Document Type : Research Paper

Authors

1 Department of Natural Resources, Markazi Agricultural and Natural Resources Research and Education Center, AREEO, Arak, Iran

2 Associate Professor, Department of Forestry and Forest Economics, Faculty of Natural Resources, University of Tehran, Karaj, Iran

3 Professor, Department of Forestry and Forest Economics, Faculty of Natural Resources, University of Tehran, Karaj, Iran

Abstract

    Grazing is one of the most important factors in providing environmental conditions for change in species composition, structure and function of ecosystems. West oak woodlands of Iran as a valuable ecosystem are not immune from this threat. Therefore, it is essential to study the various aspects of this phenomenon in these ecosystems. The aim of this study was to examine the effects of relative grazing intensity on vegetation characteristics in an oak forest dominated by Quercus brantii. The research was conducted in Dalab Park, located in Ilam province, west of Iran. Information of vegetation, soil and other environmental variables were collected from 53 sample plots (16×16 m) using the random sampling method in various disturbances classes. Two-way indicator species analysis was used for classification of the ecological groups. Indicator species analysis was used to determine indicator species in each class and canonical correspondence analysis to identify the relationship between factors and the plant groups studied. The results showed that the grazing as well as soil, topographic factors and the light reaching to the forest floor was identified as the most influential factors on plant composition. Grazing explained the highest percentage of variance (11.2%) in floristic composition and caused an increased frequency of non-palatable species and resistant species to grazing and soil compaction as well as increasing of annuals including Bromus tectorum, Picnomon acarna, Minuartia picta, Rochelia disperma, Holesteum umbellatum, Lophocloa phlorides, and Valerianella vesicaria. These species were identified as invasive species based on density, abundance, and available resources. On the other hand, it seems that the spread of palatable species such as Vicia sativa,Trifolium physodes, Lens cyanea, and Lathyrus inconspicaus in the moderate grazing site indicates the role of balanced livestock grazing in maintaining the proper species composition in rangelands.
 

Keywords

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