Trade-off Between Seedling And Sprouting In The Regeneration Layer Of Karst Plant Communities

The karst ecosystem is an important part of the world ecosystem and an important place for human survival and development,but the karst ecosystem in Southwest China has been or is facing the threat of Karst Rocky Desertification(KRD).Vegetation restoration is the key step and fundamental in the KRD control.With the background of “rewild” the degraded ecosystem management,choosing the appropriate mode of vegetation restoration is increasingly important,but the biggest key is where the plant propagules come from?Plants propagate by seed(spore)or vegetative propagation.In the process of forward or reverse succession of plant communities,plant propagules have their own rules that differences and tradeoffs between vegetative and sexual propagules,and the differences are more obvious in heterogeneous habitats.The seed(spore)bank and bud bank constitute the reproductive pool of a plant community as the source of vegetation restoration.There are a lot of research results mainly concentrated in sexual reproduction(seed bank,seed rain)research,less attention to the resprouting,especially the trade-off between seedling and resprouting.Study on the characteristics of the trade-off between seedling and resprouting,affecting the restoration of degraded ecosystems directly,and the coordination of artificially assisted restoration,and then affect the restoration and sustainability of species diversity and the restoration of ecosystem functions.Microhabitat is an important unit of interpretation of environmental heterogeneity and a bridge between geological diversity and biodiversity.In karst areas,the types of karren are diverse and numerous,which are the basis of microhabitat for plant growth,conservation and regeneration.The karren-habitats are the karren that there is soil and plants distribution and growth.The characteristics of karren-habitats have an important influence on the types and tradeoffs of the propagule in the community.In this paper,chose one of the centers of the “South China Karst” —Shilin Geology Park(located in Shilin county,Yunnan Province)as the research site,according to the relationship between karren,soil and plant growth divided the karren-habitat into five types:solution corridors;solution wells or shafts;kluft karren;deep solution pits;and solution rock debris.In order to explore the propagule sources of the natural restoration of karst vegetation,this study is expected to be beneficial and provide theoretical and technical support for the restoration of degraded karst ecosystem(KRD control).The main conclusions of this study are as follows:(1)The characteristics of propagule bank distribution and conservation are profoundly affected by the karren-habitats.The morphological characteristics and spatial structure of karst karren-habitats form some special "habitat islands",which can preserve a certain number of vegetative propagula,because of the change of disturbance accessibility of the habitats.However,the anti-interference ability of different habitats is different,and the order of anti-interference ability is roughly in the order of solution rock debris > kluft karren > solution wells or shafts > deep solution pits > solution corridors.Generally,the narrower the habitat,the more residual,but this kind of habitat is not the ideal habitat for plant growth and development.Once the disturbance stopped,the sprouting preserved in karren-habitat matured which could provide a new source of propagules(sexual reproduction)for the maintenance and ecological restoration of karst biodiversity.There were also differences in the fate of sexually propagula after entering the indentation habitat.(2)The karren-habitat has a profound impact on the tradeoffs of species reproduction patterns in communities.The proportion of sprouting was more than 50% among species with both sprouting and seedling,especially in kluft karren and solution rock debris.However,with the degradation of the community in different succession stages,the kluft karren,pits,corridors and derris tended to be more and more sprouting,while the change trend of the wells was not obvious.Corresponding to this,seedling is reduced,and even there is no seedlings in the rocky desertification grass except for debris.(3)The species dispersal patterns of karst plant communities affect the species composition of restored communities.Different communities were mainly distributed by zoochory.With the degradation of the community,the proportion of zoochory gradually decreased,but it increased to rocky desertification.The proportion of anemochorous increases roughly as the community degrades.The proportion of seed(spore)dispersal in different karren-habitats did not change much,and the dispersal was mainly zoochory,followed by anemochorous,and auto dispersal.Community degradation also affected the change of seed dispersal pattern in the karren-habitat.(4)The protection of karst habitats is beneficial to the maintenance of karst biodiversity and vegetation restoration.A certain number of vegetative propagula are preserved in karst karren-habitats,and their maturity will provide a new source of propagules(seeds)for vegetation restoration(comprehensive control of KRD),increasing the possibility of natural restoration of degraded karst vegetation.At the same time,selecting native species with strong natural transmission capacity or key zonal vegetation species for replanting,assisted by corridors and management,is conducive to the vegetation restoration of karst.