Effect of altitude, slope and canopy on absorbable phosphorus, carbon and total nitrogen in forest soils (Case study: The forest of Ilam province, Dalab)

Different ecological factors influence on forming, development and sustaining of plant communities, among which physiographic variables are the most important ones. Physiographic factors including altitude, slope and aspect can impact on qualitative and quantitative characteristics of soils. The purpose of this study was determination of relationship between slope, altitude and canopy on soil chemical properties. The study was carried out in Tang-e-Dalab in Ilam province which is situated in southern Zagros. Three transects were sampled in oak stand (Quercus brantii). In each transect, samples had 50 meters interval. Soil samples were collected from soil surface (0-20 cm). Ten samples separately were located inside and outside of canopy in each transect. Totally, the number of 60 samples were selected. In each sample, altitude and slope percent was recorded. The results showed concentration of absorbable P, total N and organic C were decreased by increasing of altitude and slope percent in both inside and outside of canopy. Cumulation of soil nutrient has inverse relationship with altitude and slope. Phosphorus accumulation in soil showed the most correlation with altitude in both inside and outside of canopy but amount of N showed the less correlation with altitude and slope outside of canopy.