بررسي الگوي تغيير چرخه‌اي پوشش گياهي در مراتع نيمه استپي: اثر متقابل چراي دام و آتش‌سوزي در منطقه‌‌كرسنك شهركرد

Cyclical Pattern of Succession in Semi-Steppe Rangelands: Interactive Effect of Grazing and Fire

Several important factors such as grazing and fire drive dynamic of plant community in semi-steppe rangelands. Although, a wealth of information is available on separate effect of grazing and fire, interactive effect of fire and grazing attracted less scientistsʹ consideration. The aim of this study was to examine an expected model of plant community dynamic driven by interactive effect of grazing and fire in annually burnt semi-steppe rangelands of Karsanak, Chaharmahal& Bakhtiari province. Sampling executed within 4 m2 plots installed along a 200meter transect in burnt and control treatment in different grazing intensity. Non-metric Multidimensional scaling, Multi-Response Permutation Procedures and Man-Whitney test were used in order to analysis plant community and life form replacements in burnt and control areas. Fire+ light grazing resulted in a higher percent cover of perennial grasses and forb compared to control treatments in brushlands, whereas the brushes negatively responded to fire+ light grazing. Although a significant increase in perennial grass was observed in shrubland in response to fire+ moderate grazing, there were no significant response of brush and forb towards fire+ moderate grazing. The same responses were observed for brushland-grassland areas in the way that perennial grasses and forb reacted positively and brushes negatively towards fire+ light grazing. Although, the results confirmed a conversion from brushland to grassland due to fire, grazing intensity may direct fire effects. If grazing intensity is low, a shift from brushland to grassland might be the observed pattern of community dynamic; otherwise a shift from brushland to brushland-grassland is more likely to be occurred. This confirms a cyclical pattern of plant community dynamic in response to grazing and fire.