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| Titel |
Net ecosystem CO2 exchange of sub-Arctic heath and lichen communities across a forest to mire transition |
| VerfasserIn |
Rafael Poyatos, Andreas Heinemeyer, Phil Ineson, Brian Huntley, Robert Baxter |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055304
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| Zusammenfassung |
| Landscape level measurements of net ecosystem CO2 exchange (NEE) in Arctic tundra show
that seasonal and annual values of NEE vary considerably due to site-specific factors and
interannual variation of climatic drivers. The taiga-tundra ecotone in northern Fennoscandia
is representative of these complex sub-Arctic landscapes, a mosaic of mountain
birch woodland and palsa mires associated to waterlogged areas. In the margins
of these mires, the growth of cryogenic peat hummocks introduces yet another
factor inducing fine-scale vegetation heterogeneity, creating a variety of habitats
which differ in snow cover during the winter and substrate moisture during the
growing season. Using an in-situ automated chamber system, we measured hourly
NEE in four vegetation types from June to September of the year 2008 in Petsikko,
near the Kevo Subarctic Research Institute, in Finnish Lapland. The system was
installed within the hummocky area, sampling: (1) Empetrum hermaphroditum
-dominated hummock tops adjacent to wet areas in the mire-wetland transition, (2)
E.hermaphroditum-dominated hummock tops by the sparse birch area, (3) Dry hollows
covered by Calluna vulgaris and (4) eroded hummock tops, partially covered by lichen.
These lichen-covered hummocks behaved as a CO2 source for most of the study period.
Within the tundra shrub communities, variation in NEE was explained by differences
in vegetation structure rather than by vegetation type. NEE fluxes modeled using
seasonally variable light response curves showed that maximum values of light-saturated
photosynthesis and the respiration parameter were highly and positively correlated with
patch-scale NDVI. The seasonal variation of the respiration parameter was also
related to air temperature and peat moisture content. Finally, different methods
for decomposition of NEE into Gross Primary Productivity (GPP) and Ecosystem
Respiration (Reco), combining night-time NEE fluxes and semiempirical NEE modelling
(photosynthetic irradiance-response and temperature-sensitive respiration model,
PIRT), were compared against actual measurements of Recousing dark chambers. |
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