Abstract:

Based on the meteorological data and k-drought index data for many years, this paper analyzes the characteristics of climate change and its drought background in Yelang Lake region, calculates the NDVI and MNDWI of the region by using the remote sensing data of four Landsat satellites in drought years (November 2009 -March 2010), and focuses on the impact of Yelang lake vegetation on drought events The effects of extreme drought on lake ecosystem are discussed. The results show that: (1) Yelang lake water reservoir and its surrounding areas show the climate characteristics of becoming cold and dry. The temperature shows a significant trend of becoming cold from 1995 to 2012 (R² = 0.54, P < 0.05), while the annual precipitation shows a trend of fluctuation and decline (R² = 0.42, P < 0.05). In 2009, the precipitation of Yelang lake is relatively rare since 1995, and it is also a severe drought year (K< 0.6). (2) When the k-drought index of the reservoir is less than 0.4 (extreme drought), NDVI and vegetation area show the characteristics of significant decline, that is, large-scale water shortage death. At the beginning of the drought, the reservoir has a certain regulating effect on the surrounding vegetation, basically maintaining the original level, and then the regulating capacity of the reservoir decreases, and the vegetation growth is extremely inhibited, resulting in large-scale death. However, due to the increase of evaporation and the decrease of precipitation, the water content of the reservoir surface is gradually lost and the area is gradually decreasing. (3) In the face of severe drought, the response ability of vegetation in lake ecosystem is relatively poor, the surface water is extremely scarce, the plant root system can not obtain the water to maintain its survival, and with the deepening of drought, a large area of death occurs. At the same time, the living space and resources of aquatic animals and plants in the reservoir are relatively reduced, the lake ecosystem is degraded and the ecosystem service value is reduced.

Key words: remote sensing, K drought index, NDVI, WNDWI, Yelanghu Reservoir, vegetation

摘要：

根据多年的气象资料和K干旱指数，分析了夜郎湖区域气候变化特征及其干旱背景，运用干旱年份（2009年11月—2010年3月）的4景Landsat卫星遥感数据计算了区域的归一化植被指数（NDVI）和修正的归一化水体指数（MNDWI），重点分析了夜郎湖植被对干旱事件的响应特征，并探讨了极端干旱事件对湖泊生态系统的影响。结果表明：（1）夜郎湖水库及其周边地区表现出变冷变干的气候特征，1995—2012年间气温呈显著变冷的趋势（R²=0.54，P<0.05），而年降水量表现出波动下降的趋势（R²=0.42，P<0.05）。2009年是夜郎湖自1995年以来降水相对稀少，同时也是干旱最为严重的年份（K<0.6）。（2）当水库的K干旱指数小于0.4（特旱）时，NDVI和植被面积呈显著下降的趋势即表现出大范围的缺水性死亡，干旱开始时水库对周边植被具有一定的调节作用，基本维持原有水平，之后水库调节能力下降，植被生长受到极度抑制，出现大范围的死亡。而水库水面因受到蒸发量增大与降水量减少的影响，水分逐渐丧失，面积呈逐渐递减的特征。（3）湖泊生态系统在面对特大干旱时植被的应对能力相对较差，地表水极其缺乏，植物根系无法获得维持其生存的水分，随着干旱程度的加深而大面积死亡。

关键词: 遥感, K干旱指数, NDVI, MNDWI, 夜郎湖水库, 植被