Micrometeorological Methods for Predicting Environmental Effects on Photosynthesis
This chapter discusses several micrometeorological methods for measuring the photosynthetic uptake of CO2 by plant canopies. It provides a brief development of some background theory in surface layer turbulence and discusses both direct and indirect micrometeorological methods for determining CO2 uptake and then consider results from several field studies. The most direct method for measuring fluxes in the atmospheric surface layer is probably "eddy correlation." The name refers to the direct measurement and subsequent correlation of the turbulent fluctuations of the appropriate quantities. Several instruments are available for measuring vertical velocities — sonic anemometers, drag or thrust anemometers, pressure sphere anemometers, hot wire anemometers, and propeller anemometers. Each of these instruments has its peculiarities so that vertical velocity fluctuation measurements remain essentially a research level task, rather than a routine-level measurement. The chapter also discusses five methods: aerodynamic, energy balance component tracers, miscellaneous tracers, dry matter sampling, and field chamber.