Variation And Inner Relationships Of Leaflets Traits For Three Hardwood Tree Species In The Northeastern China

The compound-leaved plants have the characteristics of rapid growth ability and high productivity,and play an important role in the material cycle and energy flow process of the ecosystem.Leaf functional traits can reflect the adaptation mechanism of leaves to environmental changes.Based on leaf functional traits,discussing the variation and inner relationships of leaflet traits at different leaflet grades in compound leaves can provide theoretical guidance basis for understanding the role of the compound-leaved plants in ecosystem.Taking three species of compound-leaved species with opposite leaflet grade in the Xiaoxing’an Mountains area as the research objects: Fraxinus mandshurica,Phellodendron amurense,Juglans mandshurica,by measuring the leaf thickness(LT),leaf area(LA),specific leaf area(SLA),leaf mass per area(LMA),leaf dry matter content(LDMC),palisade tissue thickness(PT),spongy tissue thickness(ST),carbon content(C),nitrogen content(N),phosphorus content(P),etc.,13 leaflet traits,to analyze the variation of leaflet traits of different functional types among different tree species and at different leaflet grades,to explore the variation coefficient and phenotypic plasticity index of leaflet traits in compound leaves;to analyze the effect of leaflet grade on the binary and multivariate correlation among leaflet traits,and explore the similarities and differences among different species;the direct and indirect effects of leaflet grade,PT,ST and leaf tissue density(LD)on LMA were explored.The results showed that leaflet grade can significantly affect LA,LDMC,ST,the ratio of palisade tissue thickness to spongy tissue thickness(PT/ST),and LD,and they mainly produced three changes with the increase of leaflet grade: increase,decrease,first increase and then decrease.Within the intact compound leaves,the variation coefficient and phenotypic plasticity index of the morphological traits(LT,LA,SLA,LDMC,LD)and anatomical traits(PT,ST,PT/ST)of the leaflets of the three trees were 6.1%～28.6% and 0.14～0.70respectively;the degree of variation of LA in J.mandshurica leaflets was greater than that in F.mandshurica and P.amurense leaflets,with the variation coefficient of 28.6%,6.1% and 6.1%respectively.In general,the coefficient of variation and plasticity index of leaflet anatomical traits were greater than that of leaflet morphological traits.The variation coefficient of chemical traits(C,N,P,N:P)of the first five grades of leaflets was 1.6%～23.0%,and the variation range of plasticity index was 0.05～0.70.Leaflet grade can significantly affect the binary and multivariate correlation among leaflet traits.Most bivariate correlation relationships had a common slope of standardized major axis,and the correlation direction of some relationships had interspecific differences.LDMC of F.mandshurica and J.mandshurica leaflets at different leaflet grades had significant negative correlation with SLA(no common slope of standardized major axis),LT and SLA,while LT of P.amurense leaflets had significantly positive correlation with SLA;there was a significantly positive correlation between LA and SLA in leaflets of F.mandshurica and P.amurense(no common slope of standardized major axis)at different leaflet grades.There were significantly positive correlations between LT of leaflets and anatomical traits and between the anatomical traits of leaflets and the anatomical traits of leaflets at different leaflet grades.The study on the bivariate correlation between the chemical and morphological traits of leaflets found that there was a significant correlation between the multiple binary traits of the second to fourth leaflet grade,and there was a significantly negative correlation and a significantly positive correlation between the N and P of the leaflets of F.mandshurica and J.mandshurica at different leaflet grades.The first and second leaflets of J.mandshurica compound leaves(the farthest from the base of the petiole is the first leaflet)had high LDMC and low SLA,which showed the resource conservation strategy;the seventh and eighth leaflets had low LDMC and high SLA,which was represented by resource acquisition strategy;the leaflets of F.mandshurica and P.amurense at different leaflet grades did not show significantly different resource utilization strategies.Leaflet grade no significantly direct effect on LMA of three compound leaf species,but had a significantly negative indirect effect on LMA of leaflets of F.mandshurica(through LT)and P.amurense(through PT)through PT and LT;PT had a significantly positive direct effect on LT of F.mandshurica and P.amurense leaflets;LD had a significantly positive direct effect on LMA of F.mandshurica and P.amurense leaflets.There were differences in leaflet traits of F.mandshurica,P.amurense and J.mandshurica at different leaflet grades.By discussing variation and inner relationships of leaflet traits at the level of leaflet grade,it was contributed to further analyzing the reasons for the differences in leaf resource utilization strategies,and it was also a supplement to the previous study on intraspecific variation of leaf functional traits.In the future,leaflet grade should be considered in the study on leaf trait variation.