Photosynthesis (NPP, NEP, Respiration)

Abstract

Photosynthesis is the key process in the carbon cycle. GPP, NPP, and NEP are key variables in carbon cycle study. Accurate estimation of these variables at regional and global scale will improve our understanding mechanism of the carbon cycle in terrestrial ecosystem and interaction between terrestrial ecosystem and atmosphere in the background of climate change. That can help human make right strategy to face the climate change. In this chapter, we systematically reviewed GPP, NPP, and NEP measuring methods in the field and retrieving models based on remote sensing. Field measurements can capture the season dynamic of carbon fluxes very well and get accurate carbon flux quantity estimation, but it is difficult to upscale these carbon flux measurements to regional or global scale, and it is expensive to build and maintain flux net. Remote sensing based carbon flux estimation models is effective way to get the carbon fluxes at a regional or global scale, but parameters and forcing data of these models could result in great uncertainties in carbon flux estimation. Therefore, integrating the carbon fluxes of the two methods by data assimilation methods can get most accurate carbon fluxes at the regional or global scale. Mean- while, some new technology will contribute to the estimation of carbon fluxes, such as SIF sensor boarded on satellite.