Simulating terrestrial carbon fluxes using the new biosphere model “biosphere model integrating eco‐physiological and mechanistic approaches using satellite data” (BEAMS)

Abstract

In this study we present a new biosphere model called the Biosphere model integrating Eco‐physiological And Mechanistic approaches using Satellite data (BEAMS). BEAMS provides a new method of calculating the environmental stress affecting plant growth (Stress). Stress is calculated eco‐physiologically using a photosynthesis model and stomatal conductance formulation, providing a more realistic result than previous models. Stress values are used to estimate Gross Primary Production (GPP) estimates via the light use efficiency concept. We used BEAMS, including our new Stress approach, to investigate global spatial and temporal patterns of net primary production (NPP) and net ecosystem production (NEP). BEAMS was run for the years 1982–2000 using global scale satellite and climate data. Comparison of model results with observational measurements at flux sites reveals that GPP values predicted by BEAMS agree with measured GPP. Obtained Stress values were compared with those of MOD17 and CASA; the three methods produce contrasting spatial patterns. Upon comparing predicted and observed NPP, the pattern of NPP for each plant functional type can be adequately estimated. In terms of trend analysis, NPP increased for the years 1982–2000 in most regions. Different NPP trends were observed in Europe, Russia, and northeast Canada than those proposed by Nemani et al. (2003); we attribute these differences to climate‐related processes. Simulated interannual variations in global NEP are similar to results from inverse modeling. A sensitivity study of obtained NEP shows that the interannual variability in NEP is strongly controlled by air temperature, precipitation, CO2, and the fraction of absorbed photosynthetically active radiation.