Variations And Correlations Of Current-year Twig Traits Of Three Broadleaved Species In A Broadleaved Korean Pine Forest

The current-year twig includes leaves and twig,while a leaf consisted of lamina and petiole,their structures and functions affect the carbon and water cycle of the plant.As wood structures,petiole and twig have similar anatomical structures,which play an important role in regulating plant water and nutrition transport,and supporting lamina and crown.And the lamina plays an important role in light interception and photosynthesis.Interspecific difference and intraspecific variation common drive variation in current-year twigs traits,but there are few systematic studies on the affecting factors between current-year twigs traits variation and traits trade-offs.In this study,we sampled Betula platyphylla,Tilia amurensis and Acer pictum subsp.mono in a mixed broadleaved-Korean pine（Pinus koraiensis）forest in northeast China.For each species,we selected 10 trees for small（diameter at breast height:1-6 cm）,middle（diameter at breast height:15-20 cm）,and large sizes（diameter at breast height:35-45 cm）,respectively.For the large-sized trees,we took canopy position into account.To explore the effects of species,tree size and canopy position（large trees）on variations and correlations between lamina and petiole traits,and explore the effects of species and tree size on variations and correlations between petiole and twig traits.The results indicate that:The lamina and petiole traits significantly varied with species and tree size.PL and PDM of the small trees were significantly lower than those of large trees for the three species.LDM of the small trees was significantly lower than that of the large trees for T.amurensis and A.pictum subsp.mono,while LA of the small trees was significantly greater than that of the large trees for B.platyphylla and T.amurensis.For the large trees,the effect of canopy position on the variations in lamina and petiole traits was species-depended.There was a significant allometric scaling relationship between the lamina and petiole traits for all the three species.The regression slopes of the relationship between lamina-petiole traits ranked as T.amurensis>B.platyphylla>A.pictum subsp.mono;the slopes for B.platyphylla ranked as small size>large size>middle size,while the slopes for the large-sized trees were the greatest among different tree sizes for T.amurensis（2.150,0.890）and A.pictum subsp.mono（1.490,0.944）.Canopy position had no significant effect on the regression slope for the large-sized trees.Tree species and tree size and their interactions had significant effects on petiole and twig traits.Values of the twig anatomical traits(T_CA、T_XA、T_PHA、T_CSD)were significantly greater than those of the petiole anatomical traits(P_CA、P_XA、P_PHA、P_CSD).Variability in petiole and twig traits across tree sizes varies by species.The petiole traits of large trees were significantly greater for B.platyphylla and A.pictum subsp.mono;the twig traits of large trees were also significantly greater for B.platyphylla and T.amurensis.While the petiole traits vary less between tree sizes for T.amurensis,the twig traits of middle trees were the greatest for A.pictum subsp.mono.Petiole traits and twig traits showed a very significant positive correlation.There were significant differences in the correlation of twig-petiole traits among three species,and the regression slope of A.pictum subsp.mono was the smallest.There were significant differences in the correlation among the different tree sizes,and the regression slope of small trees was the greatest.Overall,the current-year twig traits significantly varied with species and history stages,indicating that tree species and tree sizes have important effects on the biomass allocation of current-year twig traits.It is important to understand the mechanisms of plant growth,resource utilization and adaptation to the environment by studying the influencing factors of current-year twig traits variations and correlations.