The Role of SHE Analysis in Definig Species Diversity Components of Mountain Rangelands (Ziarat Basin, Gorgan)

Diversity indices mainly composed of two components: Species Richness and Evenness. Critical to the analysis of diversity is a clear understanding of the relationships among S (species richness), H’ (information), and E (evenness) (i.e., SHE). Two historically intractable problems in biodiversity analysis have been: How to separate species richness and evenness into distinct components within the same system? and How to disassociate diversity with sample size? This is important because H’ may actually not vary at all, even in the face of increasing species richness. In other cases, H’ can increase while E remains constant. Due to the importance of these components, a simple solution has only recently been derived. In this study, SHE analysis was used to define the role of each diversity components in plant species and family levels, species biological and life forms as well as life period in mountain rangeland of Ziarat basin, Golestan province. 142 random quadrates (1 by 1 meter) were used to define plant species list and their canopy cover percentage. Shannon-Winner Index was used to define plant species diversity. SHE analysis was employed to separate species diversity into its richness and evenness components. Results show that the role of evenness is much more important than species richness in defining diversity index at species and family levels whereas they are playing the same role in defining diversity at the level of biological and life forms as well as life periods.