Modelling Soil Detachment Capacity by Soil Properties and Root Diameter in Soils Under Tree Species in Northern Iran

Aims: It is well known that root characteristics and soil properties can be used to predict soil detachment capacity (Dc). However, few investigations have explored the effects of root diameter and plasticity index on rill erosion process, particularly for soils under mixed modes of tree species. Materials & Methods: To fill this gap, this study has evaluated the effects of root diameter, soil organic matter content and plasticity index on the Dc in soils under mixed modes of Crataegus ambigue, Fraxinus excelsior Linnaeus, Acer velutinum and Pterocarya fraxinifolia species, in planted forests of Gilan province (northern Iran). Moreover, these three variables were used to propose a model for predicting soil detachment capacity. For measuring Dc, the slopes (۶.۵, ۱۲.۳, ۱۸.۴, and ۲۶.۱%) and water discharges (۰.۲۶, ۰.۳۴, ۰.۴۴, ۰.۵۲, and ۰.۶۵ L m−۱ s−۱) were adjusted to the desired values using a laboratory flume with ۳.۵ and ۰.۲ m in length and width, respectively. These values were selected based on the field measurements of concentrated flows in the study area. Moreover, shear stress values were calculated using the hydraulic radius and the bed slope. Findings: The results showed that when root diameter, soil organic matter and plasticity index increase, Dc decreases in soils under the studied species (p ˂ ۰.۰۱). These changes in the studied variables were confirmed by principal component analysis (PCA), which did show root diameter and plasticity index influenced the first PC (loading over ۰.۵۰) and organic matter significantly influenced PC۲ (loading ۰.۵۶) (p < ۰.۰۱).

کلیدواژه ها:

PCA ، multiregression equation ، organic matter ، rill erosion ، soil conservation