Near neighbor pollination and plant vigor in coastal Douglas-fir
1997
Sorensen, F. | Campbell, R.K. (Pacific Northwest Research Station, Corvalis, Oregon (USA))
Nineteen seed parents in a young, patchy, second-growth stand were control pollinated by near (NN) and by far neighbors (FN) and by wind (W) in a heavy flowering year. The progenies were compared in the nursery and for 10 additional years at close spacing in a field test. In a separate test, the after-effect of isolation-bag environment was evaluated using plants of 10 of the same seed parents. Progeny from W and NN pollinations were slightly, but non-significantly, smaller than progeny from FN pollination; seed parent pollen type interactions were very highly significant. Bagging effect was significant for nursery seedling size but could be eliminated by using seed weight as a covariant; the effect disappeared in the field test, and did not interact with seed parent at any age. Estimated rates of biparental inbreeding in Douglas-fir, based on this test and values from the literature, range from zero to about 20%. Such variation seems compatible with the variation in natural regeneration habits of the species. If the biparental inbreeding is considered to result from half-sib mating, the associated inbreeding depression in height is estimated as zero to 2.3%. At the close spacing used in this study, depression in biomass appeared to be 4-5 times as great as depression in height at age 12
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