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 NH4NO3) 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.