荒漠灌丛内降雨和土壤水分再分配

通过对降雨再分配,荒漠灌丛可改变降雨在灌丛内的水平空间分布,进而影响植被冠层下土壤水分的空间响应.本文以腾格里沙漠东南缘人工植被区柠条和油蒿灌丛为研究对象,分析了灌丛干扰下的降雨再分配过程及灌丛下土壤水分的空间响应.结果表明: 柠条和油蒿灌丛的穿透水、树干茎流分别占降雨量的74.4%、11.3%和61.8%、5.5%.次降雨过程中,柠条和油蒿穿透水空间变异性均较大,平均变异系数分别为0.25和0.30;由于可以将更多的降雨以树干茎流形式在根部富集,柠条主干基部土壤湿润锋深度明显比冠层其余位置深,而油蒿仅在大降雨事件时才较为明显.灌丛对降雨的再分配作用改变了降雨达到地表时的空间分配,致使冠层下土壤湿润锋深度呈现明显的不均一性.

Rainfall and soil moisture redistribution induced by xerophytic shrubs in an arid desert ecosystem

Rainfall partitioning by desert shrub canopy modifies the redistribution of incident rainfall under the canopy, and may affect the distribution pattern of soil moisture around the plant. This study examined the distribution of rainfall and the response of soil moisture beneath the canopy of two dominant desert shrubs, Caragana korshinskii and Artemisia ordosica, in the revegetation area at the southeastern edge of the Tengger Desert. The results showed that throughfall and stemflow ave-ragely occupied 74.4%, 11.3% and 61.8%, 5.5% of the gross precipitation for C. korshinskii and A. ordosica, respectively. The mean coefficients of variation (CV) of throughfall were 0.25 and 0.30, respectively. C. korshinski were more efficient than A. ordosica on stemflow generation. The depth of soil wetting front around the stem area was greater than other areas under shrub canopy for C. korshinski, and it was only significantly greater under bigger rain events for A. ordosica. The shrub canopy could cause the unevenness of soil wetting front under the canopy in consequence of rainfall redistribution induced by xerophytic shrub.