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| Titel |
Does size matter in peatland open-water pool biogeochemistry? |
| VerfasserIn |
Julien Arsenault, Julie Talbot, Tim R. Moore |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138821
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| Publikation (Nr.) |
 EGU/EGU2017-1948.pdf |
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| Zusammenfassung |
| Open-water pools are common features in boreal peatlands but their influence on ecosystem
biogeochemistry is poorly known. As nitrogen (N) and phosphorus (P) are often limited in
such environments, nutrient cycles in pools might have an effect on the surrounding peat, or
vice versa. We studied C, N and P biogeochemistry in open-water pools of an undisturbed
sub-boreal ombrotrophic peatland in Québec, Canada. We assessed the relationship between
the pool’s physical characteristics and biogeochemistry, and quantified the temporal evolution
of C, N and P concentrations in pools of different size and depth over a growing
season.
A one-time survey of 62 of the ∼650 pools in the peatland revealed that pool depth and
area vary from 0.15 to 2.19 m and from 34 to 1977 m2, respectively. Dissolved organic
carbon (DOC) concentration ranged from 8.6 to 36.9 mg L−1, negatively correlated to pool
depth, and pH varied from 3.72 to 4.33. Total P was extremely low (mean = 17.3 μg L−1) in
all pools and total N (0.71 to 0.27 mg L−) was negatively correlated with pool
depth.
Nine pools, selected to represent extremes in depth and area, were surveyed every 2 to 3
weeks from mid-May to late October, 2016. Average DOC concentrations slightly increased
in deep pools from 10.0 mg L−1 in May to 15.6 mg L−1 in October, but there was a stronger
increase in shallow pools (from 15.4 to 33.5 mg L−1). Water acidity tended to increase
in large and small shallow pools (mean pH = 4.02 to 3.81) but decreased in deep
pools (pH = 4.17 to 4.46). Mean total P ranged from 37.7 in May to 16.3 μg L−1 in
October with a minimum of 8.0 μg L−1 in mid-August. Total N tended to increase
(0.27 to 0.53 mg L−1) in all pools, but deeper pools tended to have lower total
N (0.25 to 0.46 mg L−1) than shallow pools. Throughout, NH4+ (mean = 9 μg
L−1) and soluble reactive phosphorus (mean = 7 μg L−1) were extremely low in
all pools. In May, NO3− was higher in deep pools (42.3 μg L−1) than in shallow
pools (large 12.0 μg L−1, small 14.3 μg L−1), but decreased (mean = 6 μg L−1) in
July and remained low for the rest of the season. DON dominated TDN, ranging
seasonally from 91 to 96%. The TDN:TP ratio rose from 7:1 in spring, to 60:1 in
summer and 30:1 in autumn, with the largest ratio in the shallow pools, indicative of
P-limitation.
The results suggest largest productivity in shallow pools. This study being one of the first
to focus on peatland open-water pool biogeochemistry, further investigations are needed to
better understand the relationship between pools and the surrounding peat, especially at the
soil/water interface. |
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