Spatiotemporal patterns and driving mechanisms of terrestrial carbon sinks in Jiangxi Province, subtropical China

BACKGROUND: Understanding the spatiotemporal dynamics of terrestrial ecosystem carbon sinks, as well as the underlying driving mechanisms, is crucial for guiding regional carbon neutrality policies. Using Moderate Resolution Imaging Spectroradiometer (MODIS) remote sensing data, field measurements data, and multi-source environmental data, we estimated net primary productivity in subtropical zone from 2000 to 2020 with the Carnegie-Ames-Stanford approach (CASA) model, and assessed net ecosystem production (NEP) by subtracting heterotrophic respiration. Regression analysis, coefficient of variation, Hurst exponent, and geodetector were applied to examine the spatiotemporal patterns and driving forces of NEP. RESULTS: The results identified distinct spatial heterogeneity in NEP across the study area, characterized by a west-south high and east-low gradient, with moderate levels in the north. The NEP exhibited positive persistence (H > 0.5) in 73.2% of the study area. Notably, natural forest areas showed strong persistent improvement (H > 0.65), whereas the Chang-Jiu urban agglomeration was characterized by strong persistent degradation (H < 0.35). The elevation range of 550-750 m exhibited the peak carbon sink capacity (345.6 g C m⁻² year⁻¹); Normalized difference vegetation index and elevation, with the q value of 0.37 and 0.34 respectively, were identified as the key individual factors influencing NEP variation. The strongest interactive effect on NEP variation was detected between soil type and land use type (q = 0.586). This evidence, combined with the impact of the climate-land use interaction on NEP, implies that synergistic management of these factors could enhance carbon sink potential. CONCLUSIONS: Our research reveals that the carbon sink dynamics in subtropical zone are governed by the interaction of topographic, climate, and human activity. Future efforts must implement zonal management strategies (e.g., conserving mountainous areas and promoting forest-grain intercropping on plains) to bolster forest carbon sinks.