Abstract:

Aims: Plant functional traits refer to a series of core attributes that are closely associated with plant establishment, survival, growth, and mortality. The trade-offs and synergies among functional traits determine the ecological strategy of plants. Exploring interspecific differences in ecological strategies based on functional traits not only enhances our understanding of species coexistence mechanisms, but also provides insights into community succession and vegetation responses under climate change. 

Methods: This study was conducted in a 21.12 ha mixed conifer-broadleaf forest dynamic plot in Jiaohe, Jilin Province. Eight key functional traits were measured for 32 tree species. Tree species were classified into different ecological types based on the competitor–stress tolerator–ruderal (CSR) strategy theory. We then integrated cluster analysis and principal component analysis (PCA) to reveal the differences in ecological strategies among different tree species. Finally, Spearman correlation analysis was employed to calculate the correlation coefficients between each species’ scores on the principal components and its C, S, R strategy values, thereby testing the functional trait basis underlying plant ecological strategies. 

Results: (1) Based on CSR classification, the 32 tree species were grouped into six ecological strategy types, with the stress tolerator/competitor–stress tolerator–ruderal (S/CSR) type having the highest proportion. (2) Cluster analysis divided species into two major groups (i.e., conifers and broadleaf trees), with broadleaf trees further subdivided into seven functional subgroups (pioneer species, transitional species, climax broadleaf species, etc.). (3) Principal component analysis and Spearman correlation analysis showed that functional traits exhibited clear differentiation among tree species. Broadleaf species tended to exhibit greater leaf area, specific leaf area, and leaf nitrogen content, indicating stronger competitive ability (high C values). In contrast, conifers exhibited greater leaf carbon content and leaf dry mass content, indicating stronger stress tolerance (high S values). Shrubs and small trees exhibited higher wood density and lower maximum height, corresponding to greater disturbance adaptability (high R values). 

Conclusion: This study highlights distinct ecological strategies among major tree species in temperate mixed forests and demonstrates a strong alignment between CSR strategies and the trait axes identified by principal component analysis. These findings thus provide important functional trait-based perspectives on species ecological strategies in temperate mixed conifer-broadleaf forests.

Key words: ecological strategies, functional traits, plant CSR strategy, trait trade-offs, mixed conifer-broadleaf forest