Development of tanoak understories in conifer stands

Abstract

The stocking, age, and growth rates of tanoak (Lithocarpusdensiflorus [Hook and Arn.] Rehd.) were studied in the understory of 13 Douglas-fir (Pseudotsugamenziesii [Mirb] Franco) and mixed conifer stands, 53–240 years old, on a range of sites in Oregon and California. The understory was uneven in both age and size in all stands. Tanoak <2.0 cm diameter at breast height (dbh) ranged from 1 to 62 years old and from 5 to 216 cm tall. The stems of tanoak >2.0 cm dbh ranged from 18 to 98 years old and from 2 to 25 m tall. A negative exponential function describing diameter distributions generally explained more than 80% of the within-stand variation in numbers of tree stems (by 5-cm diameter classes). Seedlings have a single stem for about 5–12 years, then form a burl with dormant buds below ground, lose the original stem, and produce new stems. Because of frequent stem mortality and sprouting, tanoak age cannot be determined from stems above ground but can be estimated from xylem rings in the stem below the burl. Tanoak grows slowly in the conifer understory and at 50 years of age is only 80 to 160 cm tall. Sprouting potential also develops slowly. Three years after burning, 41- to 50-year-old tanoak averaged five sprouts only 30 to 68 cm tall. The establishment of a dense, new understory with the capacity for vigorous sprouting after disturbance may take well over 100 years. Tanoak control may be less costly and less frequently needed if accomplished in 30- to 75-year-old conifer stands.

California’s Hardwood Resource: Seeds, Seedlings, and Sprouts of Three Important Forest-Zone Species

“…An individual seedling may die back several times and produce one to seven new stems with the largest stem being the oldest. On the basis of scores of samples, Tappeiner and McDonald (1984) found no reliable relationship between the age and size of the above-ground stem and the total age of tanoak seedling-sprouts. However, the total age of seedling-sprouts can be ascertained quite accurately by counting the xylem rings in the stem below the burl.…”

“…The burl on tanoak seedlings develops slowly and is strongly related to age and site quality (Tappeiner and McDonald 1984). It is just as likely to produce sprouts in a sun environment as in a shade environment; however, the number of stems tends to be less in shade ( fig.…”

“…In southwest Oregon, tanoak seedling-sprouts were studied beneath old (135-250 years) and young (50-75 years) conifer and hardwood stands, and the density-age-height relationship determined (Tappeiner and McDonald 1984). Together, these data portray the density and growth dynamics of young tanoaks over time in the understory ( fig.…”

The role of fire in the competitive dynamics of coast redwood forests

“…Available data are inadequate to predict the effects of repeated fires in redwood forests, but it is possible that frequent burning may gradually reduce the abundance of tanoak. Tappeiner and McDonald (1984) noted that stumps of tanoak less than 2 cm DBH sprouted ''much less vigorously'' than stumps of larger tanoak, and Kauffman and Martin (1990) found that the probability of whole plant mortality decreased significantly with increasing v www.esajournals.org pre-fire aboveground biomass of shrubby tanoaks, suggesting that if adequate recovery has not occurred between fire events, root systems may not survive. Donato et al (2009) found a similar pattern for all hardwoods pooled (tanoak was not analyzed separately), and documented that the percent cover of tanoak, two years postfire, was lower in a ''short interval'' burn area than in the ''long interval'' burn area; however, they also noted that this difference was slight and concluded that a ''short interval'' (15 years) should allow for indefinite site persistence.…”

Preliminary plant associations of the Siskiyou Mountain Province /

“…The competition from tanoak after cutting is directly proportional to the amount of cover before cutting (Tappeiner and McDonald 1983). Tanoak builds a basal burl early in life that is protected from surface disturbance (fire and cutting) and is capable of resprouting.…”