Modeling studies of forest responses to elevated CO2

We have been conducting modeling studies for the Duke Forest Free-Air CO2 Enrichment (FACE) project since 1996. The overall objective of the FACE project is to quantify carbon sink in forest ecosystems and to examine ecosystem processes regulating forest responses to global change. Our modeling research component of the FACE project focuses on development of conceptual and quantitative frameworks that facilitate synthesis of experimental results and extrapolation of them over time and space to predict carbon sink in terrestrial ecosystems. The FACE experiments employ a "perturbation-response" approach in which ecosystems are perturbed with a step increase in CO2 and responses to the perturbation are measured. Our study indicates that observed responses in the step experiments are transient and may not adequately represent the responses of ecosystems to a gradually changing CO2 environment. However, by decomposing observed responses in the FACE experiments into their constituent processes and deriving parameter values from experimental results, we are able to predict ecosystem responses to a gradual increase in atmospheric CO2 that is occurring in the natural world. The major components of this project include (1) development of deconvolution and inverse analysis methods; (2) scaling up of leaf- and soil core-level measurements to estimate ecosystem fluxes and pools; (3) data assimilation to improve model predictions and assess data collection strategy; and (4) uncertainty analysis on extrapolation of short-term measurements to predict long-term responses of ecosystems to global change. Visit Duke FACE website.