黄土地区防护林生态系统土壤水分条件的分析与评价

ANALYSIS AND EVALUATION OF SOIL WATER CONDITIONS OF PROTECTIVE FOREST ECOSYSTEM IN LOESS AREA

从土壤水分变化特征、土壤水分有效性、影响土壤水分的林分因子综合分析等几个方面对黄土地区防护林生态系统土壤水分条件进行了分析与评价。研究表明，黄土地区防护林生态系统土壤水分的垂直变化可分为：土壤水分弱利用层、土壤水分利用层、土壤水分调节层三个作用层次；林地土壤水分的季节变化可分为：土壤水分消耗期、补偿积累期、消退期、稳定期四个时期；根据土壤水分对植物的有效性，将土壤水分划分成易效水、中效水和难效水三种状态。在时间和深度上，阴坡土壤的有效性要好于阳坡，乔木地土壤难效水出现的机率明显高于灌木林地和荒地。通过对影响土壤水分的林分因子的综合分析，得到刺槐和油松林地含水量和难效水的机率与林分因子之间的多元回归方程。

For analysing and evaluating the soil water features, the periodical soil water measurement and stand investigation were carried out during 1988-1992 in the experimental station of Beijing Forestry University, Ji County, Shanxi Province. The results showed that according to the vertical soil water variation, the soil profile could be divided into three layers, i. e. weak utilization layer, utilization layer and regulatinglayer, and according to the seasonal soil water veriation, the calendar year of soil water condition could be divided into four periods, i. e. consuming period, accumulating period, lowering period and stable period. From the study of soil water effectiveness, it is shown that eddectiveness of northern slope is better than that of southern slope, effectiveness of bare and shrub land is better than that of forest land. A multiple regression equation is proposed to present the relationship between soil water content, frequency of noneffective water and verious stand description factors of black locust and Chinese pine plantation.