Composition And Dynamics Of Seed Rain And Soil Seed Bank In Fragmented Masson Pine Forests In The Thousand Island Lake Region

Seed is the important stages in plant life history of it's production,drop of seed rain and stored in the soil(soil seed bank).Seed rain and soil seed bank are important for community regeneration and biodiversity maintenance,and for community succession and restoration.Masson pine forests are pioneer community in secondary succession,which distribute vey widely in subtropical region,plays a critical role in maintaining regional ecosystem services and biodiversity.Globally,habitat fragmentation is increasingly impacting forest systems.Habitat fragmentation affects forest community dynamics and biodiversity through its influence on regeneration stages such as seed rain and soil seed banks.Investigating how habitat fragmentation affects seed rain and soil seed banks in Masson pine forests is meaningful to deepen our understanding on fragmented Masson pine forest regeneration and succession,which is beneficial to inferring the biodiversity maintenance in Masson pine forests,and providing theoretical knowledge to guide forest conservation and managementThe study site Thousand Island Lake(TIL)is an artificial lake,which built a dam in Xin'an river on 1959,it's owns more than 1000 islands.To study habitat fragmentation effects on seed rain of the Masson pine forests,we set up 250 seed traps distributed in Masson pine forests on both the mainland and 29 sampled islands of the year 2014 to 2015.We collect the seed rain once a month,sort and identified the collected seeds to species.To study habitat fragmentation effects on soil seed bank of the Masson pine forests,we adopted the large number small sample method and sampled soils in Masson pine forests on both the mainland and 29 study islands.We systematically sampled the soils at maximum in early winter of December of 2015 and minimum in late springof April of 2016 soil seed bank seasons.Then we conducted germination experiment on the soil samples,to estimate the upper(0-2 cm)and lower(2-5 cm)layer soil seed bank compositions and dynamics.We investigated seed rain composition and dynamics and their influencing factors;by adopting the generalized linear mixed modeling framework,we investigated habitat fragmentation factors(e.g.island area,island shape index and isolation)effects on soil seed bank composition and dynamics.The major results are as follows,(1)During January of 2014 and December of 2015,a total of 115692 seeds were collected by the 250 seed traps.These seeds belong to 24 species,27 genera and 18 families.Mean seed rain density was 331 m-2·a-1.(2)At both the community and species levels,the peaks of seed rain fall were in autumn and winter,with large anomaly between years.(3)Apart from dominant species such as Eurya muricata,other species were generally affected by dispersal limitation during the seed rain stage.(4)Island size showed an important effect on seed rain composition,shown as large islands received higher seed rain density than small islands both at the community and specie levels.(5)A total of 1422 seedlings were germinated from 316 soil samples.These seedlings belong to 41 species,40 genera and 29 families.Woody plant seedlings composed 1024 individuals and 13 species,herbaceous plant seedlings composed 398 individuals and 28 species.(6)Jaccard index and correlation analyses showed that soil seed bank composition was highly similar between seasons and soil layers.(7)Generalized linear mixed modeling showed that,in both mainland and island forests,the lower soil layer harbored less seeds than the upper layer;mainland forest soil seed bank harbored more woody plant seeds than island forests;in island forests,seed number decreased as soil layer deepened;Seed number in soil seed banks decreased as distance from edge increased,especially for herbaceous plant seeds.Among the woody plant seeds in island forest soil seed banks,shade intolerant species seed number was much larger than shade tolerant species,especially in the lower soil layer.This study suggests that habitat fragmentation largely influenced seed rain and soil seed bank of the Masson pine forests in the Thousand Island Lake Region,which might pose middle to long term impacts on the succession of Masson pine forest communities.This study deepens our understanding on the regeneration dynamics of Masson pine forests under habitat fragmentation,which is helpful to developing forest conservation and management policies,guiding the succession of such forest type,and improving the forest ecosystem function and biodiversity maintenance.