The Effects of grazing intensity on vegetation and soil in Sisab rangelands, Bojnord, Iran

It is important to know soil propoerties, particulary its chemical aspects, for the propermanagement of rangeland ecosystems. The aim of this study is to find the impact of grazing on vegetation and some soil chemical properties, in three areas, the key, reference, and critical, Sisab rangelands, Bojnord. The vegetation cover data was collected from 30, 1m2 quadrats in each area through random –systematic method. The soil data was sampled from two depths 0- 15, 15-30 cm and five composite samples were collected (each sample was mixed of six samples) from each depth in the each area. Some factors such as the organic carbon, the percentage of soil organic matters, total nitrogen, absorbable phosphorus, pH and EC were measured. The results showed that carbon, nitrogen, soil organic matters, phosphorus, and EC were been decreased by grazing, but pH was increased. According to results, forbs were the dominant life form in the reference site. Shrubs cover percentages were been increased as grazing increased. In addition, reference site had species that are more palatable and invaders were more abundant in critical area. It was concluded that heavy grazing intensity cause todecrease of vegetaton and conversion of composition of the species cause to negativeconversion in alimentary mineral of soil, sustainable of ecosystem would be endangered.