地形和土地利用对黄土丘陵沟壑区表层土壤有机碳空间分布影响

Effects of Topographies and Land Use on Spatial Distribution of Surface Soil Organic Carbon in Hilly Region of the Loess Plateau

研究地形和土地利用类型共同作用下表层土壤有机碳空间分布特征,对准确评估区域土壤有机碳的空间分布和变异特征具有重要意义。以黄土丘陵沟壑区燕沟流域3种地形部位（峁顶、峁坡、沟底）和8种土地利用类型（农田、果园、天然与人工草地、天然与人工灌木林、天然与人工乔木林）为研究对象,采集表层（0~20 cm）314个土壤样品用于研究地形和土地利用方式对黄土丘陵沟壑区小流域表层土壤有机碳空间分布的影响。地形和土地利用方式极显著（P〈0.000 1）影响小流域表层土壤有机碳含量与分布,并且交互作用显著（P=0.051 1）。地形影响下,土壤有机碳空间分布表现为沟底〉峁坡〉峁顶的变化趋势,土壤有机碳含量沟底（8.0 g/kg）、峁坡（7.1 g/kg）分别是峁顶（4.2 g/kg）的1.9、1.7倍。土地利用方式影响下,土壤有机碳空间分布表现为天然乔木〉天然灌木〉人工乔木〉天然草地〉人工灌木〉人工草地〉农田〉果园的分布变化规律。地形和土地利用交互作用下,农田、果园、天然草地在坡面水土流失条件下显示出土壤有机碳在沟底逐渐富集的特征,沟底有机碳含量农田（6.9 g/kg）、果园（8.8 g/kg）、天然草地（9.3 g/kg）分别是峁顶的1.9、2.0、1.9倍。林地（灌木林和乔木林）却表现为峁坡土壤有机碳含量远远高于沟底,天然乔木林且达到了显著水平,天然乔木峁坡土壤有机碳含量（24.6 g/kg）是沟底（16.4 g/kg）的1.5倍。

It is important to accurately assess regional spatial distribution and variation of soil organic carbon and to study effects of topographies and land use on spatial distribution of soil surface organic carbon.In Yangou watershed,hilly region of the Loess Plateau,based on three topographies（tableland,slope land,gully land） and eight land uses（farmland,orchard,manmade and secondary grassland,manmade and secondary shrub land and manmade and secondary woodland）,314 soil surface（0-20 cm） samples were collected to investigate effects of topographies and land use on spatial distribution of soil organic carbon in the watershed.Topographies and land use significantly（P0.000 1） affect spatial distribution of soil surface organic carbon in Yangou watershed,and their interaction significantly（P=0.051 1） impact on the spatial distribution of soil organic carbon.Under the influence of topographies,the spatial distribution of soil surface organic carbon expressed a changing trend of gully land slope land tableland,and the soil surface organic carbon contents of gully land（8.0 g/kg） and slope land（7.1 g/kg）were as 1.9 and 1.7 times as tableland（4.2 g/kg） respectively.Under the influence of land use,the spatial distribution of soil surface organic carbon performanced for secondary woodlandsecondary shrub landmanmade woodlandsecondary grasslandmanmade shrub landmanmade grassland farmlandorchard.Under the influence of their interaction,soil surface organic carbon of farmland,orchards and grassland were gradually concentrated on gully land under the condition of soil slope erosion.The soil organic carbon contents of gully land of farmland（6.9 g/kg）,orchard（8.8 g/kg） and secondary grassland（9.3 g/kg） were as 1.9,2.2 and 1.9 times as tableland respectively.Forests（shrub land and woodland） were different from farmland,orchard and grassland,and reflected that soil surface organic carbon contents of the slope land were much higher than the gully land.The soil organic carbon content of the slope land of secondary woodland（24.6 g/kg） which was 1.5 times of gully land（16.4 g/kg） reached a significant level compared with gully land.