ABSTRACT
The objective of this research was to assess vulnerable soil erosion risk with qualitative approach using GIS in Ankara-Guvenc Basin. The study area is located about 44 km north of Ankara and covers 17.5 km2. The selected theme layers of this model include topographic factor, soil factors (depth, texture, impermeable horizon) and land use. Slope layer and land use-land cover data were prepared by using DEM and Landsat-TM satellite image. According to land use classification, the most common land use type and land cover are rangeland (50.5%) then, rainfed (36.4%), week forest land (3.2%), irrigated land (0.7%) and other various lands (rock out crop and lake) (9.2%). Each land characteristic is also considered as a thematic layer in geographical information systems (GIS) process. After combination of the layers, soil erosion risk map was produced. The results showed that 44.4% of the study area is at high soil erosion risk, whereas 42% of the study area is insignificantly and slightly susceptible to erosion risk. In addition, it was found that only 12.6% of the total area is moderately susceptible to erosion risk. Furthermore, conservation land management measures were also suggested for moderate, high and very high erosion risk areas in Ankara-Guvenc Basin.
ABSTRACT
Natural forestland soils in the high land mountain ecosystems on the eastern Black sea region of Turkey are being seriously degraded and destructed due to intensive agricultural practices. In this study we examined four soil profiles selected from four sites in each of three adjacent land use types which are native forest, pasture and cultivated fields with corn and hazelnut to compare the soil physical, chemical and morphological properties modified after natural forestland transformation into cultivated land. Disturbed and undisturbed soil samples were collected from four sites. The effects of agricultural practices on soil properties taken from each three adjacent land use types were most clearly detected in the past 50 years with the land use change. Land use change and subsequent tillage practices resulted in significant decreases in organic matter, total porosity, total nitrogen and reduced soil aggregates stability. However, contents of available P were improved by application of phosphorous fertilizers in cultivated system. There was also a significant change in bulk density among cultivated, pasture and natural forest soils. Depending upon the increase in bulk density and disruption of pores by cultivation, total porosity decreased accordingly. The data show that long term continuous cultivation of the natural forest soils resulted in changes in physical and chemical characteristics of soils.