Effect of Altitude on Factors of Pollen Contamination of Douglas-Fir Seed Orchards
Abstract:Upslope progression of pollen shedding and female receptivity in Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) was studied by weekly observations at stations along four transects in western Oregon and Washington ranging from 25 to 4,250 feet in elevation. The attainment of a prescribed stage of pollen shedding or female receptivity progressed upslope at an average rate of about 77 feet per day. Pollen shedding occurred over a 7- to 15-day period on the individual tree and over a 20- to 30-day period at a single location. Effects on the progression from variations in weather were minor. Relative earliness or lateness of bud bursting has not proved to be predictable from differences in elevation of seed source. In this instance, observation of grafts from 2,600-foot elevation on understock native to the Dennie Ahl Seed Orchard at 600-foot elevation showed only an 8- to 10-day average delay in corresponding phenological stages. Although this delay may be of some significance in avoiding the peak of local pollen shedding, the local 20- to 30-day shedding period means that considerable local pollen was still in the air when the clones were receptive. Incidental observations indicate that on the majority of individual trees, female receptivity occurs almost simultaneously with pollen shedding.
Document Type: Journal Article
Affiliations: Staff of the Pacific Northwest Forest and Range Expt. Sta., Forest Service, U.S. Dept. Agric., Portland, Ore.
Publication date: 1963-04-01
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