Natural vegetation coverage in arid regions is valuable to climatic change and human activities, while the shrinkage of vegetation causes complex changes in the structure, function, and carbon sinks/sources of the surrounding ecosystems. The regional drought and heat may reduce plant productivity that need several years to cancel the net uptake of atmospheric CO 2. The expansion of dryland and erosion-induced land degradation may reduce the soil organic carbon storage and increase emission of carbon into the atmosphere. These changes have a great influence on carbon balance in artificial vegetation, and the disturbed natural vegetation. Human activities have quenched river runoffs, decreased groundwater levels, accelerated desertification, and changed spatiotemporal patterns of land use. The eco-environment is undergoing drastic changes, such as soil erosion, land salinization, farmland desertification, sharp reduction in green corridors, and ecosystem degeneration. Under a warming climate scenario that is exacerbated by human activities, the drylands continue to expand, intensifying the desertification process. The scientific outcomes of this study are of great importance for maintaining ecological stability and sustainable economic development along China’s Silk Road Economic Belt. Recent positive trends in NDVI, FVC and NPP have enhanced the capacity of vegetation carbon sinks, and improved the eco-environment of NWC. Specifically, the RSEI increased from 0.34 to 0.49, the NDVI increased by 0.03 (17.65%), the FVC expanded by 19.56%, and the NPP increased by 27.44%. The entire ecological security of NWC was enhanced during the study period. The vegetation NEP in the mountain exhibited only intermittent changes (2.55 gC m −2 yr −1) during 2000–2020 it exhibited a negative trend during 2000–2010, but this trend has reversed strongly since 2010. The vegetation NEP in the plains exhibited a positive trend (1.21 gC m −2 yr −1) during 2000–2020, but this speed has slowed since 2010. Some 65.78% of the vegetation areas in NWC were carbon sources during 2000–2020, which were concentrated in the plains, and SXJ, the majority carbon sink areas are located in the mountains. Obvious geographically heterogeneous distributions and changes occurred in vegetation carbon sinks and carbon sources. Spatially, the annual NEP in northern Xinjiang (NXJ), southern Xinjiang (SXJ) and Hexi Corridor (HX) increased at even faster rates of 2.11, 2.22, and 1.98 gC m −2 yr −1, respectively. The results show that the annual average carbon capacity of vegetation in NWC changed from carbon sources to carbon sinks, and the vegetation NEP increased at a rate of 1.98 gC m −2 yr −1 from 2000 to 2020. It quantitatively evaluates regional ecological security over a 20-year period (2000–2020) via a remote sensing ecological index (RSEI) and other ecological indexes, such as the Normalized Difference Vegetation Index (NDVI), fraction of vegetation cover (FVC), net primary productivity (NPP), and land use. This study analyzes the spatio-temporal patterns of vegetation carbon sinks and sources in the arid region of northwest China (NWC), using the net ecosystem production (NEP) through the Carnegie–Ames–Stanford approach (CASA). Drylands, which account for 41% of Earth’s land surface and are home to more than two billion people, play an important role in the global carbon balance.
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