The interrelation between landform, land-use, erosion and soil quality in the Kan catchment of the Tehran province, central Iran

The objective of this study was to better understand the functional links between soil quality, erosion, geomorphology and land-use. This was done for the Kan catchment of the Tehran province, central Iran. Soil quality was assessed by using the integrated quality index (IQI) and the Nemoro quality index (NQI): this enabled the total and minimum datasets (TDS) to be obtained by using the principal component analysis. Soil erosion was calculated using the revised universal soil loss equation (RUSLE) model using the InVEST software. The calculated erosion rates are very high (on average 7 t ha(-1) yr(-1)) in the region due to the variety of topography, steep slopes and lack of suitable vegetation. The variety of topography and steep slopes are a caused by the high uplift rates. Consequently, the modelled actual erosion rates are in the same order of magnitude as measured, long-term denudation rates (Be-10). The erosion rates in the rangeland were higher than in agriculture land and built-up areas and exhibit a positive correlation with elevation and slope angle. The integrated soil quality index produced more plausible results than the NQI. According to the IQI, the soils in the study area mostly have a moderate to low quality. The statistical analyses showed that organic matter and sand play a more important role on the soil quality than all the other soil characteristics. Slope and elevation seem to significantly influence the soil quality. We demonstrated that soil quality can be evaluated precisely enough by using the minimum dataset (which reduces costs and time) and that it is dependent only on a few soil parameters. Soil quality and erosion rates vary strongly in areas having a rough and steep topography and the effect of land-use is partially overshadowed.