Lab 2 FE.docx - Lab 2 Structure and Development of...

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Lab 2: Structure and Development of Uneven-Aged Stands Sarah Kerr FOR-2060-004 9 March 2016
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Introduction According to Chadwick Oliver (1980) mixed stands are not intensively managed because people see them as unpredictable. Many foresters and industries do not understand how mixed- species stands develop and therefore they are considered undesirable. Uniform ages and species among a forest is ideal for foresters. On the contrary however, mixed stands can be very manageable and even the management of certain mixtures can reduce the silvicultural costs and increase the quality and amount of timber. It is during the brushy stage that stand improvement for timber and precommercial thinning is done to ensure adequate spacing and species composition. The brushy stage as described by Oliver in his report as the stage in which all species are competing for resources in the first couple of decades after a stand begins to form over a cut area. During this stage the trees are at their tallest and widest, with the most abundant species being known as pioneers. Over time the species begin to cut back on growth as the resources become limited and competition will wipe out the weaker species. Determining which species will dominate in a mixed stand can be easy to do based off of what the soil conditions are and the already present species. Oaks for example, as said by Oliver from a central New England perspective tend to grow taller than maples and birches. Once certain species begin to out compete other species, suppression takes place by either physical clashing of branches or by shading from the taller trees. If the shaded trees do not die than they are shade tolerant trees and continue to live in the understory, causing the forest to be vertically stratified. Vertical stratification can be a very good thing, for trees in the under story keep the upper story trees well pruned and can be used for “less-quality specific products” such as pulp. Also some mixed forests as opposed to pure forests create more volume and better quality trees. Oliver explains further that some mixed forests are more resistant to pathogens and insects than pure forests are
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since there is multiple different species and not a single host species that has potential to be wiped out entirely. An article by A. F. Hough also shows that in studies found from an area of tree growth after a fire that as age progresses in a stand, the diameter increases. Also due to competition the tree population grows rapidly at first and then as the age increases the amount of trees on the plot decreases. The trees who obtain the resources from the area and continue to grow without dying off will continue to receive nutrients and therefore their heights and diameters will increase. The understory trees who become shade tolerant will also continue to grow but will not exceed the dominant trees in the over story. People cause problems with mixed stands simply by selectively cutting certain species when they are assumed to all be the same age. The understory trees then are often too old or suppressed to give quality growth for timber.
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  • Fall '17
  • ian morrison
  • Oak, Human height, DBH, Chadwick Oliver

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