Characteristics Of Livestock Dung Seed Bank And The Effect Of Yak Dung Retention Time On Vegetation Variation In Alpine Grassland

Under the grazing ecosystem system in alpine grasslands on Qinghai-Tibet Plateau,we researched that:1)the seed bank characteristics both yak and Tibet-sheep dungs in alpine meadow and alpine shrubs,2)the effects of yak dung on the botanical community characteristics,herbage,soil nutrients and grazing animals defoliation performance in regions around dung patches(0-10cm,10-20cm and 20-30cm)at three periods after yak dung deposition in alpine meadow.We clarified the relationship between livestock dung seed bank and botanical community characteristics in alpine grassland and determined the temporal and spatial effects of yak dung deposition on vegetation changes in alpine meadow.From the perspective of Tibetan livestock dung deposition,revealing the ecological mechanism of vegetation change in alpine grassland to provide practical basis for the livestock feces management.The main results are following:1)The seed density in alpine meadow was sheep dung>yak dung,while for alpine shrub it was yak dung>sheep dung.The number of seeds defoliated by yak was alpine shrub>alpine meadow,while the seeds defoliated by sheep was alpine meadow>alpine shrub.Under two vegetation types,the number of germinated plant species in both yak and sheep dungs was initial grazing stage>middle grazing stage>final grazing stage.The seed density in yak dung on the alpine meadow was initial grazing stage>middle and final grazing stages,while for alpine shrubs it was middle grazing stage>initial grazing stage>final grazing stage.The seed density in sheep dung in alpine meadow and shrub was initial grazing stage>middle and final grazing stages.The plant species in grazing animals dung was similar to that in the pasture.2)The effect of yak dung on its surrounding herbage nutrient related to their distance from the dung patch.The P,Cu,Mn,Ca and Zn contents in herbage in different dung areas was 0-10cm or 10-20cm>20-30cm.The yak dung had a promoting effects on the plants growth that in dung surrounding areas.The influence of dung deposition on soil nutrients related to the duration of dung deposition,which can increase the soil N,P and K contents.The Fe,Mg,Mn and Zn contents in soils around the dung at three periods after yak dung deposition was in this year>that for a year and for two years.The dung nutrient takes two and a half years or longer to decompose in soil completely.3)Tibetan livestock abandoned the 0-20cm plants around yak dung.With the increasing of yak dung deposition time,the degree of abandonment was gradually reduced.The negative effect of livestock abandon the yak dung surrounding plants was greater than positive effect of dung fertilized on its surrounding plants.