Spatial-temporal Patterns Of Cropping Intensity On The Jianghan Plain Over Recent 20 Years

For a long time,cultivated land is an important type of land cover formed under the agricultural production activities of human beings.It is the basis and guarantee for our survival and plays an important role in the sustainable development of agriculture.At present,the total amount of arable land resources in China is continuously decreasing and the degree of utilization is not high.The intensive use of arable land resources faces severe challenges.Therefore,grasping the planting intensity and distribution characteristics of cultivated land resources is very important for improving the utilization efficiency of cultivated land resources in the region and optimizing the planting structure of crops,and it is also conducive to solve increasingly serious food security problems.This paper takes Jianghan Plain as the research area,uses NDVI data of vegetation index in MOD13Q1 product from 2000 to 2017,adopts S-G filtering method to fit and reconstruct the time series NDVI data,and extracts other three phenological parameters which include the start of growing season,the end of growing season and the length of growing season.Then,the unsupervised classification method was used to classify the reconstructed time series data and extracted phenological parameters.The distribution of cropping frequency and cropping intensity in Jianghan Plain between 2000 and 2017 was obtained,and the spatial-temporal pattern distribution characteristics were analyzed.At the same time,through the definition of the double-season cropping intensity,average cropping intensity and total cropping intensity,the distribution characteristics of cropping intensity of cultivated land in the Jianghan Plain were analyzed over the past 20 years,and the SOM self-organizing neural network analysis was used to analyze the three indicators.By supervising the cluster analysis,the zoning of cropping intensity of cultivated land in Jianghan Plain was obtained.The main findings are as follows:(1)In the past 20 years,the total crop cropping area in the Jianghan Plain has shown a decreasing trend,and its total area has decreased by about 1,000 square kilometers.The cropping area of double-crop crops showed a slow increase,which was mainly distributed in the central and northern regions of Jianghan Plain.The cropping area of single-crop crops showed a slow decrease,which was mainly distributed in the eastern region of Jianghan Plain.(2)Studying the inter-conversion of crop planting frequency in Jianghan Plain at intervals of three years found that the total area of the single-double-season crops in Jianghan Plain increased first and then decreased,indicating that the cropping distribution of single and double-season crops was frequently transformed,and then it tends to focus on stability.At the same time,the conversion of single crops to double crops is mainly concentrated in the traditional double cropping areas.The main crops for the conversion of double crops to single crops are mainly concentrated in single cropping areas..(3)Analyzing the distribution trends of crop cropping frequency in Jianghan Plain based on administrative divisions.It was found that except for the single-double cropping areas of Zhijiang City and Xiaoting District,the cropping area of both single-double cropping crops showed a decreasing trend.The trend of the area shows the opposite trend,that is,the cropping area of double crops decreases while the cropping area of single crops increases,the cropping area of single crops decreases while the cropping area ofdouble crops increases.Among them,the double-season crop acreage in the traditional double cropping area shows an increasing trend,and the single-crop cropping area in the traditional single cropping area shows an increasing trend.(4)In the past 20 years,most of the cultivated land in the Jianghan Plain has high cropping intensity.In areas where the crop cropping frequency is high,the cropping intensity of cultivated land is high,and in areas where the crop cropping frequency is small,the cropping intensity of cultivated land is low.