Effects of Cold Soil on Water Relations and Spring Growth of Douglas-fir Seedlings

Abstract

Abstract Effects of low soil temperature on the water relations, shoot growth, and root growth of Douglas-fir seedlings ( Pseudotsuga menziesii (Mirb.) Franco) were studied to evaluate the significance of reduced water uptake and growth in seedlings outplanted in cold soils. Transpiration rate declined linearly with decreasing soil temperature, and at 1.3°C, was 18.8 percent of the rate at 20.2°C. Xylem pressure potential of seedlings maintained under high evaporative demand for 10 days in soil at 1.3°C averaged -20.0 bars, compared to a higher potential (-13.4 bars) for seedlings in soil at 26°C. Stomatal conductance of seedlings in cold soil was 50 percent or less of seedlings in warm soil. Low soil temperature reduced shoot growth and completely prevented root growth. The results indicate that for seedlings planted in cold soil, reduced water uptake does not immediately cause lethal water stress. The primary cause of poor field survival probably is suppressed root growth at low soil temperature resulting in increased susceptibility to summer drought. Forest Sci. 30:628-634.