Spatiotemporal Variation And Influencing Factors Of Slope Farmland In Yunnan Province,China

Yunnan Province is located in the southwestern border of China and is ecologically sensitive.Slope farmland is widely distributed.It is one of the most prominent regions in which people and land are inconsistent.Excessive reclamation of sloping farmland will cause severe vegetation degradation and soil erosion,which is not only related to the safety of the southwestern ecological barrier,but also closely related to local food production and agricultural development.This study uses data from the land use data for the four periods of 2000,2005,2010,and 2015.It includes comprehensive data on topography,meteorology,soil,hydrology,highways,and statistical yearbooks,time-varying trajectory method and Pearson correlation analysis were used to explore the spatial-temporal pattern of slope farmland,analysis of the differentiation characteristics of slope farmland in terrain,weather,soil,distance to the nearest road,and distance to the nearest river,describe the change path of sloping farmland from2000-2015 from the shift of gravity and the complete time-change trajectory,finally the key factors influencing the distribution of slope farmland from natural and human factors were identified,which provided scientific basis and reference for the governance of slope farmland and sustainable agricultural development in Yunnan Province.The results are as follows:(1)From 2000 to 2015,the area of sloping farmland increased by 464.07 km~2,the proportion of sloping arable land in the province increased from 12.74%in 2000 to12.86%in 2015,with an average annual increase of 0.008%.The intensity of cultivated land on the slope land has a strong continuity in time series.Traditional farming areas continue to maintain high cultivation rates.The cultivation rate in northwest is the lowest.The province's high cultivation rate areas are mainly in Baoshan,Lincang,Wenshan and Zhaotong city.The most prominent time and area of change occurred in the 2005-2010 Gengma and Cangyuan county and the 2010-2015 Longyang sistrict of Baoshan city.(2)By 2015,the total area of sloping arable land in Yunnan Province is4.93×104km~2.These sloping arable lands are mainly distributed at an elevation of1000-2000m;the slope is 6-15°;the annual rainfall is 1000-1400mm;the annual average temperature is 15-20°C,the level of farmland(<2°farmland)and steep slope farmland(>25°farmland)of the province are decreasing.Slope farmland shifts towards moderate slope(6-25°)and mid-elevation(1000-2000m).The distribution characteristics of rivers on the 6th level is that with the increase of the buffer distance of the river,the cultivation rate increases first and then decreases,reaches the peak at a distance of250m from the river,and is then constrained by the elevation and gradient.The distribution on the village-level highway is that as the buffer distance of the highway increases,the cultivation rate keeps increasing but there is a gradient effect in increasing the intensity.The nearest gradient separation line is 500m away from the highway.(3)From 2000 to 2015,the distribution center of slope farmland is in the territory of Shuangbai county and migrated in the northeast direction.The center of gravity changed from 2005 to 2010 was the most intense,and after 2010 it was relatively stable.The constant non-slope farmland in time trajectory accounted for 84.55%of the total area of the province,10.27%of constant slope farmland,and 5.27%of the changeable slope farmland,of which the number of transient slope farmland accounted for 1/3 of the constant slope farmland,abandoning cultivation,reclaiming wasteland and abandoning cultivation are common in the sloping arable land.The farmland is the third largest source of land-based output.The main destination is converted into forest,followed by grassland,and the area of land transferred from 2000 to 2015 is decreasing year by year.(4)PCC shows that the cultivated rate of sloping farmland is significantly negatively correlated with the elevation in natural factors,followed by the annual mean temperature and elevation,and the other factors are less related.There is a significant positive correlation between rural population and human factors,while other factors are lower.It shows that the elevation of natural factors has the greatest impact on the differentiation of slope farmland,and the rural population has the greatest impact on human factors.Based on the analysis of the overlaying of sloping farmland and environmental factors,this study identifies the key factors affecting the distribution of slope farmland from natural and human factors.This result can provide scientific basis and reference for related departments in the governance of slope farmland and sustainable development of agriculture.