Ecological Stoichiometry and Adaptations to Drought and Nitrogen in Hevea Brasiliensis and Dalbergia Odorifera in Different Planting Patterns

Two tropical forest trees (Dalbergia odorifera T. Chen and Hevea brasiliensis Muell. Arg), cultivated both in pure or mixed planting systems under drought and nitrogen-applied conditions, were selected at seedling stages as experimental materials to investigate their eco-physiological responses, interactions with neighboring trees, and the stoichiometry of carbon (C), nitrogen (N), and phosphorus (P). The results highlighted significant differences in biomass allocation between D. odorifera, which allocates more to root growth, and H. brasiliensis, favoring stem growth. It demonstrates that mixed planting enhances tree growth under well-watered conditions, while nitrogen application promotes growth across different moisture levels, with species-specific responses. Water and nitrogen interaction notably affects H. brasiliensis growth but less so for D. odorifera, revealing complex effects on their biochemical responses to oxidative stress. The mixed planting benefits both species, influencing nutrient dynamics and stoichiometry in D. odorifera. The study also shows that nitrogen application under well-watered conditions alters nutrient ratios, particularly affecting nutrient availability and competition between species in mixed planting setups. In conclusion, this research emphasizes the complex interplay between planting patterns, water, and nitrogen, which significantly impacts tree growth, nutrient dynamics, and stress responses, suggesting that specific management strategies could optimize forestry practices.