Abstract:

The diurnal and seasonal dynamics of soil respiration in the Cinnamomum camphoraforest ecosystem of a subtropical area were measured at Huitong ecological station for Chinese Fir plantations (Changsha station) in Hunan, China. CO₂ effluxes rate was monitored using an infrared gas exchange analyzer (LI COR640009) from Aprip to October 2006, and the controlling factors, such as soil temperature and moisture were also recorded in the C. camphora forest. The results showed that the diurnal fluctuation of soil respiration accorded with that of the soil temperature at 5 cm depth, appearing single peak. The soil respiration exhibited an irregular fluctuated curve during the expenmental period with a mean rate of 4.0 μmol·m^-2s^-1. A significant exponertial corelation was found between soil respiration rate and soil temperature at 5 cm depth. However, significant relationships were not found between the soil respiration and the soil moisture at 5 cm depth. Soil temperature and moisture were able to be used to explain changes in soil respiration by 90.3% and 43.6% in the C. camphoraforest. The relationship between soil respiration rate (y) and the variable of soil temperature (t) and soil moisture (w) at 5 cm soil depth could be described by the following exponential equation:y=0.324 2e0.106 4x, R²＝0.903, P＝0.001, and by quadratic equation: y=－0.026 1w2+1.869w－28.406, R²=0.436, P＝0.05, respectively. Q¹⁰ value of the soil respiration was 29 during the growing season of C. camphora. The Q¹⁰ values were 3.08, 1.59 and 2.72, respectively in April to June, July to August. and September to October. Q¹⁰ value descended with soil temperature raised. When soil humidity less than 35.8%, the soil respiration rate was positively correlated to soil humidity, however, the highest soil respiration rate was under the condition of soil humidity more than 35.8%.

Key words: urban forest, Cinnamomum camphora, soil respiration, soil temperature, soil water, Changsha