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| Titel |
Carbon dioxide flux and net primary production of a boreal treed bog: Responses to warming and water-table-lowering simulations of climate change |
| VerfasserIn |
T. M. Munir, M. Perkins, E. Kaing, M. Strack |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 4 ; Nr. 12, no. 4 (2015-02-20), S.1091-1111 |
| Datensatznummer |
250117825
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| Publikation (Nr.) |
 copernicus.org/bg-12-1091-2015.pdf |
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| Zusammenfassung |
Midlatitude treed bogs represent significant carbon (C) stocks and are
highly sensitive to global climate change. In a dry continental treed bog,
we compared three sites: control, recent (1–3 years; experimental) and older
drained (10–13 years), with water levels at 38, 74 and 120 cm below
the surface, respectively. At each site we measured carbon dioxide
(CO2) fluxes and estimated tree root respiration (Rr; across
hummock–hollow microtopography of the forest floor) and net primary
production (NPP) of trees during the growing seasons (May to October) of
2011–2013. The CO2–C balance was calculated by adding the net CO2
exchange of the forest floor (NEff-Rr) to the NPP of the trees.
From cooler and wetter 2011 to the driest and the warmest 2013, the control
site was a CO2–C sink of 92, 70 and 76 g m−2, the experimental
site was a CO2–C source of 14, 57 and 135 g m−2, and the drained
site was a progressively smaller source of 26, 23 and 13 g CO2–C m−2. The short-term drainage at the experimental site
resulted in small changes in vegetation coverage and large net CO2
emissions at the microforms. In contrast, the longer-term drainage and
deeper water level at the drained site resulted in the replacement of mosses
with vascular plants (shrubs) on the hummocks and lichen in the hollows
leading to the highest CO2 uptake at the drained hummocks and
significant losses in the hollows. The tree NPP (including above- and
below-ground growth and litter fall) in 2011 and 2012 was significantly
higher at the drained site (92 and 83 g C m−2) than at the experimental
(58 and 55 g C m−2) and control (52 and 46 g C m−2) sites.
We also quantified the impact of climatic warming at all water table
treatments by equipping additional plots with open-top chambers (OTCs) that
caused a passive warming on average of ~ 1 °C and
differential air warming of ~ 6 °C at midday full sun
over the study years. Warming significantly enhanced shrub growth and the CO2 sink function of the drained hummocks (exceeding the cumulative
respiration losses in hollows induced by the lowered water level ×
warming). There was an interaction of water level with warming across
hummocks that resulted in the largest net CO2 uptake at the warmed
drained hummocks. Thus in 2013, the warming treatment enhanced the sink
function of the control site by 13 g m−2, reduced the source function
of the experimental by 10 g m−2 and significantly enhanced the sink
function of the drained site by 73 g m−2. Therefore, drying and warming
in continental bogs is expected to initially accelerate CO2–C losses
via ecosystem respiration, but persistent drought and warming is expected to
restore the peatland's original CO2–C sink function as a result of the
shifts in vegetation composition and productivity between the microforms and
increased NPP of trees over time. |
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