@article{MunjonjiAyisiMudongoetal.2020, author = {Munjonji, Lawrence and Ayisi, Kingsley Kwabena and Mudongo, Edwin I. and Mafeo, Tieho Paulus and Behn, Kai and Mokoka, Malesela Vincent and Linst{\"a}dter, Anja}, title = {Disentangling drought and grazing effects on soil carbon stocks and CO2 fluxes in a semi-arid African Savanna}, series = {Frontiers in Environmental Science}, volume = {8}, journal = {Frontiers in Environmental Science}, publisher = {Frontiers Media}, address = {Lausanne}, issn = {2296-665X}, doi = {10.3389/fenvs.2020.590665}, pages = {14}, year = {2020}, abstract = {Grasslands cover ca. 30\% of the global land surface and provide critical ecosystem services. Among them, carbon storage is one of the most important. However, grasslands are increasingly threatened by drought and overgrazing which might negatively affect soil carbon stocks. Despite this threat, there is a dearth of information on how drought and grazing jointly impact soil carbon stocks and CO2 fluxes in dryland grasslands. With the aid of a large field experiment, we studied the combined effects of a 5-year extreme drought and moderate grazing on soil carbon stocks, CO2 fluxes and soil chemical properties. Extreme drought was induced by reducing ambient rainfall by 66\% using large rainout shelters. We found CO2 fluxes to strongly respond to the 5-year experimental drought. Extreme drought reduced CO2 emission rates by 32\% compared to ambient conditions. CO2 fluxes averaged 5.7 mg m(-2)min(-1) under drought compared to 8.3 mg m(-2) min(-1) under ambient conditions. CO2 fluxes were, however, not influenced by grazing. At the end of the growth period, grazed plots under ambient rainfall had released 16.3 tons of CO2 ha(-1) which was 58\% higher than observed on grazed plots subjected to severe drought. Soil carbon stocks were higher under drought conditions due to slower decomposition rates. Drought resulted in increased concentrations of primary macronutrients (N, P, and K), micronutrients (Zn and Mn) and pH in the top 30 cm of the soil relative to ambient conditions. The results also showed that grazing reduced the concentration of N and P in the topsoil compared to the ungrazed plots. This study provided insights on the soil carbon storage, CO2 emission rates and nutrient dynamics in a semi-arid dryland grassland as influenced by both drought and grazing. Our study also revealed that long-term extreme drought may be favorable in terms of preserving the existing soil carbon stocks through reduced CO2 release. This finding is critical for understanding future soil carbon dynamics in dryland grasslands in the face of climate change.}, language = {en} } @article{BochMuellerPratietal.2018, author = {Boch, Steffen and M{\"u}ller, J{\"o}rg and Prati, Daniel and Fischer, Markus}, title = {Low-intensity management promotes bryophyte diversity in grasslands}, series = {Tuexenia : Mitteilungen der Floristisch-Soziologischen Arbeitsgemeinschaft}, journal = {Tuexenia : Mitteilungen der Floristisch-Soziologischen Arbeitsgemeinschaft}, number = {38}, publisher = {Floristisch-Soziologische Arbeitsgemeinschaft}, address = {G{\"o}ttingen}, issn = {0722-494X}, doi = {10.14471/2018.38.014}, pages = {311 -- 328}, year = {2018}, abstract = {Bryophytes constitute an important and permanent component of the grassland flora and diversity in Europe. As most bryophyte species are sensitive to habitat change, their diversity is likely to decline following land-use intensification. Most previous studies on bryophyte diversity focused on specific habitats of high bryophyte diversity, such as bogs, montane grasslands, or calcareous dry grasslands. In contrast, mesic grasslands are rarely studied, although they are the most common grassland habitat in Europe. They are secondary vegetation, maintained by agricultural use and thus, are influenced by different forms of land use. We studied bryophyte species richness in three regions in Germany, in 707 plots of 16 m(2) representing different land-use types and environmental conditions. Our study is one of the few to inspect the relationships between bryophyte richness and land use across contrasting regions and using a high number of replicates. Among the managed grasslands, pastures harboured 2.5 times more bryophyte species than meadows and mown pastures. Similarly, bryophyte cover was about twice as high in fallows and pastures than in meadows and mown pastures. Among the pastures, bryophyte species richness was about three times higher in sheep grazed plots than in the ones grazed by cattle or horses. In general, bryophyte species richness and cover was more than 50\% lower in fertilized than in unfertilized plots. Moreover, the amount of suitable substrates was linked to bryophyte diversity. Species richness of bryophytes growing on stones increased with stone cover, and the one of bryophytes growing on bark and deadwood increased with larger values of woody plant species and deadwood cover. Our findings highlight the importance of low-intensity land use and high structural heterogeneity for bryophyte conservation. They also caution against an intensification of traditionally managed pastures. In the light of our results, we recommend to maintain low-intensity sheep grazing on sites with low productivity, such as slopes on shallow soils.}, language = {en} } @article{StantonBooneSotoShoenderetal.2017, author = {Stanton, Richard A. and Boone, Wesley W. and Soto-Shoender, Jose and Fletcher, Robert J. and Blaum, Niels and McCleery, Robert A.}, title = {Shrub encroachment and vertebrate diversity}, series = {Global ecology and biogeography : a journal of macroecology}, volume = {27}, journal = {Global ecology and biogeography : a journal of macroecology}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {1466-822X}, doi = {10.1111/geb.12675}, pages = {368 -- 379}, year = {2017}, abstract = {Aim: Across the planet, grass-dominated biomes are experiencing shrub encroachment driven by atmospheric CO2 enrichment and land-use change. By altering resource structure and availability, shrub encroachment may have important impacts on vertebrate communities. We sought to determine the magnitude and variability of these effects across climatic gradients, continents, and taxa, and to learn whether shrub thinning restores the structure of vertebrate communities. Location: Worldwide. Time period: Contemporary. Major taxa studied: Terrestrial vertebrates. Methods: We estimated relationships between percentage shrub cover and the structure of terrestrial vertebrate communities (species richness, Shannon diversity and community abundance) in experimentally thinned and unmanipulated shrub-encroached grass-dominated biomes using systematic review and meta-analyses of 43 studies published from 1978 to 2016. We modelled the effects of continent, biome, mean annual precipitation, net primary productivity and the normalized difference vegetation index (NDVI) on the relationship between shrub cover and vertebrate community structure. Results: Species richness, Shannon diversity and total abundance had no consistent relationship with shrub encroachment and experimental thinning did not reverse encroachment effects on vertebrate communities. However, some effects of shrub encroachment on vertebrate communities differed with net primary productivity, amongst vertebrate groups, and across continents. Encroachment had negative effects on vertebrate diversity at low net primary productivity. Mammalian and herpetofaunal diversity decreased with shrub encroachment. Shrub encroachment also had negative effects on species richness and total abundance in Africa but positive effects in North America. Main conclusions: Biodiversity conservation and mitigation efforts responding to shrub encroachment should focus on low-productivity locations, on mammals and herpetofauna, and in Africa. However, targeted research in neglected regions such as central Asia and India will be needed to fill important gaps in our knowledge of shrub encroachment effects on vertebrates. Additionally, our findings provide an impetus for determining the mechanisms associated with changes in vertebrate diversity and abundance in shrub-encroached grass-dominated biomes.}, language = {en} } @article{ManningGossnerBossdorfetal.2015, author = {Manning, Pete and Gossner, Martin M. and Bossdorf, Oliver and Allan, Eric and Zhang, Yuan-Ye and Prati, Daniel and Bl{\"u}thgen, Nico and Boch, Steffen and B{\"o}hm, Stefan and B{\"o}rschig, Carmen and H{\"o}lzel, Norbert and Jung, Kirsten and Klaus, Valentin H. and Klein, Alexandra-Maria and Kleinebecker, Till and Krauss, Jochen and Lange, Markus and M{\"u}ller, J{\"o}rg and Pasalic, Esther and Socher, Stephanie A. and Tschapka, Marco and T{\"u}rke, Manfred and Weiner, Christiane and Werner, Michael and Gockel, Sonja and Hemp, Andreas and Renner, Swen C. and Wells, Konstans and Buscot, Francois and Kalko, Elisabeth K. V. and Linsenmair, Karl Eduard and Weisser, Wolfgang W. and Fischer, Markus}, title = {Grassland management intensification weakens the associations among the diversities of multiple plant and animal taxa}, series = {Ecology : a publication of the Ecological Society of America}, volume = {96}, journal = {Ecology : a publication of the Ecological Society of America}, number = {6}, publisher = {Wiley}, address = {Washington}, issn = {0012-9658}, doi = {10.1890/14-1307.1}, pages = {1492 -- 1501}, year = {2015}, abstract = {Land-use intensification is a key driver of biodiversity change. However, little is known about how it alters relationships between the diversities of different taxonomic groups, which are often correlated due to shared environmental drivers and trophic interactions. Using data from 150 grassland sites, we examined how land-use intensification (increased fertilization, higher livestock densities, and increased mowing frequency) altered correlations between the species richness of 15 plant, invertebrate, and vertebrate taxa. We found that 54\% of pairwise correlations between taxonomic groups were significant and positive among all grasslands, while only one was negative. Higher land-use intensity substantially weakened these correlations(35\% decrease in rand 43\% fewer significant pairwise correlations at high intensity), a pattern which may emerge as a result of biodiversity declines and the breakdown of specialized relationships in these conditions. Nevertheless, some groups (Coleoptera, Heteroptera, Hymenoptera and Orthoptera) were consistently correlated with multidiversity, an aggregate measure of total biodiversity comprised of the standardized diversities of multiple taxa, at both high and lowland-use intensity. The form of intensification was also important; increased fertilization and mowing frequency typically weakened plant-plant and plant-primary consumer correlations, whereas grazing intensification did not. This may reflect decreased habitat heterogeneity under mowing and fertilization and increased habitat heterogeneity under grazing. While these results urge caution in using certain taxonomic groups to monitor impacts of agricultural management on biodiversity, they also suggest that the diversities of some groups are reasonably robust indicators of total biodiversity across a range of conditions.}, language = {en} } @article{RochaGaedkeVasseur2011, author = {Rocha, Marcia R. and Gaedke, Ursula and Vasseur, David A.}, title = {Functionally similar species have similar dynamics}, series = {The journal of ecology}, volume = {99}, journal = {The journal of ecology}, number = {6}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0022-0477}, doi = {10.1111/j.1365-2745.2011.01893.x}, pages = {1453 -- 1459}, year = {2011}, abstract = {1. Improving the mechanistic basis of biodiversity-ecosystem function relationships requires a better understanding of how functional traits drive the dynamics of populations. For example, environmental disturbances or grazing may increase synchronization of functionally similar species, whereas functionally different species may show independent dynamics, because of different responses to the environment. Competition for resources, on the other hand, may yield a wide range of dynamic patterns among competitors and lead functionally similar and different species to display synchronized to compensatory dynamics. The mixed effect of these forces will influence the temporal fluctuations of populations and, thus, the variability of aggregate community properties. 2. To search for a relationship between functional and dynamics similarity, we studied the relationship between functional trait similarity and temporal dynamics similarity for 36 morphotypes of phytoplankton using long-term high-frequency measurements. 3. Our results show that functionally similar morphotypes exhibit dynamics that are more synchronized than those of functionally dissimilar ones. Functionally dissimilar morphotypes predominantly display independent temporal dynamics. This pattern is especially strong when short time-scales are considered. 4. Negative correlations are present among both functionally similar and dissimilar phytoplankton morphotypes, but are rarer and weaker than positive ones over all temporal scales. 5. Synthesis. We demonstrate that diversity in functional traits decreases community variability and ecosystem-level properties by decoupling the dynamics of individual morphotypes.}, language = {en} } @misc{SommerAdrianDomisetal.2012, author = {Sommer, Ulrich and Adrian, Rita and Domis, Lisette Nicole de Senerpont and Elser, James J. and Gaedke, Ursula and Ibelings, Bas and Jeppesen, Erik and Lurling, Miquel and Molinero, Juan Carlos and Mooij, Wolf M. and van Donk, Ellen and Winder, Monika}, title = {Beyond the Plankton Ecology Group (PEG) Model mechanisms driving plankton succession}, series = {Annual review of ecology, evolution, and systematics}, volume = {43}, journal = {Annual review of ecology, evolution, and systematics}, number = {2-4}, editor = {Futuyma, DJ}, publisher = {Annual Reviews}, address = {Palo Alto}, isbn = {978-0-8243-1443-9}, issn = {1543-592X}, doi = {10.1146/annurev-ecolsys-110411-160251}, pages = {429 -- 448}, year = {2012}, abstract = {The seasonal succession of plankton is an annually repeated process of community assembly during which all major external factors and internal interactions shaping communities can be studied. A quarter of a century ago, the state of this understanding was described by the verbal plankton ecology group (PEG) model. It emphasized the role of physical factors, grazing and nutrient limitation for phytoplankton, and the role of food limitation and fish predation for zooplankton. Although originally targeted at lake ecosystems, it was also adopted by marine plankton ecologists. Since then, a suite of ecological interactions previously underestimated in importance have become research foci: overwintering of key organisms, the microbial food web, parasitism, and food quality as a limiting factor and an extended role of higher order predators. A review of the impact of these novel interactions on plankton seasonal succession reveals limited effects on gross seasonal biomass patterns, but strong effects on species replacements.}, language = {en} }