am a (co-)PI of the following projects: BEF-Loops, GrazeLife, and the beta diversity x soil pathogen experiment. Furthermore, I am also involved in various other projects.
A major question in the field of ecology is how plant species richness is related to grassland biomass production. Ecologists have studied this question from two perspectives, namely the perspective in which biomass production drives variation in plant species richness (Productivity Richness Relationships or PRR), and the perspective where a reverse causality is assumed, and plant richness drives variation in plant productivity (Biodiversity and Ecosystem Functioning or BEF perspective). While PRR and BEF mechanisms may jointly operate and are inherently related, they are typically studied in separation by different researchers representing different schools of thought. However, PRR relationships cannot be fully understood without accounting for BEF relationships, and vice versa, thus limiting our understanding of how both both plant diversity and biomass production are driven in grasslands.
The aim of the DFG-funded BEF-Loops project (part of the Biodiversity Exploratories) is to compare the relative strength of BEF and PRR relationships in driving overall relationships between plant diversity and biomass production in agricultural grasslands. This work is done by PhD student Karl Andraczek, under my supervision. We combine experiments and comparative observations along a land use intensity gradient in Germany. In the experiments, factors related to standing biomass removal (grazing and mowing), biomass production (fertilization) as well as plant diversity are manipulated within the same fields, and the relative strength of the effects of these manipulations is assessed. Within the same fields, data from unmanipulated grasslands will be collected and analysed using structural equation models in order to investigate the direct and indirect relationships between standing biomass, plant productivity and plant species richness, as well as covarying factors (e.g. soil fertility, light interception, grassland management).
In the European Union, two major developments are strongly driving land use change. On the one hand, land use is being intensified in various regions in Europe, while on the other hand, land abandonment is a common phenomenon in many parts of Europe where agriculture is no longer economically attractive. There are concerns that both these processes may be harmful for biodiversity and the provisioning of various ecosystem services.
With Grazelife, we aim to assess which forms of grazing models (e.g. intensive livestock grazing, extensive livestock grazing, pastoralism, uncoordinated land abandonment and rewilding) are best for both biodiversity conservation and the provisioning of several ecosystem services, including wildfire mitigation (see e.g. this paper), soil carbon storage and cultural ecosystem services. In addition, we investigate to which extent these competing forms of land use (and thereby their associated levels of biodiversity and ecosystem services) are supported or hampered by the Common Agricultural Policy, and to which extent this drives how land users are managing their land. This work is done using a combination of literature reviews and stakeholder interviews. PhD student Julia Rouet-Leduc is leading most of this work, under supervision of Guy Pe’er and myself.
Beta diversity Experiment
Based on biodiversity experiments, it is well established that random species loss can impair the ability of ecosystems to provide various ecosystem functions, including biomass production. What is less well understood, is whether these relationships also hold at larger scales, and how they depend on factors such as heterogeneity and dispersal. With the beta diversity x soil pathogen experiment, which was set up together with Liesje Mommer, Jasper van Ruijven, Eline Ampt and Jose Maciá Vicente, we aim to bridge the gap between small scale biodiversity experiments and larger scale biodiversity loss, by investigating how beta diversity, i.e. the spatial turnover in the composition of plant communities, drives biomass production and other ecosystem functions. In particular, we look at the role that soil pathogens have in underlying effects of plant beta-diversity and ecosystem functioning.
We set up the beta diversity experiment in spring 2021, and we manipulated both beta diversity and the presence or absence (through inoculation) of a key soil pathogen (Rhizoctonia solani). A main expectation is that beta diversity can promote biomass production, because it allows disease-prone plant species to disperse to patches without pathogens, whereas more resistant species can disperse to, and become dominant in, patches with pathogens.
Photo of the beta diversity x pathogen experiment. 2 factors (Rhizoctonia presence, β-diversity) are manipulated. β-diversity (dissimilarity in species composition among subplots) is 0 (no turnover) or 1 (complete turnover). Half of the sub-plots are inoculated with Rhizoctonia solani, and the other half is not.
I am also collaborating with the following projects