Effects of simulated drought on C/N/P stoichiometry and lignin decomposition dynamics in the deadwood-soil system...

Temperate forests are increasingly exposed to drought, yet the biogeochemical linkages between deadwood and soils under water stress remain poorly understood. The balance between decomposing wood and soil determines nutrient cycling and the composition of organic matter in forest ecosystems. There is a lack of studies assessing how drought affects nutrient fluxes within the deadwood-soil system. In a two-year field experiment across six temperate tree species (Common beech, aspen, pedunculate oak, Norway spruce, Scots pine and silver fir), we investigated how drought alters the stoichiometry of biologically important elements (C, N, P) and lignin dynamics within the coupled deadwood-soil system. We simulated drought by installing a rain-exclusion shelter over one of two adjacent plots and placing equally sized, highly decomposed logs from six tree species on the soil surface. Moisture and temperature were continuously monitored, and wood and soil samples were collected from both treatments. To assess how drought influences C/N/P stoichiometry and nutrient transfer between deadwood and soil, we measured the content of C, N, P, and lignin. Drought markedly increased C/N and C/P ratios, on average by 22.39 % and 47.99 %, respectively, compared with the control. It also reduced N and P transfer from wood to soil (by 29.96 % and 84.55 %) and enhanced the accumulation of lignin-derived carbon (by 62.64 %), particularly in coniferous systems. Statistical analyses further revealed species-specific drought responses shaping soil properties. C/N/P stoichiometry can be used to assess drought effects on nutrient flow within the deadwood-soil system. Our findings highlight the importance of cross-compartment interactions in controlling soil nutrient availability and carbon persistence under increasing drought frequency.