Publication Date:
2010-01-26
Description:
Two years of continuous measurements of net ecosystem exchange (NEE) using the eddy covariance technique were made over a Mediterranean alpine shrubland. These ecosystems are little studied, since they have little CO2 exchange potential. Nevertheless, their high susceptibility to environmental changes is far from being understood, introducing some uncertainty in terrestrial CO2 and water vapour assessments. High altitude sites might be undergoing a transition from sink to source of CO2, due to their high vulnerability to climate change. Indeed, this ecosystem was found to be a net source of CO2 (+52 g C m-2 and +48 g C m-2 for 2007 and 2008) during the two-year study period. To understand the reasons underlying this net release of CO2 into the atmosphere, we analysed the drivers of seasonal variability in NEE across these two years. We observed that the soil water availability – driven by the precipitation pattern – and the photosynthetic photon flux density (PPFD) are the key factors for understanding both the carbon sequestration potential and the duration of the photosynthetic period during the growing season. Finally, the effects of the Burba correction for both NEE and evapotranspiration (ET) are evaluated. This correction can sometimes be neglected on a daily basis, but becomes rather important in long-term assessments. For instance, the annual CO2 budget in 2007 turned from sink (-136 g C m-2) to source (+52 g C m-2) when the Burba correction was taken into account.
Print ISSN:
1810-6277
Electronic ISSN:
1810-6285
Topics:
Biology
,
Geosciences
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