Diurnal Patterns of Water Potential in Abiesconcolor and Pinusponderosa

Abstract

Diurnal patterns of water potential for Abiesconcolor and Pinusponderosa were studied in relation to concurrent environmental conditions. Up to 86% of variation in water potential was accounted for using irradiance, square root of vapor pressure deficit, height, and stomatal aperture as independent variables in A. concolor while up to 76% was accounted for in P. ponderosa using the same variables. Under comparable environmental conditions, A. concolor experienced lower water potentials than P. ponderosa due to its relative lack of stomatal control and its greater sensitivity to changes in vapor pressure deficit. Height effects were very nearly identical to those predicted by the cohesion theory. A procedure for estimating available soil moisture is suggested.