不同植被类型沙地表层土壤水分变化特征

通过对沙坡头地区不同植被类型沙地土壤表层水分时空变化特征的研究表明，该区不同植被类型沙地土壤表层水分的分布均符合正态分布，降雨使表层土壤水分的空间变异性减小，空间自相关性减弱，分维数减小，空间自相关范围由干旱时的5m左右内变化扩大到几十米，土壤表层水分的空间依赖性增强；在土壤表层水分含量极低的情况下，土壤表层水分的空间变异性规律与土壤水分含量的变化规律一致；在土壤水分含量不是很低的情况下，其空间变异性与土壤表层水分含量变化趋势相反，流沙地、柠条地A、柠条地B、油蒿地、1956年人工固沙植被区土壤表层水分空间变异性与土壤表层水分含量关系发生改变的转折点，分别在土壤表层体积水分含量为1．5％，2．5％，3％，3％，4％左右。

Variability Characteristic of Surface soil Moisture Content in Sand Areas Covered by Different Vegetation Types

This paper researched the temporal and spatial variability characteristic of surface soil moisture content in sand areas where were covered by different vegetation types in Shapotou,the results indicated that the distribution of surface soil moisture was normal distribution,the surface soil moisture content increased obviously and the fragmentation degree minished after precipitation,the distribution of soil moisture was more even.When surface soil moisture content was extreme low,the variance trend of surface soil moisture spatial variability and soil moisture content was consistent,when the surface soil moisture content wasn't quite low,the variance trend of soil moisture spatial variability and surface soil moisture content was reverse.The turning points where the relationship between surface soil moisture spatial variability and soil moisture content changed occurred when surface soil moisture content was 1.5%,2.5%,3%,3% and 4% in moving sand area,Caragana korshinskii area A,Caragana korshinskii area B,A.ordosica area,sand-binding vegetation area respectively.