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  • 1
    Publication Date: 2009-03-07
    Description: Amazon forests are a key but poorly understood component of the global carbon cycle. If, as anticipated, they dry this century, they might accelerate climate change through carbon losses and changed surface energy balances. We used records from multiple long-term monitoring plots across Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events. Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 x 10(15) to 1.6 x 10(15) grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the potential for large carbon losses to exert feedback on climate change.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Phillips, Oliver L -- Aragao, Luiz E O C -- Lewis, Simon L -- Fisher, Joshua B -- Lloyd, Jon -- Lopez-Gonzalez, Gabriela -- Malhi, Yadvinder -- Monteagudo, Abel -- Peacock, Julie -- Quesada, Carlos A -- van der Heijden, Geertje -- Almeida, Samuel -- Amaral, Ieda -- Arroyo, Luzmila -- Aymard, Gerardo -- Baker, Tim R -- Banki, Olaf -- Blanc, Lilian -- Bonal, Damien -- Brando, Paulo -- Chave, Jerome -- de Oliveira, Atila Cristina Alves -- Cardozo, Nallaret Davila -- Czimczik, Claudia I -- Feldpausch, Ted R -- Freitas, Maria Aparecida -- Gloor, Emanuel -- Higuchi, Niro -- Jimenez, Eliana -- Lloyd, Gareth -- Meir, Patrick -- Mendoza, Casimiro -- Morel, Alexandra -- Neill, David A -- Nepstad, Daniel -- Patino, Sandra -- Penuela, Maria Cristina -- Prieto, Adriana -- Ramirez, Fredy -- Schwarz, Michael -- Silva, Javier -- Silveira, Marcos -- Thomas, Anne Sota -- Steege, Hans Ter -- Stropp, Juliana -- Vasquez, Rodolfo -- Zelazowski, Przemyslaw -- Alvarez Davila, Esteban -- Andelman, Sandy -- Andrade, Ana -- Chao, Kuo-Jung -- Erwin, Terry -- Di Fiore, Anthony -- Honorio C, Euridice -- Keeling, Helen -- Killeen, Tim J -- Laurance, William F -- Pena Cruz, Antonio -- Pitman, Nigel C A -- Nunez Vargas, Percy -- Ramirez-Angulo, Hirma -- Rudas, Agustin -- Salamao, Rafael -- Silva, Natalino -- Terborgh, John -- Torres-Lezama, Armando -- New York, N.Y. -- Science. 2009 Mar 6;323(5919):1344-7. doi: 10.1126/science.1164033.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Ecology and Global Change, School of Geography, University of Leeds, Leeds LS2 9JT, UK. o.phillips@leeds.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19265020" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; *Biomass ; Brazil ; Carbon ; Carbon Dioxide ; Climate ; *Droughts ; *Ecosystem ; South America ; *Trees/growth & development ; Tropical Climate
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © Elsevier B.V., 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Palaeogeography, Palaeoclimatology, Palaeoecology 294 (2010): 56-71, doi:10.1016/j.palaeo.2009.03.012.
    Description: Since the last deglaciation, the mid-latitudes of the southern Hemisphere have undergone considerable environmental changes. In order to better understand the response of continental ecosystems to paleoclimate changes in southern South America, we investigated the sedimentary record of Puyehue Lake, located in the western piedmont of the Andes in south-central Chile (40°S). We analyzed the elemental (C, N) and stable isotopic (δ13C, δ15N) composition of the sedimentary organic matter preserved in the lake and its watershed to estimate the relative changes in the sources of sedimentary organic carbon through space and time. The geochemical signature of the aquatic and terrestrial end-members was determined on samples of lake particulate organic matter (N/C: 0.130) and Holocene paleosols (N/C: 0.069), respectively. A simple mixing equation based on the N/C ratio of these end-members was then used to estimate the fraction of terrestrial carbon (ƒT) preserved in the lake sediments. Our approach was validated using surface sediment samples, which show a strong relation between ƒT and distance to the main rivers and to the shore. We further applied this equation to an 11.22 m long sediment core to reconstruct paleoenvironmental changes in Puyehue Lake and its watershed during the last 17.9 kyr. Our data provide evidence for a first warming pulse at 17.3 cal kyr BP, which triggered a rapid increase in lake diatom productivity, lagging the start of a similar increase in sea surface temperature (SST) off Chile by 1500 years. This delay is best explained by the presence of a large glacier in the lake watershed, which delayed the response time of the terrestrial proxies and limited the concomitant expansion of the vegetation in the lake watershed (low ƒT). A second warming pulse at 12.8 cal kyr BP is inferred from an increase in lake productivity and a major expansion of the vegetation in the lake watershed, demonstrating that the Puyehue glacier had considerably retreated from the watershed. This second warming pulse is synchronous with a 2°C increase in SST off the coast of Chile, and its timing corresponds to the beginning of the Younger Dryas Chronozone. These results contribute to the mounting evidence that the climate in the mid-latitudes of the southern Hemisphere was warming during the Younger Dryas Chronozone, in agreement with the bipolar see-saw hypothesis.
    Description: This research was partly supported by the Belgian OSTC project EV/12/10B "A continuous Holocene record of ENSO variability in southern Chile". S.B. is supported by a BAEF fellowship (Belgian American Educational Foundation), and by an EU Marie Curie Outgoing Fellowship under the FP6 programme.
    Keywords: Organic matter ; Lake sediments ; Carbon ; Nitrogen ; Southern Hemisphere ; Deglaciation
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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