To investigate the correlations among leaf functional traits and their phylogenetic signals in common woody species of Yuanjiang dry-hot valley, and to provide a scientific basis for regional vegetation conservation.

Leaves from 32 woody species representing different life forms were collected, and eight leaf functional traits were measured, including leaf area (LA), leaf dry matter content (LDMC), and specific leaf area (SLA). Trait differences were analyzed using t-tests, Pearson correlation was employed to assess trait relationships, and phylogenetic signals were quantified using Blomberg's K.

Significant interspecific trait variations were observed across life forms. Evergreen species exhibited lower LA, leaf carbon content (LCC), and leaf phosphorus content (LPC) but higher LDMC and N∶P ratios compared to deciduous species (P<0.05). Trees showed higher LA, leaf thickness (LT), LCC, and LPC, but lower LDMC, SLA, and N∶P than shrubs (P<0.05). Trait correlations varied by life form: In evergreens, LNC and LPC, as well as LDMC and SLA, were positively correlated (P<0.05), while LT and LNC, and N∶P were negatively correlated (P<0.05). In deciduous species, LT and LA, and LNC and N∶P showed positive correlations (P<0.05), whereas LT and LDMC, and SLA were negatively correlated (P<0.05). Trees displayed positive correlations between LCC and LNC, and N∶P (P<0.05), while shrubs showed positive correlations between LT and LDMC, and LNC and LCC (P<0.05). Principal component analysis (PCA) identified LA, LT, and LCC as key trait indicators, classifying the 32 species into four functional groups: high LNC, N∶P, SLA; high LA, LCC, LPC; high LT, and high LDMC. All traits exhibited detectable but weak phylogenetic signals (0<K<1, P=0.01), suggesting environmental selection outweighs phylogenetic constraints in trait evolution.

Evergreen and shrub species adapt to the dry-hot environment through high LDMC and LT, reflecting conservative resource-use strategies, while deciduous and tree species employ large LA, high C, N, P, and SLA for rapid resource acquisition. LA, LT, and LCC serve as diagnostic traits for these adaptive strategies. Phylogenetic history weakly influences trait variation, these findings provide functional evidence for understanding plant adaptation mechanisms in dry-hot valleys.