Study of grazing intensities on plant species richness and diversity indices for preserving the ecosystems of Taftan's rangelands

The comprehensive conservation of rangeland ecosystems depends on their management which is based on protection and maintenance of diversity. This comprehensive management does not take place except by studying and measuring species diversity. Therefore, it is necessory to be aware of the destructive factors in ecosystem, these factors cause shelter and biomass destruction, thus decreasing species diversity. It seems that one of destructive physical pressures on rangeland leading to the decrease of diversity and vegetation elements, is livestock overgrazing. This research was done so as to investigate the effect of various grazing intensities on vegetation diversity in Taftan rangelands. To do this, three sites including heavy grazing, light grazing and 8 years – conserved areas were selected. In each site a number of samples were determined by using statistical method. In addition, 7 transects and 42 plots overall with random – systematic method were established. In the next step, the species names and numbers were recorded. Then Margalef and Menhinick richness index, Shannon-Wiener, hill 1 and hill 2 were calculated and statistical comparison was done in SPSS 19. The results pointed out that there were significant difference in the terms of richness and species diversity at %1 level for various grazing intensities. Moreover, Tukey-test showed that species richness between conservation area and light grazing area between conservation area and heavy grazing area and also between light grazing and heavy grazing areas in 1% level were significant. Shannon-Wiener and Hill 2 indices demonestrated significant difference at 1% level among all grazing intensities. The highest species richness and diversity were in light grazing.