A Comparative Study On The Characteristics Of Soil Seed Bank Of Five Communities In Northwest Liaoning Grassland

The soil seed bank is the collection of all surviving seeds present on the soil surface and in the soil,which is a potential force for population renewal.As the basis for community settlement,survival,reproduction and dispersal,soil seed bank can predict the direction of community succession and provide the theoretical basis for scientific management of grassland.In Northwest Liaoning,grassland resources are abundant and communities of various vegetation types coexist,but the ecological stability is poor and the growth of above-ground vegetation is easily restricted,which in turn leads to the decline of ecological diversity in Northwest Liaoning grasslands.The seeds stored in the soil seed bank provide favorable conditions for the growth of vegetation and the increase of community species diversity.However,the species composition and characteristics of the soil seed bank vary greatly among communities,and such differences cause differences in the species composition and vegetation growth of above-ground vegetation.Therefore,it is very important to study the differences in soil seed bank characteristics among communities for scientific management of grasslands.However,there is a lack of comparative studies on soil seed bank characteristics among different communities in the grasslands of northwest Liaoning,where ecological stability is poor.Therefore,this experiment was conducted to study the differences of soil seed bank characteristics among different communities in northwest Liaoning,with the aim of providing technical support for scientific management of the grassland in northwest Liaoning.In this experiment,we analyzed the seed density,species diversity,richness,evenness and ecological dominance of the soil seed bank in autumn,spring and summer with two soil layers of 0-5 cm depth and 5-10 cm depth in five major communities: Leymus chinensis community,Stipa grandis community,Carex duriuscula community,Themeda japonica community and Lespedeza hedysaroides community distributed in northwest Liaoning.The characteristics of above-ground vegetation between communities were also compared,and the number and species of seedlings in the five communities were recorded to explore the differences in soil seed bank input and output between communities.The characteristics of aboveground vegetation community diversity and the similarity of species composition between aboveground vegetation and soil seed bank were comprehensively analyzed for the Leymus chinensis community,Stipa grandis community,Carex duriuscula community,Themeda japonica community and Lespedeza hedysaroides community in northwest Liaoning grassland.The main results were as follows:(1)The seed density and species diversity,richness,evenness,and ecological dominance of the soil seed bank at two soil depths showed large differences among different communities under three seasons.We found that the seed density of the soil seed bank was higher in the Themeda japonica community at both soil depths in autumn and summer,and the species diversity,richness and evenness of the soil seed bank at both soil depths were also higher in autumn,but the ecological dominance of the soil seed bank species was lower.In contrast,the Lespedeza hedysaroides community,as a shrub-based community,was able to accumulate more seeds.In spring,the seed density of the soil seed bank was higher in the 0-5 cm soil layer of the Lespedeza hedysaroides community,but the species diversity,richness and evenness of the soil seed bank were lower,but the ecological dominance of the soil seed bank species was higher.This indicates that differences among communities can lead to differences among soil seed bank characteristics.(2)The seed density and species diversity,richness and evenness of the soil seed bank in the 0-5 cm soil depth were better in the five communities than in the soil seed bank in the 5-10 cm soil depth under three seasons.In all five communities,the seed density,species diversity,species richness and evenness of the soil seed bank in the 0-5 cm soil depth were higher than those in the 5-10 cm soil depth in all three seasons.However,another important finding was that the ecological dominance of the soil seed bank was higher in the 0-5 cm depth for the five communities in the three seasons.This indicates that the soil seed bank in the soil surface layer contributes more to the growth of grassland vegetation.(3)There were differences between seed density and species diversity,richness,evenness,and ecological dominance of the soil seed bank at two soil depths for the five communities under three different seasons.In autumn,spring,and summer,the seed density and species diversity and richness of the soil seed bank at two soil depths in the five communities were lowest in summer.However,the ecological dominance of species in the soil seed bank at 5-10 cm soil depth was higher in all five communities during summer.This is more related to the seed reduction caused by the growth of aboveground vegetation.(4)There were great differences in above-ground vegetation among the five communities.Among them,the above-ground biomass and plant height of the Stipa grandis community were higher than those of the other four communities,and the plant height of the Themeda japonica community was second only to that of the Stipa grandis community.However,in terms of plant density,the plant density of the Carex duriuscula community was significantly higher than that of the other four communities.The species diversity and evenness of above-ground vegetation in the Themeda japonica grass community were lower than those in the other four communities,but the ecological dominance of above-ground vegetation was higher.And the species diversity and evenness of aboveground vegetation of Lespedeza hedysaroides community were significantly higher than the other four communities,but its ecological dominance was higher.(5)Comparing the similarity of species composition of aboveground vegetation and soil seed bank of the five communities,we found that the species composition of aboveground vegetation and soil seed bank of different communities differed significantly at two soil depths in three seasons.Among them,the similarity between the species composition of soil seed bank and above-ground vegetation was higher in both soil depths of Themeda japonica grass communities in autumn,spring and summer,which is more predictable for the species composition of grassland communities in northwest Liaoning and more beneficial to provide technical support for scientific management of grassland.In summary,the soil seed bank in Leymus chinensis community,Stipa grandis community,Carex duriuscula community,Themeda japonica community and Lespedeza hedysaroides communities showed characteristics of vertical distribution under all three seasons.In summer,the seed density,species diversity,richness and uniformity of the 5-10 cm soil seed bank were lower in all five communities.In addition,among the five communities,the Themeda japonica community had a higher seed density in the soil seed bank at both soil depths during autumn and summer,and the species composition of the above-ground vegetation and the soil seed bank were more similar.This experiment deepened the understanding of the variability of soil seed bank characteristics among different communities in northwest Liaoning grasslands and provided technical support for scientific management of northwest Liaoning grasslands.