title: After more than a decade of soil moisture deficit, tropical rainforest trees maintain photosynthetic capacity, despite increased leaf respiration.
abstract: Determining climate change feedbacks from tropical rainforests requires an understanding of how carbon gain through photosynthesis and loss through respiration will be altered. One of the key changes that tropical rainforests may experience under future climate change scenarios is reduced soil moisture availability. In this study we examine if and how both leaf photosynthesis and leaf dark respiration acclimate following more than 12 years of experimental soil moisture deficit, via a through-fall exclusion experiment (TFE) in an eastern Amazonian rainforest. We find that experimentally drought-stressed trees and taxa maintain the same maximum leaf photosynthetic capacity as trees in corresponding control forest, independent of their susceptibility to drought-induced mortality. We hypothesize that photosynthetic capacity is maintained across all treatments and taxa to take advantage of short-lived periods of high moisture availability, when stomatal conductance (gs ) and photosynthesis can increase rapidly, potentially compensating for reduced assimilate supply at other times. Average leaf dark respiration (Rd ) was elevated in the TFE-treated forest trees relative to the control by 28.2 ± 2.8% (mean ± one standard error). This mean Rd value was dominated by a 48.5 ± 3.6% increase in the Rd of drought-sensitive taxa, and likely reflects the need for additional metabolic support required for stress-related repair, and hydraulic or osmotic maintenance processes. Following soil moisture deficit that is maintained for several years, our data suggest that changes in respiration drive greater shifts in the canopy carbon balance, than changes in photosynthetic capacity.
authors.affiliation: School of GeoSciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Lucy
authors.initials: L
authors.lastname: Rowland
authors.affiliation: Forest Research Centre, School of Agriculture, University of Lisbon, Lisbon, Portugal.
authors.forename: Raquel L
authors.initials: RL
authors.lastname: Lobo-do-Vale
authors.affiliation: School of GeoSciences, University of Edinburgh, Edinburgh, UK.|Earth and Environmental Sciences, Los Alamos National Laboratory, Los Alamos, CA, USA.
authors.forename: Bradley O
authors.initials: BO
authors.lastname: Christoffersen
authors.affiliation: EMBRAPA Amazônia Oriental, Belém, Brasil.
authors.forename: Eliane A
authors.initials: EA
authors.lastname: Melém
authors.affiliation: Alterra, Wageningen UR, Wageningen, the Netherlands.
authors.forename: Bart
authors.initials: B
authors.lastname: Kruijt
authors.affiliation: EMBRAPA Amazônia Oriental, Belém, Brasil.
authors.forename: Steel S
authors.initials: SS
authors.lastname: Vasconcelos
authors.affiliation: Departamento de Biologia, FFCLRP - Universidade de São Paulo, Ribeirão Preto, Brasil.
authors.forename: Tomas
authors.initials: T
authors.lastname: Domingues
authors.affiliation: School of GeoSciences, University of Edinburgh, Edinburgh, UK.
authors.forename: Oliver J
authors.initials: OJ
authors.lastname: Binks
authors.affiliation: Centro de Geosciências, Universidade Federal do Pará, Belém, Brasil.
authors.forename: Alex A R
authors.initials: AA
authors.lastname: Oliveira
authors.affiliation: Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
authors.forename: Daniel
authors.initials: D
authors.lastname: Metcalfe
authors.affiliation: Centro de Geosciências, Universidade Federal do Pará, Belém, Brasil.
authors.forename: Antonio C L
authors.initials: AC
authors.lastname: da Costa
authors.affiliation: School of GeoSciences, University of Edinburgh, Edinburgh, UK.|ICREA at CREAF, 08193 Cerdanyola del Vallés, Barcelona, Spain.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Mencuccini
authors.affiliation: School of GeoSciences, University of Edinburgh, Edinburgh, UK.|Research School of Biology, Australian National University, Canberra, Australia.
authors.forename: Patrick
authors.initials: P
authors.lastname: Meir
mesh_terms: D001938:Brazil; D057486:Carbon Cycle; D057231:Climate Change; D055864:Droughts; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D018526:Plant Transpiration; D065947:Rainforest; D012621:Seasons; D012987:Soil / Q000737:chemistry; D014197:Trees / Q000502:physiology*; D014329:Tropical Climate
chemical_list: D012987:Soil
keywords: drought; leaf dark respiration; photosynthetic capacity; through-fall exclusion; tropical rainforest