2000—2020年我国西南地区植被NEP时空变化及其驱动因素的相对贡献

西南地区作为我国重要的生态安全屏障，探究其植被净生态系统生产力(net ecosystem productivity,NEP)的时空演变规律对该地区乃至我国的可持续发展都具有重要意义.基于MODIS数据、气象数据、DEM数据和土地利用数据等，首先，利用改进的Carnegie Ames Stanford Approach (CASA)模型和土壤微生物呼吸方程，估算2000—2020年我国西南地区植被NEP；其次，结合Theil-Sen Median趋势分析、偏相关分析和复相关分析等方法，研究西南地区植被NEP时空变化及其对气候变化和土地利用变化的响应机制；最后，利用基于情境分析的相对贡献分析法，定量评估气候变化和土地利用变化对西南地区植被NEP变化的相对贡献.结果表明：时间上，2000—2020年我国西南地区及其五省份(云南省、贵州省、四川省、重庆市和西藏自治区)生态系统植被NEP均表现为上升趋势，其中，西南地区植被NEP上升速率为4.74 g/(m2·a).空间上，西南地区及其五省份植被NEP呈上升趋势的面积均大于呈下降趋势的面积，其中，西南地区植被NEP呈极显著上升的面积占45.41...

Spatio-Temporal Variation of Vegetation Net Ecosystem Productivity and Relative Contribution of Driving Forces in Southwest China from 2000 to 2020

Southwest China is regarded as an important ecological security barrier in China. Net ecosystem productivity (NEP) is an important parameter for characterizing terrestrial ecological carbon sources/sinks. Therefore, exploring the dynamic variation of vegetation NEP is of great importance to scientifically assess the capability of terrestrial ecosystem carbon sequestration and to formulate strategies for dealing with global climate change and land use change to achieve the economy and society sustainable development goals. The vegetation NEP in southwest China from 2000 to 2020 was firstly calculated on the basis of MOD13A3/MCD12Q1 data, meteorological data, DEM data, and land use data using the upgraded Carnegie Ames Stanford Approach Model (CASA) and the soil microbial respiration equation. The spatial and temporal variation of vegetation NEP and its responding mechanisms to climate change and land use change were then explored using Theil-Sen Median trend analysis, partial correlation coefficient, and multi correlation coefficient. Therefore, the relative contributions of climate change and land use change to vegetation NEP variation were quantitatively distinguished using relative contribution analysis. Results showed that, on the temporal scale, the annual vegetation NEP showed increasing trends both on the regional and provincial scales. Among them, the vegetation NEP increased at 4.74 g/(m2·a) in southwest China for the study period, and the increasing trends in the Yunnan and Guizhou were 10.47 and 9.34 g/(m2·a), respectively, which were larger than those in other provinces. On the spatial scale, the areas with increasing trends were larger than the areas with decreasing trends both on the regional and provincial scales. In addition, the areas with a rising tendency of vegetation NEP accounted for 45.41% in southwest China, distributed in the south of Yunnan, west of Guizhou, east of Sichuan, and south of Chongqing. The areas with positive correlation between the vegetation NEP and precipitation were larger than those between the vegetation NEP and temperature as well as the vegetation NEP and solar radiation in southwest China, indicating a stronger promoting effect of precipitation on the vegetation NEP variation than that of temperature and solar radiation. The vegetation NEP variation was mainly driven by the weak combination effect of temperature, precipitation, and solar radiation, which accounted for 23.63% of the study areas. The total vegetation NEP had increased by 96.64 Tg in southwest China from 2000 to 2020 due to land use transformation, in which, the transformation of unused land to forest land had mostly promoted the vegetation NEP increase. In the carbon source areas, land use change contributed the most to the vegetation NEP variation in built-up land (69.38%). However, in the carbon sink areas, climate change contributed the most to the vegetation NEP variation in cultivated land (50.08%). The research results indicated that the ecosystems of southwest China exhibit carbon sinks from 2000 to 2020, and the carbon sink function tends to be enhanced, with climate change and land use change jointly influencing the carbon sink function in Southwest China.