Pattern of Plant Species Diversity in Related to Physiographic Factors in Melah Gavan Protected Area, Iran

Abstract

The aim was to study biodiversity of plant species including trees, shrubs and grasses in related to physiographic factors (aspect, elevation above sea level and slope percentage) in Melah Gavan protected area from northwestern Ilam province, Iran. The field data were collected using a number of 67 field plots in a systematic randomized design (each covering 20x20 m). The characters including tree and shrub species type, number and canopy coverage were recorded by measuring their small/large diameters in each plot. In order to record the herbaceous species, the Whitaker′s snail plot method was applied and the minimum plot area 81 m2 was determined. Based on the results, there are two tree species, one Shrub and 74 Grasses (belonging to 71 genus and 29 families) in the study area. The family Poaceae and the genus Euphorbia sp. form the most existing plants as well as Therophytes cover (51%) the most vegetative form in the area. The results obtained from multivariate Duncan test showed that the biodiversity is maximum in southern aspect and minimum in eastern aspect. Moreover, plant richness was the most in southern aspect while it was not significantly different in the other aspects. Investigation of biodiversity and richness amongst the altitude classes showed that the low altitudes (1400-1500 and 1500-1600 m ranges) have the most, while the upper altitudes (1800-1900 and 1900-2000 m ranges) have the least diversity. The ANOVA results also showed that the slope percentage had a significant effect on biodiversity and richness of plants. The results obtained from multivariate Duncan test showed that the biodiversity and richness are maximum in 0 - 25 slope percentage.