Soil Temperature and Drought Effects on Growth of Monterey Pine
Abstract:Experiments were conducted to determine the effects of root temperature and soil drought on growth of 2-year-old Monterey pine (Pinus radiata D. Don). Experiments were performed in naturally lit (50 percent ambient light) greenhouses, with day and night temperatures of 27° and 20°C. Seedlings in 18 1 containers were subjected to 4 root temperature treatments (6°, 10°, 15°, or 20°) or 2 soil drying cycle treatments (9 or 12 days between watering) for a total treatment period of 28 days. Lengths of preselected needles and terminal leaders were measured about twice weekly. On the 9th and 12th days, diurnal patterns of environmental conditions and plant water relations were determined. Leaf conductances of water vapor were not significantly affected by root temperature, but 9- and 12-day drying cycles severely reduced stomatal opening. Xylem pressure potential was reduced by low root temperature only during daylight hours, whereas soil drying reduced potentials during both the day and night. Needle, terminal leader, and root extension were highest with roots at 15°C. Low root temperatures and soil drying both significantly reduced growth, even though low root temperatures did not result in daytime stomatal closure or striking differences in nighttime water stress. By 113 days after the treatments ended, total needle growth and shoot extension were no longer significantly different among the treatments. FOREST SCI. 23:317-325.
Document Type: Journal Article
Affiliations: Research Forester, USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Ft. Collins, CO 80521
Publication date: September 1, 1977
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