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Global warming increases belowground carbon (C) input as plant litterfall, root biomass and rhizodeposition, which influences the stocks and dynamics of soil organic matter. To clarify the effects of labile C availability (biochemical factor) and temperature (environmental factor) on enzyme activities, we incubated typical paddy soil for 75 d at four temperatures (5, 15, 25, and 35 degrees C) under anaerobic conditions. Acetate was used as the source of labile C and methane. The potential activities of three hydrolases (beta-glucosidase, chitinase, and xylanase) were analysed on days 3, 15, and 75 after acetate addition. Activity of beta-glucosidase and chitinase in soil without acetate addition was 2.1-2.7 times higher than that with acetate. Xylanase activity increased with temperature and incubation period. The enzymes involved in the C cycle were sensitive to temperature, whereas chitinase (responsible for N cycle) activity became temperature sensitive only after acetate addition (Q(10)-V-max >= 1). Organic C mineralisation (CO2 release) was more sensitive at low temperature with Q(10) values 1.1-3.4 times higher at 5-15 degrees C than at 25- 35 degrees C. The Q(10) values for methane (CH4) emission were 2.8-13.5 times higher at 5-15 degrees C than at 25-35 degrees C. Organic matter decomposition in paddy soil was more sensitive to temperature (Q(10) of CO2 and CH4 emission >= 1) than enzyme activities. Comparison of abiotic (temperature) and biochemical (C availability) effects indicated that warming has limited effects on hydrolase activities in paddy soil. The increase in labile C remarkably stimulated microbial activity and soil organic matter turnover. We conclude that: i) enzyme activities are more sensitive to C addition than to temperature; ii) and SOM decomposition is accelerated by both C input and warming, especially at low temperatures.