Spatiotemporal variations and driving mechanisms of carbon sinks in Populus euphratica Oliv. forests in China from 2000 to 2023

It is essential to accurately assess the carbon sink of Populus euphratica Oliv. (P. euphratica) forests, given their long-term sequestration ability, to understand the carbon balance in arid zones, yet quantitative studies are still lacking globally. This study applied an optimised Carnegie–Ames–Stanford Approach (CASA) incorporating biomass and unmanned aerial vehicle (UAV) data to examine the spatiotemporal heterogeneity of the net ecosystem productivity (NEP) in China’s P. euphratica forests during 2000–2023 and to analyse the impacts of climatic factors, Ecological Water Conveyance (EWC) and land-use changes. Results show that: (1) overall, NEP demonstrated a volatile upward trend notwithstanding a post-2017 downturn, with seasonal maxima in summer and minima in winter; (2) significant spatiotemporal heterogeneity in NEP was observed, with contrasting trends of increase in the Tarim, Aksu, and Heihe River basins but decrease in the lower Qarqan River; (3) human activities have now surpassed climatic factors as the primary driver of increased NEP in poplar forests, with EWC benefiting 90 % of the implementation areas; (4) the cumulative NEP of China's P. euphratica forests increased by 1200.38 Gg C over the last 20 years, largely attributable to land-use change from unused land to P. euphratica forests and cropland. This research provides a robust NEP estimation, clarifies its spatiotemporal patterns and driving mechanisms, and demonstrates that poplar forests serve as significant carbon sinks in arid regions. These findings support the development of evidence-based conservation strategies and China’s ‘dual carbon’ goals.