Frequent wild fires in mountainous grasslands of Alborz (Iran) influenced the sustainability of habitats and ecological niches of species in this ecosystem. In fact, fire has been a constant event in Golestan National Park in Alborz for a long time (67 fires during 1957 to 1997). Due to importance of this national park in northeastern Iran as a biosphere reserve, the research has been carried out in order to investigate the causes of the fires and the subsequent changes occurred in vegetation and habitat structure. Study was performed in two adjacent: burned and unburned areas in mountains of Alborz. The analysis showed that the vegetation coverage and the above ground biomass in the burned area were significantly greater in comparison to the control area. Whereas, the diversity of vegetation of the two areas did not show significant differences. It was also shown that the coverage of grass species like Stipa pennata L., Festuca valessiana, Avena wiestii Steud. and Aegilops tauschii Coss. increased with respect to the non-burned area. The coverage of woody species like Acanthophyllum pugens, Onobrychis cornuta (L.) Desv., Cotoneaster ovatus Pojark. and Rosa persica Michx. considerably decreased in burned area. Due to increase of annual species of grasses and decrease of woody species, it can be concluded that fire is a preventive factor in succession of ecosystem toward climax and the dominance of grasses can be regarded as a suitable condition for further fire occurrence.
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