Plant Functional Traits Of Twigs And Their Relationships With Environmental Factors In Beishan Mountain Of Jinhua,Zhejiang Province

Plant functional traits,the interaction between plants and the environment in the process of plant evolution,not only respond to changes of environment,but also affect ecosystem process and functions.Twig is one of the building blocks of plants and also is the most active part of branching system.It has few secondary tissues,high internal nutrient transport rate,and has obvious trait characteristics,which can directly reflect the life history strategy.By studying the basic characteristics and differences of twig traits in different growth forms,life forms,and vegetation types,and associations of these traits,as well as the relationship between traits and environment,it has scientific guidance significance for deep understanding of subtropical evergreen broad-leaved forest species living strategies and evergreen broad-leaved forest ecosystem functions.In this study,the dominant tree and shrub species in 24 plots from six vegetation types(coniferous forest,coniferous and broad-leaved mixed forest,evergreen deciduous broad-leaved mixed forest,evergreen broad-leaved forest,secondary shrubland,and primary shrubland)were studied.We chose ten functional traits: twig diameter(TD),twig bark thickness(TBT),twig tissue density(TTD),twig dry matter content(TDMC),twig carbon content(TCC),twig nitrogen content(TNC),twig phosphorus content(TPC),twig potassium content(TKC),twig carbon to nitrogen ratio(C/N),twig nitrogen to phosphorus ratio(N/P),and combined with several environmental factors such as soil pH,organic carbon,total nitrogen,total phosphorus,total potassium and topography(elevation,slope,aspect).The twig trait characteristics and their relationships with key environmental factors were further analyzed.At the end,using shrubs grown in understory of forest communities and in two shrublands as special targets,we analyzed the differences of leaf and twig traits of these three different kinds of shrub species to reveal their different life strategies.Main findings are as follow:(1)There are significant differences in twig functional traits among different growth forms.Except for TPC and N/P,the other 8 twig characteristics were significantly different among different life forms.The extents of variation in 10 twig functional traits are different in 42 species.Interspecific-intraspecific variations of twig functional traits in different growth form and life forms showed that,mostly,the intraspecific variation is bigger than interspecific variation,variation of trees larger than that of shrubs,and variation of deciduous species greater than that of evergreen species.The bigger interspecific variation than intraspecific one occurred mainly in ecological stoichiometry traits.(2)There are differences in twig functional traits among different vegetation types.Forest communities have larger TD,TBT,TCC and TKC,but smaller TTD and TDMC than shrublands.Among them,the functional characteristics of twig in coniferous forest are significantly different from the other three forest communities.Secondary shrublands have a series of characteristics combinations with higher TD and C/N and smaller TBT,TDMC,TCC,TNC,TPC and N/P to store more nutrients and tolerate environment.(3)There are significant correlations among most twig functional traits.TD vs.TBT and TTD vs.TDMC have signifant positive correlations,TNC vs.C/N,and TPC vs.N/P have signifant negative correlations,and these four traits combinations have the greatest correlation.(4)The twig functional traits are mainly affected by species.Among them,the morphological traits of twigs were mainly affected by growth forms,and the ecological stoichiometry traits of twigs were mainly affected by habitats.The interaction between vegetation types and growth forms,the interaction between vegetation types and growth forms,and life forms have the least effect on the twig functional traits.(5)There are different extents of correlation between twig functional traits and topography,soil factors.The orderation results of redundancy analysis(RDA)showed that the impacts of topography factors on plant traits are greater than soil factors.The main environmental driving factors for twig functional traits of woody plants in Beishan Mountain of Jinhua are elevation and soil total potassium.The traits of TD,TBT,TPC and TKC increased with increasing altitude,while TTD,C/P and N/P decreased with increasing altitude.It reflects that twigs adapt to changes in slope and aspect may through resource conservation strategies.The TD,TBT,TCC,TPC and TKC are positively correlated with soil total potassium,and TTD,C/N,N/P are negatively correlated with it.Along with changes in soil elements and pH,twigs strengthen their defenses by increasing BT,TDMC,and TNC,TPC,and TKC probably.(6)Shrub traits of forest and shrubland revealed different life strategies in subtropical evergreen broad-leaved forest.Compared to shrubs from shrublands,understory shrubs in forest communities form a series of trait combinations that are larger leaf area(LA)and specific leaf area(SLA),smaller leaf tissue density(LTD),TTD and leaf dry matter content(LDMC)to grow faster to adapt to the understory environment with less light and stronger competition.This is a quick investiment-return(resource acquisitive)strategy.Secondary shrubland and primary shrubland have a series of shrub trait combinations that are larger leaf thickness(LT),LTD,LDMC and TTD,smaller LA,SLA to store more nutrients and grow slower.This is a slow investiment-return(resource conservative)strategy.This study indicates that the twig functional traits of dominant species in the Beishan Mountain of Jinhua are both closely related and different.Twigs of forest communities prefer to adopt acquisition resource strategies to develop a series of fast-growing traits.Twigs of secondary shrubland prefer to adopt a more resource-conservative strategy compared to primary shrublands to adapt to changes in the environment of limited succession of resources.Twig traits are formed under the influence of environmental and biological conditions.Different environmental conditions have an important impact on various traits and their variation in growth forms,life forms and inter-intraspecific variations.Twigs can adapt to changes in the topography and soil environmental factors by enhancing their defense capabilities and adopting tolerance strategies.Different combinations of shrub functional traits and their various life strategies can provide guidance to the ecological restoration of degraded vegetation in the subtropical region of China.