Modeling the Effect of Winter Climate on High-Elevation Red Spruce Shoot Water Contents
Abstract:During the winter of 1989-90, meteorological towers were erected at two sites (880 and 1010 m elevation) within the spruce-fir zone on Mt. Moosilauke, New Hampshire. Hourly means of temperature, wind velocity, relative humidity, and solar radiation were collected and stored on data loggers. Previous-year shoots were collected from four spruce trees at each site on a weekly basis, and their relative water contents (RWC) were determined. Measured meteorological parameters were used to simulate changes in the RWC of previous-year spruce shoots through the winter. Our model suggests that shoot water is replenished throughout the winter, presumably from water stored in older woody structures or by root uptake. Recharge was defined to be directly dependent on shoot water saturation deficit (WSD = 100% - RWC), with a temperature cutoff of -4°C. The predicted output of the model generally followed measured RWC. According to our model, periods of high transpiration were associated with low relative humidities, sometimes accompanied by high temperatures and high levels of radiation. Our results suggest that winter water relations in spruce are governed by a balance between transpirational losses, which are primarily dependent upon meteorological conditions, and the rate of recharge, which is dependent on shoot water potential, temperature and perhaps soil water availability. For. Sci. 37(6):1567-1580.
Document Type: Journal Article
Affiliations: Environmental Studies Program, Dartmouth College, 324 Murdough Center, Hanover, NH 03755
Publication date: December 1, 1991
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