2000-2010年青海湖流域草地退化状况时空分析

青海湖流域属于高寒草地生态系统,草地退化状况是反映该流域生态环境状况的有效指标。在对青海湖流域退化草地分类的基础上,利用遥感手段获得流域退化草地的空间分布和变化信息。采用Markov模型、退化草地动态变化度、转类指数和景观指数对青海湖流域草地退化状况时空变化进行多角度分析。研究表明2010年青海湖流域草地状况良好,未退化草甸与未退化草原在整个流域占绝对优势,是流域面积的38%。2000-2010年期间,流域草地变化不大,退化草地转类指数为-0.0384;草地变化整体上呈极轻微退化趋势,在这11a期间呈现先退化、后改善的状况。流域内不同退化草地类别的空间景观格局表现比较稳定。青海湖流域的优势草地类别是未退化草甸,主要分布在流域中部,2000-2010年期间该类别的动态变化度为1.82%,没有发生大幅度变化,时空变化都比较稳定。中度退化草甸是退化最明显的类别,即使在流域草地呈改善状况的2006-2010年期间,有近7.4万hm²退化为重度退化草甸,占中度退化草甸转变为其他类别的65%。流域中与其他类别相互转换频繁,面积变化幅度最大的类型是轻度、中度退化草甸,及重度退化草原,在流域草地退化发生改善的2006-2010年期间,这3个类别的动态变化度达到15%-21%之间;空间上它们主要分布在流域西北部、青海湖北部以及环青海湖区域。

Analysis on grassland degradation in Qinghai Lake Basin during 2000-2010

Qinghai Lake Basin (QLB) belongs to the alpine grassland ecosystem. The grassland degradation is an effective detector to reflect the ecological environment condition in QLB. In this study, the spatial distribution and change information of the degraded grassland in QLB were firstly mapped and extracted using remote sensing techniques. Then the spatial-temporal changes of the degraded grassland between the year 2000 and 2010 were analyzed in different perspectives using Markov model, index of dynamic variation degree, landscape pattern index and grassland change index. Results show that the grassland in QLB was in good condition in 2010, and the non-degraded meadow and non-degraded grassland dominated QLB and covered about 38% of this region. The grassland has little variation during these 11 years, and the index of dynamic variation degree is -0.0384. The grassland was improved after the first degradation, but still had slight degradation in the overall trend. The spatial landscape pattern of the degraded grassland was stable in this study. The non-degraded meadow is dominantly distributed in the central region of QLB. The spatial-temporal changes of this land cover type were stable during these 11 years, and its dynamic variation degree was 1.82%. The change of moderate-degraded meadow was the most significant. During the period of 2006-2010, even the grassland in QLB was obviously improved; there was almost 7.4 ten thousand hectare of heavy-degraded meadow from moderate-degraded meadow, covering 65% area of land cover types from moderate-degraded meadow. Light-degraded meadow, moderate-degraded meadow and heavy-degraded grassland were dominantly located in northwest region of QLB, north and surrounding area of Qinghai Lake. The spatial changes of these three land cover types evolved from and into other types were the most significant, and their dynamic variation degree floated between 15% and 20% from the year 2006 to 2010.