黄土丘陵区浅沟表层土壤容重的空间变异特征

Spatial Variation of Soil Bulk Density of Ephemeral Gullies in Hilly Areas of Loess Plateau

选取陕西省安塞县纸坊沟小流域2条发育完整的浅沟（长90m,宽40m）作为研究对象,运用经典统计学和地统计学方法研究浅沟表层（0-5cm）土壤容重的空间变异。经典统计学分析表明：土壤容重从浅沟上部到下部总体上呈逐渐减小的趋势;配对T检验表明,平行浅沟分布的9条样线在垂直浅沟方向上土壤容重差异不明显,浅沟分水线、浅沟沟坡和浅沟沟底之间差异不明显;方差分析表明,浅沟上部与中部和下部土壤容重差异显著,而中部和下部无显著差异。地统计学分析表明：在2,4,6,8,10,20m的采样间隔下,随着采样间隔的增大,理论变异函数的拟合精度逐渐降低;变异函数理论模型、块金值、基台值和变程各不相同;块金值和基台值之比变化范围为0.00∽0.55,为强度空间依赖性和中度空间依赖性;垂直和平行浅沟的各向异性分析结果表明,土壤容重的空间异质性以各向同性为主。

Selected two well-developed ephemeral gullies as study slope which located in Zhifanggou drainage basin, Ansai county, Shaanxi province and had length of 90 m and with of 40 m and then studied the variation of soil bulk density of ephemeral gullies surface （0--5 cm） by means of classical statistics and geostatistics. Classical analyses showed that generally speaking, soil bulk density decreased from upper part to the down part of gully. There were no significant differences between 9 transects which was up and down slope in direction that was to the transect, divide line, slope and bottom showed no obvious differences, using paired T test. One-way ANOVA analysis indicated that the soil bulk density of upper part of gullies was sig- nificant different from that of middle and down part of the gullies, while there was no significant difference between the middle and clown part. Geostatistical analyses revealed that under the 2 m, 4 m, 8 m, 10 m and 20 m interval sampling points, the accuracy of theoretical variogram decreased with the decreasing sampling points. Variograms had different theoretical variogram models, nugget values, sills and ranges under different sampling scales. The ranges of nugget ratio was 0.00--0.55, which was strong spatial dependent and moderate spatial dependent. Anisotropic analyses that were perpendicular and parallel to gullies demonstrated that the soil bulk density was mainly isotropic. Soil and water conservation measures should be enhanced at middle and down part of gullies.