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- Title
Environmental and Vegetation Drivers of Seasonal CO Fluxes in a Sub-arctic Forest-Mire Ecotone.
- Authors
Poyatos, Rafael; Heinemeyer, Andreas; Ineson, Phil; Evans, Jonathan; Ward, Helen; Huntley, Brian; Baxter, Robert
- Abstract
Unravelling the role of structural and environmental drivers of gross primary productivity (GPP) and ecosystem respiration ( R) in highly heterogeneous tundra is a major challenge for the upscaling of chamber-based CO fluxes in Arctic landscapes. In a mountain birch woodland-mire ecotone, we investigated the role of LAI (and NDVI), environmental factors (microclimate, soil moisture), and microsite type across tundra shrub plots (wet hummocks, dry hummocks, dry hollows) and lichen hummocks, in controlling net ecosystem CO exchange (NEE). During a growing season, we measured NEE fluxes continuously, with closed dynamic chambers, and performed multiple fits (one for each 3-day period) of a simple light and temperature response model to hourly NEE data. Tundra shrub plots were largely CO sinks, as opposed to lichen plots, although fluxes were highly variable within microsite type. For tundra shrub plots, microsite type did not influence photosynthetic parameters but it affected basal (that is, temperature-normalized) ecosystem respiration ( R). PAR-normalized photosynthesis ( P) increased with air temperature and declined with increasing vapor pressure deficit. R declined with soil moisture and showed an apparent increase with temperature, which may underlie a tight link between GPP and R. NDVI was a good proxy for LAI, maximum P and maximum R of shrub plots. Cumulative CO fluxes were strongly correlated with LAI (NDVI) but we observed a comparatively low GPP/LAI in dry hummocks. Our results broadly agree with the reported functional convergence across tundra vegetation, but here we show that the role of decreased productivity in transition zones and the influence of temperature and water balance on seasonal CO fluxes in sub-Arctic forest-mire ecotones cannot be overlooked.
- Subjects
CARBON; ECOSYSTEM management; ECOTONES; PLANTS; PHOTOSYNTHESIS; MOISTURE
- Publication
Ecosystems, 2014, Vol 17, Issue 3, p377
- ISSN
1432-9840
- Publication type
Article
- DOI
10.1007/s10021-013-9728-2