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!