Effect of geographical direction of slope on plant diversity indices in the Astraglaus shrubland of Nazluchai, West Azerbaijan

Awareness of biodiversity status is one of the requirements for adopting a conservation approach in rangelands ecosystems. In this regard, the present research was conducted in order to investigate the effect of slope direction on the values of plant diversity indices in the Astraglaus shrubland of Nazluchai region in 2017. For this purpose, in total, with the use of 230 sample plots of one square meter, which were placed at a distance of five meters from each other, along 50-meter transects; the crown cover percentage of plant species were collected in each of the main directions of the range (eight northern directions, five southern directions, five eastern directions and five western directions). Then, with the PAST software, the most important and widely used indicators of species diversity (Margalef, Taxa, Menhinick and Berger-Parker as species richness indices, Dominance, evenness, Simpson and Pielo as species evenness indices, Shannon and Brillouin as heterogeneity indicators) were calculated. Finally, using the one-way analysis of variance method, statistical comparison of the averages was carried out. The results showed; A total of 41 plant species were identified in the studied areas, and Margalef, Taxa, Shannon, Brillouin and Fisher's Alpha indices had a significant difference at the five percent level in different geographical directions. So that the highest value of these indices was related to the western direction, respectively 2.55, 12.2, 2.1, 1.88 and 4.05. Simpson's, Menhenik's, Dominance, evenness, Pielo and Berger-Parker indices were also not significantly different from each other in different directions. Although the two western and southern aspects were significantly different from each other regarding most of the indicators, nevertheless, the clustering results of the plant composition of the sites classified these two domains in one cluster with high similarity rate (around 70%). This finding indicates that the diversity indices are not able to provide information about the plant composition and should pay attention to the plant composition when using these indices. Finally, it should be mentioned that although Margalef, Taxa, Shannon, Brillouin and Fisher's alpha indices were able to separate the sites, but the proposal of using these indices in the monitoring plans of rangleands with the dominance of Astragulus microcephalus species in the northwest of the country, requires another researches.