Abstract: In order to explore the potential impact of increasing nitrogen deposition on lichen diversity in the Shennongjia Natural Reserve, four common epiphytic lichens (Lobaria pulmonaria, L. orientalis, Usnea luridorufa and U. dasopoga) in this area were collected, then they were soaked in deionized water and KNO₃ (0.05, 0.5 mol·L^-1), NH₄NO₃ (0.05, 0.5 mol·L^-1), and (NH₄)₂SO₄ (0.025, 0.25 mol·L^-1) solutions for half an hour. The fluorescence induction curve parameter, solution electrical conductivity (RE, namely cell membrane integrity) and chlorophyll degradation (OD₄₃₅/OD₄₁₅) were measured. The sensibilities of the four lichens to nitrogen additions and the stress of ammonium nitrogen, nitrate nitrogen and mixed nitrogen on F_v/F_m, RE and OD₄₃₅/OD₄₁₅ were analyzed. The results showed that: (1) There were significant differences among the responses of lichens to different nitrogen forms. The toxicity of different nitrogen forms to F_v/F_m, Y(Ⅱ) and OD₄₃₅/OD₄₁₅ were in the order of mixed nitrogen > ammonium nitrogen > nitrate nitrogen, and their toxicity to cell membrane integrity presented as ammonium nitrogen > mixed nitrogen > nitrate nitrogen, while nitrate nitrogen alone had little toxicity to F_v/F_m, Y(Ⅱ), OD₄₃₅/OD₄₁₅ of these four lichens. (2) Nitrogen sensitivities of these four lichens were speciesspecific. When treated with nitrate nitrogen, OD₄₃₅/OD₄₁₅ of U. dasopoga appeared more sensitive than that of L. pulmonaria. If mixed nitrogen was used, the toxicity to F_v/F_m was in the order of L. pulmonaria≈L. orientalis>U. luridorufa≈U. dasopoga, while the toxicity to RE was L. pulmonaria≈L. orientalis<U. luridorufa≈U. dasopoga. When they were treated with ammonium nitrogen, the toxicity to F_v/F_m was in the order of U. luridorufa≈L. orientalis>U. dasopoga≈L. pulmonaria, and the toxicity to OD₄₃₅/OD₄₁₅ presented as L. pulmonaria≈L. orientalis<U. luridorufa≈U. dasopoga. Under an increasing nitrogen deposition background, our result is of special importance in lichen diversity protection and management in Shennongjia Nature Reserve.

Key words: leaf anatomical structure, heat resistance, Rhododendron, comprehensive evaluation