Contribution of Aboveground Litter Decomposition to Soil Respiration in a Subtropical Coniferous Plantation in Southern China

Soil CO2 efflux (R-S) was monitored in a 23-year-old subtropical coniferous plantation in southern China from January 2004 to December 2006. Field measurements of R-S with litterfall (CK) and without litterfall (NL) were conducted to evaluate the contribution of aboveground litter decomposition to R-S. The results indicated that annual R-S from CK ranged from 11.5 mg (C) m(-2) h(-1) in 2004 to 186.2 mg (C) m(-2) h(-1) in 2006. The R-S of NL was significantly lower than the R-S of CK. R-S was mainly determined by soil temperature (T-S), but it was also affected by soil moisture. Together, both factors explained > 70% of the observed variations in R-S. The temperature sensitivity (Q(10)) of R-S from NL was lower than that from CK by considering the soil moisture effect. On average, the annual R-S of the coniferous plantation was estimated to be 669 g (C) m(-2) yr(-1) over the study period. The litterfall greatly enhanced the R-S, and the respiration from aboveground litter accounted for about 33% of the total R-S, in which the fresh litterfall decomposition accounted for a large proportion. The carbon pool of aboveground litter in this young conifer forest is expected to increase continuously.