风蚀条件下人类活动对高寒草地水分保持功能影响的定量模拟

青藏高原是我国重要的生态屏障,具有重要的水源涵养功能。高寒草地生态系统退化将严重地影响高原的水源涵养功能。为了定量研究人类活动对青藏高原高寒草地水分保持功能的影响,采用大型风洞实验,模拟人类不同的干扰方式和干扰程度对高寒草地土壤水分保持功能的影响。实验样品采自青藏高原三个草地类型:高寒草甸、草原化草甸和高寒草原。干扰方式包括破坏草地地上部分和根系,干扰程度包括轻干扰、中度干扰、重度干扰和全部破坏。实验结果表明,地上部分破坏后,土壤含水率均有下降,降幅分别为:QZ1为6.9%～9.2%、QZ2为6.8%～10.1%、QZ3为9%～10%;当根系遭到破坏后土壤含水率的降幅则分别为:QZ1为16%～30%,QZ2为17.25～32.1%,QZ3为22%～50%,显然,根系破坏后土壤含水率降幅远大于地表植被破坏后的情形。因此,植被根系是高寒草地水分保持功能的关键。随着干扰程度的加剧,土壤含水率在迅速下降。从试验模拟结果看,三个草地类型中土壤水分保持功能分别是高寒草甸>草原化草甸>高寒草原。

Wind tunnel simulation and assessment of soil moisture conservation of alpine grassland in Qinghai-Tibet Plateau

The alpine grassland play an important role in maintaining ecological balance in Qinghai-Tibet Plateau. This study aimed to simulate impact of human activities on services of water conservation of alpine grassland by using the wind tunnel laboratory. Three types of grassland were selected which included alpine meadow,alpine steppe meadow and alpine steppe. The treatment pat-terns included cutting surface vegetation and broken root system. The results showed that compared with the original status,the per-cent of soil moisture content of three grassland samples decreased with increasing wind velocity under different treatments but the changes are greater after broken the root system than that after cutting ground vegetation. And as the root system was broken the soil moisture content ranged from high to low in turn QZ1 (alpine meadow),QZ2(alpine steppe meadow) and QZ3(alpine steppe). With the disturbed degree increase the changes of soil moisture content from high to low are QZ1,QZ3 and QZ2 respectively. In terms of the results,the ecosystem function of soil moisture conservation for three types of grassland should be alpine meadow>alpine steppe meadow>alpine steppe.