Abstract: As the main pigment for plant photosynthesis, chlorophyll content is closely related to soil nitrogen availability, with consequence on plant growth and nutrient absorption. We conducted a long-term nitrogen addition experiment (N1: 6 g·m^-2·a^-1; N2: 12 g·m^-2·a^-1; N3: 24 g·m^-2·a^-1) in the permafrost region of the Great Hing’an Mountains to investigate the effects of nitrogen addition on plant growth and nutrient characteristics of peatland. The response patterns of leaf chlorophyll content and carbon, nitrogen, and phosphorus contents and their stoichiometric ratios to nitrogen addition were analyzed for typical peatland plants, including Betula fruticosa, Chamaedaphne calyculata, and Vaccinium uliginosum. The results showed that nitrogen addition increased leaf chlorophyll contents of B. fruticosa, C. calyculata, and V. uliginosum. Chlorophyll contents showed a trend of first increasing and then decreasing with increasing nitrogen addition levels. Mid-level of nitrogen addition significantly increased total leaf carbon contents of B. fruticosa and C. calyculata, but did not affect that of V. uliginosum. Nitrogen addition significantly increased total nitrogen contents of B. fruticosa and C. calyculata leaves, while simultaneously reduced the total phosphorus content and C/N ratio, and increased foliar N/P ratio of all the three species. Leaf chlorophyll contents of B. fruticosa, C. calyculata and V. uliginosum were significantly positively correlated with total leaf nitrogen content, whereas negatively correlated leaf C/N ratio. The chlorophyll content of C. calyculata was significantly positively correlated with C/P and N/P. In contrast, the chlorophyll content of V. uliginosum leaves was significantly positively correlated with total nitrogen, C/P, and N/P, and significantly negatively correlated with total phosphorus and C/N. Our results suggested that the growth of peatland plants was limited by nitrogen. Nitrogen addition can improve the photosynthetic capacity of peatland plants in permafrost regions, promote nitrogen absorption and accumulation, and change ecological stoichiometry.

Key words: nitrogen nutrition, permafrost peatland, chlorophyll, nitrogen limitation, stoichiometric ratio