title: 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.
authors.affiliation: Laboratoire Evolution et Diversité Biologique CNRS/Université Paul Sabatier, Toulouse, France. chave@cict.fr
authors.forename: Jérôme
authors.initials: J
authors.lastname: Chave
authors.forename: Richard
authors.initials: R
authors.lastname: Condit
authors.forename: Helene C
authors.initials: HC
authors.lastname: Muller-Landau
authors.forename: Sean C
authors.initials: SC
authors.lastname: Thomas
authors.forename: Peter S
authors.initials: PS
authors.lastname: Ashton
authors.forename: Sarayudh
authors.initials: S
authors.lastname: Bunyavejchewin
authors.forename: Leonardo L
authors.initials: LL
authors.lastname: Co
authors.forename: Handanakere S
authors.initials: HS
authors.lastname: Dattaraja
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Davies
authors.forename: Shameema
authors.initials: S
authors.lastname: Esufali
authors.forename: Corneille E N
authors.initials: CE
authors.lastname: Ewango
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Feeley
authors.forename: Robin B
authors.initials: RB
authors.lastname: Foster
authors.forename: Nimal
authors.initials: N
authors.lastname: Gunatilleke
authors.forename: Savitri
authors.initials: S
authors.lastname: Gunatilleke
authors.forename: Pamela
authors.initials: P
authors.lastname: Hall
authors.forename: Terese B
authors.initials: TB
authors.lastname: Hart
authors.forename: Consuelo
authors.initials: C
authors.lastname: Hernández
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Hubbell
authors.forename: Akira
authors.initials: A
authors.lastname: Itoh
authors.forename: Somboon
authors.initials: S
authors.lastname: Kiratiprayoon
authors.forename: James V
authors.initials: JV
authors.lastname: Lafrankie
authors.forename: Suzanne
authors.initials: S
authors.lastname: Loo de Lao
authors.forename: Jean-Rémy
authors.initials: JR
authors.lastname: Makana
authors.forename: Md Nur Supardi
authors.initials: MN
authors.lastname: Noor
authors.forename: Abdul Rahman
authors.initials: AR
authors.lastname: Kassim
authors.forename: Cristián
authors.initials: C
authors.lastname: Samper
authors.forename: Raman
authors.initials: R
authors.lastname: Sukumar
authors.forename: Hebbalalu S
authors.initials: HS
authors.lastname: Suresh
authors.forename: Sylvester
authors.initials: S
authors.lastname: Tan
authors.forename: Jill
authors.initials: J
authors.lastname: Thompson
authors.forename: Ma Dolores C
authors.initials: MD
authors.lastname: Tongco
authors.forename: Renato
authors.initials: R
authors.lastname: Valencia
authors.forename: Martha
authors.initials: M
authors.lastname: Vallejo
authors.forename: Gorky
authors.initials: G
authors.lastname: Villa
authors.forename: Takuo
authors.initials: T
authors.lastname: Yamakura
authors.forename: Jess K
authors.initials: JK
authors.lastname: Zimmerman
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Losos
mesh_terms: D044822:Biodiversity; D005075:Biological Evolution; D018533:Biomass; D017753:Ecosystem; D004777:Environment; D004784:Environmental Monitoring; D016468:Forestry; D008296:Malaysia; D010176:Panama; D011647:Puerto Rico; D013188:Sri Lanka; D013785:Thailand; D013997:Time Factors; D014197:Trees / Q000254:growth & development / Q000502:physiology*; D014329:Tropical Climate