2000—2014年石羊河流域植被覆盖变化研究

Change of Vegetation Coverage in Shiyang River Basin 2000-2014

植被覆盖度是衡量地表植被长势和评价区域生态系统健康程度的重要指标,研究石羊河流域植被覆盖度的时空变化,对研究内陆干旱地区陆地生态系统环境变化具有重要意义。利用EOS/MODIS卫星数据,借鉴景观生态空间分布格局分析方法,从植被覆盖度面积变化和类型转换趋势方面分析2000—2014年石羊河流域植被的空间分布变化与格局演变。结果表明,2000—2014年石羊河流域内以低覆盖植被为主,其中极低覆盖植被年际波动最大,中高覆盖植被年际波动最小。在2001年、2004年、2009年和2013年前后,石羊河流域出现了4次植被生态退化过程。4种土地生态类型的植被覆盖度在年际变化中均呈增加趋势,其中耕地植被生态恢复明显,未利用土地生态恢复比较缓慢。15年石羊河流域内生态向恢复的方向发展。前期与后期的各植被覆盖等级的面积转移途径与幅度基本相似,后期的生态变化程度比前期更加剧烈。植被覆盖变化多集中在人类活动较多的区域。植被生态变化以稳定和轻微恢复为主。各土地生态类型中,耕地植被覆盖度空间变化最大。水资源的空间分布和利用不均是导致植被覆盖变化的空间分布不均的主要因素,中游平原区生态恢复较好,下游民勤绿洲在2010年后的生态退化明显。

Vegetation coverage is an important indicator to measure vegetation growing and evaluate regional ecosystem health. It is of great significance to study the temporal and spatial changes of vegetation coverage in the Shiyang River Basin for the research on environmental changes of terrestrial ecosystem in inland arid areas of China. Based on the EOS/MODIS satellite data and the analysis of landscape ecological spatial distributioh patterns, the evolution of spatial distribution and pattern of vegetation in the Shiyang River Basin during the period of 2000-2014 were analyzed by the change of vegetation coverage area and the trend of type conversion. The results showed that the vegetation coverage in the Shiyang River Basin was mainly low vegetation coverage type from 2000 to 2014, the very low vegetation coverage＇ fluctuation was the most intense and the mid-high vegetation coverage＇ fluctuation was the least. The Shiyang River Basin vegetation ecological degradation process appeared four times in 2001, 2004, 2009 and 2013. Vegetation coverage in four land cover types showed an increasing trend in inter-annual variation, ecological restoration of farmland vegetation was evident, ecological restoration of unused land was relatively slow. The ecological quality of the Shiyang River Basin was restored in recent 15 years. The area transfer paths and the amplitudes of all the vegetation cover grades were similar between the early stage （2000-2009） and late stage （2005-2014）, and the ecological restoration degree of the late stage was more severe than that of the early one. The change of vegetation coverage was concentrated in the areas with more human activities. Ecological changes of vegetation were mainly stable and slight recovery. Among several land cover types, the spatial change of farmland vegetation coverage was the largest. The spatial distribution and unequal use of water resources were the main factors leading to the uneven spatial distribution of vegetation coverage change. The ecological restoration in the middle reaches plain area was better, and the ecological degradation was significant in Minqin oasis after 2010.