Effect of Canopy Structure and Open-Top Chamber Techniques on MicrometeorologicalParameters and the Gradients and Transport of Water Vapor, Carbon Dioxide and Ozone in the Canopies of Plum Trees ('Prunus salicina') in the San Joaquin Valley

摘要

Plum trees (Prunus salicina cv. Casselman) were exposed to ozone in open-topchambers (OTC) or chamberless plots, and trace gas concentrations and microenvironmental conditions were monitored within tree canopies inside the outside the OTC. Concentrations of ozone, carbon dioxide and water vapor, leaf and air temperature, light intensity, and wind speed were measured at nine positions in the tree canopies. The objectives were to: (1) map the distribution of microenvironmental parameters within the canopies inside and outside the OTC; (2) determine transport parameters for gas exchange, and (3) calculate ozone flux. Significant vertical and horizontal gradients were observed; gradients were diminished and often inverted inside relative to outside the OTC due to air distribution at the bottom of the OCT. Ozone flux was readily modeled from measures of stomatal conductance, nonstomatal conductance and ozone concentration at the leaf surface.