Reaction to Competition
Open-grown trees commonly remain single stemmed and fine branched until they are 9 to 12 ni (30 to 40 ft) tall, although old specimens can become as broad crowned as an elm. With even slight crowding, the single-stemmed characteristic can easily be maintained throughout a rotation. Shade-killed branches drop quickly-small ones within a year or two and larger ones within 4 or 5 years (16).
Uninjured terminal buds suppress the growth of all lateral buds on the current year's growth, and they suppress the growth of other laterals to such an extent that each internode has only one pair of branches that persist more than a few years. Even the strongest lateral branches grow only half as fast as the terminal except on old, open-grown trees. Little or no epicormic branching occurs on the boles of released trees. The branches of dominant trees emerge from the bole at about a 35° angle from the vertical, whereas the branches of intermediate trees emerge at about a 55° angle (16).
When young, white ash is a shade-tolerant tree. Seedlings can survive under a canopy with less than 3 percent of full sunlight but grow little under these conditions. Seedlings that receive sufficient sunlight grow rapidly. With increasing age, white ash becomes less tolerant of shade and is classed overall as intolerant. The decrease in shade tolerance with increasing age is reflected in the fact that young white ash is abundant in the understory of northern hardwood stands, but few grow into the overstory unless provided with light from above.
Despite its low shade tolerance, white ash is characteristic of intermediate as well as early stages of natural plant succession. Throughout its range it is a minor but constant component of both the understory and overstory of mature forests on suitable soils. It owes its position in the final overstory to its ability to persist for a few years in moderately dense shade and to respond quickly to openings in the canopy created by death or other causes.
White ash can be maintained more easily in a dense stand than can some of its more shade-intolerant associates, such as northern red oak. In contrast, dominant or codominant white ash responds readily to thinning and within a few years will increase its crown area to take full advantage of any reasonable release (16).
- Burns, Russell M., and Barbara H. Honkala, technical coordinators. 1990. Silvics of North America: 1. Conifers; 2. Hardwoods. Agriculture Handbook 654 (Supersedes Agriculture Handbook 271,Silvics of Forest Trees of the United States, 1965). U.S. Department of Agriculture, Forest Service, Washington, DC. vol.2, 877 pp. http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm
No one has provided updates yet.