黄河源区天然草地沙化机理分析研究

Study on the desertification mechanism of natural grassland in the source regions of the Yellow River

黄河源头区是我国重要的水源涵养地区,是“中华水塔”的重要组成部分。地处黄河源区的玛曲县,自20世纪80年代以来,天然草地沙化面积不断增加,沙化程度日趋严重。本研究以玛曲县为例,对引起草地沙化的主要自然因素和人为因素与草地沙化的相关性及驱动作用进行定量辩识和贡献率分析,结果表明,1)各因子对草地沙化的驱动力大小依次为:牧业产值>人口数量>年均气温>羊只存栏数>牛羊肉产量>年均降水量>大牲畜存栏数>黄河年径流量>年大风日数>年均风速;2)区域年均气温的不断升高,使地面水分蒸发损失和土壤干旱程度加剧,这种变化对土地沙化产生的驱动作用要大于降水量的小幅减少和风力因子变化的影响,是引起该区土地沙化最重要的自然驱动因子;3)对2类因子的相对贡献率进行综合,得到人为因子的驱动力比重为61.55%,自然因子的驱动力比重为38.45%。说明在高寒阴湿的气候条件下,区域气候和水文因子在一定程度上的不良变化只是天然草地沙化的一种诱导力,而人为过度和不合理利用是导致草原植被衰退的根本原因,二者结合导致了黄河源头区草地沙化的加速发展。

The source, regions of the Yellow River are crucial water resources in China and the important part of China＇s Watertower. Since the 1980s, desertification of natural grasslands in Maqu County have increased and the extension of the desert has gradually become more and more severe. In this paper, Maqu County was taken as an example plot to differentiate quantitatively and analyze the correlation and action mechanism of natural factors and artificial factors to desertification severity of natural grassland respectively, and in addition to determine the contribution rate of all factors mentioned above. The results showed that. 1） The total cumulative effect is the total value, in decreasing order of importance of： animal husbandry〉the human population〉meanannual air temperature〉year--end number of sheep and goats〉beef and mutton〉mean annual preeipitatiou〉 year end number of large animals〉runoff volume of the Yellow River〉annual count of gale days〉annual average wind speed. 2） Water loss due to ground evaporation and soil aridity were intensified by an increase of mean air temperature in the region. The driver functions of the above change processes that resulted in soil desertification were more than the effects on a reduction of rainfall： the change of wind power was the most important natural driver factor causing soil desertification in this region. 3） Based on an analysis of the contribution rate to desertification, artificial factors accounted for 61.55% and natural factors for 38.45%. This result indicated that in conditions of cold and dankness,some degree of unfavourable changes in regional climate and hydrological factors were merely the accentuating forces for natural grassland desertification By comparison, artificial excessive use or some unreasonable utilization could be regarded as the root causes for decline of grassland vegetation, and the combined action of these two processes resulted in acceleration of grassland desertification in the source regions of the Yellow River.