Abstract: Soil fauna has an important effect on litter nutrient release, and the effect could vary with litter types and be controlled by environmental factors such as temperature and precipitation. We to characterized the effect of soil fauna on C dynamics in different sized forest gaps (G1: 100 m², G2: 400 m², G3: 900 m², G4: 1 600 m²) during litter decomposition of a Pinus massoniana plantation in a hilly area of the upper reaches of Yangtze River. A field litterbag experiment was conducted in P.massoniana plantation of Sichuan, China, from January 2014 to November 2014. Samples of airdried leaf litter for P.massoniana(Pm) and Cinnamomum camphora(Cc) were placed in nylon litterbags (20 cm×20 cm, 10 g per bag) of two different mesh sizes (3.00 and 0.04 mm). The amount of C released were investigated in different sized forest gaps during the first year of decomposition, i.e., Spring, Summer, Autumn and Winter. There was a significant difference in the amount of litter C released through soil fauna among different sized gaps: medium sized gap (G3: 900 m²) promoted the C release of Cc and Pm. The content of C displayed a declining trend in Spring and Summer, but with an obvious enrichment process in Winter and Autumn. Soil fauna imposed a positive effect on C release, the contribution of soil fauna to the C loss rate displayed as Cc>Pm. Based on the above results, soil fauna imposed a positive effect on C release in P.massoniana plantation. When we reconstruct the low-function forest, we can take advantage of medium sized gap and introduce native broadleaf tree species Cc which is easier to be decomposed by soil fauna to accelerate nutrient cycling and maintains the soil fertility of P.massoniana plantation.

Key words: C dynamics, soil fauna, litter decomposition, forest gap, Pinus massoniana plantation