青海共和盆地水分的时空变化及其荒漠化成因分析

Temporal - Spatial Analysis of Water and Cause of Desertification in Gong-he Basin in Qinghai Province

在青藏高原东北缘的青海共和盆地,依据3个主要气象站(包括20多个临时气象、水文站)长、短期气象资料和2个水文站(沙珠玉和拉曲)的径流数据,以及共和县(恰卜恰站)的土壤水分资料,利用时间序列、数字高程模型(DEM)和趋势面分析等方法,结合封育和未封育草地地上生物量和牧场载畜量的调查,该文对共和盆地水分时空分布和荒漠化成因进行分析,结果表明:共和盆地的年降雨量序列是平稳的,没有周期;而且进一步依据年降雨量与年蒸散发、径流和土壤水分等的相关分析,研究期内共和盆地的气候干燥和荒漠化不是由于降雨量减少直接造成;依据年降雨量的空间分布,共和盆地的两个沙带(沙珠玉-塔拉滩和木格滩)的年降雨量分别为250mm～300mm和300mm～400mm,所以降雨并非牧草生长的主要限制因子;最终,生物量和载畜量调查结果显示,过牧可能是共和盆地近50年荒漠化加剧的主要原因之一。该研究对进一步分析共和盆地和相邻的青藏高原区的气候、水文和水土资源利用有一定的指导意义。

Gong-he basin lies in the northeastern part of Qingham-Tibetan plateau. By plenty of long or short-term meteorological, hydrological data, soil water data and field investigation at three basic weather stations (Qiabuqia, Guinan and Chaka) including more than 20 temporary weather stations(Shazhuyu, Tangemu, Longyangxia, Qugou, etc.) and two hydrological observing stations (Shazhuyu and Laqu), this paper analyzes the temporal-spatial characteristics of annual precipitation and the cause of desertification by using time series analysis, digital elevation model and two power trend surface analyses. In the period of research, the results indicate that the time-series of annual precipitation is stable, no trend and no period according to the analysis of the oriented-test and periodogram in Gong-he basin; and because annual precipitation time series is a kind of stochastic change, the result deduced that the precipitation isn't the direct cause for desertification and climate drying in Gong-he basin too, which is further verified by the correlative analysis between annual precipitation and other relative factors (annual runoff, annual evaporation and potential evapotranspiration, soil water, etc.); and the amount of precipitation in the two big sand band(Shazhuyu-Tala and Mugetan) is 250mm～300mm and 300mm～400mm according to the spatial distribution of annual precipitation by the simulating result, based on the two power trend surface model and digital elevation model (DEM), so precipitation isn't the absolutely limited factor for grass growth, that is in accordance with actual investigation in the Gong-he basin; in the end, the analysis of above-ground biomass on the grazed and un-grazed grassland by fence give a good testimony that a sever stocking intensity makes grassland degenerate gradually, which is consistent with the local statistical data of stocking intensity markedly. So the paper has positive significance to analyze the climate, hydrological cycle and land use change in the Gong-he basin and the region of Qingham-Tibetan plateau further.