黄土丘陵小流域土壤水分空间格局及其影响因素

Spatial Pattern of Soil Water and its Influencing Factors in a Gully Catchment of the Loess Plateau

为了定量探讨土壤水分的空间格局及其影响因素的相对重要性,以甘肃省定西市安家沟小流域为例,对坡面44个样地的土壤水分及其环境因子进行了定点观测。研究结果表明:①时间动态:对于农地、撂荒地、灌木林地、林地和荒草地等5种土地利用类型,其土壤水分在2002年的生长季节内都表现为下降型;其中农地具有较高的土壤水分,撂荒地居中,林地、灌林地和荒草地较低。②层次格局:在湿润时段(4月24日到6月23日),5种土地利用类型的土壤水分都表现为下降型,而在干旱时段(7月12日到8月9日)都为增长型;但在中等湿润时段(8月23日到9月18日),各种土地利用类型变化格局不同。③在湿润和中等湿润时段,土地利用是影响土壤水分(表层除外)变异的主要因素。对于相同的土地利用类型来说,坡向只在湿润或中等湿润时段对部分层次的土壤水分有明显的影响;坡位、相对高程、坡度及坡面曲率等4个环境因子的影响都不显著。干旱时段土壤水分的变异格局主要受土壤性质的影响。本项研究还发现,6～7月份的极度干旱严重地影响到本地植物的生长。建议:①建立不同土地利用类型斑块的镶嵌格局是控制水土流失的基础;②间作、灌溉以及覆盖等措施都可用以促进本区的植被恢复和农业发展。

Analysis of the soil moisture dynamic and relative importance of land use and environ-mental factors on the spatial variability of soil moisture were the base to guide ecological resto-ration and agricultural development.We analysed spatial variability of soil moisture upon 44 sample plots(176 sample points)at 5 depths (0～20,20～40,40～60,60～80 and 80～100cm)in the Anjiagou catchment of Loess Plateau in China from April to September 2002. Time-averaged soil moisture of cropland was the highest among the five land use types;fallowland was in the middle; woodland,shrubland and wasteland were the lowest in wet moisture status (from 24-Apr to 23-Jun). The layer-averaged soil moisture of all the five land use types decreased with depth in wet moisture status and increased with depth in dry moisture status (from 12-Jul to 9-Aug).The layer-averaged soil moisture of fallowland,cropland and shrubland decreased with depth,but wasteland and woodland both decreased and then increased with depth in medium moisture status(from 23-Aug to 18-Sep).Land use was the key factors that influence the spatial variability of the layer-averaged moisture of the four soil layers(20～40,40～60,60～80 and 80～100cm)in wet and medium moisture status.Land use has slight influence on spatial variability of layer-averaged moisture of all the five soil layers in dry moisture status.Slope aspect has significant influence on the layer-averaged soil moisture of some soil layers in wet and medium moisture status for wasteland,shrubland,woodland and fallowland.The other four environmental factors(slope profile curvature,slope position,relative elevation and slope gradient)had slight influence on the layer-averaged soil moisture of all the five land use types under the three water status.The spatial variability of layer-averaged soil moisture was controlled by local factors in dry moisture status.Finally,it was found that the deficit of soil moisture in June and July had severe influence on plant growth.The results of this study suggest that(1)constructing a mosaic pattern of different land uses should be useful to control soil erosion;and (2)intercropping,irrigation and mulching should be implemented to advance the vegetation restoration and agricultural development.