DeMoLD: Nexus of Deadwood Moisture, Lignin Degradation and Matter Transport in Changing Forest Ecosystems

• Applicants: Professorin Dr. Kathrin Blumenstein; Professor Dr. Karsten Kalbitz; Professorin Natalie Orlowski; Dr. Kenton Stutz
• Subject Area: Soil Sciences
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569059989

Deadwood is crucial to forest ecosystems as it is habitat for ~30% of all forest species and it contributrs to above- and belowground carbon and nutrient cycling. Essential to all of the above is deadwood moisture, which is at risk of being reduced by longer dry periods and increased evapotranspiration due to changing climate and land-use intensity. However, the factors that regulate deadwood moisture, especially via lignin degradation, are unknown. Oxidation of lignin produces water and micro-pores in cell walls, thus increasing the water-holding capacity of deadwood. Subsequent water fluxes into and from deadwood can enhance lignin degradation through enrichment of metal cations and increase soil organic carbon through seepage of degraded lignin. To determine the extent to which fungi regulate deadwood moisture through lignin decay and the associated matter transport between deadwood and soil depending on water availability under changing climate and land-use intensity, we will test the following hypotheses: (HI) In decreasing order deadwood water is sourced from soil via capillary rise, atmosphere via precipitation and lignocellulose via enzymatic oxidation. (HII) When deadwood dries out, fungal enzymes oxidize more lignin in and between cell walls, which increases the proportion of micro-pores. (HIII) Lignin-derived compounds are transported to soil when deadwood is wetter than soil, and metal cations are transported to deadwood when soil is wetter than deadwood. (HIV) Sites with warmer temperatures, less precipitation and more acidic cations have the largest degree of lignin degradation in deadwood and the largest contribution of deadwood to soil organic matter. (HV) Water-soluble organic matter indicates lignin degradation in deadwood and the potential contribution to soil carbon. We will test these hypotheses through a laboratory experiment, the new BEClimWood multi-site experiment, the 16-year-old BELongDead experiment and a synthesis. We combine stable water isotope and CO2 flux measurements with wood structure analysis, lignin degradation characterization, and advanced microscopic and spectroscopic techniques. The lab experiment uses an isotope mixing model with labelled precipitation to quantify deadwood water sources. BEClimWood examines how moisture availability altered by the degree of soil contact and precipitation exclusion affect fungal enzyme activity, lignin oxidation, pore size, water retention, and metal cation enrichment. The BELongDead experiment measures the cumulative contribution of degraded lignin to soil OM underneath heavily decayed deadwood. The synthesis integrates the results from the three experiments to deliver essential insights into the nexus of climate variability, deadwood moisture, lignin degradation and matter transport to and from soil in changing forest eco-systems.

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1374: Biodiversity Exploratories
• Co-Investigator: Professorin Dr. Friederike Lang