近45a来黄河源区沙质荒漠化土地景观格局变化

Landscape pattern change of sandy desertification land in the source region of the Yellow River during the past 45 years

应用"3S"技术,对黄河源区1975~2019年沙质荒漠化土地的景观格局变化及原因进行了分析。研究结果表明:沙质荒漠化土地分布面积先增大而后减小、总体减小,程度先增强而后减弱、总体减弱,截止2019年底,沙质荒漠化土地在研究区仍占有较大比例,程度以中度为主;沙质荒漠化的景观多样性先增大而后减小、优势度与破碎度均先减小而后增大,景观格局的复杂程度加重,出现了分割、破碎化、缩小与消失的景观变化过程;气候条件中的升温、大风与人类活动中的超载、过牧等要素的共同作用造成了沙质荒漠化土地在2000年以前的快速发展,而在2000年以后的逐步逆转与退牧还草、封山禁牧等生态修复政策密切相关。

The landscape pattern change and the cause of sandy desertification in Qinghai province in the source region of the Yellow River were analyzed by using 3 S technology. The results are as bellow: in recent 45 years, the area of sandy desertification land has increased firstly and then decreased, and decreased in general, the degree firstly increased and then weakened, and weakened in general. By the end of 2019, sandy desertification land still occupied a large proportion in the research area, with a moderate degree as the main part. The largest area of sandy desertification was in Maduo county, where is the source region of the Yellow River. From 1975 to 2019, the landscape diversity index of sandy desertification increased firstly and then decreased, the dominance index decreased firstly and then increased, the fragment index decreased firstly and then increased. The landscape pattern was more complicated and the change of sandy desertification landscape appeared a process of dividing, broken, reduce and disappear. The spatial distribution of sandy source material determined the spatial distribution characteristics of sandy desertification land. The rapid development of sandy desertification land from 1975 to 2000 was caused by the combined effects of warming, strong wind and human activities, such as overloading and overgrazing. However, the gradual reversal after 2000 was closely related to the ecological restoration policies, such as returning grazing to grassland, closing the mountain and forbidding grazing.