Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences
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Concerted changes in tropical forest structure and dynamics: evidence from 50 South American long-term plots

S. L. Lewis

S. L. Lewis

Earth and Biosphere Institute, Geography, University of Leeds, Leeds LS2 9JT, UK

School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JU, UK

[email protected]

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O. L. Phillips

O. L. Phillips

Earth and Biosphere Institute, Geography, University of Leeds, Leeds LS2 9JT, UK

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T. R. Baker

T. R. Baker

Max–Planck–Institut für Biogeochemie, Postfach 100164, 07701 Jena, Germany

Earth and Biosphere Institute, Geography, University of Leeds, Leeds LS2 9JT, UK

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J. Lloyd

J. Lloyd

Max–Planck–Institut für Biogeochemie, Postfach 100164, 07701 Jena, Germany

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Y. Malhi

Y. Malhi

School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JU, UK

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S. Almeida

S. Almeida

Museu Paraense Emilio Goeldi, 66077-530 Belém, Brazil

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N. Higuchi

N. Higuchi

Instituto Nacional de Pesquisas Amazônicas, 69011-970 Manaus, Brazil, ,

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W. F. Laurance

W. F. Laurance

Smithsonian Tropical Research Institute, PO Box 2072, Balboa, Panama

Biological Dynamics of Forest Fragments Program, INPA Ecologia, C.P. 478, 69011-970 Manaus, Brazil

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D. A. Neill

D. A. Neill

Missouri Botanical Garden, c/o Herbario Nacional del Ecuador, Casilla 17-21-1787, Quito, Ecuador

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J. N. M. Silva

J. N. M. Silva

CIFOR, Tapajos, Brazil

EMBRAPA Amazonia Oriental, 66095-100 Belém, Brazil

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J. Terborgh

J. Terborgh

Center for Tropical Conservation, Duke University, Box 90381, Durham, NC 27708, USA

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A. Torres Lezama

A. Torres Lezama

INDEFOR, Universidad de Los Andes, Mérida 5101, Venezuela

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R. Vásquez Martinez

R. Vásquez Martinez

Proyecto Flora del Perú, Jardin Botanico de Missouri, Oxapampa, Peru

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S. Brown

S. Brown

Winrock International, 1621 North Kent Street, Suite 1200, Arlington, VA 22209, USA

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J. Chave

J. Chave

Laboratoire Evolution et DiversitEacute; Biologique, CNRS/UPS, F31062 Toulouse, France

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C. Kuebler

C. Kuebler

Center for Applied Biodiversity Science, Conservation International, 1919 M Street, NW, Suite 600, Washington, DC 20036, USA

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P. Núñez Vargas

P. Núñez Vargas

Herbario Vargas, Universidad Nacional San Antonio Abad del Cusco, Cusco, Peru

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B. Vinceti

B. Vinceti

School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JU, UK

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    Several widespread changes in the ecology of old–growth tropical forests have recently been documented for the late twentieth century, in particular an increase in stem turnover (pan–tropical), and an increase in above–ground biomass (neotropical). Whether these changes are synchronous and whether changes in growth are also occurring is not known. We analysed stand–level changes within 50 long–term monitoring plots from across South America spanning 1971–2002. We show that: (i) basal area (BA: sum of the cross–sectional areas of all trees in a plot) increased significantly over time (by 0.10 ±; 0.04 m2 ha−1 yr−1, mean ± 95%CI) as did both (ii) stand–level BA growth rates (sum of the increments of BA of surviving trees and BA of new trees that recruited into a plot); and (iii) stand–level BA mortality rates (sum of the cross–sectional areas of all trees that died in a plot). Similar patterns were observed on a per–stem basis: (i) stem density (number of stems per hectare; 1 hectare is 104 m2) increased significantly over time (0.94 ± 0.63 stems ha−1 yr−1); as did both (ii) stem recruitment rates; and (iii) stem mortality rates. In relative terms, the pools of BA and stem density increased by 0.38 ± 0.15% and 0.18 ± 0.12% yr−1, respectively. The fluxes into and out of these pools—stand–level BA growth, stand–level BA mortality, stem recruitment and stem mortality rates—increased, in relative terms, by an order of magnitude more. The gain terms (BA growth, stem recruitment) consistently exceeded the loss terms (BA loss, stem mortality) throughout the period, suggesting that whatever process is driving these changes was already acting before the plot network was established. Large long–term increases in stand–level BA growth and simultaneous increases in stand BA and stem density imply a continent–wide increase in resource availability which is increasing net primary productivity and altering forest dynamics. Continent–wide changes in incoming solar radiation, and increases in atmospheric concentrations of CO2 and air temperatures may have increased resource supply over recent decades, thus causing accelerated growth and increased dynamism across the world's largest tract of tropical forest.