晋西黄土区基于地形因子的土壤水分分异规律研究

以山西省吉县蔡家川小流域典型梁峁坡面为研究对象,在研究区共布设313个土壤水分监测点,用TDR测定土壤(0~30cm,30~60cm)水分,经克立格(kriging)插值得到了研究区土壤水分分布图,并与基于数字高程模型(DEM)提取的研究区域坡向、坡度、高程3个地形因子分布图叠加,生成土壤水分与地形因子相对应的数据库,用以分析坡面尺度地形因子对土壤水分的影响情况及基于地形因子的土壤水分分异规律。通过主成分分析得出:地形因子对土壤水分影响的次序依次为坡向>高程>坡度。通过对坡向和坡度聚类分析得出:影响土壤水分分异的坡向可分为两类,即292.5°~360°(0°)~112.5°(阴坡),112.5°~292.5°(阳坡);影响土壤水分分异的坡度分为:5°~20°,20°~35°两类。依据坡度和坡向的分类结果,分别拟合土壤水分和地形因子的函数关系,求出不同坡度、坡向土壤水分的关系系数:若假定坡度为5°~20°、坡向为阴坡时,土壤水分关系系数为1,则坡度为5°~20°、坡向为时阳坡时土壤水分关系系数为0.99,坡度20°~35°、坡向为阴坡时土壤水分关系系数是0.82,坡度20°~35°、坡向为阳坡时土壤水分关系系数为0.8。

VARIATION OF SOIL MOISTURE IN RELATION TO TOPOGRAPHIC FACTORS IN LOESS REGION OF WEST SHANXI

A typical slope in the Caijiachuan watershed, Loess Plateau of China was an object of research.A total of 313 soil moisture monitoring points were laid out in a 20 m×20 m grid pattern in the experiment site for measuring soil moisture in two layers, 0~30 cm and 30~60 cm, with TDR (time domain reflectrometry) in 2005.Based on the data, a soil moisture dis tribution map was plotted with the Kriging method and then superposed over on the topographic factor maps of aspect, slopes and elevation, derived from DEM, thus forming a database of relationships between soil moisture and different topographic factors for analysis of effects of different topographic factors on soil moisture, and variat ion of soil moisture attributed to topographic factors.Results show that in the 0~30 cm soil layer, the topographic factors were in the order of aspect > elevat ion> slope in effect on soil moisture, while in the 30~60 cm soil layer, the sequence is slope> elevation> aspect The cluster analysis of aspects and slopes indicated that aspects could be sorted into two categories: 292.5°~360° (0°)~112.5°(shady slope) and 112.5°~292.5°(sunny slope), and so could slopes, 5°~20° and 20°~35° according to their effects on soil moisture.Based on the sorting models for fitting functional relations between soil moisture and the topographic factors were established and coefficients of the relations worked out.Assuming the soil moisture modulus is set as 1 when a shady slope is 5°~20° in gradient, and it is 0.99 on a sunny slope the same in gradient, 0.82 on a shady slope, 20°~35° in gradient, and 0.80 on a sunny slope the same in gradient.