Arthropod communities in a changing world : combined impacts of climate change and land-use intensification on arthropod communities

Global change poses increasing threats to ecological communities and ecosystem functioning. To improve our understanding of how arthropod communities, and associated ecosystem functions respond to combined impacts of future climate change and land-use intensification in grassland ecosystems, I used the experimental set-up of the Global Change Experimental Facility (GCEF). In my first chapter, I studied the combined effects of climate change and land-use intensity on arthropod community composition at the whole community level and of four trophic groups (predators, herbivores, detritivores and omnivores). I found that climate change and land-use intensification simultaneously shift species composition across trophic levels, through changes in abundance, species richness, and evenness. In my second chapter, I present a comprehensive set of linear regressions to estimate live body mass using data on body length and width, taxonomy and geographic origin. Furthermore, I quantified prediction discrepancy when using parameters from arthropods of a different geographic region. Incorporating body width into taxon- and region-specific length-mass regressions substantially increased prediction accuracy for live body mass. In my third research chapter, I studied the impacts of future climate change and land-use intensification on ecosystem functioning and the stability of arthropod food-webs. I furthermore studied the response of underlying community characteristics driving these ecosystem processes. Specifically, I tested the response of mean body mass, biomass and community metabolism of the whole community and four trophic groups to climate change and land-use intensification. Despite changes in community characteristics of the trophic groups, community ecosystem processes and food-web stability remained stable under climate change and land-use intensification, while the composition of total ecosystem processes changed.