Changes in soil respiration and its temperature sensitivity at different successional stages of evergreen broadleaved forests in mid-subtropical China

Abstract

Aims Studies on the influences of forest succession on soil respiration (Rs) and its temperature sensitivity (Q10) are controversial, leading to uncertainties in the accuracy of global carbon budget. Our objectives were to deter- mine: (1) changes of Rs and Q10 in a succession series of mid-subtropical forests, (2) seasonal variations of Rs and its relationships with temperature and water content, and (3) the underlying mechanism of changes in Rs with suc- cession. Methods We selected stands of an evergreen broadleaved forest at the early successional stage (15 years), mid- dle successional stage (47 years), and late successional stage (110 years) under similar site conditions in Jian'ou, Fujian. Monthly Rs was measured by using an infrared gas exchange system from September 2009 through August 2010. Soil temperature and moisture were measured concurrently. The relationships of Rs with annual litterfall, fine root biomass, contents of soil organic carbon (SOC) and total nitrogen (TN) in the 0-20 cm soil layer were tested by linear regression analysis Important findings The average values of Rs were 2.38, 3.32 and 3.91 µmol·m -2 ·s -1 , and the average values of Q10 were 2.64, 1.97 and 1.79, respectively, in the early, middle, and late successional stages. Compared to in the early successional stage, Rs was increased significantly by 64.29% while Q10 was decreased by 32.30% in the late successional stage. The seasonal patterns of Rs were similar among the three successional stages; soil temperature and water content explained 69.5%, 81.9% and 61.3% of the seasonal variations. According to regression analysis, soil respiration was positively correlated with annual litterfall, fine root biomass, and contents of SOC and TN in the 0-20 cm soil layer. Succession promoted carbon emission and reduced soil respiration sensitivity in our study, which might be related to the increases in fine root biomass, carbon input and soil nutrient with forest succession.