Fungal necromass carbon contributes more to POC and MAOC under different forest types of Qinling Mountains

Microbial necromass carbon (MNC) is important to soil organic carbon (SOC) fractions formation. However, it is still not clear whether the contribution of MNC to particulate and mineral-associated organic carbon (POC and MAOC) in different forest types are various.

The Pinus tabuliformis forest (P), Quercus aliena forest (Q), and the mixed forest of Pinus tabuliformis and Quercus aliena (P + Q) of Qinling Mountains were selected. Then contents of MNC, contribution of MNC to POC and MAOC, as well as its influencing factors at 0–10, 10–20 and 20–40 cm soil layers were analyzed.

Under three forest types, contents of MNC, fungal necromass carbon (FNC) and bacterial necromass carbon (BNC) decreased with increasing of soil depth. FNC was higher than BNC, and FNC/BNC was higher than 2. At 20–40 cm layer, the ratio of MNC/MAOC in P (11.9%) was significantly lower than that in Q (23.8%) (p < 0.05), with no significant difference in MNC/POC. The ratio of MNC/MAOC (21.2%) was higher than MNC/POC (20.3%). Total nitrogen, microbial biomass carbon and nitrogen were main factors during MNC accumulation. MNC/POC and MNC/MAOC were mainly influenced by total phosphorus, soil moisture, soil texture and cellulose in litter.

Compared to BNC, FNC dominated the accumulation of MNC in different forest types, and it contributed more to MAOC than POC. Soil physicochemical properties, such as total nitrogen and phosphorus, soil texture and chemical composition of litter, especially cellulose were main factors during MNC contributing to SOC components accumulation.