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Assessing evidence for a pervasive alteration in tropical tree communities.

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 forests was attributed to global environmental change, such as an increase in atmospheric CO2 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. Aboveground 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 a single plot. Biomass of slow-growing species increased significantly 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-term studies are necessary to clarify the contribution of global change to the functioning of tropical forests.

SUBMITTER: Chave J

PROVIDER: S-EPMC2270308 | biostudies-literature | 2008 Mar

REPOSITORIES: biostudies-literature

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Assessing evidence for a pervasive alteration in tropical tree communities.

Chave Jérôme J Condit Richard R Muller-Landau Helene C HC Thomas Sean C SC Ashton Peter S PS Bunyavejchewin Sarayudh S Co Leonardo L LL Dattaraja Handanakere S HS Davies Stuart J SJ Esufali Shameema S Ewango Corneille E N CE Feeley Kenneth J KJ Foster Robin B RB Gunatilleke Nimal N Gunatilleke Savitri S Hall Pamela P Hart Terese B TB Hernández Consuelo C Hubbell Stephen P SP Itoh Akira A Kiratiprayoon Somboon S Lafrankie James V JV Loo de Lao Suzanne S Makana Jean-Rémy JR Noor Md Nur Supardi MN Kassim Abdul Rahman AR Samper Cristián C Sukumar Raman R Suresh Hebbalalu S HS Tan Sylvester S Thompson Jill J Tongco Ma Dolores C MD Valencia Renato R Vallejo Martha M Villa Gorky G Yamakura Takuo T Zimmerman Jess K JK Losos Elizabeth C EC

PLoS biology 20080301 3

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 forests was attributed to global environmental change, such as an increase in atmospheric CO2 concentration, nutrient deposition, temperature, drought frequency, and/or irradiance. We used standardized, repeated measurements of ove ...[more]

PMID: 18318600

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Project description:Inoculation of endophyte-free (E-) Theobroma cacao leaves with Colletotrichum tropicale (E+), the dominant foliar fungal endophyte in healthy T. cacao, induced significant changes in the expression of hundreds of host genes. Further, E+ leaves exhibit enhanced pathogen resistance, increased lignin and cellulose content, reduced maximum rates of photosynthesis (Amax), and enrichment of nitrogen-15 and carbon-13 isotopes that all correspond to the changes in expression of specific functional genes in related pathways. Moreover, a cacao gene highly up-regulated in E+ leaves increases pathogen resistance apart from any direct endophyte effects. Thus, benefits of increased pathogen resistance in E+ plants are partially due to enhanced induction of intrinsic host defense pathways, and potential costs include reduced photosynthetic capacity and endophyte metabolism of host tissues. Similar effects are likely to be properties of most plant-endophyte interactions, suggesting general relevance to the design and interpretation of studies of genetic and phenotypic expression in plants. The objective of this experiment was to identify Theobroma cacao genes that are differentially expressed between leaves inoculated with fungal endophyte Colletotrichum tropicale (E+ leaves) and control un-inoculated leaves (E- leaves) 14 days post last endophyte inoculation. The experiment was conducted in a Percival growth chambers (model I35LL, 115 volts, 1/4 Hp, series: 8503122.16, Percival Scientific, Inc., Perry IA) with 12/12 h light/dark photoperiod and temperatures of 30M-BM-:C and 26M-BM-:C respectively. A total of four endophyte spore inoculations (1X10^6 spore/ml) were made by aspersion to a group of T. cacao seedlings and a second group of seedlings were maintained as un-inoculated. Then six biological replicates per treatment (E+ leaves and six E- leaves) each one belonging from a different seedling were collected and processed for a two color oligo microarray analysis. A total of six arrays were processed, each one hybridized to an inoculated and a control un-inoculated sample in a dye swap design.

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Assessing evidence for a pervasive alteration in tropical tree communities.

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Assessing evidence for a pervasive alteration in tropical tree communities.

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