Studying Slope Position Effects on Soil Physico-chemical Properties in a Hardwood Forest of Lahijan Region

This research was conducted to study the effect of different slope position on some physico-chemical properties of hardwood forest soils. The study area was located in Lahijan region of Guilan Province (northern Iran). After field observations، three ridges were selected and، in each of them، three soil profiles (on the summit، shoulder، and footslope position) were used for sampling in the mountain landform with granite parent material. Physico-chemical analysis including soil texture (hydrometer method)، bulk density (clod method)، organic carbon (Walkley and Black method)، total nitrogen (Kejeldahl method)، electrical conductivity of saturated paste extract using conductivity meter، soil pH by potentiometric method with a glass electrode (in 0. 01 M CaCl2) using a soil solution ratio of 1:2، exchangeable sodium and potassium were measured by flame photometer set. Cation exchange capacity (CEC) were determined by Bower method (1N ammonium acetate، pH=7)، available P (Olsen method) and humic-fulvic acid content (freeze drying method). The results showed that summit position had the maximum amount of clay، organic carbon، total N، P، Ca+Mg، CEC، EC، humic and fulvic acid in comparison with shoulder and footslope positions; whereas، soil pH، bulk density، and exchangeable sodium were significantly higher in footslope. Based on the results، soil properties depend on slope position which in turn influence soil development and soil characteristics.