Variation And Trade-off Of Twig And Leaf Traits Of Major Species In Mixed Broadleaved-korean Pine Forests

Twig size,leaf size and leafing intensity and the relationships among them are closely related to the development pattern of twigs and leaves.And it's of great significance for exploring the adaptability and survival strategies of plants under global climate change conditions.However,it is less clear whether the variability and trade-off of the twig size,leaf size and leafing intensity of coniferous and broad-leaved species of mixed broadleaved-Korean pine(Pinus koraiensis)forests are affected by levels(such as latitude,functional types,and sampling orientations).The sampling area of this study was four different latitude areas through mixed broadleaved-Korean pine forests in Northeast China.In.this study,major coniferous species(Pinus koraiensis)and broadleaf species of mixed broadleaved-Korean pine forest,including shade intolerant species:Betula platyphylla,Populus davidiana;shade mid-tolerant species:Ulmus japonica,Betula costata,Fraxinus mandshurica;shade tolerant species:Tilia amurensis,Acer mono,were selected as the study objects.We measured twig cross-sectional area,individual leaf area,total leaf area and volume-based leafing intensity in three canopy layers(upper,middle and lower),and each canopy height was further divided into the south and north directions.At first,we used nested analysis of variance(ANOVA)to analyze the factors affecting the variation of twig and leaf traits of main species of coniferous and broad-leaved leaves,and then tested by Standardized Major Axis(SMA)method:Whether the relationships between twig and leaf traits were significant difference between different latitude,functional types and orientations.Whether latitude and orientations have significant effects on the relationship between twig and leaf traits of coniferous.The results show that:(1)Broadleaf species:Both twig and leaf traits varied with functional types and latitude.Functional types and orientations influence them together,while latitude has no significant influence in the trade-off of the twig trait and leaf traits.Slopes of regression of leaf traits(i.e.,individual leaf area,total leaf area and volume-based leafing intensity)against twig cross-sectional area were shade tolerant species>shade mid-intolerant species>shade intolerant species.Relationships between twig cross-sectional area and total leaf area in upper south and lower north canopy orientations did not vary with functional species.However,slopes of regression of twig cross-sectional area against total leaf area varied with functional species in other four sampling orientations(upper north,middle south,middle north and lower south).(2)Coniferous species:Pinus koraiensis showed significant variations in twig and leaf traits at different latitudes,and orientations also affected them.Twig cross-sectional area had significant positive correlation with individual and total leaf area while negative correlation with leafing intensity at each site,which all showing an allometric growth relationship,but leafing intensity was negative correlation with individual leaf area of Pin.us koraiensis only at Sheng Shan and showed an allometric growth relationship;The latitude had significant influence on the slopes of relationships between twig cross-sectional area and individual leaf area,total leaf area and leafing intensity;and the slope of Sheng Shan sampling site of these relationships was all the lowest among the four sites.The results suggest that there are differences in the trade-off strategies of twigs and leaves at different latitudes.There had no difference in directions,while the relationships between twig and leaf traits are different in three canopies.The different relationships between twig and leaf traits of species at different functional types reflect the regulation of genetic changes between trait-trait,and the differences in individual orientations growth verify the synergistic adaptation mechanism of plants to adjust the microenvironment variation within individuals through the plasticity of functional traits;There were significant differences in twig and leaf traits of Pinus koraiensis at different latitudes,which indicate that plant regulate the plasticity of functional traits to adapt the changing environment.There were significant different relationships between twig and leaf traits of Pinus koraiensis at different latitudes,which verify that there are differences in,the allocation of resource strategies of twigs and leaves at different latitudes,and they adapt to the environment together.This study emphasizes the important influence of sampling orientation on the experimental results,latitude has important regulating function on conifer species and functional types have important regulating function on broadleaf species.The study provides a basis for the study of variation rules and cooperative mechanisms of plant traits under the background of global climate change.