祁连山典型小流域不同植被类型降水规律分析

Analysis on Precipitation Laws of Different Vegetation Types in the Typical Small Watershed of Qilian Mountain Area

对祁连山典型小流域内的荒漠、草原、森林这三类主要植被类型进行了定位监测。结果表明,森林带和草原带年平均降水量明显高于荒漠带年平均降水量,年平均降水量分别为526.7、371.7、139.8mm。森林带较草原带和荒漠带年降水量变化幅度大,森林带能增加一个小区域年降水量变化的阈值。近23年来该区域降水量总体趋势在下降,其中森林带下降趋势最为明显,荒漠带次之,草原带最小。在一定降水范围内,降水量越大,不同植被类型降水量差异越大。不同植被类型的降水量随海拔升高而逐渐增加,海拔每升高100m,荒漠带(1700～2100m)平均递增率为13.0%,草原带(2100～2500m)平均递增率为19.7%,森林带(2500～3400m)平均递增率为4.2%。并且在一个植被类型与另一个植被类型的过渡带上,降水量剧烈变化。对于典型小流域来说,小气候同样影响了植被分布格局。同时不同植被类型从化学、物理方面都对该区域小气候产生积极的反馈作用;在海拔梯度上,不同植被类型对降水影响明显。

In order to reveal the precipitation laws of different vegetation types in the typical watershed of Qilian mountain area, the data of location monitoring to the forests, steppe and desert were analyzed. The results showed that on forest zone, steppe zone and desert zone, the average annual precipitation were 526.7mm,371.7mm,139.8mm, respectively. Annual precipitation of forest zone had a larger varied amplitude than steppe zone and desert zone. The regional rainfall precipitation in nearly 23 years was declined, the general trend of decline of forest zone was the most obvious, with desert zone was second and steppe zone was minimum. The precipitation had greater influence on different vegetation types. The precipitations of different vegetation types increased with the increase of elevation. On the transitive zone of different vegetation types , precipitation change was very big. For typical small watershed, the microclimate had influenced the vegetation distribution pattern, and at the same time different vegetation types regardless chemical or physical aspects was positively feedback to microclimate of this area. At an altitude of gradient on large scale, different vegetation types had obviously influence on precipitation.