انتقال بذر توسط علفخواران اهلي و اهميت آن بر پويايي پوشش گياهي در مراتع شهرستان فريدن

چكيده انگليسي :

Seed Dispersal by Domestic Herbivores and Its Importance for Vegetation Dynamics in Rangeland Ecosystems of Fereiydan Region Isfahan Anis Eghbali Anis 1242@yahoo com Data of Submission February 20 2012 Department of Natural Resources Isfahan University of Technology Isfahan 84156 83111 IranDegree M Sc Language Farsi Mehdi Basiri Email address Bassiri em@yahoo com Majid Iravani Email address majid iravani@cc iut ac irAbstractThe change in regeneration pathway of plants by seeds or soil seed bank dynamics is one of the most importantimpacts of herbivores in grazing ecosystems with long history of grazing However this role of herbivores andits importance for the dynamics and composition of the vegetation is often neglected Herbivores consume seedsof many plant species and disperse them within and among sites where they graze This is in particular veryimportant in highly degraded ecosystems with no proper seed reserve in the soil so that the natural regenerationof the vegetation relies on the seed dispersal of target species from the distant seed sources To assess thepotential seed dispersal of semi steppe rangeland plant species by domestic herbivores various degradationlevels of rangelands in the central Zagros region moderate to good rangelands degraded rangelands andploughed ones or old rainfed sites were considered 12 different rangeland sites each at least 1000 m2 including 4 replicates with homogeneous vegetation were selected for each of the three degradation levels Ineach site vegetation cover relative frequency and flowering pattern of plant species was studied using ten1m2 plots systematically located along two 100 meter transects 10 meter apart from each other For each site a pooled dung sample of 10 freshly pellet groups of domestic herbivores was collected in four different periods June July August and September during grazing season in total 48 pooled dung samples Dung sampleswere dried in a dark room by exposing to open air and then from each a 150 gram sample was taken and kept fortwo months in the refrigerator at 3c for cold stratification treatment Seed content of dung samples then wasassessed in a greenhouse germination experiment over a period of six months In total 2039 seedlings from 50different species 16 families and 52 plant genuses were germinated from dung samples Seed content of dungsamples was mostly composed with palatable herbaceous species with no dispersal mechanism or adaptationexcept the production of many small seeds The highest and the lowest dung seed densities were observed inJuly and June respectively At the beginning of grazing season seed content of dung samples was composedwith palatable annual forb species while it was composed with less or unpalatable perennial species towards theend of season Seed species composition of dung samples was clearly different from plant species compositionof the vegetation plots where they had been dropped but it was more similar to plant species composition ofvegetation plots studied in the moderate to good rangeland sites Moreover the highest dung seed density wasobserved in the dung samples collected from degraded and ploughed rangelands These findings togethersuggest a likely transfer of seeds of plant species from moderate to good rangeland to the other sites in differentdegradation levels As most of the plant species recorded in the vegetation plots regenerate by seed seeddispersal by this vector may have significant role in natural regeneration of the vegetation only if otherenvironmental and management factors met Results of this study as the first one in the country increase ourknowledge about seed dispersal of range plant species and can be applied for regeneration and protection of thevegetation in the semi steppe grazing ecosystems Keywords Central Zagros region dung samples grazing ecosystems seed germination experiments semi steppe rangelands soil seed bank dynamics vegetation natural regeneration

اقبالي، انيس

انتقال بذر توسط علفخواران اهلي و اهميت آن بر پويايي پوشش گياهي در مراتع شهرستان فريدن

آزمايش هاي جوانه زني بذر , احياي طبيعي پوشش گياهي , اكوسيستم چرايي , پويايي بانك بذر خاك , مراتع نيمه اسپتي , منطقه زاگرس مركزي , نمونه هاي سرگين