Ecological Adaptation Of Plants On Karst Tiankeng Of South China

Karst tiankeng,a new number in karst topography family named in the early 21th century,is a special and grand negative terrain.Its plant community structure structure and function in the inside-tiankeng habitats have important conference value to the vegetation restoration of karst region.Recently,the special habitats characteristics and plant community of karst tiankeng gradually has been valued along with the tiankeng value has been excavated,but the response and adaptation on tiankeng habitat is relatively weak.Starting with the plant diversity and functional traits,moderate degraded tiankeng which has high accessibility-Bajiaxiantang has been selected to calculate the community species composition,plant diversity,species indicator value,plant functional traits and plasticity index by the methods included R,PAST and SPSS statistics software.Ecological adaptation of karst tiankeng vegetation has been discussed from three contents including the plant community diversity structure and characteristics,the plant functional traits characteristics and the relationship between traits and environmental factors.The results showed that:1)There were 65 species belonging to 33 families and 62 genera inside the tiankeng,and the species composition was relatively diverse.Indicator species including Arisaema erubescens,Eupatorium adenophorum and Arthraxon hispidus could significantly indicate the change of tiankeng habitats;2)Along with the slope position environmental gradient,significant difference in tiankeng mouth and the bottom had existed,and the change tendency of ? diversity were gradually increased and the co-existed species were gradually decreased.The community ecotone were appeared in the bottom edge with the significant habitats heterogeneity;3)The variance ratio of overall association in tiankeng's grassland community had overall significant positive inter-specific association.Combined with the difference of tiankeng's micro-environment,dominant species of degraded tiankeng could be divided into three ecological species groups and the grassland community showed the circle distribution pattern,and plant community can well adapted to the habitat of tiankeng;4)Along the slope aspect gradient,the difference of species composition were large,the energy flow in the different habitats were fast,and the species turnover rates were fast.Among of them,the obvious difference of plant diversity were existed between the northeast slope and northeast slope,and the community composition were extreme dissimilar;5)The specific leaf area(SLA)'s distribution scope of Arisaema erubescens were 22.00-38.45 m2/kg,leaf dry weight were 28.29-113.79 mg.Traits value of tiankeng mouth significantly were less than the traits value of lower slope,which had significant correlations between leaf and steam traits,and were influenced by the environmental factors included pH value,soil moisture content;6)Due to adapting the tiankeng habitats,the leaf dry weight,plant height,leaf size and basal culm thickness of Eupatorium adenophorum belonged to sensitive traits,and the length-width ratio,leaf length-petiole length ratio belonged to the insensitive traits;7)In inside and outside-tiankeng habitats,the functional traits of Eupatorium adenophorum existed significant difference,and the traits value of outside-tiankeng all higher than the traits value of inside-tiankeng except for SLA.Common adaptation of multiple traits had been taken by the tiankeng plant,rather than the adaptation of single trait.In all environmental factors,soil factors had greater effect on the distribution of plant traits.