Recovery Plan for the Northern Spotted Owl - DRAFT
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Recovery Plan for the Northern Spotted Owl - DRAFT

Recovery Plan for the Northern Spotted Owl - DRAFT Recovery Plan for the Northern Spotted Owl - DRAFT

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10.07.2015 Views

technology probably will allow somewhat more intricate treatments. Therefore,because of new information on harvesting and reforestation methods, Kirklandand Brandstrom's (1936) ideas of group selection, and group shelterwood andirregular shelterwood (Smith 1986, Troup 1928) should be reviewed. They canbe considered for use on certain sites in young and mature forests along withgreen tree-retention and other "new perspective" practices.E. Stand Simulators and Growth ModelsGrowth models can be used to predict the development, growth, and yield offorest stands with and without treatments. These models will predict averagetree diameter, height, total stand basal area, volume, and mortality. Simulatorssuch as DFSIM (Curtis et al. 1981), CRYPTOS (Krunimland and Wensel1980), ORGANON (Hester et al. 1989), and PROGNOSIS (Stage 1973) predictthese variables for entire stands and/or by tree size classes within stands. Thetrends in simulated stand growth and development are consistent among thesemodels. We used them to project the effects of different silvicultural systemson stand growth for owl habitat. When compared with data from actualstands, DFSIM and ORGANON predict trends in stand growth quite accurately(Hann 1991, Stere 1991).The snag recruitment simulator provides a means to predict snag longevity bydiameter and decay class for natural snags or those created by management.This program was developed by Bruce Marcot (PNW Research Station, Portland,Oregon) based on information in Neitro et al. (1985).IV. Examples of Silviculture PrescriptionsFollowing are silviculture systems for different types of stands commonthroughout the range of northern spotted owls. We used data from actualstands and-simulated the development of structures following treatments togrow large trees and produce multilayered stands. When actually implementingthese systems the following points should be evaluated to see if they applyto the stand in question. They are suggestions which will help ensure thatsilviculture systems "mimic" natural disturbance and stand development. Thelist is not exhaustive: other ideas will be appropriate on a stand by stand basis:* Favor some large, trees with many limbs for potential nest sites.* Use hardwoods to help develop a multilayered stand.* Encourage the growth of advanced regeneration of shade-tolerant coniferand hardwood species, even in young (30 to 50+ years old) stands.* Establish new regeneration by planting or seeding in young (50+ year-old)stands after making small openings or reducing overstory density in partsof a stand.* Consider varying the distribution of overstory trees when thinning. Varyspacing and tree density, make openings for new regeneration and releaseadvanced regeneration.* When thinning, leave some trees in the smaller crown size classes (intermediateand suppressed) to help promote a layered stand.* In stands with irregularly spaced trees, consider a crown thinning torelease individual trees while maintaining the irregular spacing.502

A. Douglas-fir and Western Hemlock Stands(Oliver et al .1991)The following examples from Douglas-fir and western hemlock stands 30 to 70years old (Oliver et al. 1991) show trends of stand development under differentdensities. Diagrams are drawn to scale using information from stand simulators.Stands are projected with no treatment (Figures G.8, G.9, G.10). Inaddition, the 30-year-old stand (Figure G.8) is projected with two thinningregimes (low and moderate density); the 70-year-old stand is projected with athinning regime (moderate density) and a treatment to produce a multiplecanopystand (Figure G.9). In these stands, the second story would result fromrelease of conifers and hardwoods, or planting and seeding of conifers followingthinning. Development of a young plantation is shown in Figure G.10. Here,too, thinnings stimulate large tree and early understory development. Thesesimulations indicate that there are several advantages of manipulating overstorydensity to produce owl habitat:a) The size of the average tree, and the size of the largest 5 percent of thetrees in the stands, are increased. For example, the 30-year-old stand(stand B, Figure G.8) under a low density thinning regime is simulated atage 90 (year 2050) to have an average diameter of 36 inches and thelargest 5 percent of the trees have diameters of about 44 inches; whileStand A, with no activity, has trees of 18-inch average diameter and for thelargest 5 percent of the trees have 27-inch diameters.b) In stands which have had trees thinned, the canopy is "deeper," and treeshave larger crowns. For example, stands managed under the low-densitythinning regime, at age 90 years (year 2050), have crowns estimated fromabout 60 to 140 feet above ground (i.e., more than 60 percent of the lengthof the tree will have live crown on it); while on the untreated stand crownswill be about 110 to 140 feet above ground (see Figure G.8).c) Reducing overstory density will enhance development of an understory andencourage the development of multilayered stands typical of those used byowls (Figure G. 1). Without thinning, stands may be either too dense fortree and shrub seedlings to become established, or those that are presentwill grow very slowly.These stands likely will not produce large snags or logs on the forest floornaturally. Mortality due to crowding will kill trees less than 11 inches indiameter. However, stands at low density will have trees 25 inches diameterbreast height (dbh) and larger, some of which will be killed by pathogens andinsects, or which can be girdled or topped to make snags.Oliver et al. (1991) predicted that the risk of wind damage to unmanagedstands is greatest when they are about 30 to 70 years old (see Ruth and Harris1979). After about 70 years, the larger trees in the stand are likely to becomestable.The maximum possible costs and maximum possible returns for these scenarioshave been estimated (Table G.1).B. Douglas-fir from Oregon Coast Range (Birch 1991)Example 1: A 60-year-old Douglas-fir and western hemlock stand, on aproductive site (site index 130 feet at 50 years) with 280 trees per acre. Thegoal of the simulation was to produce a multilayered stand structure (similarto stand A in Figure G. 1 1) as quickly as possible.* At 60 years the stand was thinned leaving a) the largest 10 trees per acre(26 to 30 inches in diameter), b) trees in the smaller sizes (48 trees per503

technology probably will allow somewhat more intricate treatments. There<strong>for</strong>e,because of new in<strong>for</strong>mation on harvesting and re<strong>for</strong>estation methods, Kirklandand Brandstrom's (1936) ideas of group selection, and group shelterwood andirregular shelterwood (Smith 1986, Troup 1928) should be reviewed. They canbe considered <strong>for</strong> use on certain sites in young and mature <strong>for</strong>ests along withgreen tree-retention and o<strong>the</strong>r "new perspective" practices.E. Stand Simulators and Growth ModelsGrowth models can be used to predict <strong>the</strong> development, growth, and yield of<strong>for</strong>est stands with and without treatments. These models will predict averagetree diameter, height, total stand basal area, volume, and mortality. Simulatorssuch as DFSIM (Curtis et al. 1981), CRYPTOS (Krunimland and Wensel1980), ORGANON (Hester et al. 1989), and PROGNOSIS (Stage 1973) predict<strong>the</strong>se variables <strong>for</strong> entire stands and/or by tree size classes within stands. Thetrends in simulated stand growth and development are consistent among <strong>the</strong>semodels. We used <strong>the</strong>m to project <strong>the</strong> effects of different silvicultural systemson stand growth <strong>for</strong> owl habitat. When compared with data from actualstands, DFSIM and ORGANON predict trends in stand growth quite accurately(Hann 1991, Stere 1991).The snag recruitment simulator provides a means to predict snag longevity bydiameter and decay class <strong>for</strong> natural snags or those created by management.This program was developed by Bruce Marcot (PNW Research Station, Portland,Oregon) based on in<strong>for</strong>mation in Neitro et al. (1985).IV. Examples of Silviculture PrescriptionsFollowing are silviculture systems <strong>for</strong> different types of stands commonthroughout <strong>the</strong> range of nor<strong>the</strong>rn spotted owls. We used data from actualstands and-simulated <strong>the</strong> development of structures following treatments togrow large trees and produce multilayered stands. When actually implementing<strong>the</strong>se systems <strong>the</strong> following points should be evaluated to see if <strong>the</strong>y applyto <strong>the</strong> stand in question. They are suggestions which will help ensure thatsilviculture systems "mimic" natural disturbance and stand development. Thelist is not exhaustive: o<strong>the</strong>r ideas will be appropriate on a stand by stand basis:* Favor some large, trees with many limbs <strong>for</strong> potential nest sites.* Use hardwoods to help develop a multilayered stand.* Encourage <strong>the</strong> growth of advanced regeneration of shade-tolerant coniferand hardwood species, even in young (30 to 50+ years old) stands.* Establish new regeneration by planting or seeding in young (50+ year-old)stands after making small openings or reducing overstory density in partsof a stand.* Consider varying <strong>the</strong> distribution of overstory trees when thinning. Varyspacing and tree density, make openings <strong>for</strong> new regeneration and releaseadvanced regeneration.* When thinning, leave some trees in <strong>the</strong> smaller crown size classes (intermediateand suppressed) to help promote a layered stand.* In stands with irregularly spaced trees, consider a crown thinning torelease individual trees while maintaining <strong>the</strong> irregular spacing.502

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