Feedbacks Between Tropical
Forests, Climate, and Earth’s Carbon
Budget
Jacob Eisenberg
Advised by David Medvigy,
Geosciences
Background Information
• Tropical Forests are essential to Earth’s climate, and
specifically the carbon cycle
• Very substantial carbon sink (40% of Carbon in terrestrial
biosphere)
• Important to maintain this to mitigate Carbon Dioxide in
atmosphere
• Unique relationship with climate change, as they both exert
influence on each other.
• Coupling Effect
• Need to better understand this relationship to predict what will
happen
How can we do this?
•
•
•
•
One popular approach is computer models.
Ecosystem Demography Model (ED2).
Can work on a smaller scale
Uses data about the ecosystem on the plot of land (weather,
tree size, tree species, soil, etc.) to model growth and carbon
sequestration of the forest.
• Difficult to know all parameters, relationships between
variables.
• To obtain a more accurate method of looking forward, we have
to look backwards.
Checking the Model
• One way to check the accuracy of the model is to compare the
model results with known data.
• If the results are similar, it suggests the model is on the right
track.
• If not, it suggests that some parameters or relationships present
in the model are not representative of the real world dynamics
• This process is what I spent the majority of my internship
doing
• Initialization, how to run it, how to interpret results
Running the Model
Step 1: Initialization
Figure of Trees
in a plot in
Brazil, grouping
trees by
diameter, and
computing the
total basal area
of all trees in a
given diameter
class. Colors
represent
different wood
densities. This
is necessary to
initialize model.
Continued
Step 2: Running/Processing Results
• Pss/css files
• Remote access to computer
• Results Files
• Data Analysis in MATLAB
Results
• At first, results were very different than observed data.
• Mistakes, changing some parameters, results improved
• Main results of interest were Above Ground Biomass, Leaf
Are Index, and Basal Area.
• Three decade-long runs, isolating meteorological data
• Supposed discrete jump in AGB in late 80s
• Also did runs from scratch (just seedlings)
Figures
Shows the LAI in a run started from scratch in Shows the AGB in a run started from scratch.
three different decades. Results were similar, AGB was noticeably higher in the 90s than
and also reasonable.
the 80s, supporting the discrete jump
Figures
Basal Area in a run started
from scratch. Clearly
increase until it reaches an
equilibrium. (Ignore late
drop) This plot of forest
had a recorded basal area
of 26 m^2, which is nearly
identical to the results of
the model.
Conclusions
• When run from scratch, the model is accurate.
• The results suggest that AGB did increase from the 80s to 90s
• However, when the model was run with the current ecosystem
in a given plot as the starting point, the results were not as
promising.
• Could be a problem with data (first person to use this database
with this model)
• Still many interactions/relationships in tropical forests
scientists do not understand
Reflection
•
•
•
•
Importance of Computer models
Original Research
Lab Group Environment
Future Plans
Thank you to PEI, Professor Medvigy, and his research group!