Objective The differentiation of intraspecific functional traits is of great significance in adapting to the changing living environment. It is important to explore the differences in nutrient elements and metabolites in leaves of Larix gmelinii across different diameter classes for understanding the adaptation strategies of larch in diverse ecological niches and predicting of its response to global environmental change.

Method This study was conducted in three adjacent long-term sample plots within the Black-billed Grouse National Nature Reserve in the Central Station of Heilongjiang Province. A detailed investigation was conducted on 438 larch trees, categorized into small, medium, and large DBH. Elemental analysis and metabolomics techniques were employed to analyze the differences in leaf nutrient elements (C, N, K, Ca, Zn, Mg, Na, Mn, Fe, Cu, B) and metabolites (primary and secondary metabolites) across the diameter class. This analysis aimed to explore the accumulation and distribution patterns of nutrient elements and metabolites in larch trees among different DBH classes.

Result The study found that leaves of small-diameter larch trees had higher concentrations of K, Mg, N, and Mn compared to medium and large diameter trees, while large diameter trees had the highest Ca content. A total of 112 metabolites grouped into 8 categories, were identified in the leaves across the DBH classes. The highest number of differential metabolites was observed between large and medium diameters amounting to 28, with 21 upregulated and 7 downregulated. Further analysis revealed that sugar alcohols (particularly sucrose and its downstream products) and secofoc amino acids (such as proline and glutamine) were more abundant in large-diameter trees. In contrast, small-diameter trees accumulated higher levels of organic acids. Correlation analysis demonstrated that Ca was positively associated with amino acids such as glutamic acid, phenylalanine, and glycine, as well as sugar alcohols like sucrose and fructose. Conversely, Mn and B were positively correlated with organic acids, including fumaric acid, shikimic acid, and cinnamic acid.

Conclusion L. gmelinii exhibits distinct adaptive strategies based on DBH classes to optimize survival in varying growth conditions. Small-diameter trees adopt resource acquisition strategies, accumulating organic acids and elements such as K, Mg, and Mn to thrive in shaded and less favorable environments. In contrast, large-diameter trees rely on conservative growth strategies, emphasizing the storage of C, Ca, sugar alcohols, and amino acids to sustain growth and maintain stability in their ecological niche.