Abstract: Nitrogen and water are two important factors affecting the photosynthetic characteristics of plants. The responses of plants with different photosynthetic pathways to water and nitrogen can reflect the relationship between plants and the environment. To investigate the effects of nitrogen deposition and precipitation changes on the growth patterns of C₃ plants and C₄ plants,the C₃ plant Reaumuria soongorica and the C₄ plant Salaola passerina were used as the research objects. A pot experiment was used in this research. In this experiment,different nitrogen deposition levels (0 g·(m·a)^-1,4 g·(m²·a)^-1,8 g·(m²·a)^-1) and different precipitation treatments (W-30%,W,W+30%) were used. The differences were compared in photosynthetic pigments,photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of the two plants under solitary and mixed growth. The results showed that the water-nitrogen coupling enhanced the photosynthetic capacity of R. soongorica and S. passerina. The photosynthetic capacity of R. soongorica and S. passerina reached the maximum when the precipitation increased by 30% and the nitrogen application rate was 8 g·(m²·a)^-1. The chlorophyll content and net photosynthetic rate of R. soongorica increased by 3.63 times and 1.19 times respectively. The chlorophyll content and net photosynthetic rate of S. passerina increased by 0.95 times and 1.13 times respectively. The mixed growth significantly enhanced the photosynthetic capacity of R. soongorica. Meanwhile,the mixed growth strengthened the competitive intensity of S. passerina. The water-nitrogen coupling can significantly reduce the intensity of competition,which indicates the environment with nitrogen deposition and increased precipitation could be conducive to the development of the mixed community of R. soongorica and S. passerina.

Key words: Nitrogen Settlement, Precipitation, Growth modes, Photosynthetic characteristics, Reaumuria soongorica, Salsola passerina

摘要： 氮素和水分是影响植物光合特性的重要因素，而不同光合途径植物对水、氮的响应能反映出植物与环境的关系。为探究氮沉降和降水变化对C₃植物和C₄植物生长方式的影响，以C₃植物红砂（Reaumuria soongorica）和C₄植物珍珠猪毛菜（Salaola passerina）为研究对象，利用盆栽试验，设置不同氮沉降水平（0 g·（m²·a）^-1，4 g·（m²·a）^-1，8 g·（m²·a）^-1）和不同降水处理（W-30%，W，W+30%），比较两种植物单生和混生下的光合色素、光合气体交换参数和叶绿素荧光参数等的差异。结果表明：水氮耦合使红砂和珍珠猪毛菜光合能力均增强，且在降水增加30%和施氮量8 g·（m²·a）^-1时达最大；红砂的叶绿素、净光合速率分别最大可增加3.63倍、1.19倍，珍珠猪毛菜最大分别增加0.95倍和1.13倍。二者混生显著提高红砂的光合能力，而珍珠猪毛菜的竞争加强，氮水耦合可显著减弱竞争强度，说明在未来氮沉降和降水增加环境下，有利于红砂-珍珠猪毛菜混生群落的发展。

关键词: 氮沉降, 降水, 生长方式, 光合特性, 红砂, 珍珠猪毛菜