Assessing Evidence for a Pervasive Alteration in Tropical Tree Communities

Chave, Jerome and Condit, Richard and Muller-Landau, Helene C and Thomas, Sean C and Ashton, Peter S and Bunyavejchewin, Sarayudh and Co, Leonardo L and Dattaraja, Handanakere S and Davies, Stuart J and Esufali, Shameema and Ewango, Corneille EN and Feeley, Kenneth J and Foster, Robin B and Gunatilleke, Nimal and Gunatilleke, Savitri and Hall, Pamela and Hart, Terese B and Hernandez, Consuelo and Hubbell, Stephen P and Itoh, Akira and Kiratiprayoon, Somboon and LaFrankie, James V and Lao, Suzanne Loo de and Makana, Jean-Remy and Noor, Md. Nur Supardi and Kassim, Abdul Rahman and Samper, Cristian and Sukumar, Raman and Suresh, Hebbalalu S and Tan, Sylvester and Thompson, Jill and Tongco, Ma. Dolores C and Valencia, Renato and Vallejo, Martha and Villa, Gorky and Yamakura, Takuo and Zimmerman, Jess K and Losos, Elizabeth C (2008) Assessing Evidence for a Pervasive Alteration in Tropical Tree Communities. In: PLoS BIOLOGY, 6 (3). 0455-0462.

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Abstract

In Amazonian tropical forests, recent studies have reported increases in aboveground biomass and in primary productivity, as well as shifts in plant species composition favouring fast-growing species over slow-growing ones. This pervasive alteration of mature tropical forestswas attributed to global environmental change, such as an increase in atmospheric $CO_2$ concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of over 2 million trees in ten large (16–52 ha each) forest plots on three continents to evaluate the generality of these findings across tropical forests. Above ground biomass increased at seven of our ten plots, significantly so at four plots, and showed a large decrease at a single plot. Carbon accumulation pooled across sites was significant (+0.24 MgC $ha^{-1} y^{-1}$, 95% confidence intervals [0.07, 0.39] MgC $ha^{-1} y^{-1}$, but lower than reported previously for Amazonia. At three sites for which we had data for multiple census intervals, we found no concerted increase in biomass gain, in conflict with the increased productivity hypothesis. Over all ten plots, the fastest-growing quartile of species gained biomass (+0.33 [0.09, 0.55]%$y^{-1}$) compared with the tree community as a whole (+0.15%$y^{-1}$) however, this significant trend was due to single plot. Biomass of slow-growing species increased ignificantly when calculated over all plots (+0.21 [0.02, 0.37]%$y^{-1}$) and in half of our plots when calculated individually. Our results do not support the hypothesis that fast-growing species are consistently increasing in dominance in tropical tree communities. Instead, they suggest that our plots may be simultaneously recovering from past disturbances and affected by changes in resource availability. More long-termstudies are necessary to clarify the contribution of global change to the functioning of tropical forests.

Item Type:	Journal Article
Publication:	PLoS BIOLOGY
Publisher:	Public Library of Science (PLoS)
Additional Information:	Copyright of this article belongs to Public Library of Science (PLoS).
Department/Centre:	Division of Biological Sciences > Centre for Ecological Sciences
Date Deposited:	07 Jul 2008
Last Modified:	09 Jan 2013 05:27
URI:	http://eprints.iisc.ac.in/id/eprint/14780

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