Harvesting Timber to Achieve Reforestation Objectives Christopher B. Jarmer John W. Mann William A. Atkinson Introduction 203 A Review of Harvesting Systems 204 Ground-based systems 205 Cable systems 206 Highlead 207 Skyline 208 Aerial systems 209 Harvest Planning to Achieve Reforestation Objectives 210 Harvest planning philosophy 210 Selecting the harvesting system 210 Planning the project 213 Marking leave trees 214 Designing the harvest pattern 215 Ground-based systems 215 Cable systems 217 Harvesting Operations 219 Ground-based systems 219 Cable systems 221 Minimizing Damage to the Residual Stand 222 Ground-based systems 222 Cable systems 223 Site Preparation and Planting 225 Maintaining Site Productivity 225 Harvesting Considerations in Uneven-aged and Alternative Silviculture 226 Summary 227 Literature Cited 228

202 Harvesting Timber to Achieve Reforestation Objectives 203

The methods chosen to accomplish non- INTRODUCTION clearcut harvesting methods will vary depending on silvicultural objectives and on whether resid- Besides providing a commodity, timber har- ual trees will be retained for relatively short vesting alters the characteristics of an existing periods (as in conventional shelterwood manage- stand on a forest site. The nature of this distur- ment) or for the entire rotation (as in some alter- bance varies widely depending on the approach native silvicultural proposals such as those to harvesting and the equipment used. When being explored in the Forest Service's New the harvest is carefully planned, the disturbance Perspectives program). Operational costs and the can be managed to help meet other resource skills required of personnel will also vary with objectives, especially over the long term. The frequency of entry, ruggedness of the terrain, harvesting operation can help provide the oper- amount and type of residual to be retained, and ational environment necessary to promote refor- other factors. estation and the development of target species Understanding the importance of harvesting and stand structures. In fact, timber harvesting in relation to reforestation is best approached is one of the few tools available to silviculturists in an interdisciplinary manner. Coordination for making significant alterations to current between harvesting specialists and silviculturists species composition or stand structure if man- is essential; since harvesting is a part of silvi- agement objectives should call for this. Others culture, the silvicultural prescription must on the short list of such tools are prescribed include the harvesting plan. Preparing a timber burning, machine site preparation, and applica- harvesting plan without dialogue between the tion of fertilizers and chemicals (Tesch et two disciplines often leaves a site poorly pre- al. 1990). pared for reforestation, with resulting higher Harvesting strategies fall generally into two costs of site preparation and planting. Equally main categories: those in which all trees are ill-conceived is the silvicultural prescription pre- removed and those in which some trees are left pared without harvesting input. Such a prescrip- in place. Both these strategies can be managed tion may accomplish some of the silvicultural to promote successful reforestation. In the first goals, but at unnecessarily high harvesting caseclear-cuttingthe chief considerations are costs. The harvest plannerswhether in public operational efficiency and ease of reforestation. agencies or private industrymust be good com- In the seconda set of harvesting techniques municators and must understand the capabili- associated with the range of regeneration meth- ties and limitations of harvesting systems. Also, ods from shelterwood through group selection to sufficient care must be given to inspection of the single tree selectionmore care is required to logging operations. promote a favorable environment for new trees In addition, good communication between the while protecting existing regeneration and resid- harvesting specialists and the sale administra- ual trees. tor is necessary to make sure the job is done 204 Harvesting Timber to Achieve Reforestation Objectives

Table 9-1. A comparison of characteristics for harvesting systems used in southwestern Oregon and northern California.

Harvesting system Comparison factors Ground-based Cable Aerial Yarding direction Flat to downhill Up- or downhill Up- or downhill

Yarding distance 1,200 ft 4,000 ft 7,500 ft (Practical maximum)

Ground disturbance Most Minimal Landing/service areas only

Costs Lowest Higher Usually highest

Control over resid- Good Fair Best ual stand damage

Forest worker Safe Dangerous Fairly safe safety

Production levels Low-medium Low-high High-very high

according to the plan. The final key to success reforestation in the context of such methods tends or failure is the people who do the actual timber to require more harvesting care and skill than does harvesting work. Future management options for regenerating after clear-cutting. The chapter the stand ultimately rest in the hands of equip- includes a short review of harvesting methods used ment operators, timber cutters, and choker set- in the region, a discussion of timber harvest plan- ters.These workers must understand the ning as it relates to reforestation, a discussion of objectives and desired results of each harvesting the reforestation implications of harvest opera- job. Their cooperation and conscientious effort tions, and a brief treatment of these concerns as while cutting and moving logs from stump to land- they apply in particular to uneven-aged and alter- ing is essential in making the logging techniques native silviculture. dovetail en-vironmentally and economically with the reforestation plan. This chapter will not be a rigorous treatment of harvesting technology. That topic is a textbook in A REVIEW OF HARVESTING itself, and since several such texts already exist SYSTEMS (Studier and Binldey 1974, Conway 1982, Stenzel et al. 1985), readers can seek these and other Timber harvesting is both a manufacturing pro- sources to find specific information about harvest- cess and a transportation process. Standing trees ing technology. The chapter will instead concen- are felled and manufactured into logs. Value is trate on how harvesting interacts with the added to the product along the waylogs on the reforestation process in southwestern Oregon and ground, bucked into lengths preferred by the northern California. Our discussion focuses in sawmill, are worth more than standing trees. Logs particular on the array of regeneration methods must be transported, first from the stump or felling that call for retaining overstory trees and surviv- site to a landing area (primary transportation), and ing regeneration beneath the canopy: both then by truck, rail, or water to a processing fa- because, for a variety of reasons, they are being cility (secondary transportation). Primary trans- prescribed more and more, and because achieving por-tation is the aspect of harvesting that has Harvesting Timber to Achieve Reforestation Objectives 205

Figure 9-1. Optimum yarding distances and slope percent for different logging systems used in southwestern Oregon and northern California. From Studier and Binkley (1974). the greatest impact on the forest site and the oper- schematic display of yarding distances and terrain ational environment for reforestation. To be limitations for the basic harvesting systems. A sure, well-planned harvesting operations must comparison of the amount of ground disturbance integrate both primary and secondary transporta- caused by each is shown in Figure 9-2. Other char- tion systems; selection of one harvesting system acteristics are compared in Table 9-1. over another will affect road density, for example. which in turn affects the ability to use prescribed fire. However, this chapter will concentrate on Ground-based Systems the connection between primary transportation Yarding, or primary transportation, is defined as and regeneration. the initial movement of logs from the felling site to The various timber harvesting systems in com- a landing area in preparation for further transport. mon use in the region fall into one of three cate- In a ground-based yarding system, the yarding gories: ground-based (tractors and skidders), cable machine travels to or within winching distance of (highlead and skyline), and aerial (mostly heli- each log being yarded. Yarding can be done by copters). Each of these has its own capabilities, animals (mainly draft horses), tracked vehicles limitations, costs, and effects on the site. A good including both rigid-tracked machines (crawler- understanding of the capabilities of each system tractors) and flexible-tracked machinesand is essential if the operational environment for four-wheel-drive articulated tractors (rubber-tired reforestation is to be optimized. Figure 9-1 gives a skidders). Yarding with horses has been done 206 Harvesting Timber to Achieve Reforestation Objectives

50 cies can sometimes be used on steeper slopes if the steep areas occur in short pitches with gen- 40 erally more gentle slopes surrounding them. A key question when considering the use of ground-based machines on steeper slopes is whether or not skid trails will be excavated into 20 the hillside. Excavated skid trails are safer because they are more level, but they can be unsightly and can cause soil displacement. A key environmental concern in harvesting with ground-based equipment is soil compaction. Tractorl Highleadl Helicopter2 Compaction by ground-based logging equipment 1 From Dyrness (1965, 1967, 1972) has been shown to reduce tree growth (Perry 2 From Clayton (1981) 1964, Foil and Ralston 1967, Moehring and Rawls 1970, Holman et al. 1978, Froehlich 1979, Wert and Thomas 1981). The amount of growth reduction on a given site depends on the increase 60 in soil density, depth of compaction, and per- centage of compacted soil around the roots. Severely compacted soils may also impede tree 40 planting. Crawler-tractors, rubber-tired skidders, and 20 draft animals vary in their compacting effect on the soil when only the first five passes are con- sidered. However, when more passes are made (as on any main skidding trail), the resulting total Tractor Highlead Skyline Helicopter soil compaction is often not significantly different among the three operations (Froehlich 1980). The Figure 9-2. Comparisons of soil disturbance from most effective way to reduce soil compaction different logging systems. Ranges are also shown. in ground-based operations is to designate skid (A) Percent compacted. (B) Percent mineral soil trails so that the area affected by the skidding exposed. machines is kept below 10 percent of the total harvesting area (Garland 1983). Properly desig- nated skid trails can also increase the efficiency of logging operations. recently in southwestern Oregon. but the practice Istypically used only in small-scale operations and In areas where mechanized systems are restrict- Cable Systems ed. Most ground-based yarding in the region is Cable yarding systems have proved their use- done with machines. fulness in the mountainous terrain of the region. Ground-based systems are usually the least Cable systems transport logs from the felling site expensive of all the harvesting systems when to a landing area by a yarder equipped with mul- applied to the appropriate terrainflat or gently tiple winches. In contrast to ground-based log- sloping ground. On steeper terrain, ground-based ging, the yarder remains in a stationary position. systems can be not only more costly but opera- Long lengths of wire rope are spooled off the tionally more difficult and more dangerous yarder's winch drums and suspended over the for workers. Practical limits to the slope of the harvesting area to transmit the pulling forces ground are usually considered to be about 40 per- necessary to move logs. cent for tractors and 25 percent for skidders. These Cable systems, once used mainly to log clear- limits are not absolute: ground-based logging vehi- cuts, are well suited to yarding other types of Harvesting Timber to Achieve Reforestation Objectives 207

Guyline

Hau!back line

Mainline

Mobile spar Haulback & yarder Hau!back strap block Butt-rigging shackle Butt-rigging Dumm swivel Luka swivel

Haulback line Buzzard hook Line swivel Chokers Mainline Butt hook (:Zz o 4:17 ") Strawline hook Strawline \-Rig-up Rig-up block block strap Butt-rigging

Figure 9-3. The highlead yarding system. From Studier and Binkley (1974). harvest patterns as well. Cable systems have advantages in areas where ground-based systems Highlead are inadvisable because of traction, stability, safe- The highlead system is the simplest form of ty, and site-impact considerations. Depending on cable logging used in the region. This system has the yarding system, logs can be pulled uphill, two operating lines, the mainline and haulback downhill, or along the terrain contour. Yarding dis- line. These are connected at the butt-rigging, a tances of more than 5,000 ft are possible, but series of swivels and other hardware that keep the a more realistic average maximum for systems lines from twisting. The butt-rigging also serves as used in this region is about 2,000 ft. These long the attachment point for the chokers that are fas- yarding distances give cable systems two impor- tened around the logs being yarded (Figure 9-3). tant advantages over ground-based systems: The mainline pulls the butt-rigging and logs to the (1) fewer haul roads are needed, and (2) ridgetop landing, and the haulback line pulls the butt-rig- roads can be used; these minimize soil movement, ging and mainline back to the logging area for the lessen the visual impact of roading, and provide next turn of logs. Lateral yardingbringing logs ready-made fire breaks in strategic locations. In from the side of the cableway into the path of the general, cable logging results in less site distur- mainlineis limited to the length of the chokers. bance than ground-based systems, but it tends to Therefore, the highlead method is best used for be more expensive. clear-cutting. It is not well suited to regenera- 208 Harvesting Timber to Achieve Reforestation Objectives

Guyline

Skyline

Mainlines

Mobile tower Landing Mechanical slackpulling carriage

Haulback block and strap

Tail spar Skyline

Haulback line Mainline \I-laulbackline

Slackpulling line Haulback block Dropline and strap

Figure 9-4. A typical skyline yarding system. From Studier and Binkley (1974). tion methods in which overstory trees are re- tained or survival of seedlings or advance regener- Skyline ation is desirable. In skyline logging, a cableway, the skyline, is The highlead system is, for the most part, a suspended between two points to serve as a track ground lead system; the entire length of the log is for a block or carriage (Figure 9-4). Because sky- skidded along the surface of the ground. One end lines can be used to yard timber from difficult har- of the log can be lifted clear of the ground if neces- vesting sites with very little soil disturbance, they sary; to accomplish this, the yarder operator are an important improvement over the highlead applies the brakes to the haulback drum while method. Appropriately rigged skylines can also pulling in on the mainline drum, a procedure yard logs laterally to the skyline corridor. Logs are called "tightlining." However, this procedure is then moved along the skyline either completely hard on yarding equipment and is usually done suspended or with one end on the ground, depend- for only short distances to avoid obstructions. ing on topography and type of equipment used. Thus, highlead logging can cause considerable dis- Logs can be moved either up- or downhill. These turbance to the soil and to logging slash. This may capabilities make skylines applicable both to clear- be an adverse impact in steep areas with highly cutting and to situations in which some portion of erodible soils. If soil erosion is not a major con- the existing stand is to be retained. cern, the highlead method can often provide some Many different types of skyline yarders and rig- site-preparation benefits, sometimes negating the ging configurations are available. The important need for prescribed burning or mechanical site- thing for silviculturists to know is that skylinesys- preparation treatments. tems will generally cause less soil disturbance ona Harvesting Timber to Achieve Reforestation Objectives 209

Table 9-2. A comparison of highlead and skyline cable yarding systems.

Highlead characteristics Skyline characteristics

Rigging Uses butt-rigging to connect main Uses carriage to ride the skyline and and haulback lines and chokers. as choker connection point. Lift Limited lifting capability, unless Greater lifting capability with drum brakes can maintain tension in shelterwood; full suspension of lines-a ground lead system. logs possible. Lateral reach Lateral yarding distance limited by Depending on carriage design, can choker length. accomplish lateral yarding. Silvicuftural system Principally a clearcut system. Can be used for all situations. Soil disturbance Because a ground lead system, more Because of suspension capabilities, soil disturbance expected. less soil disturbance. Yarding costl Generally more expensive than skyline Because of better outhaul speed and at longer distances. suspension, about 50-75% less than highlead. Productionl Good for short distances, but Depending on distance and other generally less than skyline. yarding conditions, 25-100% greater than highlead.

1Adapted from Dykstra (1975). given site than either ground-based or highlead however, as environmental and aesthetic concerns systems. Some pertinent comparisons between become more important. the highlead and skyline systems are shown in Aerial harvesting operations are considerably Table 9-2. different from ground-based or cable systems. A typical helicopter yarding cycle consists of (1) flying from the landing to the log pick-up area, (2) Aerial Systems hovering over the logs while a worker on the Aerial harvesting systems, those that employ ground attaches chokers to a hook at the end of a helicopters and balloons to yard timber, are less cable, (3) lifting logs out of the pick-up area, and (4) common than other systems. Because balloon log- returning to the landing where the logs are elec- ging is very uncommon, we will concentrate on tronically disengaged from the hook. Often another helicopters in this discussion, but the concepts of light-utility helicopter returns chokers to the rig- vertical-lift logging apply equally well to helicopters ging crews as required. Operations are interrupt- and balloons. ed about once an hour for refueling and twice a Helicopters were first used for timber harvest- day for scheduled maintenance. ing in the region in the early 1970s. To date they Because high volumes of timber can be moved in have accounted for only a small portion of the total a short period of time with helicopters, two or more timber harvest because they are typically more landings will often be used. The helicopter can expensive than other harvesting systems. This sit- either alternate between landings or fill one uation may change dramatically in the future, landing completely and then move to the other. 21 0 Harvesting Timber to Achieve Reforestation Objectives

Roads themselves can be used for landing logs, plan a silviculture project, they must understand but safety concerns and other operational difficul- how the harvesting operation will contribute to ties can arise. achieving silvicultural objectives and, conversely, The aerial system is less constrained than oth- how silvicultural requirements influence the har- er harvesting systems by yarding distance and tim- vesting operation. ber volume per unit area. A helicopter can often economically yard logs a mile or more. Very low timber volumes per acre are acceptable provided Harvest Planning Philosophy the volume is in relatively large logs or concentrat- In all harvesting operations, no matter what ed in a few areas, or both. Yarding with helicopters type of equipment is used, some "logging footprint" Is dramatically more costly if many small pieces is imposed on the ground. The character of this must be gathered together to make up a load. One footprint, or area of disturbance, depends on the or two relatively large trees per acre may prove to harvest plan. For instance, the footprint left be quite economical to yard, while many small by ground-based yarding systems consists of the trees per acre may not (Studier and Neal 1990). area disturbed by skid trails, landings, and access Fog, shifts in wind direction, or other weather- roads used to remove timber. For cable sys- related problems can greatly affect the cyclical tems, the footprint is limited to roads, landings, operation of aerial logging. Also, machines may not and the small areas of the skyline corridors (or be available when and where they are needed. On highlead roads). In aerial systems, the footprint is the plus side, aerial logging causes none of the minimal and consists of access roads, if needed, ground disturbance associated with other harvest- and landings. In all operations, of course, the ing systems. Moreover, damage to the residual impact of the falling trees must be considered as stand is negligible because logs are lifted straight part of the footprint. up and flown to the landing free of the ground. The area covered by the logging footprint is the Some other advantages are: area with which protection measures and amelio- Little, if any, road construction is needed in rating steps are concerned. In brief, managing aerial systems. harvesting operations in the context of regenera- They can be used on any terrain. tion methods consists of ensuring that this foot- They can be used in both even-aged and print provides the best possible operational uneven-aged silvicultural systems. environment for successful reforestation. They can work in highly sensitive visual- resource areas where other systems would not meet management objectives. Selecting the Harvesting System They can move large volumes quickly and are The fundamental principle in selecting a har- thus well suited to rapid harvest of timber dam- vesting system is to choose one that lends itself aged by fire, insects, and disease. to both site conditions and the management objec- tives for the site. To arrive at the best possible match, three different but related questions must be addressed: HARVEST PLANNING TO What is the physical feasibility of this system? ACHIEVE REFORESTATION Can the harvest be accomplished readily, with a OBJECTIVES reasonable expenditure of energy, while creat- ing a good operational environment for suc- The plan for timber harvesting cannot logically cessful reforestation? be isolated from the other planning steps impor- What is the economic feasibility of this system? tant to reforestation success (Mann 1985b). Each Will there be an acceptable return on invest- step is interrelated, with harvesting used to ment? Will some other system be less expen- accomplish much of the work that must be done sive in the long term? to meet silvicultural objectives. When resource What is the operational feasibility of this managers of different disciplines work together to system? Are the equipment and the harvesting Harvesting Timber to Achieve Reforestation Objectives 211

Yes Is ground slope limited to <35%

No

Yes Will ground-based Are steeper pitches systems meet resource limited in number and soil management No and length? objectives?

Yes Yes Is this a thinning or selective harvest? Will cable systems meet management No Ilk No objectives; i.e., soil, water, and visual impact? Yes I Is soil compaction a major consideration? 117 Yes 4, No No Are cable systems economically feasible? Use designated skid "Loggers choice" trailslow-impact patternany machinery (use winch ground vehicles; Yes and line pulling) i.e., grapple skidders and crawlers, feller-bunchers

Willa cable system and the Are aerial systems corresponding transportation economically feasible? plan provide greater No presentnet worth than Yes No 1 aerial systems? Use horses or other animals if feasible Yes Re-evaluate management objectives for this area Cable yarding systems Aerial system; (Continued on next page) i.e., helicopter or balloon

Figure 9-5. Flow chart for matching harvesting system tosite and management objectives. expertise available in the immediate area must be made (Figure 9-5). Thoughtful choices sufficient to do the job, or will specialized equip- at these points will lead planners toward the ment and specially skilled workers have to be best harvesting system or systems for a given sit- brought in? uation. Planners must thoroughly understand the intricate operational and economic details Developing answers to these questions is not of harvesting in order to make consistently always a straightforward analysis. More often good choices. it is a complicated process in which many dif- When silvicultural prescriptions require reten- ferent factors must be weighed. However, there tion of some portion of the existing stand, the are several identifiable points at which decisions characteristics of the stand to be left after each 212 Harvesting Timber to Achieve Reforestation Objectives

No Is full suspension required to meet management objectives? Yes lir Is partial suspension required or desirable? Questions/concerns Yes Clearcut Yarding distances Cutting prescription Thinning 0-200 ft200-800 ft 8010 ft t Selective* Lateral yarding required? / Slope steepness Highlead Landing size limitationsTimbersize system no. of log sorts 1 Road network in place? Shovel logging and/or winching with ground-based systems Equipment (yarders, carriages) available? Logging expertise available?

Uphill vs. downhill yarding

Yarding distances necessary *Selective harvestaerial system may Convex vs. concave slopesSingle span? be best due to economic difficulty Mutti-span? associated with low volume/large areas Special considerations: and the use of cable systems Riparian zones Wildlife leave trees Visual impacts

Skyline system typescapabilities/limitations Standing skylineskyline length fixed, slackpulling carriage required, long yarding distances possible, two-drum yarder required, all multi-span skylines this type. Running skylineuphill or downhill, clear-cut or other regeneration methods, lateral yarding with correct carriage, interlock drums desirable. Live skylinegravity outhaul with uphill yarding only, clear-cut or partial cut with proper carriage, lateral yarding with proper carriage. Slackline systemuphill or downhill, long yarding distances possible, good for full suspension, three-drum yarder required, can be expensive. Multi-span sytemgood for convex slopes, broken terrain, uphill or downhill, good for thinning, supports require additional rigging time and expertise. Figure 9-5 (continued). entry should be assessed. The number, size and Here is an example of how data and calculations distribution of residual treeswillinfluence what can be used to help determine the logging footprint can be done in the harvesting operation, whatever within a harvest area, and hence, the need for spe- system is proposed. The more trees remaining on cial harvesting considerationsin this case, deter- the site, the greater the difficulty of harvesting mining the need for stage felling in a shelterwood operations and the potential for damage to regen- overstory removal. If some assumptions are made eration during subsequent entries. based on Paine and Hann's work with crown Harvesting Timber to Achieve Reforestation Objectives 213

Table 9-3. Tree dimensions by diameter and percent of area covered when trees are felled from stands with 50-percent crown ratio.

Species DBH (in) Height (ft) Crown width Area in Trees per Maximum (ft) footprintl acre3 %of (ft f 2 area covered 4

Douglas-fir 18 100 30 825 30 57 24 130 38 1,365 20 63 30 150 44 1,837 14 59 36 170 50 2,380 11 60 48 190 59 3,182 8 58 60 200 65 3,750 7 60 Ponderosa pine 18 80 25 560 44 57 24 110 31 962 29 64 30 130 36 1,332 21 64 36 150 41 1,762 16 65 48 160 49 2,280 12 63 60 180 54 2,880 9 60

1 Area in footprint for trees of various diameters according to model developed in Figure 9-6. 2Percent of area covered by felled trees = area in footprint x trees per acre -I- 43,560ft2(100). 3No tree overlaps another. 4Single-stage felling.

dimensions (1982), the ground area a tree will occupy when it is felled can be estimated (Figure 9-6 and Table 9-3). If significant damage to the understory is expected from felling or yarding, it may be advisable to plan for overstory removal in stages, so that the footprints from the first-

F stage entry can serve subsequent entries.

Planning the Project IP. h/2 2 Here are some important points to Area within imprint of felled tree [-Iix61+ x remember in the project planning y, h in ft phase: d in inches Equipment should be suitable to the size of the timber. The logging pattern should be matched to the equipment. For instance, if trees to be removed in Figure 9-6. Dimension model for felled free From Mann (1985a and either stage of harvest are large and 1985b). 214 Harvesting Timber to Achieve Reforestation Objectives

a log-skidding tractor of the D-7 category is size. Seedlings between about 30 and 40 inches required, skid trails must be at least as wide as tall appear most resistant to damage (Tesch et al. the blade of the tractor. If a skyline system is 1986a and 1986b). Smaller seedlings, especially indicated and full suspension of logs is required, planted seedlings, are often seriously injured a large tower and a large landing area will be despite their flexibility. Larger seedlings are less needed. flexible and more inclined to injury due to stem Roads should be suitable for all facets of the breakage or root damage from being pushed over. harvesting operation. Existing or planned roads Scheduling a harvesting project to coincide with should be wide enough and aligned appropriate- a seedling size "window" will take extra effort ly for the type of equipment that will be neces- to accomplish. sary for the regeneration cut, removal of the overstory, and any intermediate entries required during the next rotation. Marking Leave Trees Equipment should be suited to characteristics of When it is desirable to remove only a portion of the terrain, timber stand, and surrounding area. the current stand, it is preferable to mark trees If cable systems are used, locate skyline and that will be left rather than trees that will be guyline anchors, tail spars, and intermediate removed. This makes it easier for the marking supports in the most effective places. crew to visualize spacing as they go through the stand, and the markings more clearly show the On gently sloping terrain, minimizing damage timber cutters and yarding crew what trees to pro- to residual overstory trees or regeneration can be tect during logging. accomplished relatively easily with ground-based Characteristics of desirable leave trees should systems, because more control over logs during be carefully specified to the marking crew, or felling and yarding is possible than on steeper marking operations should be closely supervised slopes. Special measures to protect residual trees, by the silviculturist, or both. Leave trees with large such as stage felling and yarding (J.W. Mann, per- crowns are generally undesirable from a reforesta- sonal communication, 1990; data on file at Forest tion perspective because they can damage regen- Research Laboratory, Oregon State University), eration during felling and yarding if they are to be directional felling (Hunt and Henley 1981), and removed during a future entry, and they also may designated skid trails (Garland 1983), can be used be more prone to windthrow. They can be desir- to great advantage. While some of these measures able, however, if they help meet other objectives, can be employed on steeper slopes, they are less such as providing shade for new seedlings. effective and more costly. Dialogue between the harvest planner and the sil- The time of year that harvesting is conducted is viculturist will be necessary to determine the most an important consideration in limiting damage to important objective in such a case. regeneration. Harvesting in early spring when bark How the leave trees are distributed will also is still quite loose will cause more wounding of have an impact on seedling damage when they are stems than logging in late summer or fall. A recent removed. If trees are left in groups, seedling dam- study showed that harvesting in spring, when age can be high in the immediate vicinity of the seedlings were actively growing, caused greater group when trees are cut. On the other hand, leav- damage to terminal leaders than logging done in ing trees in a uniform (rather than grouped) pat- late summer and fall after bud set (J.W. Mann, per- tern could result in more total seedling damage sonal communication, 1990). Logging in the winter because of the ground disturbance associated may help protect seedlings; winter logging on with removing each tree. Operational experience frozen ground may reduce soil impacts, and log- indicates that it is more efficient to leave residual ging on snow may protect both soil and regenera- trees in clumps or strips (Figure 9-7). Such pat- tion.However, winter logging may present terns will permit safer working conditions around scheduling problems. tall snags and trees, limit bole damage to residu- The susceptibility of regeneration to damage al trees, increase logging production, leave the during removal of overstory trees is related to its harvest unit in a more favorable condition for Harvesting Timber to Achieve Reforestation Objectives 215

II v... .0* k... I II ,..--:-ape...... -N ii 11 Road g I 11 e,,el1 /ii t to ; ,e; 11 1 %I Road 14 I I Iesti:Wiattein II i It °' I 1" Eli,ti; 0° 11 / is 1 i ire1 II I It IA *:V\ Ii Road Landing ill A . " Landing II,/it ; it fr. 1 ..e.8'.% t a:. t t %,a.... l r :" .- - 'rt.( , ....: 4° :. N.. % ./. A %.i.:'...... ° t .. ::.-2Li.arr, C.:.11. 0 t . 3 P ,elbj , I ..- CA 1 (N. .... 'A.::: ....0'.=7:41: I . I 1:::C.1..._.....,_wt...... :100 e 'L , 3, ...... ,,,,,....: I 1.:,, I0I VS, ivav...... ,,... ..";. -Road -....,,,,,,,,...z. II e . , % ...... A

Figure 9-7. Possible leave-tree patterns: (A) Trees left in spokes 15-30 degrees apart, radiating from a common landing. Used in either up- or downhill skyline logging. (B) Trees left in wedge-shaped strips approximately 40 degrees apart, maintaining about 10-15 percent of the timber stand intact. (C) Trees left in specifically chosen areas to provide a mix of species, age and size classes, snag clusters, and riparian areas, representing about 10-15 percent of the harvest area.

slash disposal and site preparation, and allow the wildlife biologist in order to provide a safe aerial application of chemicals. Trees left in such working environment. patterns may also be more windfirm than those Another important factor to consider on steep left evenly dispersed. terrain where skyline systems will be used is to If portions of the harvest unit are difficult to leave trees that might be needed for logging spars reach, few or no trees should be left in those areas and intermediate supports. Consideration should because yarding may cause excessive disturbance be given to leaving large, sound trees at the outer in the final entry. For instance, suppose a long edge of the harvest unit. The need for tail spars corner exists in a unit such that lateral yarding and intermediate supports will be determined from of 200 ft is necessary to reach the trees growing skyline analysis of the yarding area. there. Because pulling large logs laterally over Finally, remember that unsound snags and such a long distance will cause much disturbance, dead trees with branches present substantial safe- all the timber in this area should be taken out in ty hazards for loggers, especially in the vicinity of the first entry, before regeneration is established. landings and roads. Overstory trees that are dam- If overstory trees must be left for shade, it is better aged during the regeneration entry should be cut to leave smaller trees because they are easier to and removed or left as designated wildlife trees. control during the lateral-yarding phase of over- story removal. Trees needed for wildlife should be designated Designing the Harvest Pattern before the first entry and maintained through- out the regeneration process. Designation of Ground-based systems wildlife trees may have to be adjusted by the In ground-based yarding systems, the goal is to sale administrator and logger in consultation with cover as small a portion of the cutting unit as pos- 21 6 Harvesting Timber to Achieve Reforestation Objectives

Spur skid trail Main skid trail Branching trails Arrows indicate 0 log winching 200 ft 200 ft direction

Main skid trail

Figure 9-8. Parallel skid trail pattern. //Tolanding sible while accomplishing efficient and safe log- Figure 9-9. Branching skid trail pattern. ging operations. In tractor logging of a shelterwood, for example, it is desirable to use the same skid tern for each site. These kinds of considerations trails in all entries to limit soil compaction and may seem rather small and insignificant when minimize damage to regeneration. Thus, the skid- viewed individually, but if they are not taken care ding pattern developed for the regeneration cut of in the planning stage they can lead to serious must also fit overstory removal. The logging plan- reforestation problems. ner must work with the silviculturist to develop a Skid trails may be laid out in several different skid trail pattern that can be used effectively for patterns with varying amounts of disturbed area both entries. An experienced logging specialist (Conway 1982). Parallel skid trails form a low-den- working ahead of the operation can consider a vari- sity pattern where felling to lead and winching can ety of alternatives and arrive at an optimum pat- be used effectively (Figure 9-8). Parallel trails will vary in how much of the area they cover, depending Table 9-4. Percentage of harvest area covered by on their spacing. Table 9-4 shows approximate skid trails using the parallel pattern (based on 10-ft- area coverages for different spacings. wide trails). The main problem with parallel skid trails is that most of the region's topography is variable Skid trail Area in skid and does not conform to such a rigid geometric spacing (ft) trails (%)1 arrangement. Terrain features like draws, streams, rock outcroppings, slope variations, and the nor- 75 13.3 mal differences in timber concentrations make a 100 10.0 precisely parallel pattern unrealistic. If the concept 150 6.7 of parallel skid trails is adjusted to allow for stand 200 5 and terrain variability, a more realistic branching 250 4 pattern can be developed (Figure 9-9). This pat- tern's converging trails can generally be situated so that spacing is almost as good as it would be with skid trail width 1Percent area in skid trail = x 100 parallel trails. skid trail spacing Branching skid trails should intersect the main collector trails at angles of 45 degrees at the most, For example: x100 13 3% oriented toward the landing (Figure 9-10). Angles wider than this will result in damage to reproduc- Harvesting Timber to Achieve Reforestation Objectives 217

Right Wrong Stump Turning angles less than Turning angles greater 45° and branching than 45° and branching \C!, Felling skid trails alternating skid trails directly +Skid trail angle opposite one another spacing Main skid trail / Main skid trail Line pulled / 1 parallel to // IN Line pulled I perpendicular log -15/ / I to skid trail 9 1 0 >450 Skid trail

Figure 9-11. Critical variables affecting skid trail spacing. 150-175 ft. For uphill pulls, the distance is less, about a 50-ft maximum. Skid trails should be spaced so that the optimum winching distance is To landing To landing not exceeded. Log length is a more critical factor than tree Figure 9-10. Intersections of branching skid trails height in the spacing of skid trails (Figure 9-11). with main trails. For a tree exactly halfway between trails, the length of the butt log is the deciding factor because tion on the inside of the turn when long logs are the top logs will all be closer to the trail. However, skidded around corners. Branching trails should tight skid trail spacing in tall timber should be be staggered, alternating side-to-side along the avoided because the top logs of tall trees will fall main trails (Figure 9-10). Leaving high stumps on across the skid trail and be precisely out of lead. the inside curves of trail intersections can help The interaction of these variables is summarized equipment operators turn logs into the main trail for various combinations in Table 9-5. Spacings without damaging regeneration. given in the table allow for an assumed choker Depending on terrain and timber stand density, length of 15 ft and stump-jump of 5 ft, since the skid trails should be kept as straight as possible. butt end of the first log will seldom come to rest Straight trails allow for higher skidding speeds, exactly at the stump. less equipment positioning time, fewer hangups, In general, two skidding vehicles should not be and better log control. This does not mean that working on the same skid trail. The passing of the trails must be perfectly straight. As in any har- machines will cause the trail to be widened, and vesting operation, flexibility and practicality must delays often occur while one machine waits for the be considered. Gently curving trails can still pro- other to finish a job. This principle does not apply vide most of the advantages of straight trails while to a tractor swing operation, where one machine avoiding obstructions like rock outcroppings, large (usually a large tracked vehicle) is used only for trees, and dense reproduction. winching logs to the trail, while a separate, faster Skid trail spacing is a function of tree height, machine (usually a rubber-tired skidder equipped felling angle, winching distance, and log length. with a grapple) swings logs to the landing. With Skidding equipment is available in a wide variety of this technique, the winching tractor starts at the winch capacities and line sizes, ranging from 100 landing and works outward so that the two to about 500 ft of line. An average winch capacity machines do not have to pass. and line size to use for planning purposes is 200 ft of 3/4-inch line. The force required to pull such a Cable systems line off a freespooling winch allows a single choker setter to pull out about 100 ft of line on flat From a harvesting viewpoint, saving regenera- ground, on the average (Iff 1977). On downhill tion on steep terrain where skyline systems are pulls the distance is somewhat farther, perhaps used is generally more difficult than on more gen- 21 8 Harvesting Timber to Achieve Reforestation Objectives

Table 9-5. Interactions of critical variables in determining skid trail spacing. Skyline corridor at angle Felling angle Log length (ft)Amount of lineSkid trail to contourresults in cross-slope pulled (ft) spacin9 yarding and wider corridor (ft)1

30 33.0 50 88 75 113 Skyline carriage 100 138 150 188 30 16.5 50 72 75 97 100 122 150 266 45 33.0 50 101 Width of clearing 75 136 for skyline 100 172 corridor 150 243 60 33.0 50 152 75 196 100 239 150 326 60 16.5 50 124 Skyline corridor perpendicularSkyline 75 167 to contourmore log control carriage 100 210 and narrow corridor 150 297

1 Calculated from model presented in Figure 9-11 for winch line pulled parallel to the log being winched.

tie terrain. The force of gravity on steep slopes and differences in equipment capabilities make con- trol of timber more difficult with cable systems. Problems of log control and the area of disturbed Width of clearing for skyline ground can both be lessened by locating skyline corridor corridors properly. To the extent possible, corri- dors should be placed perpendicular to terrain contours. If corridors are at an angle other than Figure 9-12. Effect of skyline cross slope on width- 90 degrees, logs will swing downhill, resulting in of-clearing limits for the corridor. wider corridors and more ground disturbance (Figure 9-12). efficient operationally because they require less Road systems and landing locations should be machine rigging time. laid out to take advantage of terrain features. This Designating corridors on the ground with flag- will often mean that multiple corridors will con- ging before trees are cut is helpfulalmost manda- verge into one landing location, which will result in toryin all situations in which a portion of the a cleared area for some distance below the landing. stand will be retained. This allows the logging While this situation may not be desirable, it may be supervisor to visualize the harvesting pattern and the lesser of two evils. If the alternative, parallel plan in detail how yarding must proceed. Flagging corridors, were used in the same terrain, they shows timber fallers where the skyline corridors would require more landings and probably more will be so that they can fell trees in lead to facilitate roads, taking even more land out of seedling pro- yarding, protect residual trees, and save reproduc- duction. Moreover, converging corridors are more tion. However, locations of predesignated skyline Harvesting Timber to Achieve Reforestation Objectives 219

Area affected by lateral excursion dors. Because the skyline will deflect to both sides of skyline of its neutral position, corridor width equals twice the lateral excursion distance. While healthy, undamaged seedlings on either side of a 15-ft cor- ridor may constitute a desirably spaced young stand, seedlings on either side of a 30-ft corridor may not. To limit lateral excursion, residual trees Log Landing adjacent to the corridors can be used as "rub trees" during lateral inhaul (Figure 9-13). Rub trees on a particular corridor can be cut at the completion of yarding and yarded to the landing before equip- Rub trees reduce the area affected ment is moved to the next setting, or they can be felled toward adjacent skyline corridors and yard- ed to the next corridor. Rub trees take extra planning to work properly. Approximate corridor locations must be designated prior to felling, and timber cutters must know which trees to leave. Location of rub trees will depend on timber concentrations in lateral yarding areas and on characteristics of the terrain in the Figure 9-13. Overhead view of rub trees and their harvesting area (Figure 9-14). If rub trees are left in effect on lateral excursion of the skyline. areas where the skyline is quite high above the ground, the line may be rubbing in the tops of the trees, knocking out branches and creating a safe- corridors must be somewhat flexible and subject to ty hazard for the rigging crew. The skyline may adjustment once timber is on the ground. Things even be pulled over the top of a rub tree and come look different when all the trees to be felled are down on the wrong side, causing hangups during down, and minor corrections to the yarding pattern yarding and possibly widening the corridor. may be necessary. A rigid corridor-spacing rule Even if it is not certain in the planning stage can impose unnecessary restrictions on loggers. whether rub trees will be useful, extra trees can As with skid trails, spacing of skyline corridors be left near the corridor just in case. If they prove depends on the lateral yarding capabilities of the to be unnecessary, they can be felled and yarded equipment to be used. For most types of manual during the regular progression of the operation. and mechanical slackpulling carriages used in the region, a reasonable distance that the rigging crew can pull line on a sustained basis is 75 ft to either side of the skyline. A starting point, then, for plan- HARVESTING OPERATIONS ning the spacing between parallel corridors is 150 ft. Additional distance can be added if trees are Ground-based Systems felled to lead. However, to minimize seedling dam- The proper felling method to be used with des- age to steep ground, lateral yarding distance (and ignated skid trails in ground-based harvesting therefore corridor spacing) should be decreased as operations is called felling to lead. Trees are felled slope increases. In a direction parallel to, or in lead with, the direc- Deflection of the skyline to one side of the corri- tion in which they will be winched to the skid dor during lateral yarding, a movement called lat- trails. Trees can be felled toward or away from skid eral excursion, is necessary for the system to pull trails depending on their natural lean and the logs into the corridor, but it may create unaccept- characteristics of the terrain. Trees are felled at ably wide corridors. This means more area in the an angle of 30-45 degrees from the skid trail, with logging footprint and commensurately more dam- either butt or top end in line with the direction of age to regeneration and residual trees near cord- winching (Figure 9-15). When trees are felled out of 220 Harvesting Timber to Achieve Reforestation Objectives

Skyline yarder

Rub trees

Rub tree zone: Skyline below crown; Tail anchor on number of trees needed opposite slope depends on length of span and location of timber in lateral yarding area

Rub trees here can cause problems. Skyline is in crown of trees and can go over top to come down on wrong side

Figure 9-14. Location of rub trees along the skyline profile.

lead, logs must be turned as they are winched toward the tractor, increasing the probability of damage to seedlings and residual trees and often causing logs to hang up or break during winching. Logs felled in lead with winching and Trees immediately adjacent to skid trailsare felled skidding direction 0 .-NIncorrect. parallel to the trail rather than out into the resid- Log felled ual stand. Trees that are in the skid trails should \ out of lead be felled and skidded before cutting other timber (if Possible); otherwise, fallers may have trouble find- ing the trails and felling trees to lead (Aho et al. 1983). In stands with heavy volume and a particularly valuable understory, stage felling and yardingcan help save regeneration (Barrett et al. 1976). In this 'a-177d technique, only a portion of the canopy treesare felled, bucked, and skidded at one time. Remaining To landing trees are then felled, bucked, and skidded inone or more subsequent stages, using the areas already disturbed in the first stage. The decisions of how much volume to take in each stage and howmany stages to use depend on total volume to be har- Figure 9-15. Proper tree placement in felling to lead. Harvesting Timber to Achieve Reforestation Objectives 221 vested, number of residual overstory trees, and must be on the site during all felling operations value of seedlings in the understory. A rule of and each tree must be climbed so that a pulling thumb for stage-felling operations on tractor-har- line may be attached. Tree jacking is less. costly vested areas calls for removing about 40 percent and usually provides the control needed to fell of the overstory in the first stage to open up trees in the desired direction. Tree jacking can be enough area to get the remaining 60 percent on the helpful in tractor-logged areas as well as on steep- ground in one more stage while leaving an ade- er terrain. quately stocked understory. Stage felling is more difficult in skyline logging than in ground-based logging because all operating lines must be taken down after yarding is finished Cable Systems and re-rigged after the next stage is felled. Unless Herringbone felling patterns have been proposed the yarder is used on another site while fallers are as the best way to minimize damage to regenera- working, it is inactive during this time. Moreover, tion during overstory removal with skyline systems stage felling has yet to prove effective in saving (Studier and Binkley 1974). If harvesting condi- regeneration on steep terrain (J.W. Mann, person- tions are ideal, this is theoretically true, but suc- al communication, 1990; data on file at Forest cessful use of a herringbone pattern depends on Research Laboratory, Oregon State University). skyline corridors that do not deviate from their However, this technique should not be abandoned planned locations. When corridor locations shift in cable logging without more research into its slightly after all the timber is downa common effects on stocking levels, distribution of under- occurrencetrees felled in a herringbone pattern story trees, operational costs, and other variables. may actually be in the worst possible position. If the trees are across the corridor rather than in lead with the direction of yarding, logs will have to be turned before they can be pulled into the corridor (Figure 9-16), and seedlings in their path are sub- ject to damage. It is advisable to allow cutters, log- Skyline corridor Parallel pattern: ging managers, and sale administrators the Exact corridor mum milmumm location not critical flexibility to determine the best pattern or combi- for felling in lead nation of patterns. Felling timber parallel to the terrain contour MEM seems to be the best method to use in saving 1111111111111ffilin regeneration. With this type of felling, turning logs during lateral yarding is minimized and location Contour--. of the corridor is not as critical, especially if corri- lines Herringbone pattern: dors are laid out perpendicular to the contour. On Must know exact location of corridor very steep terrain, however, parallel felling may or logs will have to result in logs rolling downhill when bucked; some be turned during degree of uphill lead may be necessary to hold yarding them on the slope. Mechanically assisted directional fellinga set of techniques employing mechanical means to con- trol the direction in which a tree fallsmay be nec- essary to achieve the desired felling pattern. Studies of benefits realized from mechanically assisted directional felling have concentrated on reduction of breakage (Hunt and Henley 1981), but these techniques have also been observed to help In saving regeneration (Aho et al. 1983). Tree lining Figure 9-16. Timber felling patterns used in skyline is quite expensive because an auxiliary yarder logging to save regeneration and facilitate yarding. 222 Harvesting Timber to Achieve Reforestation Objectives

Right: Wrong: Position tractor to pull Winching from the side can cable out straight to logs cause instability of machine

Figure 9-17. Winching procedures in ground-based logging operations.

MINIMIZING DAMAGE TO THE important tradeoff between maximizing yarding production and minimizing damage. Generally RESIDUAL STAND speaking, any special effort to prevent damage to overstory trees or regeneration will increase project Protecting residual trees during harvesting costs, from plan preparation through the actual operations continues to be an important problem harvesting operation. The value of reproduction associated with shelterwood or uneven-aged regen- must be balanced against the increases in operat- eration methods, particularly on steep terrain ing costs. where skyline or aerial logging systems must be used. Several studies have addressed this issue (Mann and Tesch 1985, Tesch et al. 1986a and Ground-based Systems 1986b; J.W. Mann and J. Kraemer, personal com- While skid trails should be kept narrow, they munication; FIR report 8(3)2-4, 1986). Even must be wide enough to allow for proper position- though many of the practices reported in the liter- ing of equipment during winching. The winch line ature have not been tested in replicated experi- should be pulled straight out from the back of the ments, they have been observed to be helpful in tractor (Figure 9-17). Winching at an angle to the saving reproduction (Mann 1985a). These prac- direction of tractor travel may cause the machine tices are the ones most often recommended by log- to become unstable, especially on steeper ground. ging specialists and silviculturists who have Angled winching may also cause logs to swing as experience with the problem. In considering any they start to move, thus disturbing more ground of them, however, planners should recognize the and potentially damaging nearby trees. Skid trails, Harvesting Timber to Achieve Reforestation Objectives 223 therefore, must be slightly wider than the skidding are completely suspended, they tend to roll ahead machines to allow for machine positioning. of the carriage on slopes greater than 65 percent, The pulling force of the winch line is the only flopping to one side or the other of the skyline cor- means of control that machine operators have over ridor and disturbing a larger area. logs during winching. If logs encounter an obstruc- Extremely long skyline spans (in excess of 2,000 tion or are headed for a patch of regeneration that ft) may cause more damage to seedlings and resid- should be saved, the primary way to change log ual overstory trees than short spans (Fieber et al. direction is to move the winching tractor. Good 1982). Yarding low volumes per acre over such long felling techniques and careful initial positioning of distances may also prove uneconomical: heli- winching machines will reduce the need for moving copters may be more satisfactory than cable sys- equipment once winching has begun. tems in such situations. Elevating the leading end of the log during trac- Movement of logs laterally to a skyline corridor tor skidding can help it follow a straight path, and is controlled mechanically through the carriage. A also eliminates the plowing effect that results skyline carriage used with shelterwood or uneven- from its being dragged flush with the ground. aged regeneration methods must meet two basic Log elevation is accomplished with integral skid- requirements: ding arches mounted at the rear of the machine. It must be capable of pulling slackthat is, it Such arches should be required on logging tractors must allow the dropline, or the line that extends where protection of trees or regeneration is down from the carriage to the logs, to be pulled an objective. out to the side of the corridor by the choker set- The practice of designating skid trails (Froehlich ters to reach logs between corridors. Non-slack- et al. 1981), useful for minimizing soil compaction pulling carriages are limited to yarding only on a site, has also been shown effective in reducing within reach of one choker length on either side damage to residual trees (Aho et al. 1983, Brown of the skyline. The longest length a choker can and Perry 1984). Designated skid trails are dis- reach and still be managed efficiently is rough- cussed in greater detail below, in the section on ly 40 ft, which limits the corridor spacing to 80 maintaining site productivity. ft. This is typically unacceptably close. It must be capable of maintaining a fixed posi- tion on the skyline during lateral inhaul. A car- Cable Systems riage may be made stationary by a clamp that As slopes increase beyond 35 percent, log con- holds it to the skyline, an operating line (like trol during felling, bucking, and yarding becomes the haulback) that is secured to the back of the increasingly difficult (Tesch and Mann 1991). carriage, or simply by its own weight. If the car- Felled trees and bucked logs roll downhill on steep riage is not stationary during this phase, it will slopes, and cable yarding systems cannot control creep up toward the yarder (as tension increas- log movement during yarding as well as tractors es in the dropline) when logs are being pulled can. A likely result is more area disturbed and in from the side, and logs being laterally yarded greater damage to the residual overstory trees and could damage seedlings or residual trees as they to regeneration, especially during lateral yarding. follow the carriage upslope. On slopes greater than 65 percent, controlling log movement is extremely difficult, and the decision In some cases it may be desirable to move the to use non-clearcut regeneration methods must carriage during lateral inhaul. If a log rolls down- be made cautiously. No matter what logging tech- hill, becomes hung up on a stump or other niques are used, there is a physical limit to what obstruction, or is carrying a large amount of slash can be done to control log movement on slopes as it moves toward the corridor, a change in direc- greater than 65 percent (Lindsay 1985). Using tion is necessary. Moving the carriage up or down mechanically assisted directional felling to fell the skyline will change the direction of pull and trees uphill may help hold logs in place. thus the track of the log (Figure 9-18). It is usual- Downhill skyline logging should usually be ly better to move the carriage uphill in this case avoided except perhaps in clearcuts. Unless logs because a downhill move will put slack in the 224 Harvesting Timber to Achieve Reforestation Objectives

.--Landing dropline, resulting in the log's rolling or sliding downhill. It should be noted that not all carriages can be moved while the dropline is outmany are clamped to the skyline until the logs reach the carriage. Logs should be brought as far into the corridor as possible (unless they are fully suspended) before starting carriage movement to the landing. New carriage position If the carriage begins to move be- Original fore logs are all the way in, the area carriage through which they will turn is greatly position -I-1 increased and more damage could occur (Figure 9-19). The rigging slinger Log (the person in charge of properly get- Patch of ting the logs into the corridor) may regeneration sometimes signal for carriage inhaul to be saved before the logs have reached the corri- dor as a means of speeding up produc- Figure 9-18. Moving the skyline carriage during lateral inhaul to tion. This practice should be avoided avoid an obstacle or area of dense reproduction. when minimizing damage is important. Lateral inhaul and inhaul to the land- Landing ing should be separate elements of the yarding cycle. Sufficient deflection and carriage clearance are mandatory if logs are to be controlled during lateral yarding. In general, the higher the carriage, the greater the lift exerted during lateral inhaul, and the greater the con- trol afforded over gravitational forces on the log. More control means less damage to regeneration (Gaas 1974, Course of log movement if Burditt 1982, Fieber et al.1982). carriage moves toward landing before log reaches Depending on the terrain and the line corridor capacity of the yarder, deflection and carriage clearance are obtained by rig- x x Patch of ging the outer skyline anchor (the tail- regeneration hold) across a draw on a slope facing the area to be yarded, or by rigging a Log lift tree or a tail spar (Figure 9-20). Lift trees can be very important in saving Skyline carriage regeneration, especially when logs are being yarded close to the tailhold. If the skyline were anchored directly to a Anchor stump on a continuous slope, the car- riage would be quite close to the Figure 9-19. Increased seedling damage associated with beginning ground at the outer end of the skyline carriage movement before lateral yarding is complete. corridor, which could cause much Harvesting Timber to Achieve Reforestation Objectives 225 damage to nearby reproduction. On continuous A constant slope with skyline slopes, a lift tree is the only practical way to obtain anchored to opposite hillside deflection with a single-span skyline system. Trees to provide deflection to be used as logging spars or lift trees must be designated in advance of felling. In terrain with convex slopes, extremely long continuous slopes, or broken ground, it may be difficult to get enough deflection with a single- A constant slope using a lift span skyline. In these situations, a multi- tree to gain deflection span skyline should be considered. Multi-span skylines have intermediate supports to keep the skyline and carriage elevated well above the ground (Mann 1984). A convex slope with lift tree The skyline should not, however, be suspended requires a shorter span in or above the tops of leave trees in the first entry. When the skyline is this high, excessive top dam- age is likely (Fieber et al. 1982). Planners must realize that keeping the skyline and carriage below the branches of overstory trees also means that full suspension of logs is not feasible. An exception Figure 9-20. Single-span skyline conditions and must be made, of course, when full suspension is methods for obtaining deflection and carriage mandated, as over stream buffer strips. clearance. Adapted from Studier and Binkley (1974).

If artificial regeneration is planned, seedlings SITE PREPARATION AND should be planted where they will likely be pro- PLANTING tected from subsequent logging damage. For trac- tor-logged areas, the most effective planting area is Although site preparation and planting are not on the landing side of a stump from a tree that was usually addressed as harvesting concerns, some cut during the first entry. Around remaining trees, consideration should be given to them in the con- the planting location least likely to be disturbed text of harvesting. As we have noted before, the during overstoty removal is the side away from the steps taken to implement any regeneration skid trail. In areas to be logged with a skyline, the method are notdiscrete but interrelated. downhill side of stumps and overstory trees should Harvesting can affect the ease or difficulty of sub- be used as planting sites. Planting is covered more sequent site-preparation and regeneration efforts. thoroughly in Chapter 14. With the shelterwood method, to the greatest extent possible, logging slash should be disposed of and the site prepared for regeneration between the first (regeneration) cut and removal of the MAINTAINING SITE residual trees. Ideally, slash should be burned or PRODUCTIVITY otherwise thoroughly removed so that it will not have to be dealt with after the second entry, when Maintaining the quality of the site is one of the additional seedling damage might result. greatest concerns involved in coordinating har- Some site preparation can be accomplished by vesting operations with reforestation requirements. harvesting operations, depending on the degree of Soil disturbance, particularly soil compaction, is ground disturbance desired and the harvesting the chief concern. Soil compaction is one measure system used. Planners should consider the site- used to describe the overall condition of a forest preparation capabilities of the various types of site after machine operations. Soil displacement harvesting machinery (Chapter 10). and other disturbance may also result from the 226 Harvesting Timber to Achieve Reforestation Objectives same machinery activity (Dyrness 1965), and these small, private tracts. Managing forests by alterna- are also indicators of site condition. Some clay soils tive silvicultural methods to avoid clear-cutting may remain compacted for 30 years or more, while and improve forest biodiversity is still in the proof- others, especially sandy soils in areas of yearly of-concept stage and, in our opinion, is not ready freezing and thawing, may recover in only 3 years for large-scale implementation until many opera- (Holman et al. 1978). tional questions have been answered. However, The use of designated skid trails (Froehlich et al. information from other, more traditional harvest- 1981) may be the most effective way to avoid exces- ing operations can be used to hypothesize what sive compaction of soils. These have been used might happen when these proposed approaches to operationally in southwestern Oregon and north- forest management are taken. ern California. In this practice, harvesting equip- No matter what the harvesting system or leave- ment is restricted to operating only on pre-marked tree arrangement used in overstory retention travelways. In operations where skid trails are not systems, the cost of harvesting and other stand designated, as much as 50 percent of the harvest- management activities will be increased, some- ed area is typically covered (Froehlich 1977). Skid times greatly increased, over those of more tradi- trail coverage can be reduced to around 10 percent tionalclear-cutting techniques.Kellogget with proper planning and layout (Table 9-4), al. (1991) showed a 23-percent increase in cost depending on the skidding pattern used and how of implementing a two-storied stand development far the winch line is pulled. Some research has over the cost of clear-cutting, and a 25-percent shown that using designated skid trails sometimes Increase in the cost of implementing a group increases logging costs (Bradshaw 1979), while selection harvest prescription over the cost of other experiments record no increase or even a clear-cutting. The volume left in standing trees reduction in costs (Froehlich et al. 1981, Tesch and in windfall that cannot be efficiently re- and Lysne 1986). covered representslostrevenue, and the Strategies to manage soil compaction should Inevitable damage to residual trees during har- Involve all machinery, not only that used for har- vesting and site preparation results in decreased vesting. In particular, equipment used for site future yields. Depending on the leave-tree pat- preparation and fuels management should be tern selected, managers may also have to deal deployed as efficiently as possible. The anticipated with decreased timber yields, disease passed from benefits from logging with cable systems or us- overstory to new regeneration (for example, ing designated skid trails can easily be negated mistletoe), and brush competition problems as by indiscriminate use of machines in site prepara- understory vegetation is exposed to light. Another tion and slash piling. However, it may be possible critical issue in any uneven-age management to minimize machine coverage by combining scheme is safety; residual trees present certain some elements of site preparation into the harvest- dangers to fallers and other workers. Costs of ing job. these problems must be balanced against poten- tial gains in increased structural and biologi- cal diversity promised by alternative silvicul- HARVESTING CONSIDERA- tural methods. Uneven-aged management will often result in TIONS IN UNEVEN-AGED AND the removal of only a few trees per acre in an ALTERNATIVE SILVICULTURE entry, with periodic entries scheduled at some predetermined interval. Alternative silvicultural At present, there is little experience or research proposals are currently somewhat unspecific and on which to base recommendations for harvest- difficult to interpret, but their rationale is topro- ing in uneven-aged management situationsor in vide a mixture of species, variations in ages and the cutting prescriptions of alternative silvicultur- sizes of trees, clusters of snags, and wooded ripar- al methods (Franklin 1989), with their emphasis ian areas in future stands. A prevalent alterna- on heavy conifer retention. Most uneven-aged tive silviculture prescription in this region would management on west-side forests has occurred on leave 6-12 green trees per acre as well as standing Harvesting Timber to Achieve Reforestation Objectives 227 snags. Such a prescription is similar to that used Leave-tree patterns that should be tested in the regeneration stage of traditional two-stage include systematically placed "spokes," wedge- shelterwood management, but it differs in that no shaped areas radiating out from landings, and overstory removal is plannedresidual large trees clusters, representing some predetermined per- will be retained throughout the next rotation and centage of the harvest area (Figure 9-7). Any of perhaps beyond. these patterns could help provide the values The elements of planning and implementation intended by alternative silviculture proposals. In that pertain to any kind of non-clearcut harvest- marking leave trees, consideration should be giv- ing discussed previously in this chapter can be en to factors that will (1) facilitate future harvesting applied judiciously to uneven-aged and alterna- entries without excessive damage to regeneration tive cutting prescriptions. Some ideas on specific in the event of blowdown, (2) permit broadcast planning and operating strategies follow. burning to reduce fire hazard, (3) permit safe and Gentle terrainUse designated skid trails that will effective application of chemicals in the event that become a permanent part of the forest transporta- conifer release is necessary, and (4) provide an aes- tion system. Problems associated with this include thetically pleasing landscape. locating and maintaining trails on large areas as Steep or gentle terrain: aerial systemsAerial log- well as damage to residual trees during potentially ging with a variety of different-sized machines may frequent entries. The initial location, mapping, and be the only practical way to harvest timber from permanent marking of skid trails on large areas of uneven-aged or alternatively managed stands in forest land is a task that will require increased difficult terrain. Aerial systems have two advan- manpower. If restriction of skidding equipment to tages over the others: their yarding distance is not designated skid trails is not strictly enforced, soil physically restricted and they do not rely on high compaction and site degradation could become volumes per unit area for economical production. major problems. Diligent administrative oversight Flight speeds of 90 mph and vertical lift of the logs is essential. make helicopter logging almost independent of Steep terrain: cable logging systemsCable sys- most of the variables that affect costs and produc- tems may or may not prove to be of use in uneven- tion rates of other harvesting systems. An excep- aged management areas where frequent entries tion is the time involved in moving ground workers will be made to harvest a few trees per acre. The relatively long distances from tree to tree for felling, expense of preparing landing areas, cutting skyline bucking, and hooking. corridors, and moving and rigging the cable equip- ment for this kind of selective logging would, in most cases, be high and might cause more visual SUMMARY site disturbance than desirable. However, large- scale cable systems are very flexible. Given the Timber harvesting, reforestation, and silvicul- generally higher value of selective-cutting con- ture go hand in hand. Harvesting is the major sil- tracts, cable systems may become a viable alter- vicultural tool used to manipulate forest vegetation native. Also, small swing-boom cable cranes that to achieve a variety of management goals. This can operate from small landings with only two or chapter deals with capabilities, limitations, costs, three guylines will likely be useful in salvage log- and impacts of harvesting systems. In particular, it ging and selective cutting of green trees within discusses how these systems interact with refor- 1,000 ft of established roads. estation activities. Strong consideration is given to Skyline systems will be quite useful in New describing the "logging footprint," or characteris- Forestry applications, just as they have proven to tics left behind in the forest after logging opera- be with the shelterwood method on steep terrain. tions. Choosing a timber harvesting system and Skyline harvesting techniques discussed previous- setting the standards of quality control to be exer- ly can be applied to this type of management as cised over operations are probably the most impor- well, with the added consideration that large leave tant decisions made by forest managers, because trees will have to be strategically located for effi- they determine the "logging footprint." This foot- ciency and safety and to limit damage to the trees. print can be managed to help achieve successful 228 Harvesting Timber to Achieve Reforestation Objectives reforestation and to minimize or eliminate the neg- Trees should be felled in lead with skid trails in ative effects of harvesting on regeneration, residu- ground-based operations, and generally parallel al trees, and soil. This chapter focuses on the to the terrain contour in cable systems; some techniques for such management, particularly in uphill lead may be necessary on steeper slopes. regeneration methods calling for retention of some Mechanically assisted directional felling is helpful part of the stand. in controlling direction of fall. Three harvesting systems are common in the Additional techniques to minimize damage to region: ground-based, cable, and aerial systems. regeneration in ground-based logging include Ground-based systems, usually the least expensive keeping the winching line straight out from the of the three, are best suited to gentler slopes. Their back of the tractor and raising the leading end of main environmental drawback is their potential to the log. In cable systems, such techniques include cause compaction of the soil. Designated skid trails avoiding downhill yarding on steep slopes, using concentrate impacts of machinery onto a small intermediate supports or tail spars to achieve percentage of the harvest area, and thus help greater deflection, bringing logs fully into the cor- reduce the extent of soil compaction and associat- ridor before yarding, designating rub trees to limit ed seedling growth losses. lateral excursion of the skyline, and fully suspend- Generally, cable systems disturb the site less ing the load in some situations. than ground-based systems and are thus well suit- There is little research or experience on which to ed to harvesting operations where overstory trees base harvesting recommendations for the concepts or seedlings are to be retained. Cable logging tends proposed under the title of "New Forestry." Such to be more expensive than ground-based logging. concepts are certain to be more costly to imple- Aerial logging is usually the most expensive of ment, and they will require more care in layout. the three, but it causes the least disturbance to the Information from traditional harvesting systems ground and to residual trees or seedlings, giving it can be extrapolated with care to hypothesize an advantage in situations where environmental or results from such approaches. aesthetic concerns predominate. In sum, emphasis should be placed on the har- Each system has benefits and limitations that vest planning process: decisions that must be apply at every stage of a harvest operation. Before made, their hierarchy and sequencing, information choosing a system for a given job, planners should required, and how harvesting decisions support consider size of the timber, characteristics of the reforestation and overall forest management goals. terrain, time of year the harvest will be conducted, Harvesting systems are evaluated on basic physi- and amount and distribution of trees and seedlings cal, economic, and operational criteria, but atten- to be retained. In addition, such management con- tion should also be given to the myriad of siderations as placement of skid trails, skyline cor- operational quality-control considerations that, in ridors, spars, landings, and haul roads, as well as aggregate, determine success or failure. ral economic constraints on equipment and person- nel, should be well thought out. In ground-based harvesting, skid trail patterns LITERATURE CITED should be designed with future entries in mind. A branching pattern of more or less straight AHO, P.E., G. FIDDLER, and M. SPRAGO. 1983. trails with relatively narrow-angled intersections is Logging damage in thinned, young-growth true recommended. In cable systems, skyline corridors fir stands in California and recommendations should be placed perpendicular to the ter- for prevention. USDA Forest Service, Pacific rain contour so that logs are easier to control as Northwest Forest and Range Experiment they are yarded. Two patterns exist: a converging Station, Portland, Oregon. Research Paper PNW- pattern, with several corridors meeting at a single 304. 8 p. landing, and a parallel pattern. The one that best BARRETT, J.W., S.S. TORNBOM, and R.W. SASS- matches the terrain should be selected. Both skid MAN. 1976. Logging to save ponderosa pine trails and skyline corridors should be flagged pri- regeneration: a case study. USDA Forest or to harvest. Service, Pacific Northwest Forest and Range Harvesting Timber to Achieve Reforestation Objectives 229

Experiment Station, Portland, Oregon. Research Francisco,California.Division of Timber Note PNW-273. 13 p. Management Report. 25p. BRADSHAW. G. 1979. Preplarmed skid trails and FOIL, RR, and C.W. RALSTON. 1967. The estab- winching versus conventional harvesting on a lishment and growth of loblolly pine seedlings on partial cut. Forest Research Laboratory, Ore- compacted soils. Soil Science Society of America gon State University, Corvallis. Research Note Proceedings 31:565-568. 62. 4 p. FRANKLIN, J. 1989. Toward a new forestry. BROWN, G.W., and D.A. PERRY. 1984. Comparison American Forests 95(11/12):37-40. of alternative harvest systems in shelterwood FROEHLICH, HA 1977. Soil compaction: why the overstory removal and impact on understory controversy? Loggers Handbook 37:20-22. seedlings. Part 1: designated skidtralls vs. con- FROEHLICH, H.A. 1979. Soil compaction from log- ventional tractor logging. Oregon State University ging equipment: effects on growth of young pon- report to USDA Forest Service, Pacific Northwest derosa pine. Journal of Soil and Water Forest and Range Experiment Station, Portland, Conservation 34:276-278. Oregon. PNw Supplement PNW-82-319. 18 p. FROEHLICH, H.A. 1980. Predicting soil com- BURDITT. A.L. 1981. Damage to the residual stand paction on forested land. USDA Forest Service, due to skyline yarding. Master's thesis. Oregon Equipment Development Center, Missoula, State University, Corvallis. 70 p. Montana. CLAYTON, J.L. 1981. Soil disturbance caused by FROEHLICH, H.A., D.E. AULERICH, and R CUR- clearcutting and helicopter yarding in the Idaho TIS. 1981. Designing skid trail systems to Batholith. USDA Forest Service, Intermountain reduce soil impacts from tractive logging Forest and Range Experiment Station, Ogden, machines. Forest Research Laboratory, Oregon Utah. Research Note INT-305. '7 p. State University, Corvallis. Research Paper 44. CONWAY, S. 1982. Logging practices: principles of 15p. timber harvesting systems. Miller Freeman GAAS, A.A. 1974. Rational logging technology with Publications, Inc., San Francisco, California. preservation of advance growth. Lesnoye 432 p. Khozyaistvo 1:28-32. DYKSTRA, DENNIS P. 1975. Production rates and GARLAND, J.J. 1983. Designated skidtrails mini- costs for cable, balloon, and helicopter yarding mize soil compaction. Oregon State University systems in old-growth Douglas-fir. Forest Extension Service, Corvallis. Extension Circular Research Laboratory, Oregon State University, EC 1110. 6 p. Corvallis. Research Bulletin 18. HOLMAN, G.T.,F.B. KNIGHT,andR.A. DYRNESS, C.T. 1965. Soil surface conditions fol- SIRUCHTEMEYER. 1978. The effects of mech- lowing skyline logging. USDA Forest Service, anized harvesting on soil conditions in the Pacific Northwest Forest and Range Experiment spruce-fir region of north-central Maine. Station, Portland, Oregon. Research Note PNW- University of Maine at Orono. Life Science and 55. 8 p. Agriculture Experiment Station Bulletin 751. DYRNESS, C.T. 1967. Soil surface conditions fol- HUNT, D.L., and J.W. HENLEY. 1981. Uphill felling lowing skyline logging. USDA Forest Service, of old-growth Douglas-fir. USDA Forest Service, Pacific Northwest Forest and Range Experiment Pacific Northwest Forest and Range Experiment Station, Portland, Oregon. Research Note PNW- Station, Portland, Oregon. Research Paper PNW- 55. 8 p. 122. 18 p. DYRNESS, C.T. 1972a. Soil surface conditions fol- IFF, R.H. 1977. An analysis of the slackpulling lowing balloon logging. USDA Forest Service, forces encountered in manual thinning car- Pacific Northwest Forest and Range Experiment riages. Master's thesis. Oregon State University, Station, Portland, Oregon. Research Note PNW- Corvallis. 65 p. 182. 8 p. KELLOGG, L.D., S.J. PILKERTON, and R.M. FIEBER, W.F., T.A. DURSTON, and R. VARNER. EDWARDS. 1991. Logging requirements to meet 1982. S.C.O.U.T. Hawkins logging study. USDA new forestry prescriptions. P. 43-49 in J.F. Forest Service, Pacific Southwest Region, San McNeel and Bjorn Andersson, eds. Forestry 230 Harvesting Timber to Achieve Reforestation Objectives

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