Objective Plants can use resources more efficiently by adjusting their own traits. Exploring the variation and correlation between twig and leaf traits of plants with different diameter classes is of great significance for understanding the intraspecific variation of plant functional traits and the resource acquisition strategies of plants.

Method In Liangshui National Nature Reserve of Heilongjiang Province of northeastern China, three diameter classes of Betula platyphylla were selected (including small tree, middle tree and large tree). The twig cross-sectional area, individual leaf area, total leaf area, total leaf dry mass, twig dry mass and volume-based leafing intensity were measured in different diameter classes. One-way analysis of variance was used to test whether there were significant differences in twig-leaf traits among varied diameter classes. The method of standardized main axis estimation was used to test whether the diameter class had an effect on the correlation between the twig and leaf traits.

Result With the increase of diameter class, twig cross-sectional area showed an upward trend, individual leaf area and total leaf area showed a downward trend, but there was no significant difference in total leaf dry mass, twig dry mass, volume-based leafing intensity. The twig cross-sectional area was significantly positively correlated with individual leaf area, total leaf area and total leaf dry mass, but was significantly negatively correlated with volume-based leafing intensity, among them, the cross-sectional area of small trees and large trees had an isokinetic growth relationship of close to 1 with the total leaf area and total leaf dry mass, while the medium tree had an allometric growth relationship close to 1.5; individual leaf area exhibited significantly negative correlations with volume-based leafing intensity, showing an allometric relationship; the diameter class had a significant effect on the slope or intercept of the correlations between twig-leaf traits.

Conclusion Within the same community, the difference in branch and leaf traits among different diameter classes of B. platyphylla is its own resource acquisition strategy, and the branch and leaf traits undergo collaborative changes in order to obtain effective resources.