The Temperature Sensitivity of the Processes of the Initial Stage of Microbial Decomposition of Woody Litter in Forest Soil

Abstract—Soil organic matter of forest ecosystems is characterized by high sensitivity to increased temperatures, which makes soil organic matter more vulnerable under the conditions of global warming. In this study, evaluation of the effects of different components of woody litter (leaves and small branches of aspen) on the dynamics of the activity and quantitative characteristics of microbial communities of soils under the conditions simulating climate warming was carried out. In our experiment we used samples of gray forest soil from the forest biocenosis of the Moscow area, which is typical of the European part of Russia. Incubation of soil samples to which crushed leaves and branches were added (0.5 wt %) was carried out at constant temperatures of 5, 15, and 25°C for 28 days. The dynamics of CO₂ emission, organic carbon content, microbial biomass, as well as the number of the ribosomal genes of bacteria, archaea, and micromycetes, were evaluated. The optimal temperature for plant litter decomposition was 15°C; a decrease or increase in the temperature resulted in a decrease in the intensity of the litter decomposition process. Addition of plant residues in the temperature range of 5–15°C resulted in a significant increase in the temperature sensitivity of the soil-respiration process and the temperature coefficient increased from 1.75 to 3.44–3.54. In the temperature range of 15–25°C an inverse correlation was observed. At high temperatures addition of plant residues stimulated decomposition of soil organic matter. These results contribute to the understanding of the dynamics of soil carbon and can be used in predictive models of the processes of plant-litter decomposition and the dynamics of soil organic matter in forest biocenoses in Eurasia under the conditions of climate change.