Contrasting responses of spatiotemporal patterns of cropland to climate change in Northeast China

Understanding the relationship between climate change and cropland spatiotemporal patterns is critical for developing government policy and assisting agriculture in adapting to future climate change. The land use dataset was used to extract the area of cropland expansion and contraction as well as to calculate the cropland landscape indices. The impacts of climatic factors on the spatiotemporal patterns of cropland were quantified for different time periods by Random Forest (RF) classification and regression models, and the accuracy of the models was used as the intensity of the influence of climatic factors on cropland change. The results revealed that the total cropland area has consistently increased by 17.74% in the last four decades. The Sanjiang Plain (SJP) and Songnen Plain (SNP), with high aggregation and a simple shape of cropland landscapes, were the main regions where the cropland area has increased. Cropland landscape aggregation was low in mountainous areas. Before 2000, the total cropland area expanded more (46,748 km(2)) in response to the pressure to ensure food security, whereas there was less cropland loss. The accuracy of the RF model during this period revealed that the changes in cropland spatiotemporal patterns were highly influenced by climatic factors. After 2000, the climate conditions gradually became warmer and wetter. The total area of cropland increased slightly (10,587 km(2)) under the influence of the contradictory relationships among economic development, food production and ecological conservation, and the conversion between cropland and natural landscape types was drastic. The impact of climatic factors on changes in cropland spatiotemporal patterns has declined. Our results suggest that the response of spatiotemporal pattern changes in cropland to climatic factors differs under different policy contexts in different periods. The findings are intended to aid in the balance of agricultural production and ecological conservation in Northeast China in the face of climate change.