Peatland Vascular Plant Leaf N Concentrations (10 Species) From Leaves Collected From N-Addition Plots in an Alberta Peatland, 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). In July of each year, we collected
new growth of ten species of vascular plants, returned them to the
lab, cleaned them, dried and ground them, and ran them on a Flash EA
1112 Series CN Soil Analyzer. Leaf N concentration responses to
increasing N input differed between species. Increasing N input led to
increasing leaf N concentrations in A. polifolia , C. calyculata , V.
vitis-idaea , and V. oxycoccos , with
differences in N concentrations between years for all of these species
except V. vitis-idaea . There was no leaf N
concentration response to increasing N input for E.
vaginatum , R. chamaemorus , S. trifolia , or K.
polifolia . Water input alone had no significant effect on
leaf N concentration for any of the species (p >= 0.18). Although
aboveground growth of bog vascular plants may be a general response to
increasing N deposition, we do not have a species-specific mechanistic
understanding of how growth and leaf/needle N concentrations respond
to increasing N deposition, however, there appeared to be no strong
evidence for luxury consumption of N.

油砂开发活动导致大气氮沉降（atmospheric N deposition）规模持续扩大，最高沉降通量可达17 kg N·ha⁻¹·yr⁻¹；区域背景氮沉降通量仅不足2 kg N·ha⁻¹·yr⁻¹。雨养型泥炭沼泽（ombrotrophic）作为仅依赖大气降水获取养分的湿地生态系统，对氮沉降增加的敏感性尤为显著。为探究该类沼泽对氮沉降的响应，本研究在五年实验周期内，于加拿大阿尔伯塔省马里亚纳湖附近的一处泥炭沼泽开展原位施氮操控实验：以硝酸铵（NH₄NO₃）作为氮源，设置0、5、10、15、20、25 kg N·ha⁻¹·yr⁻¹共6个施氮梯度，同时设置对照组（不施加水与氮素）。每年7月，研究人员采集10种维管植物的新生枝叶，带回实验室后经清洗、烘干、研磨制样，再使用Flash EA 1112系列碳氮土壤分析仪（Flash EA 1112 Series CN Soil Analyzer）测定样品的全氮含量。不同物种的叶片氮浓度对氮输入增加的响应模式存在显著分化。其中，A. polifolia、C. calyculata、V. vitis-idaea及V. oxycoccos的叶片氮浓度随氮输入量提升而显著升高；除V. vitis-idaea外，其余三个物种的叶片氮浓度均存在明显年际差异。而E. vaginatum、R. chamaemorus、S. trifolia及K. polifolia的叶片氮浓度对氮输入增加无显著响应。仅施加水分的处理对所有供试物种的叶片氮浓度均无显著影响（p ≥ 0.18）。尽管泥炭沼泽维管植物的地上生长可能普遍对氮沉降增加产生响应，但目前尚未明确各物种的生长及叶片/针叶氮浓度响应氮沉降增加的物种特异性机制；不过本研究未发现显著的氮奢侈消费证据。