Carbon fluxes and remote sensing in crop ecosystems

Monitoring carbon, water and energy fluxes exchanged between terrestrial ecosystems and the atmosphere is essential to better understand 1) the biological and ecological processes within an ecosystem, also in relation with climate variability and climate change; and 2) to assess the carbon balance of different ecosystems and their ability to sequester CO2 from the atmosphere. Repeatable and accurate monitoring of terrestrial gross primary productivity (GPP) is critical for quantifying the dynamics of regional-to-global carbon budgets. Remote sensing provides high frequency observations of terrestrial ecosystems and is widely used to monitor and model spatiotemporal variability of ecosystem properties and processes that affect terrestrial GPP. Biogeochemical models and empirical biophysical parameters based on remotely sensed vegetation indices have been widely used to monitor different ecosystem’s characteristics strictly related to GPP. Focusing on cropland and grassland ecosystems, this approach can help to improve global models for more accurate projections of agricultural productivity and climate impact on crop yields. But a limitation of this approach is the lack of a strong link between crop photosynthesis and traditional remotely sensed vegetation indices, nor with more complex carbon cycle models (Guanter et al., 2014). In order to improve the capacity of estimation and validation of aircraft and satellite-derived GPP products a better understanding of the relationship between ground-based vegetation spectral signal and eddy covariance-based estimates of GPP is needed