Functional Traits And Functional Diversity Of Forest Vegetation Plants In Karst Hills Of Guilin

Plant functional traits reflect the evolutionary responses of plants to biotic and abiotic factors in a community.The methods based on plant functional traits have been widely used to analyze the adaptive mechanisms of plant growth and community assemblage.In order to explore the characteristics of plant functional traits and functional diversity of forest vegetation in karst hills of Guilin,this paper takes deciduous broad-leaved forest,mixed evergreen and deciduous broad-leaved forest,and evergreen broad-leaved forest in karst hills of Guilin were chosen as the research objects.A1 hm2 forest dynamic sample site was established in each location in Mao Village,Lingchuan county,Long Village,Yongfu county,and Beitou Village,Yangshuo county,respectively.By means of field investigation,through the collection of plant and soil samples,the measurement of indoor plant functional traits and soil sample physical and chemical indexes.The methods of data statistics,one-way analysis of variance,null model analysis,redundancy analysis combined with Monte Carlo random replacement test and the like are adopted.The effects of environmental factors on plant functional traits and functional diversity,and to clarify the driving mechanism in the process of forest vegetation community assembly and the response mechanism of the community to environmental changes.It is expected to provide a scientific basic for the protection of karst forest vegetation and species coexistence.The results were as follows:(1)A total of 151 plant species,belonging to 104 genera and 46 families,were recorded through investigation and collection in 75 plots from 3 sites in the study area.There were 11546 live woody plant individuals in the study area,including 5784 trees,5312 shrubs and 450 lianas;2940 in deciduous broad-leaved forest,1605 in mix evergreen and deciduous broad-leaved forest,and 7001 in evergreen broad-leaved forest.Among the different forest vegetation types,63 plant species were recorded in the deciduous broad-leaved forest,belong to 33 families and 58 genera.There were 91 species of mixed evergreen and deciduous broad-leaved forest,belong to 37 families and 66 genera.There were 84 species of evergreen broad-leaved forest,belong to 35 families and 66 genera.(2)Environmental factors vary with the change of vegetation type,specifically manifested as soil water content,p H value,and total phosphorus gradually increase in the development process of deciduous broad-leaved forest to evergreen broad-leaved forest,and total nitrogen content is the opposite;The available potassium content is the highest in evergreen broad-leaved forest,but the available nitrogen content is the lowest.The contents of available potassium and available nitrogen were the highest in deciduous broad-leaved forest.On the whole,deciduous broad-leaved forest contains higher soil nutrients,while mixed evergreen and deciduous broad-leaved forest and evergreen broad-leaved forest contain relatively lower.(3)The community functional traits showed significant differences among different vegetation types.Among them,the leaf dry matter content,leaf thickness and wood density have maximum values in the evergreen broad-leaved forest and show a gradual increasing trend in the development process from deciduous broad-leaved forest to evergreen broad-leaved forest.The maximum values of leaf area and specific leaf area appear in the deciduous broad-leaved forest,and show a gradually decreasing trend.It indicated that in the process of development from deciduous broad-leaved forest to evergreen broad-leaved forest,the survival strategy of plants has changed from the open strategy of quickly obtaining external resources to the conservative strategy of saving resources.(4)The results of null model analysis based on community functional traits showed that both environmental filtration and limitation similarity had certain effects on the assembly of three forest vegetation communities in karst hills,and the importance of these two mechanisms for community assembly varied with the vegetation type.The specific performance was that the three forest vegetation types under the special habitat of karst hills were all subjected to strong environmental filtration;In the deciduous broad-leaved forest with suitable environmental conditions,the limited similarity effect affecting the distribution of functional traits was more obvious.(5)By analyzing the changes of species diversity index and functional diversity index in different forest vegetation,it can be known that the change rules of species diversity and functional diversity were similar,among which Patrick richness index and functional richness index show the law of evergreen broad-leaved forest > deciduous broad-leaved forest > mixed evergreen and deciduous broad-leaved forest,and Pielou evenness index and functional evenness index show the law of mixed evergreen and deciduous broad-leaved forest > deciduous broad-leaved forest > evergreen broad-leaved forest.(6)The effects of environmental factors on species diversity and functional diversity in different forest vegetation are slightly different.Among then,the main environment factors affecting species diversity of deciduous broad-leaved forest were canopy openness and soil water-soluble calcium,and main factors affecting functional diversity were rock exposure rate and soil water-soluble calcium.The environmental factors that affect the species diversity and functional diversity of mixed evergreen and deciduous broad-leaved forest were rock exposure rate and soil thickness,and the species diversity was also significantly affected by soil available nitrogen.The main environmental factors affecting the species diversity and functional diversity of evergreen broad-leaved forest were the rock exposure rate,soil water content and soil thickness.To sum up,forest vegetation in karst hills has formed different environmental adaptation strategies in different habitats.The reasonable collocation of community structure and the diversity of species and functional traits should be considered in the research on the protection and management of biological diversity and vegetation restoration.