祁连山东段景观格局变化及其驱动因子研究

综合利用RS、GIS技术和景观生态学方法,分析了祁连山东段地区1994-2008年的景观格局变化及其驱动因素。结果表明,1)在斑块类型水平上,与1994年相同,2008年研究区整体景观仍属于粒级结构。微小型斑块数量多,面积占比小;中斑块、大斑块和巨斑块面积占比大,斑块数量少。1994-2008年,研究区景观发生了较大变化。森林保存了原有面积的78.2%,灌木保存了原有面积的66.7%,28.1%的灌木面积由森林景观演化而来;草地保存了原有面积的86.3%,4.8%的草地面积退化为裸地;12.7%的冰雪面积转化为裸地,森林与灌木、冰雪与裸地之间转化演变剧烈。森林、冰雪和水域景观斑块形状朝简单、规则方向变化。2)与1994年相比,2008年祁连山东段地区景观多样性、均匀度、破碎度指数增大,景观优势度、分离度减小。研究区景观整体多样性水平升高,异质性增大,优势斑块在景观中控制作用减弱,景观向着多元化、均匀化方向发展。3)自然因素中气温升高是导致冰雪景观面积减少的主要原因,降水量增加则遏制了水域面积减少的趋势。人为因素特别是过度砍伐是导致研究区森林面积减少,森林退化为灌丛的根本因子。

Changes in landscape patterns and the driving force in the Eastern Qilian Mountains

Based on the techniques of RS & GIS and methods of landscape ecology, changes in landscape patterns and the driving force in the Eastern Qilian Mountains were analyzed. 1) At the patch level, the research area landscape was a grain grade structure in 1994 and 2008. There were large numbers, but a small area of mini- and small-patches while in contrast, there were few middle-, large- and huge-patches but they occupied a large area. There were great changes in the Eastern Qilian Mountains landscape from 1994 to 2008. The areas of forest, shrub and grassland remained at 78.2%, 66.7% and 86.3% of the original area respectively, and 28.1% of the shrub area came from the forest landscape. Additionally, 4.8% of the original grassland area and 12.7% of the original snow area had degenerated into bare land, and there was a dramatic transformation between forests and shrubs, snow and bare areas. The shape of patches of forest, snow and water became more simple and regularized. 2) The analysis of landscape diversity showed that evenness and fragmentation indexes of the Eastern Qilian Mountains in 2008 increased compared with those in 1994, while landscape dominance and isolation indexes decreased. The overall level of landscape diversity and heterogeneity increased, the dominant role of main plaque control decreased in the landscape which developed towards diversification and homogenization. 3) Natural factors were the main reason for temperature rise and the reduction of snow area, while precipitation increasingly influenced the decline in water area. Human factors, especially excessive logging, was fundamental for the reduction of forest area and for the degradation to shrubland.