Dynamic of exposed bare soils and its impact on local thermal environment

Large area exposure of bare soils caused by soil erosion has serious impact on the regional ecological environment, such as the rise of land surface temperature. As a typical reddish soil erosion region in southern China, the hilly areas in Changting county of Fujian province have been called flame hill areas, due to extensively exposed reddish soils and resultant hot weather in the areas. This study utilizes remote sensing technique to investigate dynamic of bare-soil exposure intensity and accompanied soil heat flux and land surface temperature (LST) changes during the period from 1988 to 2010 in main soil loss areas of the county. Results show that owing to the 22 yeas of treatment of soil loss, the bare-soil exposure intensity in the main soil loss areas has declined by 20.26%, the area of high exposure intensity has decreased by 81.95%, and the soil heat flux has reduced by 33.28%. All of these have contributed to the decrease in LST differences between exposed and vegetated areas by 20.8% during the study period. This indicates an improvement of thermal environment in the areas once severely exposed. Regression analysis suggests that each 10% decrement of bare-soil exposure intensity would reduce LST difference by 0.72-0.94℃.