| As China’s second largest plain, the North China Plain is the main crop producing regions in our country. The water consumption of agricultural development in the region is bigger. High yield was guaranteed by irrigation, especially for the main food crop, such as winter wheat and the economic crops, such as fruit and vegetables. The North China Plain has become the largest complex underground drawdown funnel area of the world due to persistent over-pumping. It is important to precisely determine the distributions of land areas under different crops and analyze the driving force of changing. This lays the basis for not only adjustment and optimization of agricultural structure, but also the reduction of agricultural disaster and the protection of groundwater resources.At first, combining with the phenological observation data provided by the agricultural meteorological observatory, this paper simply summarized typical phenophase characteristics of the main crops in North China Plain, such as the winter wheat-summer corn, spring corn cotton and fruit. Then this paper obtained smooth NDVI time-series of different crops by Hants filter. Finally, we extracted cropping area of winter wheat, corn, cotton and fruit in the North China Plain for the period of 2000-2013 by proposing a numerical model using the CART algorithm. The planting area of vegetables and rice are lesser, and relatively broken. The changes among consecutive years were not obvious, so we only extracted cropping area of vegetables and rice in the North China Plain of the 2002 and 2012 through TM/ETM datas got with the method of maximum likelihood. The vegetables and rice planting area were used as the result of the regions of 2000-2006 and 2007-2013 to analyze the spatial and temporal variation characteristics of the use of agricultural land. The results were stable and highly precise, we analysed the spatial and temporal variation characteristics of agricultural land use in the North China Plain from different angles such as crops probability, the transfer matrix of land use and landscape pattern index,and the driving force of changing. According to out study, we draw the following main conclusions:(1) In this study, crops extracted at the county level are of high precision, The result was tested with county agricultural statistics data, which showed a statistically significant correlation in winter wheat, corn and cotton for the 13-year period with correlation coefficient greater than 0.76 at 95% confidence level. TM/ETM data’s resolution is higher, so the classification accuracy is relatively high. The classification results can be used in the study of spatial and temporal variations of crops.(2) The distribution proportion relationship of winter wheat and summer corn in the North China Plain is: North of Henan > Northwest of Shandong > South of Hebei.Single corn and fruit have the highest percentage of distribution in northern Hebei plain. Cotton has the highest percentage of distribution in the south of Hebei plain. We can see from the graph of Spatial distribution patterns of major crops in the North China Plain from 2000 to 2013 that the planting area of food crops is on the decline,while the planting area of economic crops has obvious rising trend. Statistics about the crop planting areas in the year of 2000 and 2012, show that the area of winter wheat and summer corn accounts for about 55% of the arable land in NPC, that the area of single corn, fruit and cotton accounts for 12%, which has greatly increased. The area of vegetables accounts for about 6%, which has increased 44.77%. The area of rice was the least, and it was deceasing.(3)Based on the crops probability, we analyzed the spatial and temporal variation characteristics of the use of agricultural land in the North China Plain in the periods of2000—2006 and 2007—2013. The results were as follows: there are changes in the areas of forest, fruit trees, vegetables and rice, and the changing percentages were respectively 56.45%, 35.76% and 23.16%. Furthermore, vegetables and rice areas had obvious shifts in the planting area. Large-scale winter wheat/summer maize planting area increased in the south of Hebei Plain, while the planting area of winter wheat/summer maize increased in North Henan. Because different planting areas of several kinds of economic crops in the north of Henan increased, the regional crop diversity index increased, too.( 4) In the end, we analyzed the driving force of the spatial and temporal variation characteristics of agricultural land use in the North China Plain. Influenced by the economic development, the market economy, the industrial structure changing, the technological advancing and policies, the region’s major crops were changing as we showed above. |
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