Study On The Spatio-temporal Change Of The Quality Of Cultivated Land At County Level Based On Trend Surface Analysis

The cultivated land is precious for Fujian province where most of land is mountains.It is a fundamental work to know the spatial-temporal change law of cultivated land in this area because it is essential for cultivated land protection and quality improvement,as well as guiding agricultural production.In this study,the quality of cultivated land blocks of Changtai County in 2009 and 2015 was obtained based on the cultivated land database and a quality evaluation system,following by calculation of village-level cultivated land quality score of this area.Then,the characterization of spatial distribution and temporal variation of the cultivated land in village-level were analyzed by using GIS method and trend surface analysis,based on which,the quality-improved regions and quality-degraded regions were classified.Finally,the main factors having an effect on the quality variation of the cultivated land was analyzed by using barrier model.The results are summarized as followings:1.The quality of cultivated land blocks of Changtai County in 2009 and 2015 were quantitative evaluated according to evaluation index system in consideration of farmland quality,engineering quality,and spatial quality.The cultivated land quality scores of eighty-eight villages were measured and the results shown that the cultivated land quality of Changtai County was fairly good.In 2009,the scores were mainly concentrated in the 70-90,of which,the villages scored 70-80 and 80-90 accounted for 35 and 33 respectively,only 2 villages scored below 60.In 2015,the scores were mainly concentrated in the 60-80,of which,the villages scored 70-80 and 60-70 accounted for 37 and 29 respectively.Comparing the scores of these two periods,the villages that the cultivated land quality-improved accounted for 39,and quality-degraded accounted for 49.2.The contour diagrams of the trend surface were plotted to analyze the spatial distribution and temporal variation of the cultivated land based on the quality scores of the cultivated land in 2009 and 2015.The results shown that the characterization of the cultivated land quality of Changtai County presented "West is higher than East,and central section is higher than North and South" both in these two periods from the spatial distribution.In 2009,the cultivated land quality was decreased from Southwest to Northeast,but in 2015,this was from West to East.3.Based on the D-values of the quality scores of the cultivated land in 2009 and 2015,the contour diagrams of the trend surface reflecting the quality variation was plotted to divide Changtai County into four regions,including cultivated land quality-degraded regions ? and ?,and cultivated land quality-improved regions ? and IV.Barrier model analysis shown that the factors having effect on the quality variation were different in these four regions.For regions ?,the main factors were irrigation guarantee rate,drainage and road conditions.For regions ?,the main factors were irrigation guarantee rate,drainage condition.For regions ?,the main factors were organic content and effective thickness of soil layer.For regions IV,the main factor was organic content.