Soil microbial decomposition capacity and soil properties under moderate warming in a natural forest in the Asian monsoon region.

Soil warming increases carbon emissions by enhancing soil microbial activity. However, only few soil warming experiments have been conducted in the Asian monsoon region (warmer temperate regions with very high precipitation) compared with those conducted in Europe and North America. Hence, in this study, we conducted a soil warming experiment using electric heating cables and solar-powered energy systems in a natural forest in central Japan (Asian monsoon region) to determine the effects of moderate soil warming (1.2 °C increase) on soil properties and microbial decomposition capacity. EcoPlate analysis was used to assess the multifunctionality (MF) of soil microbial decomposition capacity across 31 carbon substrates. MF was significantly higher in the warming plots than in the control plots. When each carbon substrate group was evaluated separately, the MF of labile substrates, such as carboxylic acids, carbohydrates, and amino acids, were significantly higher in the warming plots than in the control plots. Thus, the ordination plot, which was created by performing db-RDA (Distance-based redundancy analysis, constrained ordination of the principal coordinate analysis (PCoA)) with Bray-Curtis dissimilarity, showed differences in the microbial functional composition between the warming and control plots. Moderate soil warming did not cause soil drying; however, it significantly increased soil moisture. Our experimental results demonstrated that moderate soil warming enhanced carbon substrate decomposition by microorganisms and increased soil moisture during the initial decomposition stage in the Asian monsoon region.