Study on Vegetation Changes of Natural Ranges in KhoyBilehvar Semi-Steppic Area of West Azarbaijan Province

The study of the exclosure effects on the vegetation changes under grazing and non-grazing conditions in the rangeland areas has particular importance in the rangeland improvement and revivification projects. The research was accomplished in semi-steppe KhoyBilehvar area, from 1999 to 2005. Vegetation cover was annually measured within fixed plots during transact. The results showed that during nine years of research, on KhoyBilehvar exclosure, the total canopy cover has increased inside the exclosure, and the highest increase was observed in the perennial grasses (more than 3.5) and perennial Forbs (more than 2.5). Outside the exclosure, the total vegetation cover was almost constant and changes were less in vegetation cover types. Within the exclosure, some desirable species appeared consisting almost 19% of vegetation composition. Medium species proportion in the plant composition increased to more than two times and undesirable species decreased by half. Whereas, outside the exclosure, scarce desirable species and medium species of vegetation ratio has increased a little. The vegetation average of annual species during the study within exclosure is more than outside and the vegetation average of forbs inside and outside the exclosure is more than annual grasses. Nine year research in Bilehvar exclosure showed that the correlation between precipitation changes and vegetation cover was significant in the most species.