1996-2015年巴音布鲁克天鹅湖高寒湿地景观格局演变分析

Landscape Pattern Changes in Alpine Wetland of Bayanbulak Swan Lake during 1996-2015

干旱区高寒湿地是极端条件下形成的特殊生态系统,其景观格局演变受众多学者的关注。论文以1996、2006、2010年TM,2000年ETM和2015年OLI五个时期遥感影像为数据源,分析了近20 a巴音布鲁克天鹅湖高寒湿地景观格局演变特征及其与气候因子的关系。结果表明:1)近20 a,湿地面积总体呈下降趋势,减幅为5.62%,减速为1.91 km2/a。湿地面积变化以2010年为分水岭,前15 a湿地面积较为稳定,占研究区总面积的比例在77.24%～78.26%之间波动;近5 a湿地面积呈缓慢萎缩趋势,面积比例减少5.28%。2)景观水平上,景观破碎度增大,空间异质性增强,斑块形状趋于复杂;类型水平上,湿地斑块破碎度增加,形状趋于复杂,呈集中分布。3)当日最高气温低于18.7℃时,随日最高气温的增加,湿地面积趋于稳定,破碎度变化不明显;当日最高气温高于18.7℃时,随日最高气温的增加,湿地面积萎缩,破碎度增加。日最高气温对巴音布鲁克天鹅湖高寒湿地景观格局演变影响明显大于年降水量。近20 a巴音布鲁克天鹅湖高寒湿地呈现退化态势,湿地环境趋于逆向演变趋势。

The changes in landscape pattern of alpine wetland ecosystem, one of the special ecosystems in arid areas, attracted global attentions. The objective of this study was to analyze the landscape pattern changes and the relationship between the changes and climate factors in the alpine wetland of Bayanbulak Swan Lake during 1996-2015. Five remote sensing images, including three TM images in 1996, 2006 and 2010, one ETM image in 2000 and one OLI image in 2015 were used. Results showed that: 1) The area of the wetland decreased by 5.62% during 1996~2015 with a loss rate of 1.91 km2/a. The changes of the wetland area can be divided into two periods by 2010. The changes were very small before 2010 and the percentage of wetland area in Bayanbulak Swan Lake ranged from 77.24% to 78.26%. After 2010, the wetland area continued decreasing at a low speed and the area decreased by 5.28%. 2) At the landscape level, the landscape fragmentation and the spatial heterogeneity increased during 1996-2015. At the same time, the shape of patches tended to be complex. At the class level, the fragmentation of wetland patches increased and the shape of patches tended to be complex. 3) Average daily maximum air temperature had much greater effect on the landscape pattern changes in Bayanbulak Swan Lake wetland than average annual precipitation. The area of the wetland tended to be stable with the increase of the daily maximum temperature and the changes of fragmentation degree were not obvious when the daily maximum temperature was below 18.7 ℃. In contrast, the area of wetland decreased and the fragmentation increased with the increase of the daily maximum temperature when the daily maximum temperature was over 18.7 ℃. These results indicated that the wetland in Bayanbulak Swan Lake degraded and the environment of the wetland became worse during 1996-2015.