Vegetation Primary Productivity

Vegetation primary productivity is represented by the amount of carbon dioxide (CO2) fixed by photosynthesis, the process by which plants use sunlight energy to produce organic compounds from CO2 and water. Vegetation primary productivity is commonly split into gross primary productivity (GPP) and net primary productivity (NPP). GPP is the overall rate of carbon (C) fixed in the process of photosynthesis minus the C lost by photorespiration in ecosystem per unit area and time, whereas NPP is the remaining fraction of the net production of organic matter by plants after accounting for C lost due to respiration of the plant tissues. The amount of GPP or NPP defines the carrying capacity of the Earth for her habitants and also participates in the regulation of the global climate through the C and water cycles thus Earth's ability to support most life forms on a long-term basis. Remote sensing data provides global coverage of spatially and temporally continuous information about the land surface that can be used for the accurate retrieval and simulation of the vegetation productivity of terrestrial ecosystems. From remote sensing observations, GPP and NPP are estimated based on empirical, light use efficiency, or enzyme kinetic models. This chapter summarizes the conceptual background and progress of remote sensing measures of vegetation primary productivity.