title: Simulating forest productivity along a neotropical elevational transect: temperature variation and carbon use efficiency.
abstract: A better understanding of the mechanisms controlling the magnitude and sign of carbon components in tropical forest ecosystems is important for reliable estimation of this important regional component of the global carbon cycle. We used the JULES vegetation model to simulate all components of the carbon balance at six sites along an Andes-Amazon transect across Peru and Brazil and compared the results to published field measurements. In the upper montane zone the model predicted a lack of forest vegetation, indicating a need for better parameterization of the responses of cloud forest vegetation within the model. In the lower montane and lowland zones simulated ecosystem productivity and respiration were predicted with reasonable accuracy, although not always within the error bounds of the observations. Model-predicted carbon use efficiency in this transect surprisingly did not increase with elevation, but remained close to the 'temperate' value 0.5. Upper montane forests were predicted to allocate ~50% of carbon fixation to biomass maintenance and growth, despite available measurements showing that they only allocate ~33%. This may be explained by elevational changes in the balance between growth and maintenance respiration within the forest canopy, as controlled by both temperature- and pressure-mediated processes, which is not yet well represented in current vegetation models.
authors: Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford, OX1 3QY, UK.
authors: Toby R
authors: TR
authors: Marthews
authors: Yadvinder
authors: Y
authors: Malhi
authors: Cécile A J
authors: CA
authors: Girardin
authors: Javier E
authors: JE
authors: Silva Espejo
authors: Luiz E O C
authors: LE
authors: Aragão
authors: Daniel B
authors: DB
authors: Metcalfe
authors: Joshua M
authors: JM
authors: Rapp
authors: Lina M
authors: LM
authors: Mercado
authors: Rosie A
authors: RA
authors: Fisher
authors: David R
authors: DR
authors: Galbraith
authors: Joshua B
authors: JB
authors: Fisher
authors: Norma
authors: N
authors: Salinas-Revilla
authors: Andrew D
authors: AD
authors: Friend
authors: Natalia
authors: N
authors: Restrepo-Coupe
authors: Richard J
authors: RJ
authors: Williams
keywords: Brazil; JULES model; Peru; field measurements; maintenance respiration; tropical forest production