Abstract: We examined the variations in leaf morphology and ecological stoichiometry of Vaccinium uliginosum across an altitudinal gradient along the northern slope of Changbai Mountain, as well as the influence of environmental factors on the variations of those traits. The results showed that leaf morphological characteristics (leaf length, width, area, perimeter, and length-to-width ratio) significantly decreased with increasing elevation (P<0.05), demonstrating a shift toward smaller but more rounded leaf forms. Among the ten ecological stoichiometric characteristics, leaf nitrogen (N) content and nitrogen/phosphorus ratio (N∶P) ratio showed significant positive correlations with elevation (P<0.05), while carbon/nitrogen ratio (C∶N) decreased significantly (P<0.05). Other stochiometric characteristics displayed no significant trends along the altitudinal gradient. (2) The coefficients of variation (CV) for leaf morphological characteristics exceeded those of ecological stoichiometric characteristics, with leaf area showing the highest CV (45.54%) and leaf carbon (C) content the lowest (5.41%), suggesting that leaf morphological characteristics were more sensitive to environmental change than ecological stoichiometric characteristics. (3) There was significant covariation between leaf morphological and stoichiometric traits. Leaf N∶P ratio was significantly negatively correlated with all the five morphological characteristics (P<0.001). Conversely, leaf length, area, perimeter, and length:width ratio showed strong positive correlations with leaf C∶N ratio (P<0.01) but strong negative correlations with leaf N content (P<0.001). (4) Mean annual temperature was the primary environmental driver for both leaf morphology and stoichiometry traits, highlighting its dominant role in shaping leaf traits. (5) Across all elevations on Changbai Mountain, leaf nitrogen/phosphorus ratio (N∶P) of V. uliginosum consistently exceeded 16. According to the N∶P threshold hypothesis, this indicated primary phosphorus limitation on the growth of V. uliginosum, with soil available phosphorus deficiency being the probable constraint in the study area. In conclusion, V. uliginosum on the north slope of Changbai Mountain demonstrated coordinated adjustments in both leaf morphology and ecological stoichiometry along the elevational gradient. Such trait covariation reflects an adaptive strategy where modifications in leaf morphology and nutrient use efficiency collectively enhance fitness across varying elevations.

Key words: Vaccinium uliginosum, altitudinal gradient, leaf morphology, ecological stoichiometric characteristics