Document Type : Research Article
Faculty of Natural Resources, Ferdowsi University of Mashhad
Shahid Beheshti University. Faculty of Earth Sciences, Department of Geomorphology
Faculty of Geography, Ferdowsi University of Mashhad
Erosion is the main factor in the process of land degradation, which has left significant effects in many ecosystems of the world during different eras. 75% of Iran's lands are subject to erosion, and the Darbadam catchment in northeast of Iran is no exception.
In this research, dendrogeomorphology technique has been used on the exposed roots of juniper trees with the aim of estimating sheet erosion rate. Using selective sampling method, 28disc samples were done from the roots of juniper trees. Then, by macroscopic and microscopic analysis of the roots in the laboratory, the exact year of root exposed from the soil due to sheet erosion was determined. In the macroscopic analysis, the index of sudden changes in the width of the growth ring, and in the microscopic analysis, the indicators of the changes in the size, number and orientation of the vessels, the size of the lumen of the cells and the size of the fibers were measured indicating the exposed of the roots from the soil.
The results showed that the annual erosion rate is less than 1 mm per year. The average annual erosion rate in trees less than 50 years old is 0.52 mm and for trees between 50 and 100 years old it is 0.33 mm which shows the positive effect of tree roots in soil protection. The highest annual erosion rate was recorded in pastures with poor coverage and the lowest rate in forests with low canopy cover. These results showed that there is a positive relationship between the degree of slope and the amount of sheet erosion. Finally, it was found that the technique of dendrogeomorphology is a suitable, low-cost and easy method for estimating the erosion rate in areas with juniper tree species.