Warming and Nitrogen (N) deposition are key global changes that may affect eco-physiological process of territorial plants. In this paper, we examined the effects of warming, N deposition, and their combination effect on the physiological performances of Leymus secalinus. Four treatments were established in an alpine meadow of Qinghai-Tibetan plateau: control (CK), warming (W), N deposition (N), and warming plus N deposition (NW). Warming significantly decreased the photosynthetic rate (A_net ), stomatal conductance (g_s ), intercellular CO₂ concentration (C_i ), and transpiration rate (T_r ), while N deposition and warming plus N deposition significantly increased those parameters of L. secalinus. Warming significantly increased the VPD and L_s , while N deposition and warming plus N deposition had a significant positive effect. Warming negatively reduced the leaf N content, Chla, Chlb, and total Chl content, while N deposition significantly promoted these traits. Warming, N deposition, and their combination significantly increased the activity of SOD, POD, and CAT. Besides, warming and warming plus N deposition significantly increased the MDA content, while N deposition significantly decreased the MDA content. N deposition and warming plus N deposition significantly increased the Rubisco activity, while warming showed no significant effect on Rubisco activity. N deposition and warming plus N deposition significantly increased the Fv/Fm, ΦPSII, qP, and decreased NPQ, while warming significantly decreased the Fv/Fm, ΦPSII, qP, and increased NPQ. N deposition strengthened the relations between g_s , Chl, Chla, Chlb, Rubisco activity, and A_net . Under warming, only g_s showed a significantly positive relation with A_net . Our findings suggested that warming could impair the photosynthetic potential of L. secalinus enhanced by N deposition. Additionally, the combination of warming and N deposition still tend to lead positive effects on L. secalinus.

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