The effect of fire on vegetation diversity indices, a case study: Sirachal research station

. Fire affects vegetation and changes plant succession. In this paper, the vegetation of Sirachal Research Station, which burned in the summer of 2014, was studied and compared with the unburnt areas, based on biodiversity indices. The research was implemented as a factorial experiment in a completely randomized design. First, on the basis of physiognomy, the area was divided into three parts: shrubland, shrubland-rangeland, and rangeland. Each part was, then, divided into two sections, including a burnt area and an adjacent unburnt area (control area). In each area (burnt and unburnt), three sampling units were randomly assigned using PNP method, and vegetation measurements were subsequently performed. Based on data analysis, a total of 141 taxa were identified, belonging to 28 families and 95 genera, including one species of Gymnosperm, 19 monocotyledons and 121 dicotyledons in two burnt and unburnt areas of Sirachal Station. Based on the statistical analysis, using Past3 and SPSS softwares, there was no significant difference in the number of taxa between the vegetation of the burnt and unburnt areas. Of the indicators analyzed in Past3, the number of individual, the index of Menhinick's richness and the Shannon diversity index were significantly different in the treatments sampled from the burnt and unburnt areas. According to the Duncan test average, the number of individuals in the unburnt area, with a canopy cover below 25%, was greater than that in the burnt area, with the same canopy cover, however, no significant difference was observed between the individuals in the burnt area and unburnt area, with the same canopy cover of more than 25%. Also, the richness of the burnt area with a canopy of less than 5% is significantly higher than that in the unburnt area with the same canopy cover.