Characteristics Of Soil Seed Bank During Natural Restoration Process Of Populus Deltoides Cutting Slash In Lake South Dongting

Soil seed bank is referred to all the viable(dormant as well as ready to germinate)seeds contained in the soil and lying on the soil surface,it not only play an important role in vegetation development during succession but also considered to be an important potential seed source for the restoration of plant communities.To understand the potential of soil seed bank in natural vegetation restoration of Populus deltoides cutting slash in Lake South Dongting,and the influence of flooding season on the restoration and succession of aboveground vegetation,the structure and diversity of soil seed bank and its relationship with aboveground vegetation and soil physical and chemical factors were observed and analyzed in different season on the lake beach 1 year and 2 years after P.deltoides cutted,with P.deltoides lake beach as control(CK).And which provide some theoretical guidance for studying the response of Dongting Lake wetland ecosystem to water regime and subsequent ecological restoration,protection and management.The main results were as follows:(1)A total of 65 species were germinated in soil seed bank of the study plots,belonging to 59 genera and 23 families,the density of soil seed bank was 2238.58～11810.55 seeds.m-2 and decreased along with the soil depth.Compared with ck,the number and density of species in the soil seed bank was increased as well as the species diversity index of the soil seed bank and the similarity coefficient between soil seed bank and aboveground vegetation,increased significantly(P<0.05).The proportion of perennial mesophytes and hygrophytes gradually increased,and the community species structure tends to be complex.(2)The number and density of species in different soil layers and recovery years in autumn decreased compared with that in spring,and the characteristics of the soil seed bank changed significantly before and after the flooding season(P<0.05).The species diversity index of the soil seed bank in autumn decreased compared with that in spring,while the coefficient of similarity with the aboveground vegetation increased,and species in seed bank are more closely related to plant species.The proportions of dominant species in soil seed banks and aboveground vegetation differed in different restoration years in spring and autumn,annual or biennial mesophytes in autumn decreased compared with spring,while the proportion of perennial hygrophyte species,such as Phragmites australis and Carex spp.,which reproduce mainly asexually,increased.It can be seen that the fluctuation of the water level promotes vegetation succession towards to later stage during the natural restoration process of cutting slash.(3)The soil physicochemical properties between cutting slash and ck significantly different(P<0.05).The soil pH,bulk density and electrical conductivity decreased,while the soil moisture content increased by 7.68%after P.deltoides is cutted.Total nitrogen,available nitrogen,available phosphorus,total carbon content,urease,alkaline phosphatase and sucrase activities increased first and then decreased with recovery years.The content of total phosphorus,total potassium and available potassium gradually increased with recovery years,soil fertility is significantly improved.(4)Soil water content,total nitrogen and et al have a very significant positive correlation with soil seed bank density,while pH has a significant negative correlation with soil seed bank density.Soil water content and organic matter were closely related to the distribution of hydrophytes such as Polygonum hydropiper,and total potassium and phosphorus had a greater influence on the distribution of species of perennial plants such as Phalaris arundinacea.Therefore,during the natural restoration process of P.deltoides cutting slash,with the change of soil physicochemical properties,the species number and density of the soil seed bank increased significantly,therefore,the diversity of aboveground vegetation species increased.Soil seed bank had become an important propagule source for the restoration of wetland vegetation in cutting slash.