Impact of Different Canopy Schemes in the E3SM Land Model on Energy and Carbon Flux Simulations in an Amazonian Swamp Peatland

Amazonian peatlands play a critical role in the global carbon cycle. Accurate simulations of energy and carbon fluxes in these tropical peatlands are crucial for understanding their response to changes in the environment, as well as for predicting their future behavior and assessing climate feedbacks. One of the key factors affecting the accuracy of these simulations is the choice of canopy scheme used in the land model, which governs the interaction between the atmosphere and vegetation. We used the US Department of Energy’s Energy Exascale Earth System (E3SM) Land Model to investigate the effects of two different canopy schemes (single-layer and multi-layer) on simulating net radiation (R_n), turbulent energy exchanges (i.e., fluxes of latent heat, LE, and sensible heat, H), and net ecosystem CO₂ exchange in an Amazonian palm swamp peatland in Peru. Model simulations were validated against ecosystem fluxes measured using the eddy covariance technique. Overall, the multi-layer model significantly improved diel and seasonal simulations of energy and carbon fluxes compared to the single-layer model. The largest improvement was found for LE, although simulation biases in R_n and H persisted in dry seasons, further influencing the simulation of CO₂ fluxes in different seasons. To identify sources of modeling biases for different canopy schemes, we also screened key parameters and analyze simulations for other important variables, such as leaf temperature, leaf area index, stomatal and boundary-layer resistances, and the different contributions of sunlit and shaded leaves. This study suggested that the multi-layer canopy scheme can improve the simulated energy and carbon fluxes, and also identified knowledge gaps that need to be addressed to better predict biogeochemical cycles in tropical peatlands.

Keywords: Ecosystem model; Canopy scheme; Radiation; Forest; Tropics.