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About Applegater. (Jacksonville, OR) 2008-current | View Entire Issue (Sept. 1, 2012)
16 Fall 2012 Applegater Thin for quality and health, not spacing bY mAx bEnnETT AnD STEPhEn fiTzGERALD Your chainsaw is revved up and • Poor form or has signs of damage or internal decay you’re about to sink the bar into a nearby Douglas fir sapling. But which one? • Species not well suited to the site You’re surrounded by hundreds of them— some smaller, some larger, all pretty close Crown ratio Crown ratio is the percentage together, but not uniformly spaced. There are some madrone trees, too, and of the total height of the tree that cedar, and a few spindly pine. You heard is occupied by the live green somewhere that trees should be 10 feet or crown. For example, a tree that 12 feet apart…or was it 15 feet? You can’t is 75 feet tall and has crown on quite remember. What to do? the upper 25 feet of the tree has The tree on the right has a sparse, thinning crown, Many landowners ask about proper a live crown ratio of one-third possibly due to stress, insect attack, or root disease. or optimum spacing when thinning trees. or 33 percent. Crown ratio is Trees on the left have full crowns, We’d suggest not getting too hung up important because the bigger the indicating relatively better health. initially on spacing, but instead focus on crown (the tree’s “food factory”), tree quality and health (vigor). If you leave the better the tree’s growth. The rate from needle loss is another sign of stress. primarily high-quality trees and take out of growth slows down in most species This can often be best determined by mostly low-quality trees, it’s hard to go when the live crown ratio drops below comparing a thin or sparse crown with wrong. You’re likely to have a healthier, 40 percent. Trees with crown ratios of 30 a denser crown on a nearby tree. An more vigorous, more fire-resistant, and percent and greater often respond well to abundant crop of undersized cones (distress more valuable stand in the long run. release (removal of surrounding competing crop) is sometimes an indication that the Is spacing between trees), while trees with tree is severely stressed and likely to die in t re e s u n i m p o r t a n t ? crown ratios below 30 the near future. Not at all. Trees need percent often respond Tree form adequate growing space poorly. These trees may The form of the tree trunk (stem) is to thrive. However, experience thinning an important consideration in thinning. In a nutshell, rigidly adhering to exact shock or sunscald, or All other things being equal, trees with spacing (e.g., 14 feet x 14 grow very slowly. Trees straight trunks and little taper that are …“cut the sick, feet) may lead you to cut with very small crown free of defect are most desirable as “leave” lame, and lazy, trees that should be left ratios may simply die trees from a timber perspective. However, and to leave trees that after thinning. This trees that are very tall for their diameter, and leave the should be cut. This is often happens after especially conifers, tend to be unstable and better ones.” especially true in natural diameter-limit thinning easily bent by the wind or snow, so some stands where spacing (removal of all trees above taper is important. Trees that have forked between trees is highly a certain diameter limit) or broken tops, crooked trunks or evidence variable. In plantations or high grading (“cut the of rot and defect may be candidates for where spacing between best and leave the rest”). removal. However, defective trees may trees is more regular, Gradual, light thinnings also make good wildlife trees, so aiming using predetermined are recommended for spacing or stand density rules makes more very dense stands where few, if any, “leave” sense. Remember that spacing guidelines trees have desirable crown ratios. are just that—they are guidelines and, as Height growth such, should remain flexible for leaving Height growth can be determined by the best trees. Also, remember that as examining the length of the leader if visible, trees grow bigger, they progressively need or on many conifer species (including the more space, so space trees out wide enough true firs, pines, Douglas fir), the length of so that they will grow well until the next internodes, which is the distance between thinning. branch layers or whorls. Trees with good So what makes a high-quality, height growth are preferred as “leave” trees. vigorous tree? Following are some Crown shape/form guidelines for “leave” and “cut” trees Pointy-topped or A-shaped crowns related to tree quality that you can use to indicate rapid height growth. Rounded “eyeball” out in the woods. While these tops mean height growth has slowed. points focus on conifer trees, the basic Good height growth is a sign of good vigor. principles also apply to hardwoods. However, as trees age, height growth slows, Characteristics of “leave” trees and trees tend to develop a round or flat • Good live crown ratio (30% or top. Full, symmetrical crowns are preferred greater) over ragged or lopsided crowns. Lopsided • Good height growth for species crowns develop when a tree is crowded on and age one or more sides. Trees with lopsided • A-shaped crown (pointy top) crowns are more vulnerable to blow down • Abundant foliage with good color or breakage in snow and ice storms. • Good form (straight, without sweeps, Crown color/needle density crooks, forks, etc.) A dark green color indicates good • Species is well suited to the site over vigor. Light green or greenish-yellow the long term foliage (chlorotic foliage) is a sign of stress. Characteristics of “cut” trees This may be due to nitrogen deficiency, • Poor crown ratio (less than 30%) root disease, bark beetle attacks, or simply • Poor height growth and crown form moisture stress. (flat or rounded top, lopsided) Crown sparseness • Foliage is sparse or off-color A sparse or thinning crown resulting For other informative woodland articles Visit the online E-Newsletter of SW Oregon Woodland News at http://extension. oregonstate.edu/sorec/small-woodlands-july-enews-2012. Check out the following stories: • The chain saw circle: Women of the woodlands • Supreme Court to decide if logging road runoff is pollution • Environmental groups say it will take 20 years to thin northwest forests • Forest Capital Partners sells its timber portfolio • The importance of burls and four other surprises from The Biscuit Fire for a balance is important. For example, large deformed black oak trees with broken branches or heart rot are some of the best habitat trees around. Unless they threaten to demolish your house or barn if they topple, consider leaving them alone. Other considerations These guidelines touch on a few key indicators of tree quality. You should also be on the lookout for evidence of insect and disease problems, some of which may warrant tree removal regardless of other factors. Tree species should also be considered. Many landowners like to leave a mixture of tree species, both for esthetic reasons and because a mixed-species forest is often thought to be less vulnerable to a pest problem that might devastate a single-species stand (monoculture). That’s generally true, but make sure that the species is well suited to your site. For example, hot, dry south-facing slopes in the Applegate are good for pine and oak, but aren’t so favorable for Douglas fir. In a nutshell, these guidelines follow the old adage, “cut the sick, lame, and lazy, and leave the better ones.” As you thin for quality, you will probably also be reducing stand density to more desirable levels. It may not be too scientific, but forestry, after all, is a science and an art. Max Bennett 541-776-7371 x221 Forestry/Natural Resources Agent Oregon State University Extension Service Jackson-Josephine Counties max.bennett@oregonstate.edu
