bee species in 22 newly established flowering fields (0.21–0.41 ha) in Hessen, Central Germany, over two consecutive years. Study sites were located in a ca. 80 ha landscape context of increasing habitat fragmentation. We analysed the pollen loads of the most abundant species. Body size within local populations of the two medium-sized bees increased with fragmentation, suggesting intraspecific selection for higher dispersal capacity. Pollen analysis carried out for the most common species revealed that larger individuals visited a significantly smaller plant spectrum. Habitat fragmentation may thus alter pollination services without necessarily affecting species richness or composition. Systematic body-size variation at the population level thus explains the considerable variability between simple community measures and ecosystem functioning. Filtering processes at the individual level require increased understanding for targeting pollination services under current and future land-use change.

Regional Conditions and Land-Use Alter the Potential Contribution of Soil Arthropods to Ecosystem Services in Grasslands

Abstract: We investigated the impact of regional conditions and land-use intensity on eight selected arthropod taxa of Mesostigmata (Parasitidae), Oribatida (3 species), Collembola (1 species), Chilopoda (2 species) and Diplopoda (1 species) sampled in differently managed permanent grasslands of three German study regions. By jointly analyzing changes in abundance and trophic behavior (measured as natural variation in 15N/14N and 13C/12C ratios) we intended to develop a framework for evaluating the impact of local and regional conditions on the ecosystem services delivered by soil animals (mainly decomposition- and predation-related services). The investigated taxa could be assorted to three major groups: (1) numerical response only, (2) numerical and trophic response and (3) trophic response only. Since the combination of taxa assembled in the individual groups does not correspond to any of the conventional soil ecological classification systems, this grouping offers a new approach for analyzing soil communities. The complementing consideration of both the direction of the numerical response and the type of the trophic response (change of the basal food source vs. trophic level shift vs. variations in isotopic niches) provided a differential insight into the effect of management and geographic differences on soil arthropods. It could be shown that the effect of land-use on the abundance of detritivorous microarthropods varies among regions, but does not induce any changes in feeding behavior. Our findings on Parasitidae indicate that carnivorous microarthropods exert substantial predation pressure on soil mesofauna and may be quite resistant to environmental changes due to high trophic flexibility. If conditions are favorable, centipedes may reach comparatively high densities in permanent grasslands and could be very important for controlling belowground pests. Concerning millipedes, isotopic signatures suggest that some species could exert a substantial disservice by feeding on roots over a wide range of land-use intensities and regional conditions. We conclude that the many consistent and significant effects found in our study support our contention that the combined analysis of numerical and trophic responses provides a promising framework for designing spatially explicit models that quantify the impact of human interventions on the delivery of ecosystem services by the soil fauna.

Organic farming affects the potential of a granivorous carabid beetle to control arable weeds at local and landscape scales

Abstract: Organic farming not only increases plant diversity, but also simultaneously promotes biological weed control through provisioning of ample resources to seed predators. Harpalus affinis (Schrank, 1781) was collected from organically or conventionally managed winter-wheat fields with high or low surrounding shares of organic fields, aiming to test the impact of agricultural management on its activity density, body size and nutritional condition. Body size and nutritional condition were then related to the arable weed seed predation of this granivorous carabid beetle. Activity density of H. affinis was 3.5-fold higher in organically compared with conventionally managed fields, if these were primarily surrounded by conventional fields. Body size was larger in fields surrounded by large proportions of organically managed land, independent of local management. The nutritional condition of beetles was unaffected by local or landscape scale farming. Per capita seed predation significantly increased with body size, whereas nutritional condition had no effect. The results of the present study suggest that organic farming at local and landscape scales enhances the potential of species to control arable weeds by increasing activity densities and intraspecific body size. Seed predation therefore not only depends on local and landscape effects on the community composition of local guilds of granivores, but also on the contribution of individual species to this important ecosystem service. (Less)

Regional Patterns of Ecosystem Services in Cultural Landscapes

Abstract: European agricultural landscapes have been shaped by humans to produce marketable private goods such as food, feed, fiber and timber. Land-use intensification to increase provisioning services in such productive landscapes alters the capacity of ecosystems to supply other services (often public goods and services) that are also vital for human wellbeing. However, the interactions, synergies and trade-offs among ecosystem services are poorly understood. We assessed the spatial distribution of the services carbon storage, sediment regulation, water yield, crop production, timber supply, and outdoor recreation in the counties Wetterau and Vogelsberg (Hesse, Germany). These counties represent a gradient from intensive arable land use to more extensive mixed land use systems with domination of grassland and forests. Spatially explicit models were used to map the location and quantity of service supply. We addressed the following questions: (1) Where are areas of high and low supply of individual and multiple ecosystem services? (2) Where do the strongest trade-offs and synergies between different services occur? Our results show a pronounced spatial aggregation of different ecosystem services, with locations where at least four services are being supplied at high levels occupying only 5% of the landscape. Indicators for water provision, timber supply, carbon storage, erosion control, and outdoor recreation are positively related to each other, but this relationship is influenced by the trade-offs associated with the ecosystem service food production. Optimization of ecosystem services at the landscape scale has to take these patterns into account.

The 2016 release of the PREDICTS database

Abstract: A dataset of 3,250,404 measurements, collated from 26,114 sampling locations in 94 countries and representing 47,044 species. The data were collated from 480 existing spatial comparisons of local-scale biodiversity exposed to different intensities and types of anthropogenic pressures, from terrestrial sites around the world. The database was assembled as part of the PREDICTS project - Projecting Responses of Ecological Diversity In Changing Terrestrial Systems; [www.predicts.org.uk](http://www.predicts.org.uk).\r \r The taxonomic identifications provided in the original data sets are those determined at the time of the original research, and so will not reflect subsequent taxonomic changes.\r \r This dataset is described in [10.1002/ece3.2579](http://dx.doi.org/10.1002/ece3.2579). A description of the way that this dataset was assembled is given in [10.1002/ece3.1303](http://dx.doi.org/10.1002/ece3.1303).\r \r * `columns.csv`: Description of data extract columns\r * `database.zip`: Database in zipped CSV format\r * `database.rds`: Database in RDS format\r * `sites.zip`: Site-level summaries in compressed CSV format\r * `sites.rds`: Site-level summaries in RDS format\r * `references.csv`: Data references in CSV format\r * `references.bib`: Data references in BibTeX format\r

Notes on the ecology of the colombian leaftoed gecko (phyllodactylus transversalis), endemic to malpelo island

Abstract: The Colombian leaf-toed gecko (Phyllodactylustransversalis) is the least known reptile species of Malpelo Island (Eastern Tropical Pacific). In the 37 years since its original description, no single study strictly dedicated to this species has been conducted. With the goal of providing information on the ecology and population size of this gecko, data collected during two visits to the island are presented. Behavior and reproduction were studied by following individuals during the night and by searching for hidden individuals and eggs during the day. Population's density and habitat preferences were estimated by classifying the island's surfaces into four types and counting geckos inside those habitats within band transects. General morphological measurements of geckos were performed as reference points for future comparisons. Phyllodactylustransversalis lays its eggs in narrow crevices of rocks, apparently communally. Reproduction seems to take place during most of the year, probably associated with the peak breeding season of seabirds. Although conspecifics shared shelters during the day, densities during the night suggest no apparent habitat preference for foraging. Population size of this species was estimated at approximately 114000 individuals.