基于GEE和BRT的1984—2019年长三角生态绿色一体化发展示范区植被覆盖度变化

Vegetation coverage change of the demonstration area of ecologically friendly development in the Yangtze River Delta, China based on GEE and BRT during 1984-2019

长三角生态绿色一体化发展示范区是国家重大战略的区域,生态环境保护是该区域发展的优先本底。探究植被覆盖度(FVC)时空变化有利于更准确地认识生态环境质量状况,对区域绿色可持续发展具有重要意义。本研究基于Google Earth Engine(GEE)云平台,分析了一体化示范区1984—2019年植被覆盖的时空变化特征和变化趋势,并基于增强回归树(BRT)量化不同生态因子对FVC的影响。结果表明:1984—2019年间,研究区域植被覆盖整体呈先减少后增加的趋势。研究区域植被覆盖空间分布具有阶段性和区域性的特征。植被覆盖以退化为主,相较于1984年,2019年覆被退化和改善的区域面积占比分别为49.8%和12.8%。其中,覆被退化主要发生于吴江北部、嘉善南部和青浦东北部。人类活动完全削弱了自然因素对FVC的影响。基于研究结果,提出GEE平台是实现植被覆盖常态化监测的有效工具。

The demonstration area of ecologically friendly development in the Yangtze River Delta is a major national strategy area, and thus eco-environmental protection should be a priority for the sustainable development. Exploring the spatial-temporal variations of franctional vegetation coverage(FVC) is conducive to accurate assessing the ecological quality of environment, which is of great significance to regional sustainable development. In this study, the characteristics and trends of spatial-temporal variation of vegetation cover during 1984-2019 in the demonstration area were analyzed based on Google Earth Engine(GEE). The effects of different ecological factors on FVC were quantified by the boosted regression tree(BRT). Results showed that, the changing trend of FVC in the study area shifted from decreasing to increasing trend from 1984 to 2019. The spatial distribution of FVC in the study area varied with both stages and regions. FVC was mainly degraded. Compared with the year 1984, the area of vegetation degradation and improvement in 2019 accounted for 49.8% and 12.8%, respectively. The vegetation degradation mainly occurred in the north of Wujiang, south of Jiashan, and northeast of Qingpu. Human activities severely weakened the influence of natural factors on FVC. Our findings suggested that the GEE is an effective tool for monitoring the dynamics of vegetation coverage.