Beyond Yield: Balancing Grain Production and Regulatory Ecosystem Services in a Typical Black‐Soil Region of Northeast China

China's northeastern black‐soil region is vital for grain production (GP) and is an important ecological barrier in China. Population growth in China has increased the demand for grain, intensifying the competition between arable and ecological land, which may lead to the homogenization and degradation of ecosystem services (ESs) in the black‐soil region's spatial units. However, studies on the trade‐offs among ESs on high‐quality cropland, as well as the spatially explicit mechanisms driving these trade‐offs and synergies, remain insufficient, especially when considering subtle changes in cropland spatial units and environmental heterogeneity. This study investigated the trade‐offs and synergistic relationships between GP and regulatory ecosystem services (RESs) in Northeast China's black‐soil region from 2000 to 2020, and explored the impact mechanisms of these trade‐offs based on the Geodetector and MGWR method. The results showed that all four types of ESs improved over the 20 years, and the total amount of GP and sand fixation (SF) showed a significant upward trend. The relationship between GP and both carbon sequestration (CS) and soil conservation (SC) was mainly synergistic, while the relationship with SF showed a weak trade‐off. The trade‐off intensity between GP and RESs was influenced by multiple factors. Notably, the interaction between GP and CS exhibited a more pronounced dependence on Leaf Area Index dynamics, whereas the trade‐off intensity with both SC and SF was predominantly governed by land‐use intensity patterns. This study serves as a scientific basis for the stable development of regional GP and the optimization of ecological security.