Spatial And Temporal Characteristics Of Cultivated Land Fragmentation In Southern Jiangxi From 1985 To 2016

Cultivated land resources are the material basis for human survival and development,and the basic means of subsistence for agriculture.The quantity and quality of cultivated land resources are of great significance for ensuring national food security and maintaining the sustainable development of social economy.Along with the process of urbanization,industrialization and agricultural modernization in southern Jiangxi,farmland fragmentation has become a typical feature of agricultural production,while reducing the efficiency of agricultural production.Southern Jiangxi is a hilly and mountainous area with "eight mountains,half water,one field,half roads and manors".The fragmentation of cultivated land is more common.Therefore,exploring the fragmentation of cultivated land in Southern Jiangxi has a strong theoretical and practical significance for improving agricultural production efficiency.In this study,18 counties(cities and districts)in southern Jiangxi Province were selected as research objects.Based on the Landsat TM/OLI image data of the United States Land Resources Satellite(USGS EROS)(http://glovis.usgs.gov/)in 1985,1995,2005 and 2016,the cultivated land information in southern Jiangxi Province was extracted by the combination of artificial interpretation and automatic classification,and the cultivated land in recent 30 years was established.Database.ArcGIS 10.0,Fragstats 4.2,ENVI 5.1,Excel 2010 software,landscape ecology theory and fractal theory were used to analyze and evaluate the spatial and temporal characteristics of cultivated land fragmentation,and the spatial distribution pattern of cultivated land was analyzed by means of dynamic degree model of cultivated land,Markov transfer matrix model and nuclear density estimation method.(1)During the past 30 years from 1985 to 2016,the patch area of cultivated land in 18 counties(cities and districts)in southern Jiangxi showed varying degrees of change.The dynamic degree model of cultivated land landscape(K)was basically negative,indicating that the patch area of cultivated land landscape in most counties(cities and districts)in southern Jiangxi had a downward trend under external interference.According to Markov Transfer Matrix Model,the results are as follows:from 1985 to 1995,the cultivated land area in southern Jiangxi was transferred 160.21km2,56.86 km2;from 1995 to 2005,the cultivated land area was transferred 583.35km2,and the total transferred area was 367.36 km2,310.69 km2 more than the previous period;from 2005 to 2016,the cultivated land area was transferred 470.23km2,less than the previous period.The transfer area was 162.61 km2,which was113.12 km2,less than 204.75 km2 in the previous period.(2)In the four stages of nuclear density estimation in 1985,1995,2005 and2016,the high density is mainly concentrated in Xingguo County,Yudu County andXinfeng County,and the low density areas are mainly concentrated in Shangyou County and Chongyi County.The current distribution characteristics of cultivated land in the four periods are close to the estimated distribution characteristics of cultivated land nuclear density.The counties(cities and districts)with large number of cultivated land patches per unit area are concentrated in high-density areas,while the counties(cities and districts)with small number of cultivated land patches per unit area are concentrated in low-density areas.The high value area of cultivated land fragmentation mainly distributes in the sparse area of cultivated land patches,i.e.plateau and mountainous terrain areas in southern Jiangxi,while the low value area of cultivated land fragmentation mainly distributes in the large area of cultivated land patches,i.e.plain,basin and hilly areas.(3)From the perspective of cultivated land landscape pattern,based on the index of area and distribution classification,the index of Xinfeng County is the largest,while that of Chongyi County is the smallest.In 2016,the maximum cultivated land patch index(LPI)of Xinfeng County is 20.16 km2,while that of Chongyi County is0.13 km2,and that of Xinfeng County is 68.06,while that of Chongyi County is 33.02.The index is still the smallest in the whole southern Jiangxi area,and the PAFRAC of cultivated land circumference is 1.50 in 2016.Based on fractal theory,the fractal dimension(D)of cultivated land in southern Jiangxi was the lowest in Longnan County from 1985 to 2016,the highest in Dayu County,and the index was between0.99 and 1.27;the stability index of cultivated land(SI)was between 0.23 and 0.51;on the contrary,the lowest value appeared in Dayu County and the highest value in Longnan County.According to the landscape index and fractal theory of cultivated land,the fragmentation of cultivated land in southern Jiangxi is greatly disturbed by the outside world.