Seed Rain And Soil Seed Bank In Fragmented Habitats And Their Influencing Factors

Seed production,scattering(seed rain)and storage in soil(soil seed bank)are important processes in the life history of spermophyte.These processes are key factors in the regeneration of forest population and community and are affected by habitat fragmentation.The problem of habitat fragmentation in China is serious,and the Thousand Island Lake(TIL)is an ideal platform to study the impact of habitat fragmentation on forest community and its regeneration process.Therefore,exploring seed rain and soil seed bank in fragmented habitats and their influencing factors are of great significance for understanding the mechanism of habitat fragmentation on forest community regeneration.The research was conducted on 29 study islands in the Thousand Island Lake.First,using the seed rain data collected from 2015 to 2020,this study analyzed the impact of mother tree,island area,isolation,and edge gradient on seed rain of woody plant,and further explored how the island area,isolation,and climate factors(accumulated temperature above 0℃,and precipitation)effect on the temporal dynamics of seed rain of woody plant.Secondly,this study used the soil seed bank data of 6 samplings from the winter of 2015 to the spring of 2018 to analyze the temporal dynamics of soil seed bank.The impact of island area,isolation,and edge gradient on species composition and diversity of soil seed bank were explored.Finally,the similarity between soil seed bank,seed rain and woody plant community was compared.The main results are as follows:(1)In the past 6 years,877178 mature seeds of woody plant were collected from 240 seed traps on 29 study islands,belonging to 26 families,40 genera and 52 species.The top three species with the number of seeds collected were Lyonia ovalifolia var.hebecarpa,Vaccinium carlesii,and Eurya muricata.Zoochory was the major dispersal syndrome in the TIL.(2)Climate factors,island area and isolation in fragmented habitats affected the temporal dynamics of seed rain of species with woody plant.The annual density of seed rain of woody plant was positively correlated with island area and annual accumulated temperature,and negatively correlated with annual precipitation.The monthly density of seed rain of autochory was positively correlated with the distance to the nearest island,while that of zoochory was positively correlated with the distance to the mainland,and that of anemochory was positively correlated with accumulated monthly temperature.(3)Six times of soil seed bank sampling was conducted on 29 study islands in 3 years,and 80 plots,which received a total of 3083 germinated plant seeds belonging to 39 families,64 genera and 64 species.The number of seeds germinated by Eurya muricata was the largest.The soil seed bank had an obvious vertical distribution.The number of seeds in the upper layer(0-2cm)of the soil seed bank was extremely significantly higher than that in the lower layer(2-5cm).At the same time,there were also seasonal dynamics,and the number of seeds in the lower layer of spring in soil seed bank was extremely lower than that of winter.(4)Composition of soil seed banks was affected by isolation and edge gradient.The number of seeds in the soil seed bank was positively correlated with the distance to the distance to the nearest island.The number of woody plants’ seeds in the soil seed bank increased with the increase of the edge gradients.(5)The similarity between the seed rain and woody plant community was moderate,while the similarity between the soil seed bank and seed rain and woody plant community was very dissimilar.It showed that seed dispersal was an important way of plant community regeneration in TIL,and it was speculated that soil seed bank in study islands played a small role in plant community regeneration.In conclusion,habitat fragmentation affects seed rain and soil seed bank,thereby affecting ecological processes such as seed dispersal and plant regeneration.This study helps to better understand the impact of habitat fragmentation on the regeneration mechanism of forest communitiy,and provides a scientific basis for the protection and ecological restoration of fragmented forests.