The dynamic response of soil respiration to land-use changes in subtropical China

Assessing the impact of land-use changes on soil respiration (R-S) is of vital significance to understand the interactions between belowground metabolism and regional carbon budgets. In this study, the monthly in situ R-S was examined between 09:00 and 12:00 hours over a 3-year period within a representative land-use sequence in the subtropical region of China. The land-use sequence contained natural forest (control treatment), secondary forest, two plantations, citrus orchard and sloping tillage land. Results showed that the R-S exhibited a distinct seasonal pattern, and it was dominantly controlled by the soil temperature. After the land-use conversion, the apparent temperature sensitivity of R-S (Q(10)) was increased from 2.10 in natural forest to 2.71 in sloping tillage land except for an abnormal decrease to 1.66 in citrus orchard. Contrarily, the annual R-S was reduced by 32% following the conversion of natural forest to secondary forest, 46-48% to plantations, 63% to citrus orchard and 50% to sloping tillage land, with the average reduction of 48%. Such reduction of annual R-S could be explained by the decrease of topsoil organic carbon and light-fraction organic carbon storages, live biomass of fine root (< 2 mm) and annual litter input, which indirectly/directly correlated with plant productivity. Our results suggest that substrate availability (e.g., soil organic carbon and nutrients) and soil carbon input (e.g., fine root turnover and litterfall) through plant productivity may drive the R-S both in natural and managed ecosystems following strong disturbance events.