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  • 1
    In: Philosophical Transactions of the Royal Society B: Biological Sciences, The Royal Society, Vol. 368, No. 1625 ( 2013-09-05), p. 20120376-
    Abstract: The African humid tropical biome constitutes the second largest rainforest region, significantly impacts global carbon cycling and climate, and has undergone major changes in functioning owing to climate and land-use change over the past century. We assess changes and trends in CO 2 fluxes from 1901 to 2010 using nine land surface models forced with common driving data, and depict the inter-model variability as the uncertainty in fluxes. The biome is estimated to be a natural (no disturbance) net carbon sink (−0.02 kg C m −2 yr −1 or −0.04 Pg C yr −1 , p 〈 0.05) with increasing strength fourfold in the second half of the century. The models were in close agreement on net CO 2 flux at the beginning of the century ( σ 1901 = 0.02 kg C m −2 yr −1 ), but diverged exponentially throughout the century ( σ 2010 = 0.03 kg C m −2 yr −1 ). The increasing uncertainty is due to differences in sensitivity to increasing atmospheric CO 2 , but not increasing water stress, despite a decrease in precipitation and increase in air temperature. However, the largest uncertainties were associated with the most extreme drought events of the century. These results highlight the need to constrain modelled CO 2 fluxes with increasing atmospheric CO 2 concentrations and extreme climatic events, as the uncertainties will only amplify in the next century.
    Type of Medium: Online Resource
    ISSN: 0962-8436 , 1471-2970
    RVK:
    Language: English
    Publisher: The Royal Society
    Publication Date: 2013
    detail.hit.zdb_id: 1462620-2
    SSG: 12
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  • 2
    In: Proceedings of the Royal Society B: Biological Sciences, The Royal Society, Vol. 280, No. 1761 ( 2013-06-22), p. 20130171-
    Abstract: It is unclear to what extent seasonal water stress impacts on plant productivity over Amazonia. Using new Greenhouse gases Observing SATellite (GOSAT) satellite measurements of sun-induced chlorophyll fluorescence, we show that midday fluorescence varies with water availability, both of which decrease in the dry season over Amazonian regions with substantial dry season length, suggesting a parallel decrease in gross primary production (GPP). Using additional SeaWinds Scatterometer onboard QuikSCAT satellite measurements of canopy water content, we found a concomitant decrease in daily storage of canopy water content within branches and leaves during the dry season, supporting our conclusion. A large part ( r 2 = 0.75) of the variance in observed monthly midday fluorescence from GOSAT is explained by water stress over moderately stressed evergreen forests over Amazonia, which is reproduced by model simulations that include a full physiological representation of photosynthesis and fluorescence. The strong relationship between GOSAT and model fluorescence ( r 2 = 0.79) was obtained using a fixed leaf area index, indicating that GPP changes are more related to environmental conditions than chlorophyll contents. When the dry season extended to drought in 2010 over Amazonia, midday basin-wide GPP was reduced by 15 per cent compared with 2009.
    Type of Medium: Online Resource
    ISSN: 0962-8452 , 1471-2954
    Language: English
    Publisher: The Royal Society
    Publication Date: 2013
    detail.hit.zdb_id: 1460975-7
    SSG: 12
    SSG: 25
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