Stomatal conductance of Populus trichocarpa in southern Iceland in relation to environmental variables

This study provides relationships for the stomatal conductance of Populus trichocarpa (Torr & Gray) in a marginal growth environment. Using data from two successive growing seasons (1994-1995) in southern Iceland, conductance was modelled using solar radiation, air temperature, vapour pressure deficit and hours since 06:00 Coordinated Universal Time (UTC) using Jarvis' phenomenological model and the boundary line technique. Soil water was eliminated as a variable because of the excellent water-holding capability of the native soil. The best 1995 model was tested against the independent 1994 data set, resulting in a value of 0.98 for Willmott's index of agreement, a root mean square error of 14% and mean bias error of - 3%. Some systematic error was introduced and is attributable to the different range in measured conditions for each year. The results provided here may be used in future studies of energy exchange and are also of use to researchers studying fast-growing species for domestic production.