摘要:为了揭示不同季节下杉木人工林不同形态氮吸收速率对全球变暖与氮沉降的地下响应，在福建三明森林生态系统与全球变化研究站陈大观测点开展增温和氮添加双因子试验，包括对照、增温、施氮、增温+施氮4个处理。结果表明：（1）在三个季节中，4个处理的杉木细根对不同浓度下硝态氮的吸收速率基本呈现出春季较高，夏秋季较低的态势，而对不同浓度下铵态氮的吸收速率则相反，为夏秋季较高，春季较低。（2）不同季节四个处理的离体根对不同浓度下铵态氮的吸收均遵循米氏-曼氏动力学方程，而对硝态氮的吸收并不完全遵循米氏方程，表现为双相动力学。（3）春季，与无氮添加相比，氮添加提高了NH₄⁺的最大吸收速率（V_max-NH₄⁺）。夏季，与无增温相比，增温提高了V_max-NH₄⁺。秋季，与无增温相比，增温降低了NH₄⁺的半饱和常数（K_m-NH₄⁺）；与无氮添加相比，氮添加提高了K_m-NH₄⁺。增温与氮添加对不同季节100 μmol时的硝态氮吸收速率（V₁₀₀-NO₃^-）都没有显著影响。增温与氮添加对不同季节V_max-NH₄⁺、K_m-NH₄⁺和V₁₀₀-NO₃^-都没有显著的交互作用。本研究表明增温会提高杉木幼苗夏秋季的NH₄⁺吸收能力，而氮添加会提高春季的NH₄⁺吸收能力，降低秋季的NH₄⁺吸收能力，但增温与氮添加并不会改变不同季节的NO₃^-吸收能力。



Abstract:In order to reveal the influence of global warming and nitrogen addition on the ecological process of Chinese fir (Cunninghamia lanceolata) seedlings, we conducted a two-factor experiment of warming and nitrogen addition, which consisted control, warming, nitrogen addition, and warming+nitrogen addition. The study site is located in Forest Ecosystem and Global Change Research Station of Fujian Normal University in Chenda, Sanming, Fujian Province. The results showed that: (1) the absorption rate of nitrate nitrogen by the fine roots of C. lanceolata under different concentrations was higher in spring and lower in summer and autumn, but the absorption rate of ammonium nitrogen was higher in summer and autumn and lower in spring. (2) The absorption of ammonium nitrogen by the four treatments followed the Michaelis-Menten kinetic equation, but the absorption of nitrate nitrogen did not fully followed it, which showed dual-phase kinetics in different seasons. (3) In spring, compared with nitrogen-free addition, nitrogen addition increased the maximum velocity of NH₄⁺ (V_max-NH₄⁺). In summer, compared with no warming, the warming increased V_max-NH₄⁺. In autumn, compared with no warming, the warming decreased the Michaelis-Menten constant (K_m-NH₄⁺); compared with nitrogen-free addition, nitrogen addition increased K_m-NH₄⁺. Warming and nitrogen addition had no significant effect on the absorption rate of nitrate nitrogen at 100 μmol (V₁₀₀-NO₃^-) in different seasons, and there was no significant interaction between warming and nitrogen addition on V_max-NH₄⁺, K_m-NH₄⁺ and V₁₀₀-NO₃^-in different seasons. The results indicated that warming would improve NH₄⁺ absorption capacity of Chinese fir seedlings in summer and nitrogen addition would improve NH₄⁺ absorption capacity in spring and reduce NH₄⁺ absorption capacity in autumn, but warming and nitrogen addition would not change NO₃^- absorption capacity in different seasons.





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