Effects of thinning on soil saprotrophic and ectomycorrhizal fungi in a Korean larch plantation

Abstract Thinning is an important silvicultural practice for improving the productivity and stability of plantations, but how thinning influences saprotrophic and mycorrhizal microbes and its ecosystem consequence are unclear. Here we conducted a thinning experiment with four treatments (quartic thinning with low-intensity, LT4; triple thinning with medium-intensity, MT3; twice thinning with high-intensity, HT2; and control) in a 60-year-old Korean larch (Larix olgensis) plantation in northeastern China. Our objective was to examine the thinning-induced changes in the community compositions of fungi, ectomycorrhizal (EcM) fungi, saprotrophic fungi, and bacteria using a high-throughput sequencing method. Thinning treatment explained 59%, 61%, and 45% variance of the total, EcM, and saprotrophic fungal community structures, respectively, but it had no effect on the bacterial community, suggesting that fungi are more sensitive to thinning than bacteria. LT4, MT3, and HT2 increased the saprotrophic fungal abundance by 67%, 67%, and 125%, respectively, but they reduced the EcM fungal abundance by 31%, 46%, and 84%, respectively. In addition, thinning enhanced the soil C accumulation and nutrients availability. Overall, these findings suggest that saprotrophic fungi may play a critical role in microbial-mediated ecosystem functions like EcM fungi in the thinned larch stands.