A Look at Amazon Basin Seasonal Dynamics with the Biophysical ...

Modeling Net Ecosystem Exchange from Multilevel Ecophysiologicaland Turbulent Transport Models: A Symbiotic ApproachMario Siqueira 1,2,* , Antonio C. Brasil Jr. 3,4 , Chun Ta Lai 5 , Gabriel Katul 1,21 Nicholas School of Environment and Earth Sciences, Duke University, Durham, NC, USA.2 Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA.3 Center for Sustainable Development (CDS), University of Brasilia, Brasilia, DF, Brazil.4 Department of Mechanical Engineering, University of Brasilia, Brasilia, DF, Brazil.5 Department of Biology, University of Utah, Salt Lake City, UT*Corresponding Author: Mario SiqueiraDuke University, 328 LSRC, Box 90328Durham, NC, 27708USAPhone: 01-919-613-8068Fax: 01-919-684-8741e-mail:mbs4@duke.eduAbstractIn forested ecosystems, the complex vertical structure of the canopy plays a criticalrole in CO2 net ecosystem exchange (NEE). To quantify the contribution of differentcanopy layers on NEE, multiple approaches are developed and compared. The firstapproach is based on a one-dimensional ecophysiological-radiative transfer andturbulent transport model (hereafter referred to as forward model) that solveconservation equations for mean scalar mass and heat. It explicitly incorporatesbiophysical and ecophysiological mechanisms responsible for stomatal opening andcarbon assimilation. The forward model is compared with three inverse methods,which rely on mean concentration profiles as input. To assess the performance of themodels individually, they were compared to above-canopy eddy-covariance CO2 fluxmeasurements conducted at the Duke Forest AmeriFlux site. This study is the first torigorously compare such a broad range of multi-level methods for the same stand andfor a wide range of environmental conditions. The results show that the forwardmethod outperformed the inverse methods for unstable and neutral conditions. Pooragreement was obtained under stable conditions for all models. However, in ensemblesense, all methods performed comparably. Since the forward method requires detailedknowledge of the canopy ecophysiological and radiative transfer properties, which aredifficult to obtain on routine basis, a symbiotic use of these approaches isadvantageous. An optimization procedure for the ecophysiological parameters of theforward method using results from inverse calculation to be used in second growthAmazon Forest is proposed.