1. Mechanistic model for light-controlled phenology - its implication on the seasonality of water and carbon fluxes in the Amazon rainforests
Yeonjoo Kim
Lucy Hutyra, Marcos Longo, Ryan Knox, David Medvigy,
Steven Wofsy, Rafael Bras and Paul Moorcroft
Harvard University

2. Outline
Backgrounds
Models
Seasonality
Summary

3. Motivation Betts et al. (2004) Saleska et al. (2007)
Amazon rainforests dieback
Betts et al.
(2004)
Saleska et al.
(2007)

4. Net Carbon Fluxes to the atmosphere
Modeling
Net Carbon Fluxes to the atmosphere
(KM67)
Photosynthesis > Respiration
Latent Heat Flux
(Reserva Jaru)
Saleska et al. (2003)
Wang and Zhe (2007)

5. Observation Myneni et al. (2007) Regional average in the forests
Monthly
maximum of hourly
Shortwave
Radiation (W/m2)
Leaf
Area
Index
(m2/m2)
Myneni et al. (2007)
Observation in the forest at Santarem (KM67)

6. Ecosystem Demography Model (ED2)
Moorcroft et al. (2001) & Medvigy et al. (2008)
Traditional ‘big leaf’ model
v.s.
Age and Size structured model

7. Mechanistic Light-controlled Phenology model
Photosynthetic Capacity

8. Model fitting with Observations
Ecosystem measurements at KM67 site
(3 deg W and 55 deg S)
Ecosystem structure & composition
NEE - diurnal & nocturnal
Litter
Growth & Mortality
→ ED model parameters to be constrained with
measurements!
- phenology, respiration, and growth/mortality
Flux tower
Forest Inventory

9. Seasonal Dynamics Soil depth - shallow (1m) v.s. deep (6m)
 Observation
--- Initial model - shallow
— Initial model - deep
— Fitted model - deep
Soil depth
- shallow (1m) v.s. deep (6m)
Model fitting

10. Seasonal Carbon Dynamics
- NEE=R-GPP
Not directly fitted to GPP and R
Light-controlled phenology
Moisture dependency in soil respiration
 Observation
— Initial model
— Fitted model
 Observation
— Initial model
— Fitted model

11. Seasonal Carbon Dynamics
It is necessary to have a light-controlled phenology to have a right seasonality of GPP.
 Observation
— Initial model
--- Initial model with
an adjusted optimal soil moisture
— Fitted model

12. Seasonal Leaf Dynamics
 Observation
— Initial model
— Fitted model
Model fitting
LAI
not used for fitting
observation:
1km MODIS LAI
 Observation
— Initial model
— Fitted model

13. Annaul Ecosystem Dynamics
 Observation
— Initial model
— Fitted model
 Observation
— Initial model
— Fitted model
Growth and Mortality
- DBH measurements in 2001 and 2005

14. Concluding Remarks
The seasonality of ET can be captured with preventing the water stress during the dry season (e.g., deep soil).
Observations suggests that the decrease in NEE during the dry season reflects the increase in GPP and the decrease in Respiration (NEE=R-GPP).
The mechanistic light-controlled phenology model successfully captures the observed increase in productivity during the dry season.
The seasonality of respiration can be captured with adjusting the optimal soil moisture for the soil respiration.
The constrained model is capable of predicting both the fast-time scale fluxes and the slow-time scale ecosystem dynamics reasonably.
Our studies on the impact of deforestation in the regional climate using ED2-BRAMS by Longo et al. will be presented at 11:25am in the parallel session in Smauma room.