Excerpt from Germination, Survival and Early Growth of Conifer Seedlings in Two Habitat Types

Seed germination and seedling survival in the field are as important to natural forest regeneration as are the production and dispersal of seeds. Many seeds are produced and dispersed, but most do not germinate or they fail to survive after germination. This severe seed and seedling mortality multiplies the number of seeds required to obtain natural regeneration. It also acts as a selective factor in determining the genetics of future stands.

The relation of dispersed seed populations to established seedling populations is not well known for most high elevation forests in the Pacific Northwest. Production and dispersal of conifer seeds in the Abies amabilis forest zone described by Franklin and Dyrness (1973) have been well studied (carkin and others 1978; Franklin and others 1974; Franklin and Smith 1974a, 1974b), but little work has been done on the fate of those seeds. Sullivan (1978) compared forest regenera tion on clearcuts in several habitat types within the Abies amabilis zone and con cluded that regeneration differed significantly among habitat types, but he did not relate his observations and conclusions to the seed supply. Neither did Halverson and Emmingham who were unable to correlate forest regeneration in the Abies amabilis zone with habitat types, but found extremes in environment to be the most probable cause of regeneration failure. Seidel (1979a) surveyed mixed conifer regeneration on many clearcuts along the east side of the Cascade Range and in the Blue Mountains of Oregon. He measured the variation among plant community types and geographic locations, but did not relate established regeneration to amounts of seed or early seedling mortality and did not derive any ratios for seeds to established seedlings. Seidel (1979b) also studied regeneration after shelterwood cutting in a grand fir (abies grandis (dougl. Ex D. Don) Lindl.) Shasta red fir (abies magnifica var. Shastensis Lemm.) stand in central Oregon. The number of sound seeds collected in his seed traps can be compared to the number of seedlings that became established during the 5-year measurement period to derive seed-to-seedling ratios for four slash treatments under three overstory densities. Those ratios varied from about on bulldozed seedbeds under an overstory with basal area of square meters per hectare to about on undisturbed seedbeds under the same overstory.

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