Soil nitrogen availability determines the CO₂ fertilization effect on tree species (Neolamarckia cadamba): growth and physiological evidence

Urban plantation species experience multiple stresses. Among these, the two significant challenges are increasing atmospheric CO2 concentration and nutrient-depleted soils, which significantly impede growth, development, as well as the adaptation and mitigation capacity of plant species. This study hypothesized whether nitrogen availability improves CO2 fertilization effects and the growth of urban plantation tree species (Neolamarckia cadamba) under rising atmospheric CO2 concentration.The plants were grown in nitrogen regimes (low-N-200 Kg N ha(-1), medium-N-300 Kg N ha(-1), and high-N-500 Kg N ha(-1)) under elevated CO2 concentration (eCO(2); 800 +/- 20 mu molCO(2) mol(-1)) and ambient conditions (aCO(2;) 400 +/- 14 mu molCO(2) mol(-1)). We reported that growth and physiological traits were significantly improved under elevated CO2 concentration and applied nitrogen compared to low nitrogen and ambient CO2 concentration. The height, stem diameter, leaves, leaf area, and branches were increased by 25%, 13%, 12%, 6%, and 21%, respectively, under N-300 and eCO(2) than counterparts. The leaf CO2 assimilation, transpiration, and stomatal conductance were enhanced by 17%, 39%, and 57%, respectively, whereas water use efficiency declined under N-300 and eCO(2) but slightly increased in eCO(2) and N-500. We inferred that nitrogen management practices would improve the benefits of rising atmospheric CO2 concentration, resulting in improved plant growth and development and better adaptive physiological response and mitigation potential of plantation species.