We investigate the fundamentals of soil physics, their implications for plant water relations and life in soils, and the applications to drought research in both agricultural and forest systems. A key research area of our group is the interface between soils and plant roots and how the properties of this key interface are relevant for drought tolerance and terrestrial fluxes. We investigate this interface and its impact on terrestrial ecosystems with the support of numerical models and experiments on different scales.
Distribution and retention of liquid in soil biological hotspots
Life residing in the porous environment of soil has to face many challenges. A major challenge encountered by plant roots and microorganisms are fluctuations in soil moisture and its implications. While soil drying is accompanied by a fragmentation of the liquid phase soil rewetting causes a fragmentation of the gas phase. Both processes lead to severe alterations of local transport properties. The distribution and connectivity of the soil solution and how it is affected by variations in soil moisture and soil water potential defines the "liquid architecture" encountered by life in soil. In order to avoid the disadvantageous effects of such oscillations and optimize growth conditions, plants as well as microorganisms engineer their fluid surroundings. Plants, bacteria, and fungi can alter the properties of the soil solution by releasing extracellular polymeric substances (EPS). These highly polymeric blends are as diverse as their constituents are numerous, yet EPS alter the liquid phase in similar ways. They increase the viscosity of soil water, by that helping to maintain its connectedness in drying soil and in turn improve water flow and solute diffusion. At the same time, while improving the connectivity of liquid the EPS polymer network retains water in these regions due to its hygroscopic nature. Furthermore, EPS can retain nutrients and enzymes, reduce soil water evaporation, improve the desiccation resistance of bacteria, facilitate root penetration, enhance soil stability and much more. The engineering of the soil solution is most prominent in regions of high biological activity, like in soil biocrust or the within the thin layer of soil around the roots, the rhizosphere. We aim to understand how and to which degree plants and bacteria are capable to modify the liquid architecture of the rhizosphere and by that modify its transport properties. To do so, we use different methods ranging from light microscopy to X-ray computed tomography to resolve the spatial and temporal distribution of the liquid phase within the rhizosphere and other biological hotspots.
Internal Collaborators: Pascal Benard, Andrea Carminati Duration: 2020-2024
Increasing evidence suggests that the rhizosphere hydraulic properties differ from those of the bulk soil. However, the impact of rhizosphere properties on root water uptake and transpiration remains largely speculative. Small (mm) scale processes around the roots are relevant for water relations at the holobiont scale. Hence, we aim to understand by which mechanisms rhizosphere traits (e.g. mucilage exudation, root hair growth) impact soil-plant hydraulics, and transpiration, eventually. Consequently, rhizosphere traits will be included in a pragmatic hydraulic model that is capable of predicting the effect of soil drying on transpiration.
Internal Collaborators: Tina Köhler, Andrea Carminati Duration: 2021-2023