Effects of nitrogen addition and warming on growth, development, and physiological characteristics of Dalbergia odorifera T. Chen seedlings

To investigate the effects of nitrogen deposition and climate warming on the growth and physiological characteristics of one-year-old Dalbergia odorifera T. Chen seedlings, nitrogen deposition and temperature increase were simulated in an artificial climate chamber. Four treatments, including control, nitrogen addition (+ 30 kg N·ha^-1·a^-1), warming (32℃ during the day and 29℃ at night), and warming × nitrogen addition (+ 30 kg N·ha^-1·a^-1, 32℃ during the day and 29℃ at night), were designed to analyze the effects of different treatments on growth, morphological changes, biomass accumulation, and leaf and root physiology in D. odorifera seedlings. Results showed that:(1) Compared with the controls, growth, morphological development, biomass accumulation, photosynthetic parameters, maximum photochemical yield, nitrate reductase, and root activity in the D. odorifera seedlings increased under all treatments, while relative conductivity and malondialdehyde content in leaves decreased. (2) The changes in biomass accumulation, photosynthetic parameters, maximum photochemical yield, nitrate reductase, and root activity showed the greatest increase in the warming × nitrogen treatment, while relative conductivity and malondialdehyde content in leaves showed the greatest decrease in this treatment. (3) Membership function analysis showed that the warming × nitrogen treatment had the best promotion effect on the growth and development of D. odorifera seedlings, followed by warming only treatment, and nitrogen only treatment. These results indicated that short-term warming × nitrogen treatment had better promotion effects on the growth and ecophysiological adaptations of D. odorifera seedlings than single warming or nitrogen application.