Abstract:

Soil CO₂ release rates in a closed Chinese Fir plantation were investigated by using alkali absorption technique and the influence of air temperature within the stand, soil temperature, soil water content and soil C/N ratio on soil CO₂ release rate were analyzed at Huitong Ecological Station, Hunan Province. The results showed that the CO₂ release rates in the closed Chinese Fir plantation soil ranged from 0.105 2 g·m^-2h^-1to 0.559 0 g·m^-2h^-1, which followed a conspicuous seasonal change pattern. The rate of CO₂ release rate in summer was higher than that in other seasons. To some degree, soil CO₂ release rate was positive linearly correlated with air temperature within stands, soil temperature(within the depth from 0 to 5 cm depth, from 5 to 10 cm depth, from 10 to 15 cm depth and 20 cm depth, respectively), soil water content at the surface, at the depth of 10 cm and the depth of 20 cm depth, and also soil C/N ratio. The calculated Q₁₀ values based on air temperature in the stands, soil temperature at surface, 5 cm, 10 cm, 15 cm and 20 cm depth were 2.08, 2.22, 1.94, 2.28, 2.51 and 2.23, respectively. The results of the partial correlative analysis on the relationship between soil CO₂ effluxes and environment factors indicated that the greatest significant correlative relationship was found for the air temperature within stand, partial correlative coefficient was up to 0.916(p<0.01). The next greatest significant correlative relationship was observed for temperature of different soil layers, all partial correlative coefficients were up to 0.818(p<0.01). However, there were no significant for the correlative relationship between soil CO₂ effluxes and soil C/N ratio, soil water content at the surface, at the depth of 10 cm and the depth of 20 cm depth, the partial correlative coefficients ranged from 0.452 to 0.612(p>0.05).

Key words: Chinese Fir plantation, soil CO₂ release rate, temperature, soil water content, soil C/N ratio