Cellulose in situ Decomposition in a Bog Exposed to Increasing Nitrogen Treatments, 2012-2014

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). We examined the effects of N
addition on cellulose placed in the bog from 2012-2014 and collected
after 5 and 17 months. Decomposition of cellulose filter paper in
surface peat increased with N input. Water addition alone had no
significant effect on exponential decay constants
( k values). In control and 0 kg
ha -1 yr -1 treatments, k values averaged 0.58
yr -1 , corresponding to 42% of initial mass
lost in the first year, while in the 25 kg
ha -1 yr -1 treatment, k values averaged 1.27
yr -1 , corresponding to 72% of initial mass
lost in the first year. Assessment of decomposition and its controls
may be especially important in peatlands, as the development and
persistence of peat depends on an excess of NPP over decomposition
throughout the peat profile. There is some evidence that increasing N
deposition/availability stimulates cellulose decomposition in surface
bog peat, as we found at Mariana Lakes Bog.