[Objective] Carbon storage is a key indicator for measuring ecosystem functionality, with significant differences in carbon sequestration capacity among various land use types. Changes in land use directly lead to variations in terrestrial ecosystem carbon storage. Therefore, an in-depth analysis and prediction of the spatiotemporal distribution patterns of land use change and carbon storage can provide a scientific basis for achieving carbon sequestration targets and optimizing land use structures. [Methods] Taking Gaotang county, a typical plain agricultural county in Shandong province as the study area, based on land use types extracted from remote sensing data from 2009 to 2023, the spatiotemporal evolution patterns of land use were first analyzed. The InVEST model was then employed to estimate carbon storage and identify the spatial distribution patterns of carbon storage across different land categories. Driving factors were selected from the perspectives of natural conditions, socio-economic development, and locational conditions. Five scenarios: natural development, cultivated land protection, urban development, ecological protection, and sustainable development, were established. A coupled PLUS-InVEST framework was constructed. First, the PLUS model was used to simulate land use patterns under five scenarios for 2035. Then, the simulated land use maps were input into the InVEST model to estimate carbon storage and to compare changes across different scenarios. This coupling enables an integrated analysis linking policy scenarios, spatial land use patterns, and carbon storage responses. [Results and Discussions] From 2009 to 2023, significant changes occurred in land use types, with the most notable transformation being the conversion from cultivated land to forest land. Overall, cultivated land area fluctuated and decreased by 3 184.10 hm²; forest land in the southwestern region increased by 1 988.74 hm²; and construction land in the county center decreased by 109.89 hm². Total carbon storage increased by 1.14×10⁵ t. Carbon storage was significantly correlated with the spatial distribution of various land types, exhibiting a pattern of higher values in the southwest and lower values in the northeast. Carbon storage in the county center was relatively low, while the southwestern region, rich in forest land resources, had the highest carbon storage. Under the natural development scenario, all land use types except cultivated land showed a decrease in area. Under the cultivated land protection scenario, cultivated land area reached 69 116.78 hm², an increase of 8.23% compared to 2023, while forest land experienced the largest decrease. Under the urban development scenario, both cultivated land and construction land increased, whereas all other land types decreased. Under the ecological protection scenario, cultivated land, forest land, and grassland increased, while all other land types decreased. Under the sustainable development scenario, cultivated land area was slightly smaller than that under the cultivated land protection scenario, while forest land and grassland areas were similar to those under the ecological protection scenario. The spatial distribution characteristics of carbon storage were similar across all scenarios, consistently showing a pattern of lower values in the central area and higher values in the surrounding areas. Under the urban development scenario, total carbon storage was the lowest among all scenarios, decreasing by 3.01×10⁵ t compared with the 2023 level. [Conclusions] This research reveals that construction land expansion is the main cause of carbon storage loss, while ecological restoration measures can effectively increase carbon storage. The spatial distribution of different land categories remains relatively stable across scenarios, with carbon storage exhibiting a pattern of lower values in the central urban area and higher values on the periphery. Strategies pursuing only economic development or focusing solely on cultivated land protection have inherent limitations. The sustainable development scenario can better balance cultivated land protection and ecological conservation, dynamically adjust the relationship between the two, and achieve their long-term coordinated development. This research could provide a reference for achieving carbon peak, carbon neutrality, and sustainable development goals in plain agricultural regions.