Abstract: Rainfall has important effects on soil respiration. To understand the relationship between rainfall and soil respiration is of significance in accurately estimating carbon flux. In this paper, an in situ observation was conducted in a tropical secondary forest and a rubber plantation in Xishuangbanna of Yunnan to measure the soil respiration rate and the soil temperature and moisture content at the depth 5 cm after a simulated rainfall, aimed to understand the responses of the soil respiration, soil temperature, and soil moisture content under the two main vegetation types to the simulated rainfall. Under the condition of one week norainfall in dry season, the soil respiration was rapidly stimulated 2 hours after the rainfall, with the maximum soil respiration rate in the secondary forest rubber plantation reached 11.15 and 15.88 μmol CO₂·m^-2·s^-1, being 7 and 11 times greater than that of the control, respectively. This effect decreased through time, particularly in rubber plantation where the difference with the control was not significant 6 hours after the rainfall. Two days after the simulated rainfall, the soil moisture contents in the tropical secondary forest and rubber plantation were significantly higher than the control, but the soil temperature had less difference. This study supported the “Birch effect”, and showed that due to the rainfall event, the CO₂ release from the two major tropical forest types in dry season was increased several folds.

Key words: long-term fertilization, arable black soils, soil microorganism, biolog-eco, soil nutrient