Abstract: Leaf functional traits reflect the plasticity exhibited by plants in morphology, function, and physiology during environmental adaptation, embodying their fundamental physiological characteristics. Plants at different developmental stages may display varying patterns of change in leaf functional traits; thus, exploring the relationship between sapling and mature tree traits contributes to revealing the dynamic adjustments of plant functions during growth. Taking 26 subtropical tree species as the research objects, seven leaf functional traits of saplings and mature trees were systematically measured. First, the overall differences in leaf functional traits among different tree species were compared. Next, differences in leaf functional traits between arbuscular mycorrhizal（AM）and ectomycorrhizal（EM）tree species at the sapling and mature tree stages were analyzed. Finally, the correlations and trade-offs or synergies among multiple leaf functional traits across the 26 tree species were examined. The results showed that saplings exhibited higher specific leaf area and higher leaf nitrogen, phosphorus, potassium, and magnesium contents compared to mature trees, whereas mature trees generally had higher leaf carbon and calcium contents than saplings. Among them, arbuscular mycorrhizal tree species showed a significant trend of decreasing specific leaf area, leaf carbon, nitrogen, and phosphorus contents, while leaf calcium content increased. In contrast, the leaf functional traits of ectomycorrhizal tree species remained relatively stable, reflecting a conservative nutrient use strategy. In saplings, SLA was significantly negatively correlated with leaf carbon content and positively correlated with leaf nitrogen, potassium, and magnesium contents, while in mature trees, specific leaf area was significantly positively correlated with leaf nitrogen, calcium, and magnesium contents. The patterns of leaf functional traits indicated that saplings exhibited a strategy of rapid resource acquisition, while mature trees displayed different leaf phosphorus and potassium traits, reflecting changes in the combination of leaf functional traits across developmental stages. By comparing the variation patterns of leaf functional traits between saplings and mature trees, this study clarifies the differences in leaf functional traits among trees of different ages and the indicated divergence in resource utilization strategies, providing new insights into trait changes during tree growth and development and forest stand nutrient dynamics.