| As the increasing of global population and climate change issues arising, food security has become one of the challenge for human beings in the 21 st century. Ensuring national food security is a major development strategy in China. Northeast China, as an important commodity grain production area, is the main production region for maize, and it plays an important role in the agricultural production. However, there has been lack of comprehensive analysis into the spatial-temproal dynamics of a certain crop, and whether we have made the full use of thermal resource to plant enough crops under the ongoing climate warming has been the major agricultural issue in China. We therefore adopted the Spatial Production Allocation Model(SPAM) and estimated the actual maize distributions by integrating multi-source data from 1980 to 2010, including maize area statistics, cropland distribution, agricultural irrigation distribution, and crop suitability distribution. Then, investigate the spatiotemporal changes of maize cropping system, as well as the relations to thermal resources change, which will benefit a more thorough understanding of crop dynamics under climate warming and therefore provide evidence for agricultural policy making in China. The main conclusions are as following:(1) The change in the distribution of maize has significant sptial difference. Maize planting area increased by approximately 5 million ha in Northeast China during the past three decades, and it has expanded northward and eastward in Northeast China. On latitudinal variations, maize planting area expanded northwards to 48°N before 2000, after that the increased planting area mainly occurred in the central and southern parts of Northeast China. Meanwhile, maize also expanded eastwards to 127°E on longitudinal variations and lower elevation(less than 100 m) as well as higher elevation(mainly distributed between 200 m and 350 m). Additionally, maize planting density increased gradually to a moderately high level over the investigated period.(2) The shifts in the extent and location of maize planting areas roughly matched the pattern of AAT10. In general, more than 95% of increased maize planting area in Northeast China were located in regions with AAT10 greater than 2800℃?d in the past three decades. Before 2000, the dominating regions of increased maize planting area were located in the regions with AAT10 range from 2800 to 3400℃?d. However, the regions with AAT10 greater than 3600℃?d has replaced the former after 2000.Spatial distribution of maize has close relationship to the length of TAGP. Overall, about 96% of increased maize planting area were located in regions with TAGP greater than 200 days in the past three decades. Before 2000, the dominating regions of increased maize planting area were located in the regions with TAGP range from 205 to 215 days. Yet, the regions with TAGP greater than 220 days has replaced the former after 2000.(3) Change of maize spatial-temporal distribution also reflects the change of maize maturity types. Before 2000, more than 80% of area growth originated in the the medium–late to late maturing transitional zone in the middle of Jilin Province and the south and east of Heilongjiang Province. However, the growth of maize planting area in the stable zones became faster, and that in the transitional maturity zones became slower, which occurred in the mid-west of Liaoning Province and the middle of Jilin Province during the most recent 10 years.Our research demonstrated that there’s been a dramatic spatial shift in the maize cropping systems of Northeast China during the past three decades, which has close relation to the spatial change of thermal resources. It shows the change of core distribution of maize, and reflects farmers might have initiatively adapted to climate warming by adopting cultivars with longer growth period. However, there still need natural and social features to explain the mechanisms of the spatial pattern of maize in the future. |
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