Abstract: Five main species of a mixed evergreen and deciduous broad-leaved forest in Mt. Gongga were employed to investigate their plant functional traits including specific leaf area (SLA), leaf dry weight (LDW), leaf carbon (C), nitrogen (N) and phosphorus (P) concentrations, and leaf isotope (δ¹³C, δ¹⁵N). Our aims were to explore the difference of the leaf functional traits of the main species and their interrelations, and reveal the relationship between nutrient use efficiency and water use efficiency of these species and how such relationship may affect the growth and nutrient cycles of these species. The results showed that a significant difference in SLA was found between evergreen and deciduous species. Leaf C concentration was negatively related with leaf N and P concentrations. Significant positive relationships between leaf N and P concentrations and between C∶N and C∶P were observed. In addition, leaf SLA increased with increasing leaf N concentration and N∶P ratio, but decreased with increasing C concentration, δ¹³C, and C∶N ratio. No relationship between δ¹³C and C∶N ratio was detected in the study. Moreover, our results showed that plants with the higher SLA exhibited the higher leaf N, but the lower leaf C concentration, nitrogen use efficiency and water use efficiency. There was no tradeoff between WUE and NUE for the main species in the mixed evergreen and deciduous broad-leaved forest, indicating that the water and nitrogen coupling mechanism was not employed in the humid environment. The relict plants (Indigofera souliei and Cercidiphyllum japonicum) took a different nutrient use strategy compared with other non-relict tree species, and formed niche differentiation thus co-existing in the community.

Key words: Great Xing’an Mountains, moisture content, meteorological element regression., surface dead fuel