Ecological characterization of vegetation using multisensor remote sensing in the solar reflective spectrum

Vegetation is the primary producer in the terrestrial ecosystem. Vegetation absorbs the energy of electromagnetic radiation from the Sun and converts it to the energy that consumers in the ecosystem can use. As a result, vegetation is the foundation for nearly all the goods and services that terrestrial ecosystems provide to humanity. The advent of optical remote sensing revolutionized our ability to map the characteristics of vegetation wall-to-wall in space and to do so repeatedly, in a cost-efficient manner. Many of these vegetation parameters serve as key inputs to ecological models aiming to understand terrestrial ecosystem functions, at regional to global scales. This chapter summarizes the progress made in characterizing vegetation structure and its ecological functions with optical remote sensing. We first provide a brief review of the development of optical sensors designed primarily for vegetation monitoring. Second, we synthesize the progress made in mapping the physical structure of vegetation with optical sensors, including vegetation cover, vegetation successional stages, biomass, leaf area index (LAI), and its spatial organization, that is, leaf clumping. Third, we review the achievements made in understanding vegetation function with optical remote sensing, particularly vegetation primary productivity and related ecologically important functions. Primary production provides the energy that drives all subsequent ecosystem processes. Optical remote sensing has made it possible to estimate the primary productivity of vegetation over the entire Earth land surface (Running et al. 1994; Zhao et al. 2005).