Planted forest ecosystem is becoming a key component of the China’s forest resources and timber storage and plays a key role in the context of potential carbon (C) sequestration and sustainable forest management. Information on the effects of tree species composition and diversity on soil organic carbon (SOC) stability remains limited. The investigation and long-term manipulation experiment were carried out in typical subtropical planted forests. We analyzed the C chemical stability among different planted forest soils. The SOC stock was higher in the broadleaf planted forests than that in the coniferous planted forests, but SOC chemical stability was higher in the coniferous planted forests. Soil under Eucalyptus mixed with N2-fixer accumulated more SOC, and had higher chemical stability than in pure stands. Mixed stand properties promoted mass loss for recalcitrant C chemical compositions of conifer litter. Litter mixing slowed the recalcitrant C chemical compositions release of broadleaf litter. These results indicated that mixed tree species enrich the source of soil C chemical composition. Soil stable chemical composition (alkyl/O-alkyl C ratio) was positively related to soil microbial biomass and Gram-positive bacterial biomass. Considering the trade-off between broadleaf and conifer tree species, it needs to maintain soil C chemical composition balance for enhancing the resilience to changing environment. Adopting mixed silviculture appropriately based on litter quality for accelerating recalcitrant litter C decomposition to facilitate C sequestration and mitigating C emission derived from labile litter C.

02 - A broadleaf species alters and evenly distributes soil organic carbon chemical composition in a Pinus massoniana planted forest in southern China