Satellite-based modeling of gross primary production of sugarcane plantations at two eddy flux tower sites

Abstract:

Sugarcane stalks are used for sugar and biofuel (ethanol) production. Sugarcane is the largest crop produced in the world in terms of plant biomass. According to the agricultural statistics data from the Food and Agriculture Organization (FAO) of the United Nations, in 2017, 25.98 million ha of sugarcane fields produced 1.84 billion tons of cane stalk. It is important to estimate and model gross and net primary production (GPP, NPP) and aboveground biomass of sugarcane fields. In this presentation, we report the carbon fluxes data from two sugarcane eddy flux tower sites in Brazil and USA and simulation results of the satellite-based Vegetation Photosynthesis Model (VPM) that uses time series vegetation indices from the MODIS sensors and climate data to estimate daily GPP. The seasonal dynamics of GPP from the eddy flux tower sites (GPP_EC) and the VPM model (GPP_VPM) agreed reasonably well with each other, and the linear regression model with GPP_VPM and GPP_EC data at 8-day interval show strong linear relationships (ranging from R² = 0.93 to R² = 0.96, p < 0.01). The differences of the total GPP (g C/m²/year) over the sugarcane growing season (four site-years) from the eddy flux data and the VPM model are within 10%. Although additional work is still needed to further evaluate VPM at other sugarcane eddy flux tower sites in the world, the results from this study clearly highlight the potential of the VPM model as a tool for estimating daily GPP of sugarcane fields.