内蒙古典型草原小叶锦鸡儿灌丛化对水分再分配和利用的影响

灌丛化是全球草原地区存在的主要环境问题。通过对内蒙古典型草原区小叶锦鸡儿灌丛和草地斑块冠层降雨再分配、地表径流、土壤含水量的对比观测,研究了小叶锦鸡儿灌丛化对该区水分再分配和利用的影响。结果表明,灌丛和草地斑块的冠层截留量分别占降雨量的20.86%和7.88%,灌丛和草地斑块的平均地表径流系数分别为5.95%和17.19%。土壤含水量观测结果显示,0—60 cm土层中,降雨事件过程中,灌丛斑块较草地斑块能捕获更多水分,灌丛斑块植被冠层下方土壤含水量高于草地斑块;而在雨后无有效降水补充土壤水分的前提下,0—60 cm土层中,灌丛斑块土壤水分蒸散发量高于草地斑块,其中0—10cm土层中灌丛斑块土壤水分蒸散发速率低于草地斑块,10—60 cm土层中灌丛斑块土壤水分蒸散发速率高于草地斑块。研究认为,在水分为关键性限制因子的干旱半干旱区,小叶锦鸡儿灌丛化过程增加草原生态系统中水分分布的空间异质性,灌丛斑块能捕获、利用更多水分以维持更多的生物量。

Effects of shrub (Caragana microphalla Lam.) encroachment on water redistribution and utilization in the typical steppe of Inner Mongolia

Shrub encroachment is the main environment problem at the steppe region on the earth. This study observed rainfall redistribution composition of plant canopy, surface runoff, and soil moisture content at the shrub and interspace grass patches respectively, analyzed effects of shrub encroachment on water redistribution and utilization in the typical steppe which encroached by Caragana microphalla Lam. (C. microphalla) in Inner Mongolia. Results showed that the average canopy interception was 20.86% and 7.88% for shrub and interspace grass patches respectively, and the average surface runoff coefficient was 5.95% and 17.19% at shrub and interspace grass patches respectively. Shrub patches had greater water capability than intersapce grass patches in the same rainfall event, so soil moisture content under the canopy of shrub patches was much greater than intersapce grass patches after rainfall events in the 0-60 cm soil layers; soil evapotranspiration below the canopy of shrub patches was much greater than grass patches in the 0-60 cm soil layers, the evapotranspiration rate below the canopy of shrub patches was much lower than interspace grass patches in the 0-10 cm soil layers, but it was much greater than intersapce grass patches in the 10-60 cm soil layers. This study suggested that that shrub encroachment increased spatial heterogeneity of water distribution in grassland ecosystem at the arid and semiarid region where water was one of the key restriction factor, shrub patches could capture and utilize more water to produce more biomass than interspace grass patches.