West forests of iran are one of the most rich biological resources in iran and their understory vegetation which is the main source of the forage for rural and nomadic livestock. So these forest are center of animal husbandry in iran . Pasture yield, quality and species biodiversity were compared between zones under trees and open lands near the trees. Trees affected pasture quality and yield and their biodiversity. In this study, two species of trees were studied: Quercus Brantii Liddl and Acer moesulanum L. These trees affected pasture yields grown under the trees. Pasture yields in open lands near the trees (without trees land) were greater than under trees. Trees also affected species biodiversity. Under trees, variety of species was greater than open lands. Soil under trees had higher levels of organic carbon and greater litter cover than soil had in open areas. These effects on soil were caused that most of forage quality factors tend to be higher under trees than in open areas. Trees appeared to have a greater effect on soil nutrient availability at the low fertility site. These results indicate that, while removing trees may enhance pasture productivity, this benefit may be offset by a reduction in pasture quality. Given the beneficial effect of trees on soil nutrients, tree removal may also have longer term implications for soil nutrient dynamics.
