2000—2021年长江流域植被NPP特征及对气候变化的响应

Characteristics of Vegetation NPP and Response to Climate Change in the Yangtze River Basin from 2000 to 2021

长江流域是我国土壤保持和水源涵养的重要功能区,植被净初级生产力(net primary productivity,NPP)是陆地生态系统碳收支的重要指标,研究长江流域植被NPP变化特征和主要驱动因素,对于实现碳中和目标、改善生态系统功能具有重要指导意义。基于中分辩成像光谱仪(moderate-resolution imaging spectroradiometer,MODIS)数据和气象观测数据,利用Theil-Sen趋势分析、Mann-Kendall检验等方法,结合Thornthwaite Memorial气候模型,分析2000—2021年长江流域植被NPP时空变化特征,并定量评估气候变化和人类活动在其变化中的相对作用,研究结果表明:(1)2000—2021年植被NPP年均值为552.2 gC/m^(2);时间上波动增加,增率为3.71 gC/(m^(2)·a);空间上呈东部大于西部、南部大于北部的分布特征,城市化程度较高的成渝经济区、中游城市群和长三角地区植被NPP小于周边。(2)植被NPP与年降水量、年平均气温总体呈正相关。(3)长江流域大部植被对气候资源的利用率小于50%,大于50%的区域主要分布在青藏高原向四川盆地和向云贵高原过渡的地带。(4)气候变化和人类活动在长江流域植被NPP变化过程中的相对作用存在显著的时空差异性。气候因素主导的植被NPP变化区域最大,面积占比达55.15%,其中95.99%的区域植被NPP增加。人类活动主导的植被NPP变化区域面积占比为24.22%,其中82.08%的区域NPP减少,过度开垦、城市扩张是植被NPP减少的重要原因。

The Yangtze River basin is an important functional area for soil conservation and water conservation in China.Vegetation net primary productivity(NPP)is an important indicator of the carbon budget of terrestrial ecosystems.Studying the changing characteristics and main driving factors of vegetation NPP in the Yangtze River basin has important guiding significance for achieving the goal of carbon neutrality and improving ecosystem functions.Based on data from Moderate-Resolution Imaging Spectroradiometer(MODIS)and meteorological stations,using Theil-Sen trend analysis,Mann-Kendall test and other methods,combined with Thornthwaite Memorial climate model,the temporal and spatial variation characteristics of vegetation NPP in the Yangtze River basin from 2000 to 2021 were analyzed,and the relative role of climate change and human activities in its change was quantitatively evaluated.The results showed that:(1)The annual average NPP of vegetation from 2000 to 2021 was 552.2 gC·m^(-2).The fluctuation in time increased,with an increase rate of 3.71 gC·m^(-2)·a^(-1).Spatially,the eastern part was larger than the western part,and the southern part was larger than the northern part.The vegetation NPP in the Chengdu-Chongqing Economic Zone,the middle reaches of the urban agglomeration and the Yangtze River Delta region with a higher degree of urbanization was smaller than that in the surrounding areas.(2)Vegetation NPP was positively correlated with annual precipitation and annual average temperature.(3)The utilization rate of vegetation to climate resources in most of the Yangtze River basin was less than 50%,and more than 50% of the area was mainly distributed in the transition zone from the Qinghai-Tibet Plateau to the Sichuan Basin and to the Yunnan-Guizhou Plateau.(4)The relative role of climate change and human activities in the process of vegetation NPP change in the Yangtze River basin had significant spatial and temporal differences.The area of vegetation NPP changing dominated by climatic factors was the largest,accounting for 55.15%.In 95.99% of the regional dominated by climatic factors,the NPP of vegetation increased.The area of vegetation NPP changing area dominated by human activities accounted for 24.22%.In 82.08% of the areas dominated by human activities,the NPP of vegetation decreased.Excessive reclamation and urban expansion were important reasons for the decrease of vegetation NPP.