Studying of the vegetation changes of natural rangelands in semi-steppe area of Gomishan, Golestan province

Study of vegetation changes of grazed and ungrazed rangelands has a significant role in management. The effect of exclosure and grazing was studied on the direction of vegetation changes of rangelands in Semi-Steppe area of Gomishan in Golestan province from 1997 till 2005. The vegetation parameters were measured each year, in several fixed plots, inside and outside of exclosures. The annual forage production was measured by randomized plots by the employing clipping and weighing method. Data were compared with T test analysis by using MiniTab15. Results showed that total canopy and perennial grasses inside the exclosures significantly increased in comparsion with those of outside the exclouser, but shrubs, annual forbs and grasses inside the exclosur were decreased. Increase of the prinnial grasses inside the exclosure was due to Puccinellia distans which belongs to class I species. Reduction of shrubs in outside the exclosure because of the decrease of Halocnemum strobilaceum which belongs to class III. The perennial species such as Artemisia sieberi and Frankenia hirsuta were not inside the exclosure in the first year, but they grew naturally because of the exclosure in the next years. The results of the comparison of forage production and perennial grasses demonstrated that the rate of total forage production and perennial grasses inside exclosure in comparison with outside exclosure was increased. Moreover the range condition inside exclosure, was changed from medium state to good one.