黄土高原土壤水分变化的时空特征分析

对晋西北砖窑沟流域荒地7年土壤水分定位观测表明，生长期土壤水分动态主要受降水量及其分配的影响．一般年份生长期土壤水分动态可分为3个时段：1)春末夏初土壤水分消耗期；2)夏末秋初土壤水分蓄积期和3)秋末冬初土壤水分消耗期．0-300cm土层水分含量的季节变化与测定序号的关系方程为：1)直线型(1988，1990)，2)指数型(1992，1995)和3)抛物线型(1993)．以150cm为界，下部土壤水分与上部的比大于1．不同降水年土壤湿度与土层深度的关系方程均为三次抛物线型．土壤水分的变异系数随深度的增加而减小．0-300cm内的土壤水分剖面可分为活跃层(200cm以上)、过渡层(200—250cm)和稳定层(250cm以下)．各层深度随降水量及其分配的不同而变化．不同降水年荒地土壤水分的方差分析总体差异显著，但各组间的均值配对比较结果不同．特涝年的荒地土壤水分与其它年份差异均显著．荒地与柠条林地的土壤水分差异显著，但与河北杨林地和小叶杨林地的土壤水分差异不显著．本文采用的定量研究方法有助于黄土高原不同地区和不同植被条件下土壤水分的定量比较．

Spatial and temporal characteristics of soil moisture dynamics in Loess Plateau

Field monitoring results of wasteland soil water content of during growing season of seven years in Zhuanyaogou valley of northwestern Shanxi Province, and the results showed that the seasonal dynamics of the soil water was controlled by annual precipitation and its distribution. The seasonal dynamics of soil water in a normal rainfall year could be divided into three stages, i.e., consumption stage from late spring to early summer, storage stage from late summer to early autumn, and second consumption stage from late autumn to early winter. The relationship equation between soil water content and measuring number was linear (1988, 1990), exponent (1992, 1995) and parabola curve (1993). The vertical profiles of soil water in the wasteland in different rainfall year were different, and the soil water content increased with increasing depth. The equations between soil water content and soil depth in all years were cubic. Taking 150 cm as a boundary, the ratio of soil water content in lower layers to upper layers was larger than 1, and the variance coefficient of soil water decreased with increasing depth. The soil water profile in 0-300 cm depth for seven year's average could be divided into three layers, i.e., active layer (above 200 cm), transitive layer (between 200-250 cm) and stable layer (below 250 cm), and the depth of each layer varied with the annual precipitation and its distribution. The ANOVA result of soil water content in extremely high rainfall showed a great difference with that in other years. The difference between soil water content in wasteland and in Caragana korshinskii plantation was significant, but was not different from that in Populus hopeiensis and Populus simonii plantation respectively. The quantitative analysis methods used in this paper facilitated the comparison of soil moisture in different region and in different vegetation.