黑河下游荒漠河岸植被空间格局的动态特征及对生态输水的响应

Desert riparian vegetation plays a key role in maintaining ecosystem stability in inland river basin. Ecological water conveyance improved the growth and distribution of desert riparian vegetation, however, vegetation degenerated in some areas due to human activities and climate change. Therefore, it was important to elaborate the spatial pattern and dynamic characteristics of desert riparian vegetation and to reveal its driving mechanism. The lower Heihe River Basin was selected as the research area in this project. Long time series of hydro-meteorological data and remote sensing data were collected, and the ground survey, remote sensing interpretation and inversion, mapping and statistical analysis were conducted. This project was to analyze the dynamic characteristics of vegetation community away from the river bank from the transect scale, and to obtain the vegetation spatial distribution in regional scale, and then the spatial pattern and dynamic characteristics of desert riparian vegetation were clarified. The spatial pattern of desert riparian vegetation was compared before and after ecological water conveyance, and the relationship between spatial pattern of vegetation and hydro-meteorological factors was established to reveal the driving mechanism of spatial variation of desert riparian vegetation and its response to ecological water conveyance. This study is helpful to understand the driving mechanism of spatial variation of desert riparian vegetation, and can provide scientific basis for water resources management in the arid inland river basin.

荒漠河岸植被对维持内陆河流域生态系统稳定性具有关键作用。生态输水改善了荒漠河岸植被的生长和分布状况，但受人类活动和气候变化影响，部分区域植被出现一定退化。精细刻画荒漠河岸植被的空间格局与动态变化特征并揭示其驱动机制具有重要意义。本项目以黑河下游为研究区，基于长时间序列的水文气象数据和遥感影像资料，综合运用地面调查、遥感解译与反演、空间制图和统计分析等方法，在样带尺度分析垂直河岸不同距离荒漠河岸植被群落结构的动态特征，得到区域尺度植被高精度空间分布图，阐明荒漠河岸植被的空间格局与动态变化特征，比较生态输水前后荒漠河岸植被空间格局变化，建立植被空间格局特征与水文气象要素的定量关系，揭示荒漠河岸植被动态变化的影响机制及对生态输水的响应。本研究有助于深刻理解荒漠河岸植被空间动态变化的驱动机制，也可为干旱内陆河水资源管理提供科学依据。

植被是陆地生态系统的重要组成部分，在气候、水文和生物圈物质循环等方面起着重要作用，是反映地区的生态环境状况的重要因子。植被的变化在一定程度上反映出土地覆盖的变化和气候变化的趋势。干旱半干旱地区生态环境尤为脆弱，以黑河下游额济纳绿洲为例，计算了2000-2020年来额济纳绿洲的植被指数以及温度降水和径流对其的影响程度，分析得到20年间额济纳绿洲土地利用类型变化特点，基于GEE平台利用LandTrendr算法计算绿洲植被变化折点。本项目研究显示，2000-2020年，黑河下游额济纳绿洲植被NDVI值呈上升趋势，对该地区NDVI变化贡献最大的气象水文因子是径流，相对贡献率达到64%，其次是降水23%，气温14%。研究区植被面积扩大，生态环境有所好转，但是耕地扩张面积多于林地灌木草地等土地类型，植被退化现象一直存在。2015年以来，植被退化面积2015年有逐年增多的趋势。