Resin Deposition Data
Ammonium, nitrate, inorganic nitrogen, and sulfate deposition was
quantified using ion exchange resin tube collectors. These resin
collectors contain pre-rinsed mixed-bed cation/anion exchange resin
(Amberlite IRN 150). Collectors were deployed at each site, and within
each site, we have 5 plots. Two collectors were placed in each plot:
one in the open and one under the tree canopy. Blanks were included at
each site (resin tubes constructed with a cap on one end but otherwise
treated as the others) with all tube sets collected and exchanged
mid-May and mid-October. During the October-May deployment, a 1-m
supplementary tube was attached to the top of the precipitation
collection funnel to capture snowfall. The retrieved resins were
extracted with 1 M KI, filtered, and the extracts were analyzed for
NH4
+-N (phenate
method) on a Seal AA3 Auto Analyzer and for
NO3
--N &
SO4--S by ion chromatography (Dionex IC
5000). We subtracted volume weighted concentrations in blank resins
tube extracts from concentrations in extracts from exposed resin tubes
and corrected deposition values with laboratory-determined efficiency
values.
Veg CNS Data
Vegetation samples were collected at 5 plots at each of our sampling
sites at least three times per year (typically June, July, August)
between May and October. Five replicates of each species were taken at
each site on each sampling date. Protocols for new growth collections
were species specific. Surface moss was collected for
Sphagnum fuscum and Sphagnum
capillifolium. The entire lichen thalli of
Evernia mesomorpha and the top 2.5 cm of
Cladonia mitis thali were collected. Ericaceous
shrubs, Rhododendron groenlanicum and
Vaccinium vitis-idaea collections included the
topmost leaves from individual plants while all aboveground portions
of Vaccinium oxycoccos was collected. We
collected the current year leaves from the deciduous forbes,
Rubus chamaemorus and Maianthemum
trifolia, and the apical shoots of the current year’s
growth of the dominant tree Picea mariana. Each
sample was cleaned to remove debris, oven-dried (60 ⁰C), and ground
with a Wiley micromill. Sample were analyzed for total C, N, and S
concentrations with a LECO CNS analyzer.
Water Chem Data
To collect peatland porewater as a function of depth, we deployed
three samplers at each of our sites. These samplers are made of
stacked 20 cm long segments of 2.5 cm-diameter thinly slotted PVC
pipe, with Tygon tubing extending to the surface from the bottom of
each section. On each sampling date, a 60 mL syringe was used to empty
the full volume of water from the topmost segment, water was allowed
to slowly return to the segment, and a fresh 60 mL of porewater was
collected from that segment. Each of the samples was field filtered
through Whatman 41 filters into pre-washed sample bottles. Samples
were taken at least 3 times (June, July, and August) during each of
the summers of the study. The samples were frozen and shipped to
Villanova University for analysis of
NH4
+-N (phenate
method, Seal AA3 AutoAnalyzer),
NO3
--N and
SO4
2--S (Dionex ion
chromatograph), and total dissolved N (Shimadzu TOC-V analyzer with
prefiltration through 0.45 µm filters).