The Effects of Light and Water Stress on the Morphological and Chemical Stoichiometric Traits of Quercus dentata Thunb and Quercus variabilis Blum Seedlings

To explore the variations in leaf morphological traits and chemical stoichiometry of Quercus dentata Thunb. and Quercus variabilis Blume seedlings under different light intensities and soil moisture contents. A fully factorial experimental design was adopted, with four light gradients(100%, 75%, 50%, 25% natural light) and three soil water gradients(75%～85%, 45%～55%, 15%～25% field capacity). The study systematically analyzed the variations in 8 morphological traits and 12 chemical stoichiometric traits of the two species. The results showed that as light intensities and soil moisture contents decreased, both Q. dentata and Q. variabilis significantly increased their Specific Leaf Area(P < 0.05). The maximum leaf thickness of Q. dentata was observed at 50% natural light availability, and Q. variabilis exhibited a significant reduction in leaf thickness with decreasing light(P < 0.05). Under light and water limitation, both species tended to enhance root dry mass content to strengthen structural support. The leaf carbon content of Q. variabilis significantly decreased with decreasing water availability under 50% natural light(P < 0.05). Additionally, both species showed a reduction in root nitrogen content with decreasing light. Significant pairwise correlations were found among the leaf and root traits: specific leaf area of Q. variabilis was significantly negatively correlated with leaf dry mass content and leaf tissue density(P < 0.05); specific leaf area of Q. dentata was significantly positively correlated with leaf nitrogen content(P < 0.05); and leaf nitrogen content of Q. variabilis was significantly negatively correlated with the leaf carbon-nitrogen ratio(P < 0.05); The specific root area of Q. dentata showed a significant negative correlation with root tissue density. For both species, specific root length was significantly positively correlated with specific surface area. Additionally, root nitrogen content exhibited significant positive correlations with phosphorus ratio and nitrogen-phosphorus ratio, while showing significant negative correlations with carbon-nitrogen ratio and carbon-phosphorus ratio. In conclusion, oak seedlings adapt to heterogeneous environments through the adjustability of their morphological and chemical traits, providing valuable theoretical insights into the adaptive mechanisms of woody plants to environmental stress.