Redistribution of water via mycelia networks of saprotrophic fungi and its effect on C-mineralization in desiccated soils

• Applicant: Professor Dr. Egbert Matzner
• Subject Area: Soil Sciences
• Term: from 2014 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 260518461

Desiccation of the upper soil during the growing season is common in temperate climate. Soil desiccation is known to reduce C mineralization substantially. However, redistribution of water by mycelia of saprotrohic fungi (hydraulic redistribution) from moist to dry zones of the soil might mitigate the effects of desiccation of C mineralization, providing a larger competitiveness of saprotrophic fungi under dry conditions. Here, we will investigate if mycelia networks of saprotrophic fungi contribute to water redistribution in soil and how this influences mineralization of organic matter. Mesocosms will be used comprising two chambers, separated by a 2 mm air gap to prevent bulk flow of water and allowing only water flow via fungal mycelia. After the mycelia connection between both chambers is established, both chambers will be desiccated to a soil water tension of pF 4 - 5. Subsequently, one chamber will be reirrigated with deuterium labelled water and a florescent marker. At the end of the experiment, soil samples as well as hyphae of the desiccated chamber will be analysed for stable isotope content and fluorescent labelling. In a second set of experiments double 15N/13C labelled plant material will be exposed in the non-irrigated desiccated chamber. The effect of hydraulic redistribution on the mineralization will be studied by measuring CO2 evolution and the 13CO2 signal. 13C and 15N isotopes will be analyzed in soil samples of the irrigated chambers to determine the percentage of retransferred N and C. Furthermore, the impact of hydraulic redistribution on fungal enzyme activity will be analyzed at high spatial resolution using soil zymography. These experiments will shed new light on the role of fungal mycelia for mineralization under dry soil conditions.

• DFG Programme: Research Grants