Silvicultural Systems and 9 Regeneration Methods: Current Practices and New Alternatives
John C. Tappeiner, Denis Lavender, Jack Walstad, Robert O. Curtis, and Dean S. DeBell
Development of Regeneration Practices 151 Early Logging Practices and Regeneration Methods 152 Studies of Natural Regeneration Processes 153 Artificial ConiferRegeneration 154 Producing Stands of Diverse Structures and Habitats 156 At Harvest 156 Young Stand Establishment 158 Regeneration inYoung to Mature Stands 158 Natural Succession 159 Conclusion 160 Literature Oted 160
In this chapter, we discuss silvicuItural systems and objective 1, and considerable wildlife habitat and regeneration methods to meet the needs of society other values can be provided while producing rela over the next several decades. We begin with a brief tively high yields of wood under objective 2. The history of silvicuItural systems and what we have knowledge and skills are available to pursue both ob learned about forest regeneration.in the Pacific jectives effectively. Moreover, many ownerswill likely Northwest. We then discuss how regeneration meth manage their forests under both approaches. ods might evolve over the next several decades. We believe that the practice of silviculture gen erally will be applied to two different forest man Development of Regeneration Practices agement philosophies and objectives, providing (1) old-forest characteristics and (2) wood production. Traditional methods for regenerating forests as part Significant amounts of wood can be produced under of a timber harvest fall into two broad categories: (1)
151 152 Section ll. Silvicultural Systems and Management Concerns
even-age management systems, which include clear drew heavily on European experience and called for cutting, shelterwood, and seed-tree methods, and (2) intensive practices and detailed stand analyses. The uneven-age systems, which include single-tree and skills and techniques needed to implement this sys group selection methods. As part of these methods, tem were probably unrealistic for those times; how regeneration can be obtained by natural seeding or ever, it was used on federal lands. Sales were de planting, by release of advanced regeneration (Le., signed to remove less than 35 percent of the volume seedlings established in the previous stand), or by per stand (Munger 1950). Artificial regeneration and . coppice from sprouting tree species. tending of conifer seedlings to ensure adequate These methods all have been used successfully in conifer regeneration in unstocked parts of the stand western North America, and all will have their place were not part of this partial cutting system. in future forest management. They are the founda Debate over the use of partial cutting for Douglas tion upon which we will build new strategies to meet firwas quite lively (Munger 1950, Smith 1970). How society's desire for sustaining forests with old-growth ever, its use ended in the late 1940s. Munger (1950) characteristics as well as its demand for wood. reported that all new Bureau of Land Management and Forest Service timber sales called for clearcutting, except for the use of the shelterwood regeneration Early Logging Practices method and some selective cutting in southwestern and Regeneration Methods Oregon. Generally, early logging in the late 1800s and early Evaluation of partial cutting practices and studies 1900s was done to harvest high-quality commercial of natural regeneration helped establish the use of
:1 timber at the least cost with little concern for refor clearcutting. Isaac (1956) evaluated a series of par estation, protection of soil or water, or provisions for tially cut old stands 5 to 10 years after cutting. Be aquatic wildlife habitat. Unmerchantable trees were cause of residual tree damage and mortality, v.,rind . left standing, logged areas often were burned, and throw, change in species composition from shade cutting frequently began at the bottom of a water intolerant to tolerant species, and lack of Douglas-fir shed and continued to the uplands until an entire regeneration, he recommended abandoning V1'ide basin was logged. Ironically, this pattern of cutting spread use of this system. He acknowledged that not
.' may have more closely mimicked natural disturbance enough timehad elapsed to determine ifuneve n-age j> by large fires than the staggered-setting, dispersed management would eventually work on his study clearcutting approach that followed. Natural regen sites, but felt that in all probability there would be , ! H eration of woody plants follOwing early logging or in loss of growth and Douglas-fir stocking would be re ,II' tense fires readily occurred because mineral soil was duced. He suggested that partial-cutting or uneven lL exposed and seed was available fromresidual trees or age management might be appropriate for drier sites adjoining stands. Regeneration. however, varied from in southwestern Oregon, gravel soils of the Puget well-stocked. vigorous young conifer stands to dense Sound region, and severe southerly exposures else stands of red alder or sprouting hardwoods to dense where in the region (where moisture and shade are covers of shrubs with occasional conifers. A high pri critical factors). Smith (1970) suggested that th e un ority for early research was to provide methods for even-age system did not work in this region because conSistently regenerating forests after fires and tim "theoretical ecological considerations were not veri ber harvests. fied,thereby makingthe system inappropriate for th e .. . The early effortsat developing silvicu1tura1 systems future." in the Pacific Northwest included both clearcutting In retrospect, use of partial-cutting, uneven-age (Hoffman 1924, Isaac 1956) and partial cutting (Kirk management was probably discontinued for land and Brandstrom 1936). Kirkland and Brand reasons: strom proposed a method for managing Douglas-fir
and hemlock forests that partitioned the forest into • It was difficult and probably not appropriate to
relatively small tracts that were planned for timber plement a single policy or approach over such a
yield, logging systems, and regeneration. Their ideas range of forest stand oc nditions . 9. Silvicultural Systems and Regeneration Methods: Current Practices and New Alternatives 153
Inadequate attention was given to creating environ fine the regeneration niche (Grubb 1977).They pro ments and making use of treatments that would re vide a basis for understanding the response to silvi generate Douglas-fir and other conifer species. cultural practices.
• Insufficient thought was given to leaving vigorous, undamaged trees to provide adequate growingstock. Evaluation of NaturalRegeneration Practices • Logging planning and technology were inadequate to implement Kirkland and Brandsrrom's (1936) Studies of natural regeneration were integrated with ideas, especially on steep slopes. evaluation of reforestation projects.This work evalu ated applied regeneration practices, identified prob • Unfortunately, partial-cutting, uneven-age manage ment ended abruptly. Its long-term use, even on lem sites, and helped to develop alternative regener some sites, could have provided usefulinformation to ation practices (Roeser 1924). Lavender et al. (1956) design other silvicultural systems.· examined naturalregeneration on staggered settings, and Franklin (1963) assessed natural regenerationon stripcuts, small patch cuts (0.25 to 4 acres); and stag Studies of Natural Regeneration Processes gered cuttings. Considerable work has been done on Although some of the veryearly work on reproduc regeneration using the shelterwood method (Tesch tion of western conifers was with planted seedlings and Manh 1991; Laacke and Fiddler 1986; McDonald (Munger 1911), most of it focused on natural regen 1983; Seidel 1983; Laacke and Tomascheski 1986; eration, in both undisturbed forests and clearcuts. McDonald 1976b; Gordon 1970, 1979; Williamson Hoffman (1924) and Isaac (1930, 1955) studied the 1973). McDonald (1976a) studied natural regenera dispersal of seed and the possibility or storage of tion in the Sierra Nevada of mixed conifers in all five conifer seed in the forest floor. Later work by Isaac principal regeneration methods, ranging from single (1938, 1940, 1943) focused on determining the envi tree selection to clearcutting. Minore (1978) and ronmental variables that control natural regeneration Stein (1981, 1986) examined regeneration results fol and identifying microsites that favor seedling estab lowing harvesting on sites considered difficult to re lishment. For example, Lavender (1958) studied the generate in southwestern Oregon. For example, Mi effects of seeding date and ground cover on the ger nore (1978) found that shelter prevented forest minationand survival of Douglas-fir in the Tillamook damage to seedlings and saplings on the Dead In bum. Hooven (1958) studied the effects of rodents dian Plateau in southwestern Oregon, and both 1vli and other predators on seed supply. Hermann and nore (1978) and Stein (1981) and Williamson and Mi Chilcote (1965) simultaneously studied the effects of nore (1978) pointed out the value of advanced seed bed, shadl::, and insect predation on conifer natural regeneration and natural seeding among seedling establishment, while Christie and Mack planted seedlings on sites with extreme variation in (1984) and Harmon and Franklin (1989) compared temperatures, such as those described byHolbo and dead wood and mineral soil as a. substrate for hem Childs (1987) or on rockv soils that are difficult to lock regeneration. Parallel studies were underway plant. throughout the West (Haig 1936, Haig et al. 1941, Dunning 1923), including the classic work by Pearson (1923) in Arizona. Effectivenessof Advanced Regeneration Similar work was done on the regeneration of Use of advanced regeneration, established naturally hardwoods (Tappeiner et al. 1986; Fried et al. 1988; prior to logging, is a veryeffective way to regenerate Haeussler and Ta.ppeiner 1993, 1995; Tappeiner and forest stands and should be a common practice on Zasada 1993). Regeneration of forest shrubs was sites that are difficult to regenerate and in uneven studied by Gratkowski (1961), Zavitkowski and age systems (Minore 1978, Stein 1981). Helms and Newton (1968), Hughes et al. (1987), Tappeiner and Standiford (1985), Oliver (1986), Gordon (1973), and Zasada (1993), Huffman et al. (1994), and O'Dea et Tesch and Korpela (1993) developed methods for as al. (1995). These studies provide information on for sessing potential vigor of advanced regeneration fol est plant autecology and regeneration and help de lowing logging. Tesch et al. (1993) found that dam 154 Section II. Silvicultural Systems and Management Concerns L itH ::: .' \ . ," aged seedlings often recovered within three to six cuts (less than 10 acres) appear to be most suitable for . ../ .. . years. Growth of advanced regeneration was similar the regeneration of true firs at high elevations to that of planted seedlings (Korpela and Te sch 1992). (Gratkowski 1958, Gordon 1970, 1973, 1979), al though they will work for other species (Worthington 1953).
The following generalizations emerge fromstudies of • Natural reproduction is often patchy and variable. It seedling establishment and regeneration methods: may maintain a sparse forest cover, but does not en sure desired species composition, stocking. and dis
• Seed production is variable, often with six to eight tribution or timely stand reestablishment. years or more between adequate seed crops for some species.
• Seed predation rates of Douglas-fir; ponderosa pine, and hardwoods such as bigleaf maple and tanoak are Artificial Conifer Regeneration high both on the tree and on the forest floor. Needfor ArtificialRegeneration Practices
• Mortality rates during the first two to three years fol lowing germination are high. Causes are high soil Studies on planting western conifers began in the temperatures, pathogens and insects in the forest early 1900s (Munger 1911) and Show (1929). Refor f" ' • . ; floor, competition for light and soil water, litterfail, estation of the Cispus andl:acolt bums led to estab and frost. lishment of the Wmd River Nursery and extensive
planting programs. Also, the decisionto use clearcut • Douglas-fir, red alder, ponderosa pine, and true fir seedling survival is usually highest on bare mineral ting on federal lands (Munger 1950) and the TIllam " soil; spruce, hemlock, and large-seeded hardwoods ook bum (a series of fires in 1933, 1939, 1945, and "J. 'j'I-- survive well on both mineral soil and organic seed 1951 that burned over 460,000 acres and created the beds. area now known as the Tillamook Forest) stimulated
Moderate shade often aids seedling surviYal-even artificial reforestation work in the Pacific Northwest. for intolerant species- because during the summer it The Columbus Day storm of 1962 was also a catalyst reduces soil temperatures and the evaporative capac for artificial regeneration efforts. Large acreages of ity and temperature of the air near the ground, while vvindthrown timber were salvaged, and the areas in the winter and early springit reduces the chance of were planted. Prior to the Tillamook burn, the em frost. phasis had been on either natural regeneration or di
• Shady conditions that foster early seedling SUT\ val in rect seeding. Both of these methodologies were the understory of forest stands do not always favor stronglylimited by seed predation by small mammals later growth. Seedlings of most species tend to be (Hooven 1958, 1970; Schubert and Adams 1971) and shade tolerant when very young. but less so as they by the lack of seed trees {olloV\mg the intensive fire. grow older and larger. Earlyin the reforestation of the Tillamook bum, the
• Intense competition from established populations of emphasis was upon direct seeding with annual pro grasses, shrubs, and herbs may cause high rates of jects of 10,000 to 15,000 acres that were seeded with natural seedling mortality. Douglas-fir .seed treated with rodenticides such as
• Advanced regeneration can successfully regenerate a endrin. Such treatments were only partially success new stand after logging. especially on hard-to-regen ful in their goal of preventing seed predation. Also, erate sites. It may have to be augmented by seeding direct seeding was limited by seed supplies and loca or planting. tion of largecontiguous areas suitable for aerial seed
• Group selection and single-tree selection methods ing. Direct seeding accounted for about 50 percent of generally favor shade-tolerant species such as true the bum reforested, but as reforestation progressed, firs, western hemlock, western red cedar, tanoak, there was an increasing emphasis on planting. bigleaf maple, and Douglas-fir on dryand warm sites State forest practices acts in Washington, Oregon, in southern Oregon and northern California. and California also affected reforestation practices.
• Shelterwood methods and smaIl openings or cJear- The Oregon State Forest PracticesAct (1941), which 5ilvicultural Systems and Regeneration Methods: Current Practices and New Alternatives 155
required leavmg seed trees or planting, was changed past 20 years. Red alder, black cottonwood, and hy in 1971 to require that reforestation efforts on clear brid poplars are now intensively managed. All are alts must begin within 12 months, planting must be rapid-growing, shade-intolerant pioneer trees that completed within two planting seasons, and at least require bare or new soil to regenerate naturally. Nat 200 trees per acre must be "free to grow" within five ural standsof alder and cottonwood commonly occur growing seasons of planting. along streams and other areas where soil has been exposed and moisture conditions are favorable. Thus, plantations are established on moist sites or are irri gated. mortality was often high in many of the early Theprimary objective of pure red alder plantings is tit: Tree {- plantations, and research was done to increase raw material for solid wood products or fine papers. seedling survivaland growth.It had two major facets: Mixed plantings are established mostly for enhanc (1) studies of seedling size and morphology (Iverson ing site productivity (through nitrogen fixation) and 1984, Jenkinson 1980) and (2) studies of seedling forest biodiversity. Also, red alder is immune to root physiology wi particular reference upon theeffects rots that affect conifers and is often planted in areas of nursery practices such as lifting date, storage, and severely infected with Phelinlls. Although competing . fertilization upon seedling vigor (Lavender 1964; vegetation must be controlled, trees can be planted Hermann 1967; Lavender et al. 1968; Lavender and successfully without the extensive exposure of bare Hermann 1970; Lavender and Wareing 1972; Her soil needed for natural seeding. .. mann et al. 1972; Lavender 1984, 1985, 1988, 1990a, Hybrid poplar plantations have been established 1990b; Ritchie 1984). on marginal agricultural land along the lower Co As a result of this research, methods for producing lumbia and on irrigated, sagebrushsteppe land in the high-quality seedlings are available (Duryea and Columbia basin of eastern Washington and Oregon. Dougherty 1991, Margolis and Brand 1990). Now, These plantations are managed similarly to agricul foresters are able to prescribe stock types best suited tural crops and are harvested about five to seven to various microsites on harvest areas, the average . years after planting.· survival of seedlings has increased to 85 percent or better, and there is a physiological basis for under standing seedling growth potential and stress from Genetics planting or planting site conditions. For several decades basic and applied research in for est treegenetics has been an important part of artifi cial regeneration. The programs have two major ManagingYoung Plantations phases: (1) the identificationof large numbers of site Competition also affects regeneration success. Con adapted trees from breeding zones and (2) planting sequently, an extensive program of research (Walstad or grafting these genotypesin progeny test sites and and Kuch 1987) was designed to evaluate effects of ... seed orchards. p.rograms are· designed to increase competition and to develop methods for controlling yield while maintaining the genetic variability to en it when needed. Control of grasses, forbs, and shrubs sure long-term stability of artificially regeneratedfor is generally used to ensure adequate soil moisture for est stands (Hermann and Lavender 1968, Campbell seedling survival and growth. On moist sites, compe 1979, Silen 1982). tition for light by tall shrubs and hardwoods is gen erally of more concern. Guidelinesfor Artificial Regeneration
Successful artificial regeneration requires careful at Hardwood Plantations tention to the details of seed source and nursery and The role of hardwoods-ecologically and economi plantingpractices, as well as a thorough evaluation of cally-has received increasing recognition during the environmental conditions (Hobbs et al. 1992). Micro
kttz . 156 Section n. Silvicultural Systems and Management Concem
climate, competition from herbs, shrubs, and hard we present examples of some possible stand struc " -: . woods, and animal browsing affect seedling survival tures, and practices to produce them, that should be . ,', . and growth. fairly easy to implement given today's technology. Cafferata (1986) has prOvided an excellent over view of the applicationof current reforestationprac tices. Guidelinesfor conifers (DeYoe 1986, Strothman At Harvest and Roy 1984, Schubert and Adams 1971) and hard Retaining Trees and Wood woods (Ahrens et al. 1992) are available. In summary, capable professionals and technicians must be in Retaining large trees, snags, and down logs in some volved at all stages, includingthe following: ways mimics the results of natural disturbance by fire or wind agents (Spies and Franklin 1991). Natural Proper seed source and seed handling • disturbances usually do not kill all the trees in a
• Nursery procedures that optimize seedling root re standi they do, however, produce large pieces of dead t', generation potential, and storage and handling pro wood in the form of snags or logs lyingon the forest cedures in the nursery and field that minimize floor. Regenerationcan be accomplished by planting, seedlingdeh ydrationand respiration byuse of advanced reproduction, or by natural seed
• Carefulplanting, including onsite inspectionof plant ing, providing proper seed trees are left. The method ing procedures must be determinedsite-by-site. In a recent study on
• Site speci£ic prescriptions for site preparation and for MacDonald Forest nearCorvallis, Oregon, natural re weed and pest control generationof Douglas-firwas plentiful when 10 to 12 large trees per acre were left after logging (Ketchum • Monitoringfor three or more yearsto ensure seedling survival andgrowth 1995). Retention of large trees--especially those with • Early thinning to control stocking and species com pOSition large limbs andcavities-as well as large snags and logs will help ensure that a stand with diverse struc The ability to regenerate forests is demonstrated in ture develops after harvest.This is very similar to the the annual reforestation reports of the Oregon State irregular shelterwood method described by Smith oard of Forestry for 1992.lt shows that of the 85,689 (1986). After regenerationis established, shelterwood acres requiring reforestation by the end of 1992, trees are retained to produce large overstory trees 82,034, or 96 percent, were in compliance. and a multilayered stand. Leaving groups of large trees (small patches) rather than scattered individu als may be easier from a logging and reforestation
...... standpoint. Also, leaving undisturbed groups of trees I';..:!: : • : '" , Producing Stands of Diverse . . ;; may allow some plants and organisms in the forest : . :! . Structures and Habitats ." floorto survivefrom one stand to the next. Surveysof Habitat and biodiversity goals can be stated best in plant communities in areas that have been clearcut terms of forest stand structure and species composi and burned indicate that most herbaceous plants tion, Stand structure includes the vertical and hori that grow in old forests are adapted to disturbance zontal arrangement of trees, shrubs, herbs, grasses, (Franklin and Dymess 1971, Dymess 1973).They also ". and nonvascular plants, as well as such things as are commonly found in clearcuts five or more years snags, down logs, and forest floor depth. Thus many, of age. but not ali, components of stand structure are af fected by or can be produced by silvicultural prac tices. Small Openings
There are several periods in the life of a forest Making small openings, as in group shelterwood oT . stand duringwhich its structureand composition can group selection methods (Smith 1986), is similar to be altered by silvicultural practices (Table 9.1). Below smali:-scale disturbance by wind, insects, or root dis 9. Silvicultural Systems and Regeneration Methods: Current Practices and New Alternatives 157
Table 9. 1 Methods of producing mixed-species stands
ManagingYoung to Introducing Conifers in Harvest Considerations Stand Establishment Mid -Age Stands Riparian Zones
• Plant mixed species at to produce or Concentrate along • Thin and/or defer for • Thin • longer rotation varying spacings maintain large trees with certain reaches of
trees in Save advanced deep crowns streams • Retain green • groups or singly regeneration of seedlings, • Thin around hardwoods • Release advanced conifer especially trees with large saplings, poles to encourage mast regeneration limbs, cavities, or broken production • Leave parts of stand • Use large planting stock tops undisturbed bv site • Make snags and large . • Consider allvariables preparation o slash logs • Retain snags and logs on that affect conifer forest floor disposal • Release advanced tree establishment (browsing,
• Save advanced • Vary treatments to and shrub regeneration by flooding, and overstory regeneration of seedlings, consider within-stand thinning overstory trees and understory saplings, poles variability such as seeps, competition) • Protect within-stand rock outcrops, etc.
• Use irregular variation-lichens, rock • Avoid frequently flooded
shelterwoods to produce • Save patches of shrubs outcrops sites
two-story stands and hardwoods to • Under-plant with shade • Manage riparian zones in increase future stand • Regeneratea stand over tolerant species conjunction with the time using group variability upland part at the stand
selection, group • Encourage establishment • Use intensive site shelterwoods, strip of natural seedlings preparation in small, shelterwoods among planted ones by strategic areas leaving seed trees • Protect carrYover of herbaceous'and shrubby plants
• Protect within-stand variability, such as seeps and rock outcrops
Source: 1992 retorestation accomplishment report, Oregon Department of Forestry.
ease. Experience over four years in regenerating results, grandfir appears to be better suited to regen small openings (0.5 acre) on MacDonald Forest indi eration in small openings than Douglas-fir because it cates that the same reforestation methods used in is browsed much less and is more shade tolerant. larger clearcuts are applicable to small openings. The size of an opening, its aspect, andthe height of Growth and survival in the openings was not dif surrounding trees are all likely to affect regeneration ferent from that of the clearcuts (Ketchum 1995). success. On north aspects or where surrounding This trend may not continue unless op.enings are trees are tall, widening openings or thinning around widened. Just as with clearcuts, animal browsing them may be necessary to increase light and growing and shrub competition affect seedling survival and space for the young conifers. Natural Douglas-fir re . growth. generation was not plentiful in these small openings, There is a great deal of variability among openings: most likely due to lack of soil disturbance. It was Some with high light intensity developed covers of plentiful in adjoining stands where 10 to 12 trees per grass or low shrubs; others with low light levels be acre were left. came dominated by tall shrubs.Based On fourth-year In this study we used only O.S-acre openings for l '" 158 Section II. Silvicultural Systems and Management Concerns
experimental purposes. In practice, larger openings Shruband Hardwood Management " or a variety of opening sizes might be more appro Managingsh rub and hardwood density at the time of priate for biological, administrative, or economic rea regeneration will affect the species composition and sons. structureof the next stand. The models developed by Harrington et a1. (1991a, 1991b) for tanoak and Pa
.. cific madrone and by Knowe et al. (1995) for bigleaf >.'"
.', Young Stand Establishment maple estimate the amount of cover produced by
Use of Advanced Reproduction sprouting hardwoods, the effects on conifer Survival and Mixed Species Planting and growth rates, and the effects on the stocking of understory shrubs and herbs. Such models will help Current methods of planting and tending young forest managers forecast the development and influ stands can be altered to produce stands of diverse ence of hardwoods during early stages of stand es structures and species compositionafter fire, harvest tablishment. ing, or other disturbances. Poles, saplings, and Shade-tolerant hardwoods like tanoak and bigleaf will seedlings (fromthe previous stand) help acceler maple can be managed in groups to produce a sec ate the regeneration of the next stand. In addition, ond layer in parts of the new stand while not shading they will probably encourage more patchy stands and out understory shrubs or herbs or substantiallv re . . a variety of tree sizes andspecies (Tesch andKorpela ducing the growth of conifer regeneration in the rest 1993). of the stand. Typically, they are overtopped by Mixed species planting will produce multilayered conifers at about 40 to 50 years of age. Large over stands because of differential species growth pat topped hardwoods provide cavities as large branches terns. For example, Douglas-fir and western red die and decay. cedar planted together may form a two-story stand. On coastal sites, red alder natural regeneration Cedar grows slower than Douglas-fir, it is more sus often is abundant in conifer plantations. Mixed alder ceptible to brOWSing, and it's shade tolerance enables conifer stands could be established by spacing alder it to survivein the understory. during precommercial thinning. Like tanoak and . Mixed stands of red alder and conifers have been maple, alder's early height growth is much greater shown to be more productive than pure conifer . than that of new conifers. Therefore, it would have to ; stands in soils with low nitrogen levels (Tarrant and be spaced to enable conifers to grow among it. Un . ; . , !, Miller 1963, Tarrant 1961). These mixed species ';',,', like other hardwoods, alder is not likely to survive stands potentially can benefit some wildlife species. beneath conifer stands. Professors William Emrningham and Denis Lavender have established mixed plantations of these species at the research forest of Oregon State University's Regeneration inYoung to Mature Stands College of Forestry. Their purpose was to use alder's nitrogen-fixingability to increaseDouglas-fir growth Thinning and Tree Regeneration and to produce more diverse tree and herbaceous In the Douglas-fir region there are many layers than might occur in pure Douglas-fir. Because stocked young stands (10-50+ years of age) that of alder's rapid juvenile height growth rate and its established followingfire or timber harvest.About ability to overtop Douglas-fir within three to four to 60 percent of most watersheds on federal land years after planting, alder was planted when the stocked with these young stands. For the most Douglas-fir were over 15 feet tall. If alder is to be they have been regenerated and managed at used only as a source of nitrogen,Tarrant and Miller densities (150 to 200+ trees per acre) to. (1963) suggest that a.I! off-site alder seed source wpod, not to develop diverse structures. In might be used so that frost damage would keep it old-!rrowth stands often have onlv 10 to 30 trees o _ from overtopping the Douglas-fir. acre (Spies and Franklin 1991). Thus; to help 9. Si1vicultural Systems and Regeneration Methods: Current Practices and New Alternatives 159
is old-growth characteristics in these younger stands, inches, and there practically no understory devel ed to pro considerable reduction in stocking is need opment. duce large trees with deep crowns and provide a Pure red alder standsare common in riparian areas IXlOre open environment for understory develop and on sites with northerly exposure, especially in ment. Seedlings can be established under higher coastal forests. However, some conifer component overstory densities (100-150 trees per acre), but often is desirablein these stands to provide large logs canopy densities need to be reduced to ensure un for stream channel structure and to produce a more derstorv development. diverse forest for wildlife. Emmingham et al. (1989) T1Uncing and regulation of overstory density can successfully regenerated western hemlock under produce large trees quickly, develop stand structure, thinned red alder stands. Both overstory density re and generally aid the development of old-growth duction and intensive salmonbeny control were characteristics (Newton and Cole 1987, Curtis and needed to establish hemlock. Release of advanced Marshall 1993). In addition, thinning to improve conifer regeneration from red alder also can be used wood vields can release advanced conifer and hard to grow large conifers in some riparian areas. wood egeneration in the understory and ultimately produce multilayered stands. There are often numer Shrub Regeneration ous hardwood and conifer seedlings (Tappeiner and McDonald 1984, Fried et al. 1988) in the understory Thinning also will favor regeneration of shrub under of stands 50 or more years of age that will respond to stories. Salal (Huffman et al. 1994) and salmonberry a reduction in overstory density. In dense stands with (Tappeiner et al. 1991) clonal development and rhi no tree understory, increased light and some soil dis zome extension increase with reduction of overstory turbance favor establishment of both conifer seed denSity. Vme maple clones are spread by "layering" lings (Del Rio and Berg 1979) and hardwood seed as a result of thinning. Slash from naturaldisturbance lings (Fried et al. 1988, Tappeiner et al. 1986). of the overs tory or from commercial thinning pins In a western Oregon study that compared under the vine maple crowns to the forest floor where the story characteristics in thinned and unthinned Dou branches often root and form a dense understory of glas-fir stands, one of. the most striking differences new sprouts (O'Dea et al. 1995). Establishment of between the stands was the stocking of natural salal, vine maple, and salmonberry seedlings also is conifer seedlings in the understory of the thinned favored by thinning-however, their· rate of expan stands O. D. Bailey; personal communication, 1996): sion and the development of a dense cover probably Additional thinning to mimic natural stand develop is slower than that of vegetative clonal expansion. ment could release conifers and hardwoods and (Huffman et al. 1994, Tappeiner and Zasada 1993, leave the overstory at variable densities to encourage Tappeiner et al. 1991). Because of the potential for patchy understory development. rapid clonal expansion of shrubs, there may be a rel Shade tolerant conifers can be planted in the un atively narrow window for establishment of new derstory following thinning to develop multilayered plants by natural seeding or planting Without the stands. Professor Alan Berg at Oregon State Univer need for vegetation control. sity thinned a 40-year-old Douglas-fir stand to 50 trees per acre and planted western hemlock in the derstory. Now, apprOximately 40 years later, there Natural Succession IS a well-developed two-storied stand (Curtis and Marshall 1992, 1993).At 80 years of age, the overstory Our studies of the ecology and development of forest of 50 trees per acre is probably too dense for contin stands and our observations of forests in the Coast ued understory growth. In this example, the average Range of Oregon lead us to the hypothesis that many diameter of the Douglas-fir trees is about 30 inches. young stands in these forests will not naturally de In the unthinned stand, tree diameters average 15 velop cohorts of multistoried conifers that are con 160 Section n. Silvicu1tural Systems and Management Concerns
sidered to be typical of old growth (Spies and Conclusion Franklin 1991). Stands in the western hemlock zone often have well-developed understories of shrubs Continued research and practical experience are crit
(e.g., salal and vine maple) and little conifer regener ical to the successful implementation of the stand ation in the understory. Studies of natural regenera management treatments suggested above. Key issues bon suggest that these shrub layers will continue to requiring further investigation include the follOwing: prevent the establishment of conifers. Similarly, alder
stands that were established on many acres following • Information on the reproduction andgrowth of hard woods, conifers, and shrubs in the understory of logging frequently have well-developed understories ' as as of salmonberry, sword fern, and elderberry (Carlton conifer stands, well the effects of understory and overstorydensity on other components of the e osys 1988, Henderson 1970). As the short-lived alder dies, tern it is likely that many of these stands will be domi
nated by a dense cover of salmonberry that may per • Use of different types of stand structures by 'wildlife sist and prevent the establishment of conifers for spedes-for example, use of snags. wood on the for est floor, and shrub and tree understory layers many decades.
Thus we believe that in many cases natural succes • Growth and development of mixed species stands sion in today/s forests will not produce the same and old stands over 100 years old kinds of stands and habitats as it has in the past. Rea Practicality of implementing these different types of sons for this may be a combination of the following: treatments
• Landscape evaluations of a range of silvicultural sys • The lack of fire in these forests over the past 75 years or more has resulted in development of dense shrub tems and treatments (through space and time) to understories. evaluate their effect on wildlife populations
• Effects of stand density on insects, pathogens, wind • Exotic species have become established. throw, etc., on the morphology and strucrure of Logging has changed species composition and seed • conifer trees. supply and has favored the development of shrubs and hardwoods with the potential for vigorous The art and science of silviculture is continuing to sprouting. evolve. Fortunately, there is a good foundation of re S • tands that are established after logging are often search information and practical experience on more heavily and uniformly stocked with Douglas-fir which to build new practices for the future. The suc than the original natural stands. cess of silvicultural S)'sterns and regeneration meth
• Oimate or weather patterns are different today than ods will depend to a large extent upon public percep they were when the present old-growth forests de tion and acceptance. Increasingly, societal pressures, veloped. not always based on reliable information, constrain Consequently, treatment to facilitate understory the use of practices that would yield positive long conifer establishment and reduce shrub density and term results in terms of habitat, wood production, overstocking of the conifers in the overstory is likely and biodiversity. Therefore, forest managers and re
to benefit the development of old-forest characteris searchers need to involve the public in the develop tics on many sites. ment of alternative silvicultural systems.
I' i.: F , Literature Cited ,. I· '" Dobkowski, D. 1992. Red overview: Western Oregon and W gto In Dougltls ," Ahrens, G. R, A and E. Hibbs. ashin n. ", iii alder guidelines for successful regeneration. Special publi firstand managementfor the future, ed. C. D. Oliver, D. P. iii cation 24. Corvallis, OR: Forest Research Lab, Oregon Hanley, and J. A. Johnson. Seattle: College of Forest Re State Univ r t i'li11 e si y. sources, UniverSity of Washington. ,Ii Cafferata, S. L. 1986. Douglas-fir stand establishment Campbell, R K. 1979. Genecology of Douglas-fir in a wa
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Carlton, G. C. 1988. The structure and dynamics of red Gordon, D. T. 1970. Natural regeneration of white and red/ir: alder communities in the central coast range of western Growth, damage, mortality. Research paper PSW-RP-58. Oregon. M.S. thesis, Oregon StateUniversity, Corvallis. Berkeley, CA: USDA Forest Service.
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ment. General technical report PNW-GTR-137. Wash Tappeiner, J. c., J. c. Zasada, P.Ry an, and M. Newton. ington, DC: USDA Forest Service. Salmonberry donal and population structure: The for a perSistent cover. Ecology 72:609-618. Smith, D. M. 1970. Ap plied ecology and the new forest. In Joint Session Proceedings of Western Forest Fire, Pest, and Tarrant, R F. 1961. Stand development and soil fer tilitv. in Reforestation Coordinating Committee. Vancouver, BC, Douglas-fir-red alder plantation. Forest Science Canada: Western Forestry and Conservation Associa 246. tion. Tarrant, R. F., and R E. Miller. 1963. Accumulation of --. 1986. The practice of silviculture. New Yo rk: John ganic matter and soil nitrogen beneath a plantation Wil ey & Sons. red alder and Douglas-fir. Soil Science Society of Spies, T. A, and J. F. Franklin. 1991. Thestructure of natural Proceedings 27:231-234. young and old-growth Douglas-fir forests in Oregon Te sch, S. D., and E. J. Korpela. 1993. Douglas-fir and and Washington. In Wildlife and vegetation of unmanaged . fir advanced regeneration for renewal of mixed Douglas-firfo rests, ed. L. F. Ruggiero et. al. General tech forests. Canadian Journal of Forest Research nical reportPNW-GTR -285. Portland, OR: USDA Forest 1437. Service. Te sch, S. D., and J. W. Mann. 1991. Clearcutand shelltero'Xlnll Stein, W. 1. 1981. Regeneration outlook on BLMl12nds in the reproduction methods fo r regenerating southwest southern Oregon Cascades. Research paper PNW-RP forests. Research bulletin 7'2.. Corvallis, OR: Oregon 284. Po rtland, OR: USDA Forest Service. University. --. 1986. Regeneration outlook on BLM l12nds in the Te sch, S. D., K. B. Katz, and E. J. Korpela. 1993. Recovery Siskiyou Mountains.Research paper PNvV-RP-349.Port Douglas-fir seedlings and saplings wounded land, OR: USDA Forest Service. over story removal. Canadian Journal of Forest
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Creating a Forestry fo r the 21st Century I ; The Science of Ecosystem nagement I . I i 1
.Edited by KathrynA. Kohm and Jerry F. Franklin by Jack Ward Thomas
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Creatinga forestry for the 21st century: the science of ecosystem management I edited byKathryn A Kohm & Jen)' F. Franklin.
p. ern. Includes bibliographical references and index. ISBN 1-55963-398-0 (cloth). - ISBN 1-55963-399-9 (pbk.) 1. Forest management-Northwest, Pacific.2. Forest ecology Northwest, Pacific. 3. Forests andforestry-Northwest, Pacific. 4. Ecosystem management-Northwest, Pacific. 5. Forest management 6. Forest ecology. 7. Forests and forestry. 8. Ecosystem management. 1. Kohm, KathrynA IT.Franklin, Jeny F. SD144.A13C74 1997 634.9- Printed on recycled, acid-free paper @ Manufactured in the United States of America 10 9 8 7 6 5 4 3 2 1