title: Leaf functional response to increasing atmospheric CO(2) concentrations over the last century in two northern Amazonian tree species: a historical δ(13) C and δ(18) O approach using herbarium samples.
abstract: We assessed the extent of recent environmental changes on leaf morphological (stomatal density, stomatal surface, leaf mass per unit area) and physiological traits (carbon isotope composition, δ(13)C(leaf) , and discrimination, Δ(13)C(leaf) , oxygen isotope composition, δ(18)O(leaf) ) of two tropical rainforest species (Dicorynia guianensis; Humiria balsamifera) that are abundant in the Guiana shield (Northern Amazonia). Leaf samples were collected in different international herbariums to cover a 200 year time-period (1790-2004) and the whole Guiana shield. Using models describing carbon and oxygen isotope fractionations during photosynthesis, different scenarios of change in intercellular CO(2) concentrations inside the leaf (C(i)), stomatal conductance (g), and photosynthesis (A) were tested in order to understand leaf physiological response to increasing air CO(2) concentrations (C(a)). Our results confirmed that both species displayed physiological response to changing C(a) . For both species, we observed a decrease of about 1.7‰ in δ(13)C(leaf) since 1950, without significant change in Δ(13)C(leaf) and leaf morphological traits. Furthermore, there was no clear change in δ(18)O(leaf) for Humiria over this period. Our simulation approach revealed that an increase in A, rather than a decrease in g, explained the observed trends for these tropical rainforest species, allowing them to maintain a constant ratio of C(i)/C(a) .
authors.affiliation: INRA, UMR Ecofog, BP 709, 97387 Kourou cedex, French Guiana, France. bonal@nancy.inra.fr
authors.forename: Damien
authors.initials: D
authors.lastname: Bonal
authors.forename: Stéphane
authors.initials: S
authors.lastname: Ponton
authors.forename: Didier
authors.initials: D
authors.lastname: Le Thiec
authors.forename: Béatrice
authors.initials: B
authors.lastname: Richard
authors.forename: Nathalie
authors.initials: N
authors.lastname: Ningre
authors.forename: Bruno
authors.initials: B
authors.lastname: Hérault
authors.forename: Jérôme
authors.initials: J
authors.lastname: Ogée
authors.forename: Sophie
authors.initials: S
authors.lastname: Gonzalez
authors.forename: Marc
authors.initials: M
authors.lastname: Pignal
authors.forename: Daniel
authors.initials: D
authors.lastname: Sabatier
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Guehl
mesh_terms: D002245:Carbon Dioxide; D002247:Carbon Isotopes; D002482:Cellulose / Q000737:chemistry; D003198:Computer Simulation; D005616:French Guiana; D049671:History, 18th Century; D049672:History, 19th Century; D049673:History, 20th Century; D049674:History, 21st Century; D010103:Oxygen Isotopes; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology*; D054046:Plant Stomata / Q000502:physiology*; D018526:Plant Transpiration / Q000502:physiology; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate
chemical_list: D002247:Carbon Isotopes; D010103:Oxygen Isotopes; D002245:Carbon Dioxide; D002482:Cellulose