贵州喀斯特地区不同土地利用方式土壤CO_2体积分数变化及影响因素

为了解不同土地利用方式对土壤剖面CO2体积分数的影响,采用气相色谱法对贵州喀斯特地区土壤不同深度空气CO2体积分数进行观测。结果表明：不同土地利用对土壤平均CO2体积分数影响较大,其次序为：次生林（0.35%±0.06%）〉草地（0.34%±0.05%）〉人工林（0.27%±0.03%）〉农田（0.16%±0.03%）。次生林、草地与农田之间土壤CO2体积分数差异性显著,而人工林与农田之间无显著性差异。不同土地利用方式土壤剖面CO2体积分数的时空变化特征比较一致：从春季到夏季逐渐增加而从秋季到冬季又逐渐降低,与该区域的温度和降雨量变化趋势一致。同时随着土壤剖面深度增加CO2体积分数逐渐增大,但在土层12 cm处有突然降低现象（农田除外）。不同土地利用方式土壤空气CO2体积分数变化与大气、土壤温度密切相关（r=0.602~0.886,P〈0.05）,土壤温度升高会导致土壤CO2体积分数上升。土壤湿度虽然也在一定程度上影响了剖面CO2体积分数,但相关性分析表明二者之间并不显著（r=0.105~0.393,P〉0.05）,说明在贵州喀斯特地区,土壤温度对土壤空气CO2体积分数的影响大于土壤湿度。

Variations and affecting factors of volume fractions of CO2 in soils between different land use in Guizhou Karst region of China

In order to study the effect of different land use on volume fractions of CO2 in soil profiles,the volume fractions of soil air CO2 in different land use were studied in Guizhou karst area by GC technique,the results showed that： the average volume fractions of CO2 were affected greatly by different land use,the sequence was： secondary forestgrasslandplanted forestfarmland and the average volume fractions were 0.35%±0.06%,0.34%±0.05%,0.27%±0.03%,0.16%±0.03%,respectively.The volume fractions of CO2 in secondary forest and grassland showed significantly higher than that in farmland,but there was no significant difference in volume fractions of subsurface CO2 between planted forest and farmland.The temporal and spatial distribution of CO2 showed generally constant annual patterns of volume fractions increase from spring to summer and decrease from autumn to winter in response to temperature and precipitation changes in this region.Volume fractions of soil CO2 increased gradually with the depth increasing,but decreased suddenly at 12cm of the soil layer（except farmland）.Volume fractions of subsurface CO2 showed significant linear positive correlation（r=0.602-0.886,P0.05） with soil temperature,the increasing of temperature would lead to increase volume fractions of CO2 in soils.However,in almost all fields,there were no obvious correlations（r=0.105-0.393,P0.05） between volume fractions of soil CO2 and soil moisture（WFPS）,suggesting that soil temperature（rather than moisture） controlled volume fractions of soil air CO2 in different land use,Guizhou Karst region,southwest China.