| Crop planting structure is an important part of agricultural production structure,the essential content of agricultural green development and sustainable development,and is of great significance for high-quality agricultural development and national food security.Due to the difficulties of analyzing the spatio-temporal change of crop planting structure at grid level in Northeast China,a crop spatial information allocation model SPAM-China was developed based on cross-entropy theory.With this model,the census data of four crops,i.e.,rice,corn,wheat and soybeans in Northeast China including Heilongjiang,Jilin and Liaoning Provinces during 1980-2010 were spatially allocated to analyze the changes of crop planting area,spatio-temporal dynamics,crop center movement and planting structure adjustment.Main conclusions were concluded as follows:(1)A crop spatial information allocation model for China(SPAM-China)was proposed.With the consideration of crop planting characteristics and associated impact factors in China,a study on crop spatial information reconstruction by fusing multi-source data and multiple factors was developed.Based on cross-entropy theory,a crop spatial information allocation model suitable for Chinese crop planting characteristics was built with input data of land use/cover datasets,irrigated cropland data,socioeconomic data and meteorological data.(2)Crop planting area in Northeast China has increased significantly.During 1980-2010,the planting area of rice,corn and soybeans was increased by 2.63,6.9 and 2.24 million hectares,respectively and the number of girds increased from 1987 to 5247 for rice,from 6526 to 8029 for corn,from 6703 to 7214 for soybeans.Wheat was the only crop that the total area has reduced,with planting area of 0.98 million hectares in 2010 and the number of soybeans girds declining from 4061 to 743.(3)Spatio-temporal dynamics of crop planting area in Northeast China was obvious.During1980-2010,crop area in Northeast China has significantly increased and spatially expanded.Different crop type has shown different spatio-temporal change characteristics.In terms of change area within girds,rice,corn and wheat generally increased less than 700 ha and decreased less than 300 ha within a gird.The increased area within wheat gird is less than 300 ha,while the number of girds with area increase was much less.From the perspectives of longitude and latitude of crop planting area,the increased rice was located between 119 ° to 135 °longitude and 41 ° to 48.5 °latitude;Corn and soybeans area was increased between 125.5 ° to 131 °longitude and 47 ° to 50 °latitude;the decreased area of wheat was centered between 122.5 ° to 133.5 °longitude and 43.0 ° to 49.0 °latitude.(4)The gravity center of crop area in three northeast provinces was moving northward.Among three crops,the gravity center of rice has moved from(125.47°E,42.91°N)to(126.14°E,44.62°N)by 0.71 latitude,corn has changed from(125.13°E,44.12°N)to(125.11°E,44.28°N)by 0.16 latitude and the soybeans has migrated from(126.47°E,44.88°N)to(127.81°E,46.75°N)by 1.87 latitude,while corn has changed from(125.13°E,44.12°N)to(125.11°E,44.28°N)by 0.16 latitude and the wheat has migrated from(127.26°E,46.78°N)to(125.84°E,48.55°N)by 1.77 latitude.(5)The crop planting structure has been largely changed in three northeast provinces.During1980-2010,the sequence of crop planting structure,i.e.,“corn>soybeans>wheat>rice” was changed to“corn>soybeans>rice>wheat”.Meanwhile,the predominance of corn has intensified in northeast region and rice has become one of the most important crops.The crop planting structure within grid level has also been changed obviously.During 1980-2010,four types of crop planting structure including “cornsoybeans-wheat”,“rice-wheat”,“and rice-soybeans-wheat”,“rice-corn-wheat” almost disappeared. |
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