Heilongjiang Province is a significant region for grain production and serves as a crucial commodity grain production base in China. In recent years, due to the threat of declining cropland quality and quantity, coupled with the increasingly prominent demand for grain, there is an urgent need to enhance rice yields in Heilongjiang Province. It is imperative to accurately identify the gaps between actual and potential grain yields and effectively implement yield-enhancing measures in regions with significant yield gaps. This study aimed to determine the rice reproductive periods of Heilongjiang Province for 2000, 2010, and 2020, estimate the rice actual yields using the Vegetation Photosynthesis Model (VPM), simulate the rice potential yields based on the Global Agro-Ecological Zones (GAEZ) Model, and then identify the rice yield gaps at the pixel level by calculating the rice absolute yield gap (AYG) and relative yield gap (RYG). Additionally, yield-enhancing measures were proposed for regions with significant yield gaps. The results were as follows. (1) The rice reproductive periods of Heilongjiang Province for 2000, 2010, and 2020 were determined as days 153~249, days 145~249, and days 137~249. (2) The mean rice actual yield and potential yields decreased by 1222 and 5941 kg ha⁻¹ during the 2000–2020 period, respectively, and the total actual and potential production increased by 3.75 and 1.70 million tons in Heilongjiang Province, respectively. (3) The rice AYG and RYG in the Sanjiang Plain region, such as Jixi City, Hegang City, and Jiamusi City were relatively large compared to other regions for the three years, and the rice yield gaps continued to decrease during the 2000–2020 period. (4) With regard to the Sanjiang Plain region with a large rice yield gap, this study proposes measures to narrow the rice yield gap by establishing ecological protection forests on cropland, transforming low- and middle-yielding fields, increasing agricultural science and technology inputs, selecting better rice cultivars, etc., which are important for ensuring food security.

As one of the most serious challenges in the 21st century, climate change poses a major threat to global grain production, especially in agricultural and populous countries such as China. This study employs the Vegetation Photosynthesis Model (VPM) and Geographically and Temporally Weighted Regression (GTWR) model to systematically quantify and analyze the spatio-temporal heterogeneous responses of three major crop yields (rice, maize, and wheat) to climate change from 2000 to 2018 in China. The results are as follows. (1) During 2000–2018, all climate factors showed significant inter-annual fluctuations and regional variations. Specifically, both mean maximum and minimum temperatures rose by approximately 1 °C overall; total precipitation initially decreased before increasing, with 2011 being the turning point; total sunshine hours fluctuated sharply before stabilizing; mean wind speed increased slowly at first and then more rapidly; and mean relative humidity decreased first and then increased, turning around in 2009. (2) The VPM-based crop yield estimates were well-verified against the statistics from the China Statistical Yearbook, with the coefficient of determination (R²) ranging from 0.77 to 0.84 for the three crops (all p < 0.01), confirming the high reliability of the yield data used in this study. (3) The national mean yields of three crops based on the VPM showed a fluctuating upward trend from 2000 to 2018. Spatially, the yield changes in three crops showed significant regional differences. (4) From 2000 to 2018, crop yields based on the VPM model exhibited distinct responses to climate change: rice yields were mainly positively affected by mean maximum temperature, maize yields were mainly negatively affected by total precipitation, while wheat yields benefited most significantly from mean relative humidity. The Northeast Plain (the major production region for rice and maize) and the Huang-Huai-Hai Plain (the key region for wheat) proved most sensitive to climate change, and the impacts on all three crops intensified over time. The study suggests that in the future, attention should be focused on the adaptive management of major crop production regions under climate change, and multiple approaches such as optimizing the planting structure and layout, improving crop varieties, perfecting the risk management system, and establishing a policy support and guarantee system should be adopted to enhance the climate resilience of the agricultural system.