Dependence of Soil Respiration on Soil

The spatial and temporal variations in soil respiration and its relationship with biophysical factors in for-ests near the Tropic of Cancer remain highly uncertain. To contribute towards an improvement of actual estimates, soil respiration rates, soil temperature, and soil moisture were measured in three succes-sional subtropical forests at the Dinghushan Nature Reserve (DNR) in southern China from March 2003 to February 2005. The overall objective of the present study was to analyze the temporal variations of soil respiration and its biophysical dependence in these forests. The relationships between biophysical fac-tors and soil respiration rates were compared in successional forests to test the hypothesis that these forests responded similarly to biophysical factors. The seasonality of soil respiration coincided with the seasonal climate pattern, with high respiration rates in the hot humid season (April-September) and with low rates in the cool dry season (October-March). Soil respiration measured at these forests showed a clear increasing trend with the progressive succession. Annual mean ( ± SD) soil respiration rate in the DNR forests was (9.0 ± 4.6) Mg CO2-C/hm2 per year, ranging from (6.1 ± 3.2) Mg CO2-C/hm2 per year in early successional forests to (10.7 ± 4.9) Mg CO2-C/hm2 per year in advanced successional forests. Soil respira-tion was correlated with both soil temperature and moisture. The T/M model, where the two biophysica