The relationship of physiographic factors with woody plants diversity and soil carbon stock in the central Zagros forests (Case study: Hashtadpahlu, Lorestan)

The Zagros forests, which are one of Iran's most important forest ecosystems, contain a diversified vegetation that includes trees, shrubs, and herb-layer species. Identification and precise knowledge of their ecological role in this ecosystem can help in natural resources protection and sustainable development. In order to study the effects of physiographic factors (aspect, slope and elevation) on the woody plants species diversity and also soil carbon stock in the central Zagros, the maple tree (Acer monspessulanum Var. cinerscens ) forest in Hashtadpahlu region which located in Lorestan was selected.

Within the forest, 37 circular plots, each measuring 1000 m2, were placed in a systematic-random for this purpose. Richness and diversity indices were calculated for woody species within plots. Soil samples were taken from a depth of 0-30 cm to measure the quantity of carbon stock in the soil and the value of soil organic carbon and bulk density for soil samples were measured.

In this forest, 11 different woody plant species (trees and shrubs) from seven different families were investigated. The results showed that the highest diversity of shrub species was observed in northern aspect and the lower slopes (Class of %5-20), while the elevation has no significant effect on the shrub diversity. Also, the physiographic factors had no significant effect on shrub species richness and tree species diversity and richness. The most soil carbon stock was measured in the eastern aspect while the other physiographic factors had no significant effect on carbon stock. The reduced carbon supply on the northern slopes relative to the rest of the slopes could be owing to heavy grazing, low density and poor vegetative quality of wood species, reduction of tree litter and other plant species and climatic conditions in this slope. As a result, the most important factors impacting the number of species diversity indices in the Acer forest are the aspect and slope.

The richness and diversity of wood species in the Acer sp. forest are appropriate. and physiographic factors have played an important role in the values of their indices. Physiographic parameters have an impact on the carbon stock of the soil. As a result, environmental variables should be considered in the management of Zagros forests due to its extensive distribution.