| Crop spatial pattern is the spatial expression of crop planting structure,cropping system and planting mode in a region or production unit.It is an important information to understand crop species,structure and distribution characteristics,and is also the basis for crop structure adjustment and optimization.The timely and accurate acquisition of crop acreage and spatial distribution information is of great significance to the issues of food security and sustainable agricultural development in China.Remote sensing technology has been widely used in earth observation activities because of the advantages of large coverage,short detection period,strong presentability and low cost,which provides new technical means to quickly and accurately obtain crop information on a large scale.In recent years,China’s "rice-crayfish " area is rapidly expanding,mainly in Hubei,Jiangsu,Hunan and Anhui provinces,including Hubei to Rice-crayfish model is dominant,this model effectively improves the utilization rate of farmland resources and output benefits.the Rice-crayfish co-culture model has become a new way of using arable land in China.Therefore,accurate identification of Rice-crayfish fields,analysis of their spatial and temporal pattern changes,and analysis of the spatial pattern driving mechanism of Rice-crayfish fields are very important for scientific and reasonable layout of Rice-crayfish fields,optimization of regional land use pattern and guaranteeing regional.It is of great importance to optimize regional land use pattern and ensure regional food security.Therefore,this paper took Qianjiang City,Hubei Province,a typical Rice-crayfish crop distribution area in China,as the research area,and chose Rice-crayfish fields,a cultivated land type under Rice-crayfish crop model,as the research object,using 2-view GF-1 and 5-view Sentinel-2 remote sensing image data.Using the object-oriented decision tree analysis method,based on the spatial distribution information of rice extracted using summer images,and based on the special spectral characteristics of Rice-crayfish fields with winter soaking,we further extracted the spatial distribution information of Rice-crayfish fields and common rice fields using winter images to obtain the spatial distribution information of Rice-crayfish fields in Qianjiang City for four years of 2016 to 2019.GIS spatial analysis was used to explore and analyze the spatial and temporal variation characteristics of Rice-crayfish fields patterns in Qianjiang City,and then the driving mechanisms of the spatial distribution patterns of Rice-crayfish fields were analyzed by OLS regression and spatial regression methods using natural factors,socioeconomic factors and other driving factors selected on the basis of statistical data.In this paper,the following conclusions were obtained.(1)By constructing NDVI vegetation index and AWEI(Automated Water Extraction Index),combined with other spectral features and texture features,the spatial distribution of Rice-crayfish fields in Qianjiang City in 2016,2017,2018,and 2019 were extracted using an object-oriented decision tree method,and the overall accuracy of Rice-crayfish fields extraction in each year reached above 0.8,and the classification effect was good,and the Rice-crayfish fields was identified more accurately.The results also showed that the method of object-oriented and decision tree can identify Rice-crayfish fields accurately and quickly.(2)During 2016-2019,Rice-crayfish fields in Qianjiang City showed a rapid expansion,in terms of quantity,the area of Rice-crayfish fields increased from 15259.36 ha in 2016 to 59086.21 ha in 2019,and the area of Rice-crayfish fields increased nearly four times in four years;spatially,Rice-crayfish fields kept expanding from the central and western townships to the east and south,mainly distributed in the agriculture-oriented Haokou,Longwan,Zhangjin,Xiongkou town,Jiyukou,Laoxin,Yuyang,Bailu Lake,Yunlianghu,Houhu and other townships,with less Rice-crayfish fields in the eastern and northern townships of Qianjiang Economic Development Zone,Yuanlin,Zhugentan and Wangchang,which have a high level of urbanization and industrialization;in terms of the type of arable land conversion,paddy fields and drylands are the most important sources of Rice-crayfish fields,of which paddy fields were converted into Rice-crayfish fields between 2015 and 2019.The area of paddy fields was as high as 26688.15 ha,mainly distributed in Haokou,Longwan,Zhangjin,Bailu Lake,Yuyang,Laoxin,and Xiongkou Town;the area of dry land converted into Rice-crayfish fields was 20253.51 ha,mainly distributed in Bailu Lake,Haokou,Houhu,Xiongkou Town,Xiongkou Management Area,Yunlianghu Lake,Jiyukou,and Zongkou.(3)By analyzing the driving factors of the spatial pattern of Rice-crayfish fields from 2016 to 2019,it was concluded that the factors influencing the pattern of Rice-crayfish fields are different every year,and the agricultural output value factor is significantly related to the distribution pattern of Rice-crayfish fields in the four years,which proves that the size of agricultural output value and the high or low economic benefit are the important factors affecting the layout of Rice-crayfish fields;it also showed that Rice-crayfish fields is a new way of cultivation,which could bring greater economic benefits,and promotes farmers to choose Rice-crayfish fields.The two complement each other and promote each other.In general,because of the large water demand for crayfish farming,the smaller distance to water source,the larger distribution area of Rice-crayfish fields;with the expansion of the scale of Rice-crayfish fields,Rice-crayfish fields is not only distributed around the residential areas and near the roads,but also in the places far away from the residential areas and roads.Per capita GDP had a positive effect on the spatial distribution of Rice-crayfish fields in 2018 and 2019.Specifically,the area of Rice-crayfish fields expanded with the increase of per capita GDP. |
