不同土地利用方式下土壤CO_2时空分布特征及其影响因素——以湘西大龙洞地下河流域为例

Temporal and spatial distributions of CO_2 in soil and their influencing factors under different LUCC:A case study of the Dalongdong underground river drainage area

为了解不同土地利用方式/覆被条件土壤剖面CO_2时空分布特征及其影响因素,对湖南湘西大龙洞地下河流域的4种土地利用方式(林地、草地、玉米地、烟叶地)土壤不同深度的CO_2浓度进行为期一年的观测。结果显示,不同土地利用方式的土壤CO_2表现为草地(7 527 mg/m^3)>林地(7 197 mg/m^3)>烟叶地(4 562mg/m^3)>玉米地(4 414mg/m^3);随剖面深度加大,草地和玉米地土壤CO_2呈先增大后稳定的趋势,林地和烟叶地则表现为先增大后降低的趋势;时间变化上,不同土地利用方式下的土壤CO_2月均浓度曲线与气温的变化曲线有很好的对应性,表现为2-8月浓度升高,8-12月降低,12月至次年2月为小幅下降,土壤CO_2浓度的最低值和最高值分别出现在2月和8月。相关性分析显示,气温对土壤CO_2浓度的影响最显著,此外,不同土地利用方式下有机碳的差异,与气温相耦合的降雨因素等都对土壤CO_2浓度变化有重要影响。

The objective of this work is to further understanding the temporal and spatial distribution characteristics of CO2 in soil and its influencing factors under different land use and cover change（LUCC）.We choose four types of land usage including forest land,grassland,maize land and tobacco leaf land in the Dalongdong underground river drainage area of western Hunan as examples to observe CO2 concentration of soil under these land usage conditions for one year.The results show that the soil CO2 concentrations are of the following sequence：grassland（7,527mg·m^3）〉forest land（7,197mg·m^3）〉tobacco leaf land（4,562mg·m^3）〉 maize land（4,414mg·m^3）.With increasing depth of profiles,the soil CO2 in grassland and maize land usage rises first（at 10-30 cm depth）and then is stabilized（at 30-50 cm depth）,and the forest land and tobacco leaf land show a trend of increasing first（at 10-30 cm depth）and then decreasing（at 30-50 cm depth）.Monthly change curves of them show that the concentration of soil CO2 increases from February to August,decreases from August to December,and decreases slightly from December to February of next year.The lowest and highest values of soil CO2 concentration occur in February and August,respectively.The correlation analysis also indicates that the effect of temperature on the soil CO2 concentration is the most significant.In addition,the difference of organic carbon under different land use and the rainfall factor coupled with the temperature can pose major influence on the change of soil CO2 concentration.