Adam Taylor, Associate Professor, Forest Products
The past few years have been hard ones for the forest products industry. Rapid globalization, the bursting of the housing bubble and the economic recession combined to result in record-setting losses in jobs and production in the wood industry. However, an improving economy and housing market are leading to increased demand for wood products. At the same time, the contraction of the industry over the last few years has reduced the supply infrastructure, which should result in better pricing and business opportunities for the wood industry in Tennessee and the United States.
The Hardwood Review publishes prices and industry analysis for the hardwood lumber industry. They have been reporting strong demand for hardwood lumber, both domestically and for export, and are forecasting further demand increases. They cite increased activity in housing starts and building permits and growth in remodeling activity and non-residential construction. Exports have become an increasingly important part of the wood business in Tennessee and hardwood lumber exports have increased 10% overall this year, with increased demand seen throughout Europe and in Asia. All these trends suggest that demand for wood products in general, and hardwood lumber in particular, will continue to grow in the coming years.
Tennessee has abundant, and increasing, wood resources and the hardwood species that grow here are highly-esteemed throughout the world. However, the terrible economic conditions in the wood products industry over the past few years resulted in the closure of about 1/3 of the mills and the loss of about 2/3 of the jobs. In addition, credit for wood products producers is more difficult to obtain than it was in the past. Thus, although some of the mills will restart and rehire their workers, it is forecast that it will be difficult for the supply of lumber products to keep up with increases in demand. This should result in price increases for wood products and better business conditions for the forest landowners, loggers and sawmillers in Tennessee.
The shape of tree crowns
David Mercker, Extension Specialist, Forestry
The crown of a tree or woody plant is that portion that contains live branches and foliage. Crown shape will vary according to tree species. McCurdy, et al. (1972) identified six distinct crown shapes: oblong, round, oval, vase, pyramidal, and weeping. In forested settings, the crown shape is influenced by a tree's position within the canopy. Crown shape is of interest to foresters because it indicates the amount of growing space (or stocking) that is needed to maximize lumber production. Crown shape should be considered around buildings and in urban settings, because it influences contrast, view, shading, and screening. Although the basic shape is characteristic of a species, branch growth and death is modified by the environment, so trees grown in close proximity to others can have vastly different crowns than those grown in an open setting.
Perhaps most influential in determining crown shape is differences in the degree of apical dominance. Apical dominance is the upward growth of the leader, at the expense of lateral shoots. Flushing and growth of lateral shoots is inhibited by hormones produced by the apical bud on the leader. As a result, crowns of trees with strong apical dominance grow in height much faster than in width. Typically these species will have a single, dominating central trunk and leader. Lateral branches often grow outward, rather than upward. Such trees are said to have an excurrent crown that favors oblong or pyramidal shapes. Forks in the central trunk are rare, usually forming only when the leader has been damaged or destroyed. Sweet gum (Liquidambar styraciflua L.), tulip poplar (Liriodendron tulipifera L.) and many conifer species exhibit strong apical dominance.
In contrast, in tree species with weak apical dominance, crown width grows nearly as fast as crown height (especially when open-grown). Such species have no particular prevailing leader, but rather multiple ones. The leader with the most access to sunlight normally prevails, and sometimes compromises tree form (Oliver 1996). Such trees are said to have a decurrent crown that favors round or oval shapes. Forks in the central trunk are common, even exacerbated when the leader(s) have been damaged. Oaks (Quercus spp.) and maples (Acer spp.) are examples.
An understanding of tree growth characteristics is beneficial for the management of trees in both forested and urban settings. This knowledge can aid in maintaining proper forest stocking, in pruning and limb manipulation, in making aesthetic choices, and monitoring individual tree growth and forest health. For more information on this subject, see:
Franklin, J. and D. Mercker 2009. Tree Growth Characteristics. University of Tennessee Extension.
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