EFFECTS OF LAND-USE REGIME ON SOIL ERODIBILITY INDICES AND SOIL PROPERTIES IN UNYE, TURKEY

摘要

We evaluated the effects of land-use regime on soil erodibility indices and several soil properties in forested, deforested, and cultivated areas in the village of Unye, Turkey. Twelve sample plots (spaced 150 m apart) with northern aspects were established in each land-use regime, and samples were taken at soil depths of 0-20, 20-50, and 50-80 cm. Soil organic matter (SOM), soil reaction (pH), total lime (CaCO_3), texture (sand, silt, and clay), dispersion ratio (DR), erosion ratio (ER), colloid-moisture equivalent ratio (C-MER), structural stability index (SSI), field capacity (FC), wilting point (WP), and available water capacity (AWC) were analyzed. The average (of the three soil depths) AWC, FC, and WP values were not affected by the site, although site, soil depth, or both significantly affected other analyzed soil variables. Deforestation and subsequent tillage practices resulted in an almost 20% decrease in clay content, a 33% decrease in SOM, a 15% decrease in AWC, a 51% decrease in total CaCO_3, a 24% decrease in SSI, a 60% increase in DR, and a 98% increase in ER relative to undisturbed forest soil. At cultivated and forested sites, the ER and DR increased with increasing soil depth. At deforested sites, ER and DR were lowest at 50-80 cm. SOM was the highest at 0-20 cm in the forested sites. Decreasing SOM, clay content, and SSI, as well as increasing DR and ER were outcomes of deforestation. These results indicate that the conversion of forest into cropland deteriorates some soil properties, especially SOM and SSI, and alters the stability of soil aggregates, thus increasing the susceptibility of deforested sites to erosion.