岩溶区不同土地利用方式下土壤CO2排放模拟研究

土地利用变化作为全球气候变化研究的重要内容之一，对土壤CO₂的排放具有重要影响。岩溶区石漠化治理过程中植被恢复伴随着土地利用方式的转变，其对土壤CO₂排放的影响有待进一步研究。基于控制性实验，以土壤、岩溶含水介质初始条件相同，仅土地利用方式不同的贵州普定沙湾模拟试验场为研究对象，通过1年的土壤CO₂浓度和通量数据，研究岩溶区不同土地利用方式下土壤CO₂的排放规律及其影响因素。结果表明：(1)土壤CO₂的浓度和通量具有明显的季节变化规律，不同季节下的土壤CO₂通量呈现昼夜变化规律，温度和降雨影响着土壤CO₂的排放，前者可促进排放量，后者可抑制排放量，且不同土地利用方式受影响的程度不同；(2)耕作活动也会影响土壤CO₂的排放，耕作使得土壤变得松散，加上岩溶区下伏基岩的溶蚀作用，增加了土壤CO₂向含水层的扩散，导致春季耕地表现为负通量；(3)不同土地利用方式下土壤CO₂的年排...

Simulation experiment on soil CO2 emission by different land uses in karst area

As one of the important parts of global climate change research, land use change plays a significant role in soil CO₂ emission. In karst area, vegetation has been restored in the process of rocky desertification control, accompanied by the change of land use, and its impact on soil CO₂ emission needs to be further clarified. Based on the controlled experiment, with the same initial conditions of soil and karst aqueous media but different land uses, the Shawan Test Site at Puding, Guizhou was chosen to study the emission law and influencing factors of soil CO₂. Through the soil CO₂ concentration and flux data in a hydrological year, our results demonstrated that:(1) the soil CO₂ concentration and flux showed obviously seasonal variations, and the soil CO₂ flux had apparent diurnal variation in different seasons. They were mainly controlled by temperature and rainfall. The former could increase the emission, while the latter could decrease the emission, and the increased or decreased degrees were related to land uses. (2) Farming activities affected the soil CO₂ emission as well. Due to the dissolution of the underlying carbonate rock in karst area, farming activities could make the soil loose and increase the diffusion of soil CO₂ to the aquifer, resulting in negative soil CO₂ flux of cultivated land in spring. (3) The annual emission of soil CO₂ under different land uses were grassland (897.53 tC km^-2 a^-1) > shrub land (258.15 tC km^-2 a^-1) > cultivated land (207.66 tC km^-2 a^-1) > bare soil land (92.68 tC km^-2 a^-1). It was found that they were mainly dominated by vegetation biomass and soil organic carbon content under different land uses. (4) The contents of soil organic carbon were grassland (29.33 g/kg) > shrub land (23.31 g/kg) > cultivated land (22.08 g/kg) > bare soil land (19.00 g/kg). Given the same initial properties of these soils, we found that with the change of land use, except for the soil organic carbon content in non-vegetated bare soil land decreased, the other types increased, and the increased degree was related to the degree of vegetation coverage. Therefore, land use types could control soil CO₂ emission by affecting the biomass of overlying vegetation and the soil organic carbon content, and the emission intensity is related to temperature, rainfall process and farming activities. Further, we think that the content of soil organic matter and soil carbon storage could be increased through the adjustment of land use.