Linking microbial community composition to C loss rates during wood decomposition

• Microbial community shifted during wood decomposition.
• Fungi dominated at the early stages due to high-quality wood C and low moisture.
• Low-quality wood C and high moisture benefited bacteria during the late stages.
• Fungal PLFA content primarily explained wood C loss rates at early stages of decomposition.

Although decaying wood plays an important role in global carbon (C) cycling, how changes in microbial community are related to wood C quality and then affect wood organic C loss during wood decomposition remains unclear. In this study, a chronosequence method was used to examine the relationships between wood C loss rates and microbial community compositions during Chinese fir (Cunninghamia lanceolata) stump decomposition. Our results showed that microbial community shifted from fungi-dominated at early stages (0–15 years) to relatively more bacteria-dominated at later stages (15–35 years) of wood decomposition. Fungal phospholipid fatty acid (PLFA) content primarily explained wood C loss rates at early stages of wood decomposition. Fungal biomass was positively correlated with proportions of relatively high-quality C (e.g., O-alkyl C), but bacterial biomass was positively correlated with low-quality C. In addition, fungi appeared to be the dominated community under low wood moisture (<20%) at early stages, but fungal biomass tended to decrease and bacterial biomass increased with increasing wood moisture at later stages. Our findings suggest that the fungal community is the dominant decomposer of wood at early stages and may be positively influenced by relatively high-quality wood C and low wood moisture. Bacterial community may benefited from low-quality wood C and high wood moisture at later stages. Enhanced understanding of microbial responses to wood quality and environment is important to improve predictions in wood decomposition models.