氮沉降和生物质炭对毛竹叶片光合特性的影响

为了解氮沉降和生物质炭对毛竹Phyllostachys edulis叶片光合特性的影响，研究了4种氮沉降（0 kg·hm-2·a-1，N₀；30 kg·hm-2·a-1，N₃₀；60 kg·hm-2·a-1，N₆₀；90 kg·hm-2·a-1，N₉₀）下施加3种不同强度（0 t·hm-2，BC₀；20 t·hm-2，BC₂₀；40 t·hm-2，BC₄₀）生物质炭处理后2龄毛竹新老叶片光合及叶绿素荧光特性的变化。结果表明:氮沉降和生物质炭均促进了毛竹新老叶的最大净光合速率（P_max），气孔导度（G_s）和蒸腾速率（T_r），生物质炭同时提高了老叶实际量子产量Y（Ⅱ）]和PSⅡ潜在活性（F_v/F₀）。与不施加生物质炭相比（BC₀），N₃₀下施加20 t·hm-2生物质炭的老叶及N₆₀下施加20 t·hm-2生物质炭（BC₂₀）的新老叶叶色值显著降低；N₆₀处理下施加生物质炭，毛竹新老叶的最大光化学效率（F_v/F_m），F_v/F_o和Y（Ⅱ）均提高，而N₉₀处理下施加生物质炭，毛竹新老叶的F_v/F_m和F_v/F_o均降低。由此认为:氮沉降条件下施加生物质炭有利于毛竹新老叶片的光合固碳能力；大气氮沉降背景下，施加生物质炭有利于提高毛竹生产力。

Photosynthesis with simulated nitrogen deposition and biochar amendments on new and old leaves of Moso bamboo

To understand the effects of nitrogen (N) deposition and biochar amendments on photosynthesis of new and old leaves of Moso bamboo (Phyllostachys edulis), effects of four N additions (N₀: 0 kg·hm-2·a-1, N₃₀: 30 kg·hm-2·a-1, N₆₀: 60 kg·hm-2·a-1, and N₉₀: 90 kg·hm-2·a-1) and three biochar amendments (BC₀: 0 t·hm-2, BC₂₀: 20 t·hm-2, and BC₄₀: 40 t·hm-2) on photosynthesis and chlorophyll fluorescence characteristics of new and old leaves in two-year-old Moso bamboo were determined using LI-6400 portable photosynthesis system, PAM-2500 chlorophyll fluorescence spectrometer and SPAD-502 chlorophyll meter in Moso bamboo plantations (20 m×20 m). Results showed that N deposition and biochar amendment significantly increased (P < 0.05) the maximum net photosynthetic rate (P_max), stomatal conductance (G_s), and transpiration rate (T_r) of new and old leaves. Biochar amendments significantly increased (P < 0.001) effective quantum yield of Photosystem Ⅱ (PS-Ⅱ)Y(Ⅱ)] and potential activities of PS-Ⅱ (F_v/F₀) of old leaves. In combination with both N depositions (N₃₀ and N₆₀), BC₂₀ significantly decreased (P < 0.001) the relative chlorophyll content (SPAD) of old leaves compared with the N depositions alone. The SPAD of new leaves for N₆₀-BC₂₀ was significantly lower (P < 0.001) than N₆₀-BC₀. Also, both biochar amendments in combination with N₆₀ significantly increased (P < 0.001) maximal potential quantum yield of PS-Ⅱ (F_v/F_m), F_v/Fo, and Y(Ⅱ) of new and old leaves compared to N depositions alone. However, biochar amendments in combination with N₉₀ significantly decreased (P < 0.001) both F_v/F_m and F_v/F_o of new and old leaves compared to N depositions alone. In conclusion, this study demonstrated that biochar amendments promoted photosynthesis of leaves and thus increased productivity of a Moso bamboo forest with the background of globally increasing N deposition.