Characteristics And Correlation Of Branch Functional Traits Of Woody Plants In Evergreen Broad-Leaved Forest In Jiangxi Province,China

Bark and wood have several basic functions such as protection,storage,transportation,mechanical support,and photosynthesis,which have important effects on the physiological processes of plant growth and development.Studying the functional traits of bark and wood is of great significance for understanding the response of plants to environmental changes and the impact on the formation of ecosystem functions.A typical mid-subtropical forest ecosystem on the west side of the middle section of Wuyi Mountain is preserved in Yangjifeng National Nature Reserve,Jiangxi Province,which provided favorable conditions for the study of plant functional traits.In order to explore the differences in the functional traits of bark and wood of different leaf habits(i.e.,evergreen and deciduous)species,and whether there is an economics spectrum for bark and wood and the entire branch,80 broad-leaved woody plants from the nature reserve were taken as research objects in this study.The main functional traits(i.e.,phenotypic,chemical and anatomical traits)of bark and wood on mature branches were measured.Besides,the variation of bark and wood functional traits between different leaf habits and different light gradients and the relationships of functional traits in/between bark and wood were analyzed.The main findings of this work were as follows:(1)In terms of the characteristics of branch functional traits,evergreen and deciduous species have no significant difference in bark density(P > 0.05).Compared with deciduous species,the branches of evergreen species have higher wood density,lower bark and wood water content and lowe nitrogen and phosphorus content,as well as smaller vessel diameter and greater vessel density(P < 0.05).In addition,the branch traits of evergreen species have higher plasticity under different light gradients.(2)In terms of the relationships between bark functional traits,total bark thickness was negatively correlated with bark density(P < 0.001)but positively correlated with bark water content(P < 0.05)for evergreen species.On the whole,bark density was negatively correlated with bark water content(P < 0.001).Bark nitrogen content was positively correlated with bark phosphorus content(P < 0.001)and these two traits were significantly related with other stoichiometric ratio such as bark nitrogen to phosphorus ratio(P < 0.001).(3)In terms of the relationships between wood functional traits,wood density was negatively correlated with both the vessel diameter and wood water content(P < 0.001).Vessel density was negatively correlated with vessel diameter(P < 0.001).Wood nitrogen content was positively correlated with wood phosphorus content(P < 0.001)and these two traits were significantly related with other stoichiometric ratio such as wood nitrogen to phosphorus ratio(P < 0.001).(4)In terms of the relationships between the bark and wood functional traits,for the morphological traits,bark density and wood density were positively correlated(P <0.001),the same trend was observed between bark water content and wood water content.For the chemical traits,except for the carbon content,there were significant positive correlations between the nitrogen content,phosphorus content,carbon to nitrogen ratio,carbon to phosphorus ratio and nitrogen to phosphorus ratio of the bark and wood tissues(P < 0.001).(5)In terms of the resource trade-off strategies,there was an economics spectrum in the bark,wood and entire branches of woody plants.Different leaf habits species have different resource trade-off strategies: most of the evergreen species gathered at the slower investment and return end of the economics spectrum and tended to adopt a conservative strategy;while most of the deciduous species clusted at the faster investment and return end of the economics spectrum and tended to exhibit an acquisitive strategy.In summary,leaf habits and light gradients could affect the functional traits of the branches.The functional traits in/between bark and wood were closely correlated.The branches of different leaf habit species have formed different environmental adaptation strategies during long-term evolution.This results further enriched the theory of plant economics spectrum in subtropics,which can provide reference for understanding niche differentiation and species coexistence mechanisms,and provide a theoretical basis for the adaptive management of ecosystems.