College of Geography Science, Changchun Normal University, Changchun 130032, China; Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China.
Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun 130102, China.
Sci Total Environ. 2022 Apr 20;818:151799. doi: 10.1016/j.scitotenv.2021.151799. Epub 2021 Nov 19.
The Heilong-Amur River Basin (HARB) in Northeast Asia has experienced distinct land surface changes during the past 40 years due to extensive ecological restoration programs, agricultural management, and grassland grazing in different ecosystems. However, the regional climate impact caused by the long-term spatially heterogeneous land surface changes in this mid-high latitude region is not well documented. Therefore, this study used multi-source satellite measurements records and a high-resolution land-atmosphere coupled regional climate model (WRF) to investigate the land surface changes and their associated thermal and moisture impacts across three main ecosystems over the Heilong-Amur River basin from 1982 to 2018. Firstly, satellite observations indicated an overall greening in HARB, with variations across ecosystems. The significant summer farmland greening is the most representative, with the farmland green vegetation fraction (GVF) remarkably increasing by 7.78% in summer. The forest greening magnitude is stronger in spring (3.42%) than in summer (2.85%), while the grassland vegetation showed some local browning signals in summer. Secondly, our simulated results showed the summer farmland greening accelerated evapotranspiration (ET) by 0.161 mm/d and significantly cools the surface temperature by 0.508 °C averaged at the ecosystem scale, which was highly correlated with the satellite observations but with lower cooling magnitude. The forest greening brought less surface cooling in spring than summer due to the stronger albedo feedback, despite with greater increase in GVF and ET. While with the opposite process, the local grassland browning leads to consistent warming effects, which can be detected from both satellite observations and our simulation results. Finally, our results also found that rainfall increasing averagely at the ecosystem scale can't fully compensate the water emission from enhanced ET due to the surface greening, contributing to soil moisture decline in both farmland and relative dry forests.
过去 40 年来，由于在不同生态系统中广泛开展了生态恢复计划、农业管理和草原放牧，东北亚的黑龙江流域经历了明显的地表变化。然而，由于中高纬度地区长期存在空间异质的地表变化，该地区的区域气候影响尚未得到很好的记录。因此，本研究利用多源卫星测量记录和高分辨率陆-气耦合区域气候模式（WRF），调查了 1982 年至 2018 年期间黑龙江流域三个主要生态系统的地表变化及其相关的热和湿度影响。首先，卫星观测表明，黑龙江流域整体呈绿化趋势，但不同生态系统的变化情况有所不同。夏季农田绿化的变化最为显著，农田绿植被分数（GVF）在夏季显著增加了 7.78%。森林的绿化程度在春季（3.42%）强于夏季（2.85%），而草原植被在夏季则出现了一些局部变褐的信号。其次，模拟结果表明，夏季农田绿化使蒸散（ET）加速了 0.161mm/d，并显著降低了生态系统尺度的地表温度 0.508°C，这与卫星观测高度相关，但降温幅度较低。森林的绿化在春季对地表的冷却作用小于夏季，这是由于较强的反照率反馈，尽管其 GVF 和 ET 的增加幅度更大。而相反的过程是，草原的局部变褐导致了一致的变暖效应，这可以从卫星观测和我们的模拟结果中都检测到。最后，我们的结果还发现，生态系统尺度上的平均降雨量增加并不能完全补偿由于地表绿化而增强的蒸散所导致的水分排放，这导致农田和相对干燥的森林土壤湿度下降。
