Vascular Root Biomass and N Concentrations at Two Depths in an Alberta Peatland Subjected to Increasing Nitrogen Deposition, 2014-2015

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). From 2014-2015, we examined the
effects of N addition on root production and nitrogen assimilation in
those roots by measuring root biomass at two depths and root
production over one and two years. Root biomass in the 0-15 cm and
15-30 cm depth increments in peat increased with increasing N input;
the response was similar in the two depth increments. Root production
integrated over the top 30 cm of peat increased with increasing N
input at a rate of 5.3 g m -2 yr -1 with an increase in N input of 1 kg N
ha -1 yr -1 . Water
addition alone had no significant effect on root biomass (p > 0.72)
or root production. Given the rather consistent finding increasing N
deposition stimulates aboveground vascular plant biomass and
production, and our results that root biomass and production at
Mariana Lakes Bog are stimulated as well, further work on belowground
responses seems warranted.