川中丘陵区桤柏混交林地土壤CO2释放与Forest-DNDC模型模拟

采用静态箱-气相色谱法对长江上游桤柏混交林地土壤呼吸进行测定。结果表明:保留枯枝落叶和去除枯枝落叶处理的土壤呼吸速率季节变化趋势均呈单峰曲线，土壤呼吸速率最大值出现在6月下旬到8月上旬之间；最小值出现在12月底至翌年1月初间。试验期间，保留枯枝落叶和去除枯枝落叶处理的土壤呼吸速率变化范围分别是66.23～520.42 mg/(m2·h)、34.25～395.47 mg/(m2·h)，年平均土壤呼吸速率分别为273.18和221.82 mg/(m2·h)，枯枝落叶分解释放的CO2量对林地土壤总呼吸的贡献为18.80%。土壤温度和土壤湿度是影响该地区土壤呼吸的主要因子。双因素关系模型较好地拟合了土壤(5 cm)温度和土壤(0～10 cm)湿度对土壤呼吸的影响，土壤温度和湿度共同解释了保留枯枝落叶处理土壤呼吸变化的73%、去除枯枝落叶处理的86%。Forest-DNDC模型较好地模拟了两种试验处理的土壤CO2的释放。模型敏感性试验结果表明，该区影响林地土壤CO2释放的主要因子是土壤表层有机质含量，其次是气温和降水量。 

Soil CO2 efflux and simulation of Forest-DNDC model in the mixed plantation of alder and cypress in hilly areas of the central Sichuan Basin

Soil CO₂ efflux in a mixed forest plantation of Alnus cremastogyne and Cupressus funebris was measured by closed chamber chromatographic technique from a CERN (Chinese Ecosystem Research Network) Station in the central Sichuan Basin. Soil respiration rates varied from 66.23 to 520.42 mg/(m²·hour) at the plot with litter，from 34.25 to 395.47 mg/(m²·hour) at litter free plot，and the yearly average soil respiration rates were 273.18 and 221.82 mg/(m²·hour) respectively. It showed a similar seasonal pattern between the two kinds of plots，with a single peak occurred at summer and a minimum at winter. The contribution of litter layer to total soil respiration was 1880％. The relationship of soil respiration (R) with soil temperature (t) (5 cm) and soil moisture (w) (0.10 cm) was fitted well by a bivariate model. The results indicated that soil temperature and soil moisture together could explain 73% and 86% of seasonal variations of soil respiration rates at plots with litter and litter free ones，respectively. Forest-DNDC model was applied to simulate the CO₂ emissions at the two kinds of plots. The results showed that the model was able to simulate most of the CO₂ emission pulses and trends. Some sensitive experiments were made via simulating the CO₂ emissions，and the results showed that the content of organic carbon at topsoil was the important regulating factor while the CO₂ emission was sensitive to some other factors such as temperature and precipitation.