荒漠人工固沙植被区土壤水分的时空变异性

表层土壤水分具有高度的时间和空间变异性.研究的目的:(1)揭示沙坡头人工固沙植被区浅层土壤水分的时空变异性特征;(2)确定驱动土壤水分变异的主要环境因子.在人工固沙植被区内一个4500m2的网格样地上每隔10m设置取样点,在连续7个月的时间内 (2005年4～10月),每隔15d用时域反射仪测量各样点表层以下15cm和30cm深度的土壤容积含水量.结果表明,该区网格尺度上浅层土壤水分的分布具有明显的空间变异性,其变异性随着土壤水分含量的降低而减小;相对海拔是驱动土壤水分空间变异的主要环境因子,其作用在降雨后尤为显著,且其对土壤下层的影响比上层更明显;植被和土壤水分含量的相关性时间序列与相对海拔一致--降雨使其相关性增加;土壤质地(土壤粒径分布)和土壤水分含量的相关性时间序列特征与植被和相对海拔相反,且其对土壤上层的影响比下层更明显.因此,在沙坡头荒漠人工固沙植被区,降雨后的短暂湿润期,地形和植被是驱动浅层土壤水分变异的主要影响因子,而随着降雨之后土壤逐渐变干,土壤质地的影响变得更加明显.

Temporal and spatial variability of surface soil moisture in a re-vegetation desert area in Shapotou

Soil moisture content in surface layer exhibits large spatial and temporal variability. The purpose of this study was (a) to characterize the spatial and temporal variability of soil moisture in surface layer in an artificially re-vegetation desert area in Shapotou. (b) to make inferences regarding the environmental factors that affect this variability. During the experimental period of seven months (from April to October 2005), soil moisture content was measured using the time domain reflectometry about every half a month at a grid with 10m×10m intervals at a plot of 4500m2, the topography of the experimental area varying from dune crest to dune hollow, and again to dune crest. Results indicated that the distribution of soil moisture at grid scale was in normal distribution with a significant spatial variability; the variability of soil moisture decreased with decreasing mean soil moisture content as soil dried down following rain events. Relative elevation was a main driving factor of soil moisture variability especially after rainfall events, and its influence was more obvious in the depth of 0-30cm than in the depth of 0-15cm. The correlation between the vegetation and soil moisture content in time series was in consistent with that of the relative elevation and soil moisture content, which was strengthened by rain storm events, though the relationship between vegetation and soil moisture content was less obvious. There was an opposite time series pattern in correlation between soil texture (particle size distribution) and soil moisture content with that of the correlation between relative elevation and vegetation cover, and the relativity was higher in the depth of 0-15cm than in the depth of 0-30cm. We may concluded that local topography and vegetation cover were the main driving factors for surface soil moisture spatial variability in a short duration after the rain storm events, while the shallow soil texture exerted more influence on the surface soil moisture spatial variability as the soil dried following heavy rainfall events in this specific re-vegetated arid desert area.