HR: 12:05h
AN: B22B-08    [Abstracts]
TI:
AU: * Galbraith, D
EM: darga@ceh.ac.uk
AF: School of Geosciences, University of Edinburgh, Drummond Street, EDINBURGH, EH8 9XP, United Kingdom
AU: * Galbraith, D
EM: darga@ceh.ac.uk
AF: CEH Edinburgh, Bush Estate, Penicuik, Midlothian, Edinburgh, EH26 0QB, United Kingdom
AU: Levy, P
EM: plevy@ceh.ac.uk
AF: CEH Edinburgh, Bush Estate, Penicuik, Midlothian, Edinburgh, EH26 0QB, United Kingdom
AU: Meir, P
EM: P.Meir@staffmail.ed.ac.uk
AF: School of Geosciences, University of Edinburgh, Drummond Street, EDINBURGH, EH8 9XP, United Kingdom
AU: Sitch, S
EM: Stephen.Sitch@metoffice.gov.uk
AF: Met Office (JCHMR), Maclean Building, Crowmarsh Gifford, Wallingford, OX10 8BB, United Kingdom
AU: Fisher, R
EM: rosie.fisher@shef.ac.uk
AF: University of Sheffield, Dept. of Animal & Plant Sciences Alfred Denny Building Western Bank, Sheffield, S10 2TN, United Kingdom
AB: Some climate models predict that there may be a decrease in rainfall over the Amazon Basin by up to 50% over the next century. The uncertainties associated with this change in precipitation have been the focus of several recent studies, but less attention has been paid to the uncertainty in modelling the response of vegetation to drought stress. This study aims to compare the effect of drought in four dynamic global vegetation models (DGVMs), with regards to ecosystem carbon balance and shifts in plant functional type composition. Key objectives were to quantify the uncertainty due to model structures and parameters, and to highlight particular areas for model improvement. The study was carried out in three parts: 1) assessment of DGVMs in simulating changes in ecosystem processes along a rainfall gradient, 2) long-term future runs under a range of drought scenarios, including a factorial analysis of the effects of drought, other climate change and CO2 fertilisation and 3) a Monte Carlo based sensitivity analysis to identify key parameters influencing the uncertainty of the response to drought. Considerable differences were found in the responses of the models to drought stress, with some models, such as MOSES-TRIFFID and HYLAND predicting very little loss of carbon, even at rainfall reductions of up to 60%. This resilience was much lower, however, when climatic changes other than rainfall were included in the simulations. The reduction in rainfall needed to induce a transition in vegetation type was also considered, but this was made difficult by the inability of some models to simulate changes in plant functional type competition dynamics under drought. Other areas highlighted for future improvement include the ability of trees to access water stored in deeper soil layers and the effect of reduced soil moisture on nutrient uptake.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting