As components of terrestrial carbon sinks, vegetation and soil carbon pools are important for offsetting CO₂ emissions. However, differences in their carbon sequestration capacities and their responses to global change in the future are poorly understood. This study assessed the changes in vegetation and soil carbon and their ratios and drivers under the SSP126 scenario from 2015 to 2060, using Coupled Model Intercomparison Project phase 6 simulations in China, a major carbon sink region in global terrestrial ecosystems. The content of vegetation carbon (29 ± 1 PgC) was observed to be lower than that of soil carbon (113 ± 23 PgC), and the ratio of vegetation to soil carbon was the highest in the subtropical-tropical monsoon climatic region (0.55 ± 0.12). Moreover, the total stock of vegetation and soil carbon increased by 10 ± 1 PgC during the study period, and the increase in vegetation carbon was 4.31 times that of soil carbon, because the responses of vegetation carbon stocks to increased forest coverage and atmospheric CO₂ were greater than that of soil carbon stocks, especially in the subtropical-tropical and temperate monsoonal climatic regions. However, bare land encroachment on grasslands reduced their increments in the temperate monsoonal and high-cold Tibetan Plateau climatic regions. Furthermore, compared with SSP245 and SSP585 scenarios, vegetation and soil carbon sinks can offset a greater amount of carbon emissions in 2060 under the SSP126 scenario, accounting for 53% of all carbon emissions, offsetting 60%–79% of carbon emissions from China under its policy of increasing forest coverage. The study revealed the important role of afforestation in increasing ecosystem carbon stocks, additionally, grassland conservation and deep reductions in carbon emissions cannot be ignored in the future. This study provides a basis for determining the response of vegetation and soil carbon to environmental factors and the realization of net-zero emissions globally.

The large variation in net ecosystem productivity (NEP) with forest age was dominated by the dynamics of net primary productivity (NPP)–which in turn was determined by the different response slopes of gross primary productivity (GPP) and autotrophic respiration (Ra) with forest age. However, only few models can comprehensively represent the impacts of forest age and global changes including land‐use change, climate change, nitrogen deposition, and atmospheric CO₂ from the perspective of ecological processes. Based on a process‐based model (CEVSA‐ES) that included these global changes, we developed an ecosystem carbon sink assessment model considering forest age dynamics (CEVSA‐AgeD) using satellite‐based relationships between GPP (or Ra) and forest age to constrain photosynthesis and autotrophic respiration processes. Subsequently, we used a model data‐fusion framework combined with carbon flux observations to calibrate the model. The calibrated CEVSA‐AgeD model performed well in simulating seasonal (R² values for GPP, ecosystem respiration, and NEP were 0.86, 0.79, and 0.66, respectively) and annual carbon flux changes (R² of GPP, ecosystem respiration, and NEP were 0.83, 0.77, and 0.67, respectively). The magnitude of average NEP in China estimated using this model was 0.35 ± 0.005 TgC/yr from 2001 to 2021, which was close to previous estimates, and the dynamics of forests age increased NEP by 87–92 TgC/yr. These results indicate that the CEVSA‐AgeD model performed well in simulating carbon fluxes at the site and regional scales and that it was necessary to incorporate the effect of forest age dynamics on carbon cycling processes into process‐based models.

Previous studies of vegetation dynamics in the Yellow River Delta (YRD) predominantly relied on sparse time series or coarse-resolution images, which not only overlooked the rapid and spatially heterogeneous changes, but also limited our understanding of driving mechanisms. Here, employing spatiotemporal data fusion methods, we constructed a novel fused enhanced vegetation index (EVI) dataset with a high spatiotemporal resolution (30-meter and 8-day resolution) for the YRD from 2000 to 2020, and we analyzed the vegetation variations and their driving factors within and outside the YRD Nation Natural Reserve (YRDNRR). The fused EVI effectively captured spatiotemporal vegetation dynamics. Notably, within the YRDNRR core area, the fused EVI showed no significant trend before 2010, while a significant increase emerged post-2010, with an annual growth of 7%, the invasion of Spartina alterniflora explained 78% of this EVI increment. In the YRDNRR experimental area, the fused EVI exhibited a distinct interannual trend, which was characterized by an initial increase (2000–2006, p < 0.01), followed by a subsequent decrease (2006–2011, p < 0.01) and, ultimately, a renewed increase (2011–2020, p > 0.05); the dynamics of the fused EVI were mainly affected by the spring runoff (R² = 0.71), while in years with lower runoff, it was also affected by the spring precipitation (R² = 0.70). Outside of the protected area, the fused EVI demonstrated a substantial increase from 2000 to 2010 due to agricultural land expansion and human management practices, followed by stabilization post-2010. These findings enhance our comprehension of intricate vegetation dynamics in the YRD, holding significant relevance in terms of wetland preservation and management.