三峡库区兰陵溪流域土壤有机碳的垂直分布

Vertical distribution pattern of soil organic carbon of Lanlingxi watershed in Three Gorges Reservoir area

土壤是陆地生态系统中最大的有机碳库,土壤有机碳（SOC）储量与深度分布模式受土地利用方式的影响,SOC储量与深度分布模式对全球气候变化有着重要意义。本文利用三峡库区典型流域SOC深度分布数据库,分析SOC的深度分布模式及其影响因素。结果表明：土地利用方式显著影响SOC的深度分布,0-20 cm土层内,林地、草地、灌木地和农地等4类土地利用方式,SOC密度平均为8.47、5.90、4.65和2.64 kg·m-2,差异极显著（P〈0.001）;0-100 cm层为12.14、10.24、9.15和7.29 kg·m-2,差异显著（P〈0.05）;林地、草地,灌木地、农地中,0-20 cm层SOC密度分别占0-100 cm层的69.80%、57.6%、50.8%和36.2%;SOC密度随深度的增加而迅速下降,其中林地下降速度最快,SOC深度分布相对较浅,草地和灌木地下降较慢,SOC分布相对较深;土地利用方式和海拔对表层（0-20 cm）SOC密度影响显著,对深层（〉40 cm）影响不显著;土壤机械组成对表层（0-20cm）SOC密度影响显著,对深层（〉40 cm）SOC密度影响更为显著;用0-100 cm层碳密度来描述区域SOC储量时,估计值偏低。若考虑0-150 cm层的SOC储量,研究流域SOC密度值将增加6.2%-16.5%。

Soil is one of the largest pools of terrestrial organic carbon. Land-use types attect not only the storage but also the depth distribution pattern of soil organic carbon （ SOC）, which plays important roles in global climatic change. The SOC depth distribution and its influencing factors in Lanlingxi watershed in Three Gorges Reservoir were analyzed. The results showed that land-use types significantly affected the SOC depth distribution. The SOC densities in 0-20 cm layer aver- aged at 8.47, 5.90, 4.65, and 2.64 kg·m-2 for forests, grasslands, shrub lands, and crop- lands, respectively, and the SOC densities in the 0-100 cm were 8.47, 5.90, 4.65, and 2.64 kg·m-2 respectively. The percentage of SOC in 0-20 cm layer （relative to the 0-100 cm） aver- aged at 69.8%, 57.6%, 50.8% and 36.2% for forests, grasslands, shrub lands and croplands, respectively. With increasing soil depth, SOC density decreased rapidly, and the decline rate was fastest in forests. The forests had a shallower SOC depth distribution. On the contrary, grasslands and shrub lands decreased slowly with soil depth, and they had a deeper SOC depth distribution. Land-use type and altitude significantly affected SOC densities in top layer （0-20 cm）, but had no obvious effect on that in the deeper layers （ 〉40 cm）. Soil mechanical composition had a littleeffect on SOC density of surface layer （0-20 cm）, but had a significant effect in deeper layers （ 〉40 cm）. The soil carbon storage was underestimated when SOC in 0-100 cm layer was consid- ered. SOC density would be increased by 6.2%-16.5% in the study watershed with SOC storage in 0-150 cm layer being considered.