定量评估气候变化和人类活动对澜沧江流域植被动态的影响

Quantitatively assessing the impacts of climate change and human activities on vegetation dynamics in the Lancang River Basin

摘要

【目的】植被对水沙平衡、生源要素交换、生态系统稳定等方面具有重要影响。澜沧江是中国西南地区重要的水利工程和水资源调节中心，其植被动态事关流域防洪安全、供水安全和生态安全。【方法】以澜沧江流域为研究区域，利用1998—2020年时间序列气象、归一化植被指数(Normalized Difference Vegetation Index,NDVI)等数据，结合Mann-Kendall趋势检验和Sen’s Slope斜率估计，分析了澜沧江流域植被动态的时空变化差异，并采用偏最小二乘法结构方程模型定量评估气候变化和人类活动对澜沧江流域植被动态的影响。【结果】1998—2020年期间，澜沧江流域NDVI生长季年变化速率为0.004 2/a,呈显著增长趋势，其中青海和西藏段变化速率为0.002 0/a,云南段为0.005 3/a。流域内植被明显改善的区域占比高于40%,严重退化的区域占比低于5%,春、夏、秋三季NDVI也均呈现显著增长，其中春季增长最快，夏季增长最慢。青海和西藏段增长速率最快的季节为夏季，春季的增长速率最低；云南段增长速率最快季节为春季与秋季，夏季增长速率相对最低。地形因素对植被的平均影响量为-0.085,人类活动对植被的平均影响量为0.009,气候因素对植被的平均影响量为0.451。【结论】气温目前是影响研究区植被生长的主要气候因子，人类活动对植被动态的影响较为微弱，地形因素通过调节气候因素间接影响植被生长。

Abstract

[Objective] The impact of vegetation on aspects such as water-sediment balance, exchange of biogenic elements, and ecosystem stability is considered important. The Lancang River is regarded as an important water conservancy project and water resources regulation center in southwest China, with its vegetation dynamics being deemed crucial for flood safety, water supply security, and ecological security in the basin.[Methods] The study area was focused on the Lancang River Basin. Utilizing time series meteorological data from 1998 to 2020, as well as Normalized Difference Vegetation Index(NDVI) data, the spatial-temporal variations of vegetation dynamics in the Lancang River Basin were analyzed. The analysis included the utilization of the Mann-Kendall trend test and Sen's Slope estimation, and the impacts of climate change and human activities on vegetation dynamics in the Lancang River Basin were quantitatively assessed using the Partial Least Squares Structural Equation Model.[Results] During the period from 1998 to 2020, it was observed that the annual growth rate of NDVI during the growing season in the Lancang River Basin was 0.004 2/year, indicating a significant increasing trend. The growth rates in the Qinghai and Tibet sections were 0.002 0/year and in the Yunnan section was 0.005 3/year. It was noted that the proportion of regions with significantly improved vegetation in the basin exceeded 40%, while regions with severe degradation were less than 5%. Furthermore, it was found that the NDVI in spring, summer, and autumn all exhibited significant growth, with the fastest growth being observed in spring and the slowest in summer. The fastest growth season in the Qinghai and Tibet sections was summer, with the slowest growth occurring in spring. In the Yunnan section, the fastest growth seasons were spring and autumn, with relatively slower growth in summer. The average impact of terrain factors on vegetation was-0.085, human activities were found to have an average impact of 0.009, and climate factors were noted to have an average impact of 0.451.[Conclusion] Currently, temperature is considered to be the main climate factor affecting vegetation growth in the study area, with human activities being identified as having a relatively weak impact on vegetation dynamics. It was also observed that terrain factors indirectly affect vegetation growth by regulating climate factors.

关键词

降水 / 气温 / 人类活动 / 归一化植被指数 / 澜沧江流域 / 偏最小二乘法结构方程模型 / 时空变化

Key words

precipitation / temperature / human activities / NDVI / Lancang River Basin / PLS-SEM / spatiotemporal variation

基金资助

国家自然科学基金(52209013)

河北省自然科学基金(E2024402142)

中国水利水电科学研究院流域水循环模拟与调控国家重点实验室开放研究基金(IWHR-SKL-202214)