Abstract: By using trenching method and infrared gas analyzer, this paper studied the seasonal variation of soil respiration (SR), including root respiration (R
R) and heterotrophic respiration (HR), in tropical seasonal rain forest (RF) and rubber (Hevea brasiliensis) plantation (RP) in Xishuangbanna of Yunnan, China. The results showed that the SR and HR rates were significantly higher in RF than in RP (P<0.01), while the RR rate had less difference between the two forests. Soil temperature and moisture were the key factors affecting the SR,RR and HR. The SR and HR rates in the two forests were rainy season>dry-hot season>foggy season, but the RR rate was rainy season>foggy season>dry-hot season in RF, and foggy season>rainy season>dry-hot season in RP. The contribution of RR to SR in RF (29%) was much lower than that in RP (42%,P<0.01), while the contribution of HR to SR was 71% in RF and 58% in RP. When the soil temperature at 5 cm depth varied from 12 ℃ to 32 ℃, theQ₁₀ values for SR, HR, and RR rates were higher in RF than in RP. HR had the highest Q₁₀ value, while RR had the lowest one.

Key words: tropical seasonal rain forest, rubber plantation, soil respiration, root respiration, heterotrophic respiration, Q₁₀, litter decomposition, abiotic factor, biotic factor, semi-arid and arid region.