Simulation of Leaf Conductance and Transpiration in Juniperus occidentalis
Abstract:Western juniper (Juniperus occidentalis Hook.) is a conifer species well adapted to semiarid rangelands in portions of the western United States. Over a 2-yr period (1983-1984), water relations of mature western juniper trees were observed and soil temperature, soil water, air temperature, vapor density deficit (D a), and solar radiation were recorded. Data from 1983 were used to develop and calibrate a leaf conductance model for western juniper. The model was then tested against 1984 data. A daily soil water budget was maintained by coupling the conductance model with the hydrology component of the model SPUR (Simulation of Production and Utilization of Rangelands). Results indicate that the model successfully simulated seasonal conductance trends. Conductance was strongly affected by soil temperature and D a in spring, while soil water pressure and D a were important during summer. Simulated western juniper conductance rose to maximum in spring and was usually within one standard deviation of observed values. In the 1984 simulation, western juniper transpired 141 mm of water, 47% of the total evapo-transpiration for the site, and 44% of 1984 precipitation. Simulated western juniper conductance increased whenever environmental conditions moderated in late winter and spring. Juniper withdrew 37 mm of water between January and May 1984, suggesting it has potential to significantly alter watershed value and site productivity. For. Sci. 40(1):5-17.
Document Type: Journal Article
Affiliations: Professor of Rangeland Resources, Eastern Oregon Agricultural Research Center, Oregon State University, Burns, OR 97720
Publication date: February 1, 1994
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