不同尺度下土壤粒径分布特征及其影响因子——以黄土丘陵沟壑区为例

土地利用方式和环境因子是影响土壤粒径的重要因素,尺度不同其影响效应差异明显。研究不同尺度表层土壤粒径与土地利用、环境因子的关系对评价黄土丘陵沟壑区土壤物理性质具有积极意义。选择黄土丘陵沟壑区安塞集水区和沐浴小流域作为研究区,探讨两个尺度上表层土壤粒径含量、分布特征及其与土地利用类型和环境因子的关系。研究结果表明:(1)研究区域内表层土壤颗粒主要为砂粒和粉粒,在小流域和集水区尺度上,各粒径百分含量属于中等变异,D值为弱变异,但随着研究区由沐浴小流域变化到安塞集水区,粒径和D值的空间变异性均有所提高;(2)尺度不同,土地利用对土壤粒径的影响效应不同,在沐浴小流域不同土地利用类型的砂粒含量从高到低依次为荒草地农用地林地灌木林地园地,在集水区的变化顺序依次为荒草地灌木林地林地农用地园地,粉粒含量的次序均与砂粒相反,小流域土壤粒径分形维数D依次为灌木林地荒草地林地园地农用地,在安塞集水区为灌木林地荒草地农用地林地园地;(3)在沐浴小流域和安塞集水区,土壤颗粒分形维数与土壤砂粒、黏粒百分含量呈极显著正相关关系,与土壤粉粒百分含量呈极显著负相关关系,且砂质壤土D值高于壤土和粉壤土;(4)在沐浴小流域,植被盖度、相对海拔和坡位相对于土地利用类型、坡向和坡度对土壤粒径影响较大;而在安塞集水区植被盖度、土地利用类型和坡度对土壤粒径影响较大。

Comparative analysis of soil particle size distribution and its influence factors in different scales: a case study in the Loess Hilly-gully area

The land use types and environmental factors have a great significance on soil particle size distribution (PSD). However the effects are different in different scales. Research on the relationship between topsoil particle size distribution and land use & environmental factors can provide a basis for assessing topsoil physical properties in loess hilly-gully area. The study was conducted in the Muyu small watershed and the Ansai catchment in the loess hilly area of the Loess Plateau in China, and the comparative analysis of soil particle size distribution and its influence factors in different scales were carried out. The research results showed that: (1) The topsoil in the loess hilly-gully areas of the Loess Plateau are mainly composed of sand and silt in both small watershed and catchment. The percentage of each particle size is medium spatial variability, and the spatial variability of D is far below of the particle size. But it appears clearly that the spatial variabilities are scale dependent and it increases with the increase of study area. (2)The effects of land use types on soil particle size are different at two scales. The sand content varied with land use in the order: grassland> farmland> woodland> shrub land> orchard land in the Muyu small watershed, and grassland> shrub land> woodland> orchard land> farmland in the Ansai catchment. The silt content varied with land use in the opposite order of the sand content. The D value varied with land use in the order: shrub land> grassland>woodland> orchard land> farmland in the Muyu small watershed, and shrub land>grassland>farmland>woodland>orchard land in the Ansai catchment. (3) In both Muyu small watershed and the Ansai catchment, D is very significant positive correlation with the soil sand content and clay content, significant negative correlation with soil silt content, and D value is much higher in the sandy loam than that in the loam and silt loam. (4) Vegetation cover, altitude and position have more influence on the soil particle size than other factors in the Muyu small watershed, while vegetation cover, land use, and slope influence the soil particle much more greatly in the Ansai catchment.