Evaluation of Soil Erodibility Using FAO Fuzzy Model in Closed and Unclosed Forest Zones in Dinarkouh of Iran

Abstract

Abstract: Zagros Forest region plays an important role in conserving water and soil resources in Iran. In recent decades, the destructions caused by natural and anthropogenic factors had exacerbated soil erosion in this region. Therefore, it is important to investigate the effects of restoration management on soil erosion control in the region. In this regard, it is also important using the fuzzy inference systems to convert the qualitative index of soil erodibility into a quantitative index with the possibility to analyze the results based on the principles of parametric statistics. This study was conducted in 804 ha of Zagros forests in western Iran. Soil erosion was studied in closed and unclosed forested zones by 40 randomly selected sample profiles (20 profiles per each zone) using the FAO (Boolean logic) and FAO-Fuzzy models. The fuzzy inference of research was carried out according to the Mamdani system based on the triangular membership function. Results showed that the difference between the mean soil erodibility in the closed and unclosed zones was significant (p < 0.01). The results also showed in spite of differences between FAO-Fuzzy model indices with FAO model in all sample, the direction of these differences does not show any considerable decreasing or increasing trend. Considering the prominent features of fuzzy logic that enables data analysis in quantitative and continuous form of numbers, it is suggested to use fuzzy logic capability in FAO model and other soil erosion estimation models based on Boolean classification logic. Finally, the study demonstrated the effectiveness of “closing management” to control soil erosion on steep degrading lands in the region.