西南喀斯特地区几种主要土地覆被下土壤CO_2-C通量研究

Studies on soil CO_2-C fluxes of several major types of land covers in the karst region of southwestern China

中国西南喀斯特地区土壤营养元素流失形势严峻,揭示不同土地覆被下土壤CO2-C的释放规律,是认识喀斯特这一特殊环境诸多营养元素循环问题的一个重要途径。采用静态箱-气相色谱法对贵州喀斯特地区4种不同土地覆被下的土壤CO2-C释放通量进行观测研究。结果表明,(1)不同的土地覆被下土壤CO2-C释放通量有显著的差别,其释放顺序为:森林((134.1±78.8)mg/(m2·h))>次生林((70.8±122.3)mg/(m2·h))>玉米地((55.5±78.0)mg/(m2·h))>烧荒地((35.5±91.4)mg/(m2·h))。各样点季节变化都比较明显,夏季平均排放量最高,冬季最低。(2)凋落物对森林土壤CO2-C释放的影响较大,有凋落物覆盖的土壤CO2-C释放量((134.1±78.8)mg/(m2·h))高于无凋落物覆盖的林地土壤((111.2±80.3)mg/(m2·h)),凋落物分解对森林土壤CO2-C释放总量的贡献约占17%。基于地面气温,计算得出森林和森林(无凋落物)的Q10分别为1.92、2.10。(3)除次生林和烧荒地外,其余各样地CO2-C释放通量均与土壤各层温度呈显著正相关关系,但绝大多数样地与土壤湿度(WFPS)之间相关性不显著。

The eco-environmental problems characterized by the loss of soil nutrition elements in the karst regions of southwestern China are severe due to the increasing confflicts between land and population. Studies on the mechanisms of soil CO2-C emission in different land covers may be an important way to understand many of the problems about the nutrition elements cycles in this special ecosystem. The released soil CO2-C flux of four different land covers was studied in Guizhou karst region by static close chamber coupled with GC technique. The results showed that： 1. the released CO2-C flux of the four different land covers are significantly different, in a sequence of： forest 〉 secondary forest 〉 burned field 〉 maize field, with average fluxes of 134.1 ±78.8 mg/（m^2·h）, 70.8± 122.3 mg/（m^2·h）, 55.5±78.0 mg/（m^2·h）, 35.5±91.4 mg/（m^2·h）, respectively. The seasonal variation was obvious in all fields, with the highest average flux in summer and the lowest in winter. 2. The litter remarkably influenced the soil CO2-C flux in forest. The CO2-C flux in the forest soil covered with litter was higher than that without litter, with average fluxes of 134.1±78.8 mg/（m^2·h） and 111.2 ±80.3 mg/（m^2·h）, respectively. The contribution of litter to forest total soil CO2-C emission was about 17%. Based on ground temperature, the calculated Q10 was 1.92 in the forest with litter and 2.10 in that without. 3. Excepted burned field and secondary forest, there was a remarkable positive correlation between soil CO2-C flux and temperature in different soil layers. By contrast, no obvious correlation between soil CO2-C flux and humidity （WFPS） was observed.