Controlled Moisture Stress to Improve Cold Hardiness and Morphology of Douglas-fir Seedlings

Abstract

Abstract Nursery-grown seedlings of Douglas-fir (Pseudotsuga menziesii) were subjected to three levels of moisture stress between late July and the end of August. Measurements in October and December showed that mild stress of -5 to -10 bars significantly improved cold hardiness. In a second experiment, the effectiveness of the mild stress treatment decreased as the onset of the stress was delayed from mid-July until September 1. Furthermore, the earlier onset of stress decreased the height and shoot/root ratio, but increased the root weight and nitrogen content of the needles. For seedlings lifted in October, mild stress also decreased mortality from cold storage. Forest Sci. 25:576-582.