Radiation Fluxes in Natural Environments

Abstract

Before beginning a detailed discussion of radiant energy budgets of plants, animals, canopies, and soils, we need to determine what information will be required and how to obtain that information. An environmental biophysicist may approach the study of radiant energy exchange in two different ways. For the first, detailed observations of radiant flux densities to and from an organism are needed to compute a detailed energy budget. These detailed observations must be obtained by direct measurement at the time the energy budget is being determined. The second type of study simulates the behavior of parts of an ecosystem. Knowing the exact value of a radiant flux density may not be as important as having the correct relationship among variables. Models of the fluxes, extended from the basics covered in Ch. 10, are used for studies of the second type. The models can be counted on to give reasonable estimates (± 10%) of average flux densities, but they are usually not adequate as substitutes for careful field measurements of radiant fluxes for detailed energy budget studies. This chapter presents models for estimating solar and thermal radiant fluxes in the natural environment.