[Response of Carbon Storage Evolution to Future Climate and Policy at the Basin Scale]

In this study, we explored the impact of land-use changes on carbon sinks in terrestrial ecosystems from a watershed perspective under the backdrop of "carbon peak and neutrality." This will provide robust support for scientific decision-making and the sustainable development of integrated watershed management. Watershed ecosystems encompass natural, social, and economic dimensions and are crucial for improving regional ecological quality and ensuring sustainable development. The Dongting Lake Basin （DLB） is situated at the junction of China's Yangtze River Economic Belt and Coastal Economic Belt, playing an important role in maintaining ecological balance and coordinating economic development. In recent years, rapid economic growth, prolonged agricultural activities, and substantial population pressure have accelerated wetland degradation, the expansion of construction land, and the reduction of ecological land within the basin. Consequently, this has led to a decline in the carbon sequestration capacity of terrestrial ecosystems. This study, utilizing the PLUS model, aims to simulate the spatial dynamics of land use within the DLB across three climate-policy scenarios spanning the temporal domain from 2030 to 2060. Furthermore, employing the IPCC guidelines for national greenhouse gas inventories, the investigation projects the ramifications of prospective land use alterations on the carbon storage （CS） within terrestrial ecosystems in the DLB over the aforementioned timeframe. The outcomes delineated shifts in CS within terrestrial ecosystems under diverse future scenarios. The following key findings were emanated from the analysis： ① During the temporal span from 2020 to 2060, under the auspices of the Natural Development Scenario （NDS）, the encroachment of construction land primarily targeted arable land, forests, and grasslands. ② The Economic Co-ordination Scenario （ECS）, akin to the NDS, curtailed the diversion of cropland and aquatic resources. ③ Conversely, the Ecological Priority Scenario （EPS） prioritized the transformation of grasslands into forests, ensuring the sustained expansion of wooded areas. Moreover, the estimated CS of the DLB was at 3.6×10⁹ t as of 2020. Projections suggested that under the NDS, the CS was slated to witness a meager increase of 2.3×10⁸ t by 2060. Contrarily, the ECS and EPS anticipated CS increments of 4.5×10⁸ t and 4.7×10⁸ t, respectively. All three scenarios revealed a diminishing trend in carbon sinks over the ensuing four decades, with the NDS experiencing the swiftest decline and the EPS exhibiting a more gradual descent, stabilizing by 2050. The findings suggested that policies centered on ecological conservation could significantly augment carbon sequestration. To sustain these carbon sinks, prospective policies ought to be oriented towards substantial investments in agricultural and grassland land management, coupled with the implementation of progressive afforestation strategies. Additionally, efforts to reduce urban land sprawl and careful planning of development zones are also indispensable measures to reduce the loss of CS. In summation, this study furnishes innovative strategies and policy recommendations, thereby contributing to the discourse on the formulation of optimal land management practices.