The Influence of Slope Aspect and Position on Soil Important Properties in Kalpoosh Region, Shahrood

Topographical conditions of any given area are among the main factors which influence the variations of soil attributes, especially in small spatial scales. The current study was carried out aimed at investigating the influence of slope aspect and position on soil quality considering the local situations via comparing the amounts of soil pH, organic matter (OM), available phosphorus (P), mean geometric diameter of soil aggregates (MGD), and water-dispersible clay (WDC) in the soils located in south-facing and north-facing slopes in five different slope position, including summit, shoulder, backslope, footslope, and toeslope in the forests of Kalpoosh area, Northeast Shahrood. Surface soil samples (0 – 20 cm) were taken up from three different points which were two meters far from each other in every slope position, and after being passed from a 2-mm sieve, their mentioned properties were measured using standard methods. The data were statistically analyzed by applying Duncan test, one-way ANOVA. The results indicated the combined effects of slope aspect and position were significant on most of the selected soil properties (P < 0.01). In contrary to the most of the previous researches, the amounts of OM (2.64 %), P (10.13 mg/kg), MGD (1.30 mm), and WDC (2.23 %), in south-facing slopes were relatively more favorable compared to their corresponding values in north-facing slopes (2.13 %, 8.74 mg/kg, 0.95 mm, and 3.90 %, respectively). Considering that the area under investigation undergoes early coldness in fall as well as heavy snows, low soil temperature in north-facing slopes seemingly hinders plant growth and soil evolution. On the other hand, receiving more radiation, soils located on south-facing slopes can modify the impacts of early coldness so that they provide the appropriate temperature for plant growth and enhancement of soil conditions.