Effect of Nursery Photoperiod Manipulation on Coastal Douglas-fir Seedling Root Development Following Planting
Photoperiod manipulation (i.e., short-day treatments or blackout) is used by nurseries in northern latitudes when growing spruce and pine, as a means to arrest shoot growth, encourage high root to shoot ratios, and induce dormancy. Effects on coastal Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) are less well known, especially for provenances of lower latitudes (i.e., <45 °N). Additionally, transplant rooting responses of short-day treated seedlings at relatively cold temperatures (i.e., <10 °C [50 °F]), which characterize many outplanting sites during winter/early-spring planting, have not been well studied. Recent research suggests that nursery short-day treatment has a pronounced effect on seeding development in coastal Douglas-fir, and phenological effects may carry over through spring de-hardening. Additionally, collective evidence from the limited studies examining transplant rooting responses across a range of soil temperature suggest that short-day treated seedlings produce more roots at low soil temperatures. This implicates potential for reduced transplanting stress of short-day treated seedlings on sites characterized by low soil temperatures and/or drought. Future research should examine rooting responses across a range of soil temperatures that might be encountered throughout an entire growing season. Additionally, specific prescriptions for timing of short-day treatments should be developed that will aid in coupling of physiological status to site conditions under a range of site conditions and silvicultural prescriptions, including fall planting.
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Author(s): Douglass F. Jacobs
Publication: National Nursery Proceedings - 2013
Event:
Western Forestry and Conservation Nursery Association Meeting
2013 - Olympia, Washington
