Confronting model predictions of carbon fluxes with measurements of Amazon forests subjected to experimental drought
Article first published online: 12 JUL 2013
© 2013 The Authors. New Phytologist © 2013 New Phytologist Trust
Special Issue: Featured papers on ‘Drought-induced forest mortality’
Volume 200, Issue 2, pages 350–365, October 2013
How to Cite
Powell, T. L., Galbraith, D. R., Christoffersen, B. O., Harper, A., Imbuzeiro, H. M. A., Rowland, L., Almeida, S., Brando, P. M., da Costa, A. C. L., Costa, M. H., Levine, N. M., Malhi, Y., Saleska, S. R., Sotta, E., Williams, M., Meir, P. and Moorcroft, P. R. (2013), Confronting model predictions of carbon fluxes with measurements of Amazon forests subjected to experimental drought. New Phytologist, 200: 350–365. doi: 10.1111/nph.12390
- Issue published online: 18 SEP 2013
- Article first published online: 12 JUL 2013
- Manuscript Accepted: 20 MAY 2013
- Manuscript Received: 12 FEB 2013
- International Research and Education in Amazon Climate Interactions. Grant Number: #OISE-0730305
- carbon cycle;
- terrestrial biosphere model;
- throughfall exclusion;
- tropical rainforest
- Considerable uncertainty surrounds the fate of Amazon rainforests in response to climate change.
- Here, carbon (C) flux predictions of five terrestrial biosphere models (Community Land Model version 3.5 (CLM3.5), Ecosystem Demography model version 2.1 (ED2), Integrated BIosphere Simulator version 2.6.4 (IBIS), Joint UK Land Environment Simulator version 2.1 (JULES) and Simple Biosphere model version 3 (SiB3)) and a hydrodynamic terrestrial ecosystem model (the Soil–Plant–Atmosphere (SPA) model) were evaluated against measurements from two large-scale Amazon drought experiments.
- Model predictions agreed with the observed C fluxes in the control plots of both experiments, but poorly replicated the responses to the drought treatments. Most notably, with the exception of ED2, the models predicted negligible reductions in aboveground biomass in response to the drought treatments, which was in contrast to an observed c. 20% reduction at both sites. For ED2, the timing of the decline in aboveground biomass was accurate, but the magnitude was too high for one site and too low for the other.
- Three key findings indicate critical areas for future research and model development. First, the models predicted declines in autotrophic respiration under prolonged drought in contrast to measured increases at one of the sites. Secondly, models lacking a phenological response to drought introduced bias in the sensitivity of canopy productivity and respiration to drought. Thirdly, the phenomenological water-stress functions used by the terrestrial biosphere models to represent the effects of soil moisture on stomatal conductance yielded unrealistic diurnal and seasonal responses to drought.