The arbuscular mycorrhizal (AM) fungi are a globally distributed group of soil organisms that play critical roles in ecosystem function. However, the ecological niches of individual AM fungal taxa are poorly understood.
Anthropogenic disturbance has generated a significant loss of biodiversity worldwide and grazing by domestic herbivores is a contributing disturbance. Although the effects of grazing on plants are commonly explored, here we address the potential multi‐trophic effects on animal biodiversity (e.g. herbivores, pollinators and predators). We conducted a meta‐analysis on 109 independent studies that tested the response of animals or plants to livestock grazing relative to livestock excluded. Across all animals, livestock exclusion increased abundance and diversity, but these effects were greatest for trophic levels directly dependent on plants, such as herbivores and pollinators. Detritivores were the only trophic level whose abundance decreased with livestock exclusion. We also found that the number of years since livestock was excluded influenced the community and that the effects of grazer exclusion on animal diversity were strongest in temperate climates. These findings synthesise the effects of livestock grazing beyond plants and demonstrate the indirect impacts of livestock grazing on multiple trophic levels in the animal community. We identified the potentially long‐term impacts that livestock grazing can have on lower trophic levels and consequences for biological conservation. We also highlight the potentially inevitable cost to global biodiversity from livestock grazing that must be balanced against socio‐economic benefits.
Questions: Inter-annual variability in precipitation is expected to increase in grasslands, potentially causing additional stress to systems already impacted by anthropogenic activities such as livestock grazing, which can induce changes to grassland vegetation. Yet, the sensitivity of key ecosystem functions to these co-occurring factors is often overlooked. Here, we determine: (a) the effects of grazing on the sensitivity of above-ground net primary productivity (ANPP sensitivity) to interannual variation in water-year precipitation (the sum of precipitation from September through to the following August); (b) whether ANPP sensitivity to precipitation is associated with shifts induced by grazing in functional group biomass (grass vs forb) contribution to total ANPP, litter, and species richness, and mean annual water-year precipitation; and (c) whether the impacts of grazing on ANPP vary between dry and wet years.Location: Native grasslands in Alberta, Canada. Methods:We used long-term (14-28 years) ANPP and precipitation data from 31 grazed grasslands, each with a paired non-grazed livestock exclosure. ANPP was sampled annually within exclosures and adjacent grazed locations at each site. Results:We found that grazing increased ANPP sensitivity to inter-annual changes in precipitation. Increased ANPP sensitivity to precipitation in grazed, relative to non-grazed locations was associated with both an increase in the contribution of forbs to total ANPP and a decrease in the contribution of grasses to total ANPP; reduced litter also increased ANPP sensitivity to precipitation. Species richness was not associated with ANPP sensitivity in both grazed and non-grazed locations. Arid grasslands were more sensitive to inter-annual variation in precipitation when grazed than were mesic grasslands. Similarly, grazing reduced ANPP during dry years but had no effect during wet years. Conclusions:Overall, these findings suggest that grazed grasslands are more vulnerable to reductions in primary productivity in dry years, which may present a challenge for maintaining ecosystem services in an era of increasing precipitation variability.
1. The occurrence of multi-year drought is predicted to increase globally with climate change. However, it is unclear whether drought effects on ecosystems are progressive through time.2. Here, we experimentally reduced growing season precipitation (GSP) by 45% at seven North American temperate grasslands for four consecutive years to determine the following: (a) whether the effects of reduced precipitation on plant community structure and biomass components (shoot, root, litter) are compounding over time; (b) whether prior year climatic and soil conditions influence subsequent drought impacts on plant community structure and biomass components; and (c) whether the effects of reduced precipitation on individual ecosystem components are related to one another.3. Across the seven field sites, we observed neither consistent nor progressive effects of reduced precipitation on any biomass component during the experiment, despite having extreme drought conditions imposed for four consecutive years.Relative to the ambient treatment, above-ground net primary productivity (ANPP) declined in response to drought during the early years of the experiment but increased above the ambient treatment in the fourth year, while root and litter biomass were stable across the sites throughout the study. Similarly, graminoid cover decreased initially but recovered by the final year of the experiment, contributing to observed differences in species composition between treatments across sites.Compositional changes were not associated with any declines in species richness or evenness. Divergent responses among years were not driven by lag effects based on prior year climatic and soil conditions. Furthermore, precipitation effects on ecosystem components were largely independent as we found only two positive links: between ANPP and plant species richness, and between species evenness and composition. 4. Synthesis. Overall, our results suggest that these northern grasslands are relatively resistant to short-term multi-year drought in the context of supporting plant diversity and biomass production.
Grazing by wild and domesticated grazers occurs within many terrestrial ecosystems worldwide, with positive and negative impacts on biodiversity. Management of grazed lands in support of biological conservation could benefit from a compiled dataset of animal biodiversity within and adjacent to grazed sites. In this database, we have assembled data from the peer-reviewed literature that included all forms of grazing, co-occurring species, and site information. We reviewed 3,489 published articles and found 245 studies in 41 countries that surveyed animal biodiversity co-occurring with grazers. We extracted 16,105 observations of animal surveys for over 1,200 species in all terrestrial ecosystems and on all continents except Antarctica. We then compiled 28 different grazing variables that focus on management systems, assemblages of grazer species, ecosystem characteristics, and survey type. Our database provides the most comprehensive summary of animal biodiversity patterns that co-occur with wild and domesticated grazers. This database could be used in future conservation initiatives and grazing management to enhance the prolonged maintenance of ecosystems and ecosystem services.
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