Biotic and abiotic factors have strong influences on plant community structures and functions. Facilitation and competition are influenced by biotic factors, and in turn affected by abiotic factors such as fire and aspect. This study aimed to evaluate the effects of exposures and fire on understory of Onobrychis cornuta shrubs in mountainous grasslands. The plant cover percentage were measured in twenty-five understories of live and burned O. cornuta in both Northern and Southern aspect and their open spaces next to the species were also sampled. GLM followed by T test were performed to determine the most important factors influencing the species. According to the results, total cover in open spaces were significantly influenced by exposures (F= 16.57; P < 0.01). Aspect was also identified as the most influencing factor to determine perennial grasses and shrubs functional types. Annual herbs, cushions and geophytes plant species were more influenced by fire. Exposures and the interactions between fire and exposures had the strongest influences on total covers of the understory species (F= 5.94; P < 0.05, F= 4.76; P < 0.05), respectively. Our results indicated that although perennial grass cover percentage were more influenced by exposure, annual herbs and cushion like plants were more affected by fire.
 

Keywords: Fire, Aspect, Biotic Interactions, Functional Groups, GLMM.

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