Characteristics Of Seed Rain And Soil Seed Bank Made By Pika In Alpine Meadow

In order to understand the mechanism underlying degraded succession of alpine meadow and provide theoretical basis for ecological restoration,the relationship between the existence of pika mound and the formation of "black soil beach" type degradation was explored.Based on the investigation of seed rain and soil seed bank in alpine Kobresia meadows in Henan and Menyuan counties of Qinghai Province,we studied the role of actual seed rain and potential seed rain in vegetation restoration,the dynamics of the seeds in the soil seed bank of pika mound,and the effect of pika mound on the covered vegetations.The main results were as follows:1.The morphological characteristics of seeds or fruits in our studied sites were relatively stable.Most of the seeds entered into the soil in the form of fruits,and the most common dispersal mode of these species were wind dispersal.Most of the seeds(or fruits)were light and their surface had various patterns or reticular structures which could benefit to absorption and storage of water.2.Most of the seeds in seed rain belong to species from Leguminosae and Compositae in alpine meadow.The more distinct hierarchical structure the grassland had,the easier the seed rain to collet.The temporal patterns of seed rain dispersal showed a single peak mode,and the peak occurred in September.The time nodes and duration of seed rain were depended on vegetation types.The correlations between seed rain and its aboveground vegetation were different under different experimental sites and seeds of exotic species occurred in the seed rain.Alpine meadow contained abundant seed rain resources,and there might be even more amount of potential seed rain than that was measured in our study.3.The number,quality and germination rate of seed in natural grassland soil seed bank were higher than those in old and new pika mound soil seed bank.And the quantity and quality of seed in natural grassland soil seed bank showed obviously seasonal dynamics,that is high from October to November and low in May to June.The soil seed bank of natural grassland(control)showed obvious vertical distribution pattern,and there was no obvious vertical distribution between the upper and lower layers of new and old pika mound.The seed germination rate of pika mound soil seed bank was more than 50%,slightly lower than that of seed from seed rain(60%).4.The vegetation coverage of pika mound gradually increased after the formation of it,and the vegetational succession of pika mound towards restoration and plant settlement.The contribution of native species to germinated plants reached to 47%-65% of species composition,and most of the germinated plants belonged to forbs and broad-leaved plants,while there were no Kobresia species appeared after formation of pika mound.