Spatial-temporal changes of cropland and climate potential productivity in northern China during 1990-2010

Large areas of cropland expansion have been reported in northern China. The sustainable use of cropland may be greatly affected by climate and is vulnerable to climatic changes, particularly in northern China. Here, we investigated climate change during 1961-2010 and the spatial and temporal characteristics of climate resources in newly converted cropland during 1990-2010 across northern China. Significant climate warming occurred in the last 50 years concurrently with relative stable precipitation rates, which provided a favorable climatic background for expanding the extent of cropland. During 1990-2010, the major cropland expansion had shifted from the humid northeast of China with good natural conditions to the arid northwest with fragile environmental conditions. In the newly converted cropland areas, temperatures increased significantly with small fluctuations; the average precipitation decreased considerably from 422.40 to 257.97 mm, with high and increasing inter-annual and seasonal variability. Water shortages became the most important climatic factor, limiting sustainable use of newly converted cropland. The average climate potential productivity of newly converted cropland decreased considerably from 672.41 to 440.40 t/km(2), indicating a substantial decline in the quality of newly converted cropland. Understanding the spatial and temporal changes in climatic resources is critical to coordinating cropland expansion and sustainable land use.