Xylem pressure potential in black spruce in interior Alaska

• Published in: Canadian Journal of Forest Research
• Main Authors: Wolff, Jerry O., West, Stephen D., Viereck, Leslie A.
• Format: Article in Journal/Newspaper
• Language: French
• Published: Canadian Science Publishing 1977
• Subjects: Ecology; Forestry; Global and Planetary Change; Ice; permafrost; Alaska
• Online Access: http://dx.doi.org/10.1139/x77-053; http://www.nrcresearchpress.com/doi/pdf/10.1139/x77-053

Xylem pressure potential was measured in black spruce in interior Alaska to determine the patterns of water stress under conditions of permafrost and long photoperiods. The general shape of the daily stress curve was similar to that reported for other species at lower latitudes. The primary effect of long photoperiods was to shift the times of stress maximums and decreases. Trees on sites with maximum annual thaw depths of 26 and 100 cm equilibrated daily with maximum predawn stress values of about −5 bars (1 bar = 100 kPa). Minimum stress during the day was generally −10 to −16 bars and did not exceed −18 bars for the entire growing season. An abundant water supply in the rooting zone derived from ice in the thawing soil was probably the contributing factor which prevented large seasonal changes in the daily pattern of moisture stress.