Where does the carbon go? A model-data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free-air CO2 enrichment sites.
Bottom Line: Observed eCO2 effects on allocation were dynamic.Allocation schemes based on constant fractions or resource limitations performed less well, with some models having unintended outcomes.Our recommendations to reduce uncertainty include: use of allocation schemes constrained by biomass fractions; careful testing of allocation schemes; and synthesis of allocation and turnover data in terms of model parameters.
Affiliation: Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.Show MeSH
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Mentions: Fixed coefficient models assume that allocation fractions are not affected by environmentalconditions. In two of these models, CLM4 and GDAY (at Duke), there was no change in allocation inresponse to eCO2 (Figs2a, 3a). At Oak Ridge, GDAY assumed that root allocation was increased in response toeCO2, based on the average CO2 response measured at the site. It can be seenin Fig. 3 that this response is assumed to start in thesecond year of the experiment, because in the deciduous version of the model, growth is based on theprevious year's accumulated productivity. These models are included for completeness butoverall, the observations from both experiments indicate that allocation responses toeCO2 are dynamic, so it is clear that the constant coefficient approach is of limitedusefulness for predicting allocation patterns under eCO2.
Affiliation: Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.