| Institution: | 1. Environmental Change Institute, School of Geography and the Environment, University of Oxford, , Oxford, OX1 3QY UK;2. Universidad Nacional de San Antonio Abad del Cusco, , Apartado Postal, N° 921 Cusco, Perú;3. College of Life and Environmental Sciences, University of Exeter, , Exeter, EX4 4RJ UK;4. Sveriges Lantbruksuniversitet, Skogsmarksgr?nd, , Ume?, 901‐83 Sweden;5. Biology Department, Wake Forest University, , Winston‐Salem, NC 27109 USA;6. Centre for Ecology and Hydrology, Wallingford, , Oxfordshire, OX10 8BB UK;7. Earth and Environmental Sciences Division, Los Alamos National Laboratory, , Los Alamos, NM 87545 USA;8. Jet Propulsion Laboratory, California Institute of Technology, , Pasadena, CA 91109 USA;9. Department of Geography, University of Cambridge, , Cambridge, CB2 3EN UK;10. University of Technology Sydney, , Broadway, NSW 2007, Australia;11. Computational Ecology and Environmental Science Group, Microsoft Research, , Cambridge, CB3 0FB UK |
| 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. |
