Sphagnum fuscum Growth and N Concentration in an Alberta Peatland Subjected to Increasing Nitrogen Deposition, 2011-2015

Development of the oil sands has led to increasing atmospheric N deposition, with values as high as 17 kg N ha -1 yr -1 ; regional background levels <2 kg N ha -1 yr -1 . Bogs, being ombrotrophic, may be especially susceptible to increasing N deposition. To examine responses to N deposition, over five years, we experimentally applied N (as NH 4 NO 3 ) to a bog near Mariana Lakes, Alberta, at rates of 0, 5, 10, 15, 20, and 25 kg N ha -1 yr -1 , plus controls (no water or N addition). Data collected of the growing season using the crank wire method allowed for the calculation of NPP. Tissues were also collected and analyzed on Leco TruSpec CN analyzer. Increasing N addition had no effect on Sphagnum fuscum NPP in year 1, but inhibited S. fuscum NPP in years 2-5, with capitula N concentrations remaining consistent across all years, but with stem N concentrations increasing with N input. The decrease in S. fuscum NPP with increasing N addition that we report for Mariana Lakes Bog has implications for peat accumulation in bogs.油砂开发导致大气氮沉降（atmospheric N deposition）日益加剧，最高沉降速率可达17 kg N ha⁻¹ yr⁻¹，区域背景值则低于2 kg N ha⁻¹ yr⁻¹。 雨养型（ombrotrophic）沼泽因其养分完全依赖大气降水补给，对氮沉降增加的敏感性尤高。 为探究沼泽生态系统对氮沉降的响应，研究团队开展了为期5年的控制实验，以硝酸铵（NH₄NO₃）为氮源，向加拿大阿尔伯塔省马里亚纳湖附近的一处沼泽施加梯度施氮处理，施氮速率分别为0、5、10、15、20和25 kg N ha⁻¹ yr⁻¹，另设置对照组（不添加水与氮素）。 研究人员在生长季采用曲柄丝法（crank wire method）采集数据，以此计算净初级生产力（NPP）。 同时采集植物组织样品，使用Leco TruSpec CN元素分析仪开展组分分析。 实验结果显示，施氮量增加对第1年锈色泥炭藓（Sphagnum fuscum）的净初级生产力无显著影响，但在第2至第5年抑制了其净初级生产力；在此期间，锈色泥炭藓头状枝的氮浓度在各年份均保持稳定，而茎部氮浓度则随施氮输入量的增加而升高。 本研究在马里亚纳湖沼泽中观测到的锈色泥炭藓净初级生产力随施氮量增加而下降的结果，对沼泽的泥炭积累过程具有重要启示意义。