Department of Cartography, GIS and Remote Sensing, Institute of Geography, University of Goettingen, 37077 Goettingen, Germany.
Biogeochemistry of Agroecosystems, University of Goettingen, 37077 Goettingen, Germany.
Sensors (Basel). 2022 Mar 25;22(7):2509. doi: 10.3390/s22072509.
Vegetation in Northeast China (NEC) has faced dual challenges posed by climate change and human activities. However, the factors dominating vegetation development and their contribution remain unclear. In this study, we conducted a comprehensive evaluation of the response of vegetation in different land cover types, climate regions, and time scales to water availability from 1990 to 2018 based on the relationship between normalized difference vegetation index (NDVI) and the standardized precipitation evapotranspiration index (SPEI). The effects of human activities and climate change on vegetation development were quantitatively evaluated using the residual analysis method. We found that the area percentage with positive correlation between NDVI and SPEI increased with time scales. NDVI of grass, sparse vegetation, rain-fed crop, and built-up land as well as sub-humid and semi-arid areas (drylands) correlated positively with SPEI, and the correlations increased with time scales. The negatively correlated area was concentrated in humid areas or areas covered by forests and shrubs. Vegetation water surplus in humid areas weakens with warming, and vegetation water constraints in drylands enhance. Moreover, potential evapotranspiration had an overall negative effect on vegetation, and precipitation was a controlling factor for vegetation development in semi-arid areas. A total of 53% of the total area in NEC showed a trend of improvement, which is mainly attributed to human activities (93%), especially through the implementation of ecological restoration projects in NEC. The relative role of human activities and climate change in vegetation degradation areas were 56% and 44%, respectively. Our findings highlight that the government should more explicitly consider the spatiotemporal heterogeneity of the influence of human activities and water availability on vegetation under changing climate and improve the resilience of regional water resources. The relative proportions and roles map of climate change and human activities in vegetation change areas provide a basis for government to formulate local-based management policies.
中国东北地区（NEC）的植被面临气候变化和人类活动的双重挑战。然而，主导植被发展的因素及其贡献仍不清楚。在这项研究中，我们基于归一化差异植被指数（NDVI）与标准化降水蒸散指数（SPEI）之间的关系，综合评估了 1990 年至 2018 年不同土地覆盖类型、气候区和时间尺度下水对植被响应的变化。采用残差分析方法定量评价了人类活动和气候变化对植被发展的影响。结果表明，NDVI 与 SPEI 呈正相关的面积百分比随时间尺度的增加而增加。草地、稀疏植被、雨养作物和建成区以及半湿润和半干旱地区（旱地）的 NDVI 与 SPEI 呈正相关，且相关性随时间尺度的增加而增加。负相关区主要集中在湿润地区或森林和灌木覆盖的地区。湿润地区植被水分盈余随变暖而减弱，干旱地区植被水分约束增强。此外，潜在蒸散量对植被整体呈负效应，降水是半干旱地区植被发育的控制因素。NEC 总面积的 53%表现出改善趋势，主要归因于人类活动（93%），特别是在 NEC 实施生态恢复项目。人类活动和气候变化在植被退化区的相对作用分别为 56%和 44%。研究结果表明，政府应更明确地考虑人类活动和水资源可用性对变化气候下植被的时空异质性影响，并提高区域水资源的恢复力。气候变化和人类活动在植被变化区的相对比例和作用图为政府制定基于地方的管理政策提供了依据。
