Carbon Balance Gradient in European Forests: Should We Doubt 'Surprising' Results? A Reply to Piovesan & Adams
ABSTRACT This paper responds to the Forum contribution by Piovesan & Adams (2000) who criticized the results obtained by the EUROFLUX network on carbon fluxes of several European forests. The major point of criticism was that the data provided by EUROFLUX are inconsistent with current scientific understanding. It is argued that understanding the terrestrial global carbon cycle requires more than simply restating what was known previously, and that Piovesan & Adams have not been able to show any major conflicts between our findings and ecosystem or atmospheric-transport theories.
Full-textDOI: · Available from: Leonardo Montagnani, Jun 09, 2014
- SourceAvailable from: Ivan A. Janssens
New Phytologist 05/2011; 190(3):517-21. DOI:10.1111/j.1469-8137.2010.03499.x · 7.67 Impact Factor
- "The most commonly suspected publication bias is the tendency for authors and journals to only publish studies with statistically significant results, which has been termed the 'file-drawer problem' (Rosenthal, 1979). Moreover, researchers are under increasing pressure to publish frequently, and it is much easier to publish results that can easily be explained or support widely accepted hypotheses (Jarvis et al., 2001), than having to fight a time-consuming battle with conservative and suspicious referees (as they perhaps should be). A clear example of such a publication bias occurred in a European network of CO 2 -enrichment experiments on trees (ECOCRAFT, 1999). "
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- "To our knowledge, this NEP is the largest reported in an old-growth forest. Should we doubt this surprising result (Jarvis et al., 2001)? It is important to consider the plausibility of a carbon sink of 900 gC m À2 yr À1 for a 300-year-old evergreen forest. "
ABSTRACT: a b s t r a c t Old-growth forests are primarily found in mountain ranges that are less favorable or accessible for land use. Consequently, there are fewer scientific studies on old-growth forests. The eddy covariance method has been widely used as an alternative approach to studying an ecosystem's carbon balance, but only a few eddy flux sites are located in old-growth forest. This fact will hinder our ability to test hypotheses such as whether or not old-growth forests are carbon neutral. The eddy covariance approach was used to examine the carbon balance of a 300-year-old subtropical evergreen broadleaved forest that is located in the center of the largest subtropical land area in the world. The post-QA/QC (quality assurance and control) eddy covariance based NEP was w 9 tC ha À1 yr À1 , which suggested that this forest acts as a large carbon sink. The inventory data within the footprint of the eddy flux show that w6 tC ha À1 yr À1 was contributed by biomass and necromass. The large-and-old trees sequestered carbon. Approximately 60% of the biomass increment is contributed by the growth of large trees (DBH > 60 cm). The high-altitude-induced low temperature and the high diffusion-irradiation ratio caused by cloudiness were suggested as two reasons for the large carbon sink in the forest we studied. To analyze the complex structure and terrain of this old-growth forest, this study suggested that biometric measurements carried out simul-taneously with eddy flux measurements were necessary.Atmospheric Environment 03/2011; 45(8). DOI:10.1016/j.atmosenv.2010.12.041 · 3.28 Impact Factor
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- "r 2009 Blackwell Publishing Ltd, Global Change Biology, 15, 2905–2920 ecosystems (Valentini et al., 2000; Jarvis et al., 2001; van Dijk & Dolman, 2004; Kato & Tang, 2008 "
ABSTRACT: Over the last two and half decades, strong evidence showed that the terrestrial ecosystems are acting as a net sink for atmospheric carbon. However the spatial and temporal patterns of variation in the sink are not well known. In this study, we examined latitudinal patterns of interannual variability (IAV) in net ecosystem exchange (NEE) of CO2 based on 163 site-years of eddy covariance data, from 39 northern-hemisphere research sites located at latitudes ranging from ∼29°N to ∼64°N. We computed the standard deviation of annual NEE integrals at individual sites to represent absolute interannual variability (AIAV), and the corresponding coefficient of variation as a measure of relative interannual variability (RIAV). Our results showed decreased trends of annual NEE with increasing latitude for both deciduous broadleaf forests and evergreen needleleaf forests. Gross primary production (GPP) explained a significant proportion of the spatial variation of NEE across evergreen needleleaf forests, whereas, across deciduous broadleaf forests, it is ecosystem respiration (Re). In addition, AIAV in GPP and Re increased significantly with latitude in deciduous broadleaf forests, but AIAV in GPP decreased significantly with latitude in evergreen needleleaf forests. Furthermore, RIAV in NEE, GPP, and Re appeared to increase significantly with latitude in deciduous broadleaf forests, but not in evergreen needleleaf forests. Correlation analyses showed air temperature was the primary environmental factor that determined RIAV of NEE in deciduous broadleaf forest across the North American sites, and none of the chosen climatic factors could explain RIAV of NEE in evergreen needleleaf forests. Mean annual NEE significantly increased with latitude in grasslands. Precipitation was dominant environmental factor for the spatial variation of magnitude and IAV in GPP and Re in grasslands.Global Change Biology 11/2009; 15(12):2905 - 2920. DOI:10.1111/j.1365-2486.2009.01870.x · 8.04 Impact Factor