Forest management alters soil microbial necromass and its contribution to soil organic carbon in Moso bamboo plantations in subtropical China

Moso bamboo (Phyllostachys pubescens) is characterized by its strong carbon sequestration ability, and appropriate forest management plays an important role on its C pools. Microbial necromass is one of the important sources of soil organic carbon (SOC). We investigated the soil microbial necromass C (MNC) based on amino sugar analysis of undisturbed (M0), extensively managed (M1), and intensively managed (M2) Moso bamboo plantations to understand the response of microbial necromass in bamboo soil to different management practices. Results showed that M1 and M2 had lower bacterial necromass C (BNC), fungal necromass C (FNC), and total MNC than M0. FNC contributed more to the total organic carbon (TOC) than BNC in the bamboo stands. Compared to M0, M2 and M1 significantly increased the contribution of FNC to TOC but reduced the contribution of BNC to TOC. BNC and FNC were significantly driven by soil pH, TOC, NH4-N, and available P and K. Random forest analysis indicated that soil TOC was the best predictor. Furthermore, soil TOC had a direct effect on the accumulation of FNC and BNC based on the partial least-squares path modeling. Our results demonstrate that different management practices markedly affect soil MNC accumulation, and hence, appropriate forest management measures are critical for enhancing the sequestration of microbially derived C in the soil.