Variation of carbon allocation and competitive ability of different tree species as related to successional position and habitat

Graduation date: 1984Early and late seral tree species were compared for inter-and intraspecific competitive ability; within-population genetic variability; and allocation patterns of soluble sugars and starch seasonally and in response to shade and nitrogen fertilization. Species were Douglas-fir (early seral) and western hemlock (late\ud seral) from a low elevation habitat; and noble fir (early seral) and silver fir (late seral) from a high elevation habitat.\ud Mortality increased with density and peaked at 15% for western hemlock, 35% for Douglas-fir, 48% for noble fir, and 90% for silver fir. In general, early seral species grew faster and attained larger final size than late seral species, while species did not differ in response to competition. However, there were considerable differences among half-sibling families within each species. Ranges in average top weights for families grown at low or medium (16 or 4 cm2 of initial growing space) were: western hemlock, 50-300 mg; Douglas-fir, 100-900 mg; silver fir, 10-190 mg; noble fir, 90-250 mg. Root size was less variable resulting in highly significant density-correlated rank changes in shoot/root ratio (S/R ratio) for families of all species except noble fir. Western hemlock grown with Douglas-fir had shoots 24% smaller and roots 36% smaller than when grown with other western hemlock and Douglas-fir roots were 40% larger when grown with a mixture of Douglas-fir and\ud western hemlock than when grown entirely with one species or the other. Families of both species differed in their SIR ratio response to varying neighbor composition. In contrast, neighbor composition had little effect on silver fir and noble fir.\ud Field-grown seedlings were 30% smaller and less responsive to treatments than pot-grown.\ud In all species, 66 to 70% of total dry weight was soluble sugars and starch prior to budbreak with roughly two-thirds of\ud this as starch. Following budbreak, available carbohydrates decreased to 25 to 30% of total dry weight (maintained through the growing season). Late seral species had higher root sugars during the growing season than early seral species. Shading either decreased or did not affect growth of early\ud seral species and increased growth of late seral species. It had little effect on available carbohydrates. Nitrogen fertilization increased SIR ratio of western hemlock from 1.9 to 3.3 and of the other species from 1.2 to 2.2; and reduced sugar concentration in all species but had little effect on starch. Family variances in prebudbreak root sugars were 17 times greater in western hemlock than in Douglas-fir and noble fir. Family variance in growth traits was greater in the low elevation than in the high elevation species