Changting County of Fujian Province is one of the most typical reddish soil loss regions in southem China.Serious soil erosion has resulted in environmental and ecosystem degradation in the county.Local peo ple and governments have been struggling for the control of the soil loss for more than two decades.To investi gate and assess the changes after the effort, this study used remote sensing technology to analyze spatiotempo ral dynamics of the soil exposure degree in the county during the period from 1988 to 2010.The bare soil fea tures were estimated from the Landsat TM/ETM+ images of 1988, 1999, 2004 and 2010 based on two thematic indices-normalized difference soil index (NDSI) and normalized difference impervious surface index (NDISI).The used four images were geometrically corrected and registered to allow spatial overlay analysis between im ages.After the geometrical correction, the digital number (DN) values of the images were converted to at-satel lite reflectance.The NDSI was used to enhance and extract soil features from the four used images with proper threshold values.However, the extracted soil features were found to have been mixed with built-up land fea tures due largely to the spectral confusion between the two categories and the similar result in the NDSI perfor mance.In order to improve the accuracy of the extracted soil feature, the NDISI was further used to filter out the unwanted built-up land features from the extracted soil features using a logical tree algorithm, as the NDISI is the index specially designed for the highlight of impervious surface features represented mainly by built-up lands.This significantly improved the estimate of bare soil and the extraction accuracy can reach up to95.95％.Based on the extracted bare soil features, the exposure degree of bare soil and spatial and temporal changes of bare soil were analyzed.Results showed that the 22-year fight for treating soil loss has greatly re duced exposed bare soils in Changting County.The area of bare soil has been greatly reduced from 175.5 km2in 1988 to 85.6 km2 in 2010, bare-soil exposure intensity dropped down from 0.487 to 0.383, and fragmenta tion degree of bares soil increased from 0.103 to 0.207.In the two observed periods (1988-1999 and1999-2010), the decrease in bare soil area was in an accelerate speed, which was-3.74 km2 per year during the1988-1999 period and-4.34 km2 per year in the duration between 1999 and 2010.This corresponds closely to the two major policies issued by the Fujiang Provincial Government specially for the county' s soil loss treat ment.Obviously, government policies accompanied with effective actions were the major driving forces to the reduction of the exposure degree of bare soil in the county during the study period.
soil lossbare soilremote sensingfeature extractionChangting County
NETL
NSTL
万方数据
维普
