Document Type : Research Paper
Authors
Abstract
Study of vegetation changes of grazed and ungrazed rangelands is most important in range management programs. Vegetation changes were studied for four years (1996-99) inside and outside of the exclosure in Gian rangelands of Hamadan province. Measurements were made in permanent plots that have been established in study areas since 1996. Forage production was measured in randomized plots each year. Data were compared whit T test analysis. Results showed that there were significant differences in total cover of perennials during study period inside exclosure and the cover increased about 80 percent. The cover of all plant forms, such as shrubs, grasses and forbs increased significantly inside the exclosure in this period. The cover of perennials increased about 16 percent outside of exclosure during this period too, but there were significant differences in shrubs and grasses and no difference in forbs. Decreasers and increasers increased and invaders decreased inside, but outside of exclosure there was an opposite trend. Frequency of good quality plants increased inside and decreased outside. Range condition increased from poor to fair inside and decreased to very poor outside of exclosure. A positive and negative trend was observed inside and outside the exclosure area. In second year of study, rainfall was greater and In final year annual precipitation was more than first year but seasonal rainfall that is effective in growth, was less than the first year. Relationship between species canopy cover and annual and seasonal rainfall evaluated, however the correlation coefficient between rainfall and some species was significant. Overall, in comparison inside and outside, exclosure improved vegetation condition, forage production and range condition, under this climatic condition. Because of good precipitation condition of these years, it is necessary to continue the study to cover a series of drier years.
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