ABSTRACT The Amazonian rainforests play a vital role in global water, energy and carbon cycling. ... more ABSTRACT The Amazonian rainforests play a vital role in global water, energy and carbon cycling. The sensitivity of this system to natural and anthropogenic disturbances therefore has important implications for the global climate. Some global models have predicted large-scale forest dieback and the savannization of Amazonia over the next century [Meehl et al., 2007]. While several studies have demonstrated the sensitivity of dynamic global vegetation models to changes in temperature, precipitation, and dry season length [e.g. Galbraith et al., 2010; Good et al., 2011], the ability of these models to accurately reproduce ecosystem dynamics of present-day transitional or low biomass tropical forests has not been demonstrated. A model-data intercomparison was conducted with four state-of-the-art terrestrial ecosystem models to evaluate the ability of these models to accurately represent structure, function, and long-term biomass dynamics over a range of Amazonian ecosystems. Each modeling group conducted a series of simulations for 14 sites including mature forest, transitional forest, savannah, and agricultural/pasture sites. All models were run using standard physical parameters and the same initialization procedure. Model results were compared against forest inventory and dendrometer data in addition to flux tower measurements. While the models compared well against field observations for the mature forest sites, significant differences were observed between predicted and measured ecosystem structure and dynamics for the transitional forest and savannah sites. The length of the dry season and soil sand content were good predictors of model performance. In addition, for the big leaf models, model performance was highest for sites dominated by late successional trees and lowest for sites with predominantly early and mid-successional trees. This study provides insight into tropical forest function and sensitivity to environmental conditions that will aid in predictions of the response of the Amazonian rainforest to future anthropogenically induced changes.
As the largest tropical forest in the world, Amazonia accounts for 15% of terrestrial productivit... more As the largest tropical forest in the world, Amazonia accounts for 15% of terrestrial productivity. Precipitation across the basin is predicted to decline as global climate change and regional land transformation continue through this century. This study evaluated predictions of site-level gross, net and component ecosystem C-fluxes by five land-surface models (ED2, IBIS, JULES, CLM3. 5, SiB3) and one site-specific carbon and hydrodynamic model (SPA) for two Brazilian Amazon rainforests (Tapajos and Caxiuana National ...
Amazon forests play an important and complex role in the global cycles of water and carbon, and i... more Amazon forests play an important and complex role in the global cycles of water and carbon, and important advances have been made in understanding Amazon processes in recent years. However, reconciling modeled mechanisms with observations across scales remains a challenge. To better address this challenge, we initiated a Model Intercomparison Project for the `Large-Scale Biosphere Atmosphere Experiment in Amazonia' (LBA-MIP)
ABSTRACT The Amazonian rainforests play a vital role in global water, energy and carbon cycling. ... more ABSTRACT The Amazonian rainforests play a vital role in global water, energy and carbon cycling. The sensitivity of this system to natural and anthropogenic disturbances therefore has important implications for the global climate. Some global models have predicted large-scale forest dieback and the savannization of Amazonia over the next century [Meehl et al., 2007]. While several studies have demonstrated the sensitivity of dynamic global vegetation models to changes in temperature, precipitation, and dry season length [e.g. Galbraith et al., 2010; Good et al., 2011], the ability of these models to accurately reproduce ecosystem dynamics of present-day transitional or low biomass tropical forests has not been demonstrated. A model-data intercomparison was conducted with four state-of-the-art terrestrial ecosystem models to evaluate the ability of these models to accurately represent structure, function, and long-term biomass dynamics over a range of Amazonian ecosystems. Each modeling group conducted a series of simulations for 14 sites including mature forest, transitional forest, savannah, and agricultural/pasture sites. All models were run using standard physical parameters and the same initialization procedure. Model results were compared against forest inventory and dendrometer data in addition to flux tower measurements. While the models compared well against field observations for the mature forest sites, significant differences were observed between predicted and measured ecosystem structure and dynamics for the transitional forest and savannah sites. The length of the dry season and soil sand content were good predictors of model performance. In addition, for the big leaf models, model performance was highest for sites dominated by late successional trees and lowest for sites with predominantly early and mid-successional trees. This study provides insight into tropical forest function and sensitivity to environmental conditions that will aid in predictions of the response of the Amazonian rainforest to future anthropogenically induced changes.
As the largest tropical forest in the world, Amazonia accounts for 15% of terrestrial productivit... more As the largest tropical forest in the world, Amazonia accounts for 15% of terrestrial productivity. Precipitation across the basin is predicted to decline as global climate change and regional land transformation continue through this century. This study evaluated predictions of site-level gross, net and component ecosystem C-fluxes by five land-surface models (ED2, IBIS, JULES, CLM3. 5, SiB3) and one site-specific carbon and hydrodynamic model (SPA) for two Brazilian Amazon rainforests (Tapajos and Caxiuana National ...
Amazon forests play an important and complex role in the global cycles of water and carbon, and i... more Amazon forests play an important and complex role in the global cycles of water and carbon, and important advances have been made in understanding Amazon processes in recent years. However, reconciling modeled mechanisms with observations across scales remains a challenge. To better address this challenge, we initiated a Model Intercomparison Project for the `Large-Scale Biosphere Atmosphere Experiment in Amazonia' (LBA-MIP)
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