Global change impacts on microbiota-plant-soil processes relevant for water and matter cycling in agricultural ecosystems
Climate change, land-use change and nitrogen deposition are among the most important threats to biodiversity and associated ecosystem processes and functions, which emerge from complex interactions between organisms and their environment. To understand and predict the resulting effects on ecosystem functions, a systemic view on the interplay of above- and belowground compartments is needed. Process-based simulation models acting as a digital twin of the natural system are a promising way forward. This PhD cohort will thus work on several knowledge gaps at the interface between plants, soil organisms and soil structure to ultimately enable systemic modeling.
Biodiversity (both above- and belowground) and its dynamics importantly determine soil structure and properties and thereby the soil’s ability to provide essential ecosystem functions related to the cycling and retention of nutrients and water. Climate has been shown to mediate this link between biodiversity and ecosystem multifunctionality. Different global change drivers, however, differently affect the availability of and the competition for resources like water, light and nutrients. This leads to interacting effects of different global change drivers on the biodiversity and functional traits of aboveground and belowground communities. Further, the role of physical soil properties structuring these interactions has been largely neglected. Soil pores are considered as hot spots of root and microbial growth and soil porosity and particle size have also been shown to affect litter decomposition. Hence, dynamic interplay of structural soil properties and biodiversity determine the ability of soils to provide essential ecosystem functions. Land-use intensification is not only considered as the most important threat to biodiversity but also a strong determinant of soil structure with potential feedback effects on aboveground and belowground communities. Similarly, the complex interrelations between climate change and land-use on soil processes are poorly understood.
The PhD cohort will therefore consist of four complementary and integrated projects addressing ecosystem responses to climate and land use and the feedbacks between them (see figure below). Project P1 will investigate how global change drivers interactively affect plant diversity and plant-related ecosystem functions, project P2 will assess the interacting effects on functional traits of soil microbiota and related processes ensuring ecosystem functions and resilience, project P3 focuses on the link between root systems and soil structure with implications for water and nutrient fluxes, and project P4 will systemically analyze the different global change effects by synthesizing the outcome of the other projects in a process-based model.
We have designed the projects so that they complement each other in multiple pairwise ways as well as all contribute to an overall synthesis centered on the modelling components. Thus we aim to maximize the opportunities for cross-disciplinary research and learning. The overall hypothesis of this project is: Climate change and increasing land-use intensity will affect water and matter cycling due to negative effects on biodiversity and soil processes mediated by soil physical properties at soil-root interface. We will use the Global Change Experimental Facility (GCEF) as a unique experimental platform for the parallel investigation of climate change effects on agricultural ecosystems (croplands, grasslands) exposed to different land-use intensity. We will study the interactive effects of these drivers on major biogeochemical cycles and the subsequent changes in diversity and functioning of ecosystems. An additional N-treatment will be set-up in subplots of the grassland land-use types for analyzing effects of N fertilization to assess the influence of this further global change driver. The systemic model BODIUM developed in the framework of the BonaRes project will be used as a basis for implementing the studied process interactions and analyzing long-term effects of global change. To account for comparability, all field investigations will be synchronized regarding time and depth of sampling. These data will be used for model parametrization and verification.