Subcanopy modeling of CO2 and H2O fluxes in a Costa Rican tropical premontane canopy

Abstract:

Modeling and estimation of tropical canopy CO₂ uptake is complicated by the numerous subcanopy sources and sinks of CO₂, and the difficulty in modeling subcanopy wind and photosynthetically-active radiation. Given the hypothesized importance of tropical forests for CO₂ uptake, a better understanding of how to model this process would prove useful for a wide range of modeling efforts. As part of a project to improve the subcanopy model for the Community Land Model (CLM) for the tropical rainforest land type, measurements of canopy CO₂ and H₂O fluxes from a Costa Rican rainforest were used to test a subcanopy flux model developed from a gradient-flux approach which had been validated for a US pine forest (Katul, et al, 2009; Lauiainen et al, 2011). Using uncalibrated ecosystem parameters from the literature, it was found that the model yielded reasonably good agreement with measurements for relatively dry days. Extension of the model to capture the additional evaporative flux sources during wet days is also presented, with indications of potential means of incorporating this effect into CLM explored.