Evaluation of soil quality index to assess the influence of soil degradation and desertification process in sub-arid terrestrial ecosystem

Desertification is the process of land degradation resulting from the mutual interactions of physical, biological, political, social, economic and cultural factors with climatic changes. Desertification is considered to be the last stage of land degradation. In recent years, various studies have been carried out to reveal effective natural and human factors on desertification. Important one of the parameters commonly used in these studies is the soil quality index. Soil quality refers to the soil’s capacity to function. Soil quality index cannot be measured directly; it is obtained by combining some physical, chemical and biological soil properties in a spatial sense. In this study, the relationship between some soil criteria and desertification has been discussed and evaluated. The research area covers the boundaries of the Kalecik district of Ankara and covers 116,000 ha. The study area consists of different geomorphological units and has semi-arid climate characteristics. In this study erosion risk, soil depth, texture, organic matter content, soil reaction, main material, drainage, salinization and alkalization, lime content and soil pollution of the soils of the research area were examined, and classified by analytic hierarchy process method according to their degree of weight and assembled in geographic information systems environment in layer logic. As a result of analysis, soil quality map was obtained from the viewpoint of land degradation and desertification based on soil and land characteristics of the study area. According to the obtained result soil quality is determined: 39.2% of the study area as low, 54.5% as medium, and 6.2% as high.