Taxonomic Levels of plants as a determinant of plant diversity in communities(case study: mountain rangeland of Ziarat basin, Gorgan, Golestan province)

Diversity is one of the main subjects in ecosystem researches. It is also important in recognition of ecosystem health. Plant diversity or taxonomic diversity is medial level of biodiversity rank system. This research was done to compare Shannon diversity indices in different taxonomic levels. The study area was mountain rangelands of Ziarat in south Gorgan, Golestan province. Random quadrates, (1 m2) were used to define plant species list and their canopy cover percentage. Dependency of each plant to family, life form, biological type and vegetative life period were studied. Shannon diversity index was calculated for taxonomic level of species and family as well as life form, biological type and vegetative life period in existed vegetation communities of the study area. Results showed that diversity in species and family level carry the same amount of information thus in these levels different communities can better be compared than other levels of life form, biological type and vegetative life period.