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| Titel |
Regional variability of grassland CO2 fluxes in Tyrol/Austria |
| VerfasserIn |
Christoph Irschick, Albin Hammerle, Alois Haslwanter, Georg Wohlfahrt |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250034913
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| Zusammenfassung |
| The FLUXNET project [1] aims at quantifying the magnitude and controls on the CO2, H2O and energy exchange of terrestrial ecosystems. Ideally, the various biomes of the Earth would be sampled in proportion to their spatial extent - in reality, however, study site selection is usually based on other (more practical) criteria so that a bias exists towards certain biomes and ecosystem types. This may be problematic because FLUXNET data are used to calibrate/parameterize models at various scales – if certain ecosystems are poorly replicated this may bias model predictions.
Here we present data from a project in Tyrol/Austria where we have been investigating the CO2, H2O and energy exchange of five grassland sites during 2005-2007. The five permanent grassland sites were exposed to similar climate, but differed slightly in management. In a FLUXNET style approach, any of these sites might have been selected for making long-term flux measurements – the aim of this project was to examine the representativeness of these sites and, if evident, elucidate the causes for and controls on differences between sites.
To this end we conducted continuous eddy covariance flux measurements at one (anchor) site [2, 3], and episodic, month long flux measurements at the four additional sites using a roving eddy covariance tower. These data were complemented by measurements of environmental drivers, the amount of above ground phytomass and basic data on vegetation and soil type, as well as management.
Data are subject to a rigorous statistical analysis in order to quantify significant differences in the CO2, H2O and energy exchange between the sites and to identify the factors which are responsible for these differences. In the present contribution we report results on CO2 fluxes.
Our major findings are that (i) site-identity of the surveyed grassland ecosystems was a significant factor for the net ecosystem CO2 exchange (NEE), somewhat less for gross primary production (GPP) and not for ecosystem respiration (RECO), (ii) GPP depended mainly on the amount of incident photosynthetically active radiation and the amount of green plant matter, the scale of influence of these two factors varying fourfold between the sites, and not so much on the available water, (iii) RECO was mainly affected by the soil temperature, but some evidence for priming effects was also found, (iv) the NEE was mainly influenced by GPP and to a lower extent by RECO. Taken together our results indicate that even within the same ecosystem type exposed to similar climate and land use, site selection may strongly affect the resulting NEE estimates.
References:
[1] D.D. Baldocchi, “Breathing of the terrestrial biosphere: lessons learned from a global network of carbon dioxide flux measurement systems”, Australian Journal of Botany vol.56 (2008) pp. 1-26.
[2] A. Hammerle, A. Haslwanter, U. Tappeiner, A. Cernusca, G. Wohlfahrt, “Leaf area controls on energy partitioning of a temperate mountain grassland“, Biogeosciences vol.5 (2008) pp. 421 431.
[3] G. Wohlfahrt, A. Hammerle, A. Haslwanter, M. Bahn, U. Tappeiner, A. Cernusca, “Seasonal and inter-annual variability of the net ecosystem CO2 exchange of a temperate mountain grassland: effects of weather and management“, Journal of Geophysical Research 113 (2008) D08110, doi:10.1029/2007JD009286. |
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