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Forest management requires a range of tools to implement prescriptions from planting, fertilization, burning, and herbicide application, through thinning and product extraction. International Standard 6814 (ISO 1999) provides common definitions for individual machines. In many management activities, however, the individual machines are grouped into systems. A forest operation system is more than technology represented in equipment design. A system includes the technology of methods and human work. While the capabilities of individual machines are of interest, the overall productivity and impacts of operations are the result of the cumulative effect of systems.
Site preparation and stand establishment operations may require seedbed preparation, reduction of competition, alteration of soil moisture or physical properties, or nutrient amendment. The desired management objectives are to control stocking, species composition, survival, or growth. Given the wide range of sites and objectives in the South, there are many operations that can be employed. Since 1952, a periodic survey of southern forest land managers has been conducted to estimate the prevalence and costs of forest management practices (Dubois and others 2001). Fifty-four percent of the responses to the most recent edition of the Cost Trend Survey were from forest industry, 32 percent from consultants, and 14 percent from public agencies.
Prescribed fire is the least expensive way to prepare the forest floor for regeneration. It provides some control of herbaceous competition, exposes mineral soil for seed catch, and reduces logging debris. Prescribed fire is used in prescriptions for natural regeneration by the seed-tree, single-tree selection, and shelterwood systems as well as for artificial regeneration. Waldrop (1997), for example, describes the use of manual felling combined with fire to regenerate pine-hardwood stands in the Southern Appalachians. Fire often controls hardwood growth enough to allow pines to become established. While regeneration is an important use of fire, the Cost Trends Survey found the most common use of fire (about one-third of treated acres) is to reduce hazardous accumulations of fuels at mid-rotation.
Like prescribed fire, chemical treatment is used to control vegetative competition for light, moisture, and nutrients. Forestry herbicides can be applied by stem injection, soil application, or foliar spray. Busby and others (1998) compared herbicide treatment at stand establishment with early release applications and found that herbicide application at stand establishment had the greatest economic returns. Groninger and others (1998) describe the effectiveness of herbicide injection for precommercial thinning of oak stump sprouts. The Cost Trends Survey found that about one-fourth of the treated acres were by aerial application at the time of stand establishment. Another third were chemically treated to achieve early release or herbaceous weed control. The reported costs of herbicide treatment were about four times those for prescribed fire ($68 vs. $18/acre).
Mechanical site preparation is designed to modify soil conditions, clear planting sites, and control competing vegetation. Each type of operation addresses specific site conditions. Drum chopping, for example, knocks down standing material and breaks it into pieces using large rolling cylinders fitted with blades. In shearing, an angled blade on the front of a crawler tractor splits stumps, moves debris, and exposes mineral soil. Raking also uses a special blade on a crawler tractor to move and pile slash. Surface soil can be disked to reduce vegetative competition. Bedding loosens and moves soil to create raised planting areas. Finally, subsoiling or ripping fractures heavy or compacted soils. Site preparation prescriptions may call for a single type of treatment or a combination of treatments. According to the Cost Trends Survey, the most common treatment in the Piedmont is a combination of subsoiling, disking, and bedding accomplished in a single pass with a 3-in-1 plow. This tool was developed around 1990 to reduce site preparation costs. On the Coastal Plain, a multipass treatment combining shearing, raking, and piling is the most common mechanical treatment.
About 2 million acres were planted in the South in 1997 (Moulton 1999). The acreage was nearly evenly split between nonindustrial private forest (NIPF) landowners and forest industry. Direct seeding accounted for only 0.4 percent of the total. Nearly 1.3 billion seedlings were produced in southern nurseries, and the average planting density was 618 trees per acre. The Cost Trend Survey found that most planting (79 percent) was done by hand rather than by machine. Machine planting is slightly more expensive, averaging $45 per acre compared to $39 per acre for manual work. Machine planting is also more constrained by site conditions such as debris, slope, and soil moisture. Seedling costs vary considerably, depending on species, genetics, and product form. One source, for example, lists containerized loblolly pine seedlings for $155 per thousand, while similar seedlings in bare-root form are $46 per thousand. Thus, total costs for planting may range from $85 to $200 per acre.
With these significant investments in site preparation, improved seedlings, and planting, fertilization is increasingly common in the South. Almost 1.6 million acres were treated in 1999 (North Carolina State Forest Nutrition Cooperative 1999). Some applications are at stand establishment to promote initial growth, but about two-thirds of the treated acres are in established stands (Jokela and Stearns-Smith 1993). The most common fertilizers are dry solid forms of urea (for nitrogen) or diammonium phosphate (for nitrogen and phosphorus). The Cost Trends Survey found that nearly all fertilizer is applied by airplane or helicopter.
Many prescriptions call for manipulation of vegetation in established stands: thinning, sanitation removals of diseased or infested trees, regeneration cuttings in shelterwood or group-selection systems, and harvest of crop trees. All of these treatments involve some type of felling and, in most cases, processing and extraction. Stokes and Watson (1996) describe a range of systems for plantation thinning, and Stokes (1991) outlines systems used in southern timber harvests. These systems are sometimes defined by the forest product that is produced (pulpwood or sawlog).These distinctions, however are less definitive today as multiproduct harvesting becomes more common. A more useful description may be the level of mechanization, from animal logging systems to helicopters.
Animal logging was replaced by tractor logging in the 1930's to reduce costs. Yet, 60 years later, animal logging systems are still found in the southern forest as specialty operations. Various surveys indicate a public perception that animal logging is ecologically and visually preferred over more mechanized systems. Toms (1999) described current animal logging systems used in Alabama. In all of these operations, felling, delimbing, and processing are done with chainsaw. Trees are bucked at the stump to log lengths for primary extraction with animals. Most crews take two animals to the woods and work them as singles rather than as a team. Systems vary in extraction and loading. The "traditional" animal logging crew skids logs to a loading point where a self-loading truck (a side-loader or a big-stick loader) can access the material. Some crews use a front-end loader or knuckleboom to increase productivity. A final variant is a hybrid system that combines animal prebunching with subsequent extraction by a conventional skidder or forwarder.
Production is relatively low with animal logging systems. Toms (1999) found average weekly production ranged from 2,500 ft3 for the traditional system to 7,000 ft3 for the hybrid variant. Terrain, skidding distance, crew experience, and degree of mechanization are critical factors affecting the production rate. Uphill skidding or heavy brush can significantly reduce output. To maximize productivity, animal loggers prefer to work in large timber where 1-log loads approach full capacity and at short extraction distances. A study in the Missouri Ozarks (Ficklin and others 1997) observed mules operating at skidding distances of 1,050 ft, but Toms and others (1996) found an average skidding distance of less than 200 ft.
The low production rate and minimal move-in costs make animal logging operations most competitive on small harvest units. As long as total harvest volume exceeds several loads, there is little economic penalty associated with small tracts. In fact, the smallest unit reported by Toms (1999) was a 1-acre tract, and the median tract size was only 20 acres.
The primary advantages of animal logging are minimal soil disturbance and residual tree damage, suitability to small tracts and selective cutting, and minimal noise and pollution. Balancing these advantages, however, are the low overall production rate, a significant reduction in productivity with small diameter pieces, stand disturbance associated with loading and woods roads, and the need to minimize skidding distance.
In 1998, an extensive survey of animal logging in Alabama identified 52 contractors mostly operating in the northern half of the State (Toms and others 1998). Assuming an average production of 4,000 ft3 per week, the total output of animal loggers in Alabama represents less than 0.5 percent of the statewide roundwood harvest in 1995 (Johnson and others 1998).
Mechanizing the extraction function of an animal logging system leads to the manual cable skidder system. In this operation, trees are manually felled, limbed, and topped. A rubber-tired cable skidder pulls logs to a landing for loading. The unique feature of cable skidders is their ability to winch logs. By pulling cable from the skidder to the log, trees may be pulled into a skid trail with little soil disturbance. The winch is also useful on wet sites when the skidder loses traction. By slacking the winch and driving ahead, the load can be pulled through the trouble spot. Cable skidder systems are typically used in broken, steep, or wet terrain, in large-diameter sawtimber, and in selection harvests.
The feller-buncher and grapple skidder system has significantly increased harvesting productivity. Feller-bunchers fell trees with either a saw or shear and then place the trees in bunches for further handling. By accumulating felled trees in piles, the feller-buncher makes the subsequent skidding process more productive. Grapple skidders take advantage of the bunched wood by grasping a full load with a large pincer on the back of the machine. Cable skidder operators, in contrast, have to stop and tie a wire rope to each tree. With most feller-buncher systems, the wood is skidded in tree lengths to either a landing or a processing area for delimbing. Gate delimbers are large steel grates that are set in the woods at some distance from the landing. By backing the load of trees through the grate with the skidder, most pine limbs can be broken off. A landing sawyer may be employed to clean up the wood prior to loading. Stroke delimbers, loader-mounted pull-through delimbers, and flail delimbers (Mooney and others 2000) are gaining acceptance to improve delimbing quality, reduce waste, and eliminate manual chainsaw work. A typical feller-buncher and grapple skidder system includes one feller-buncher, two grapple skidders, a gate delimber, and a knuckleboom log loader. If products are sorted out, higher value products are bucked from the tree-length pieces at the landing either by chainsaw or slasher. These systems find greatest application in even-aged stands with trees of uniform size and high pulpwood volumes.
In-woods chipping is an extension of the feller-buncher and grapple skidder system. In these operations, a flail-chipper is added at the landing to produce pulp-quality chips from tree-length stems. A spinning chain flail removes bark and limbs, and the clean stem is chipped and blown into a waiting van. Watson and others (1991) found that in-woods chipping produced chips of comparable quality to mill-produced chips. The system is balanced to the productivity of the chipper. Thus, a typical in-woods chipping operation may require two feller-bunchers, three skidders, a loader, and the chipper. High production is necessary to support the cost of the equipment. Munn and others (1998) noted an average production of about 500 tons per day for in-woods chipping. A similar system without the flail debarker may be used to produce fuel chips.
Cut-to-length (CTL) technology produces a different product form at roadside. It is a ground-based system in which felled trees are processed at the stump into defined log lengths. Characteristically, the CTL wood is transported to roadside on a forwarder, a machine that carries rather than drags wood. Forwarders were used years ago in southern shortwood operations. CTL technology has been advanced in Scandinavia, where it is the state-of-the-art system for forest harvesting. Modern harvesters fell trees and process them through computerized harvester heads that delimb and buck trees to optimum product lengths. Eight-wheeled forwarders accumulate, sort, transport, and load wood onto highway trailers. A key advantage of CTL systems is that they process trees in the woods, leaving a layer of limbs and tops on the ground to drive over. This reduces soil disturbance and compaction. Lanford and Stokes (1996) compared a CTL system with a feller-buncher and grapple skidder system in a pine thinning and found that costs and productivity of the two systems were practically equivalent.
Several specialized systems have been developed for wet sites (Stokes and Rummer 1997). Operations typically incorporate modifications to improve driving on soft soils. Conventional feller-bunchers may adapted by using a wide tracked feller-buncher. Skidders can be equipped with either wide tires or dual tires to reduce ground pressure. Tires up to 72" wide may be used. Large-capacity extraction machines have also been developed to reduce the need for roads on wet sites. Clambunk skidders may drag up to three times the load of regular skidders. Tree-length forwarders carry a full truckload of wood supported on 10 wide tires. Both clambunks and tree-length forwarders can be combined with tracked feller-bunchers and skidders for felling and short-distance extraction.
Shovel logging is another adaptation for wet sites. Originally developed in the Pacific Northwest, shovel logging was modified in the 1990's for southern conditions. The basic system uses a tracked feller-buncher to fell and pile trees. A second tracked machine, the shovel logger, moves felled trees and aligns them into a solid mat of wood to form a skidtrail. When the skidtrail is complete, dual-tired grapple skidders start at the farthest end of the road, picking up the mat of wood as they go. By traveling on the constructed skidtrail, shovel logging reduces rutting and soil disturbance.
Cable logging is another specialized method of extracting material on adverse sites, particularly on slopes greater than 35 percent. In cable logging, a long wire rope is suspended across the stand. A winch (the yarder) sits at the landing and pulls logs along the suspended cable. Depending on terrain and equipment, a cable system may simply drag logs from the stump or it may completely lift them off the ground. Units can be relatively large, with extraction distances of one-quarter mile. With long extraction distance, it is critical to fully load the system on each turn. Thus, cable logging requires special skills among sawyers and chokersetters. Product forms are limited by the possible load sizes for the cable. Planning is critical to meeting production and cost goals. However, LeDoux and others (1995) estimate that cable systems make 14 percent of the upland hardwood forest in the Southern United States economically operable.
Helicopters also can extract forest products where access is limited by soft soils or steep terrain. Helicopters are expensive to operate, so high hourly productivity is needed to achieve economic viability. Material to be removed is felled and bucked before the arrival of the helicopter and extraction crew. During extraction, teams of choker-setters preset lines on the felled material in optimum load sized bundles. The helicopter pauses in the woods just long enough for the choker-setters to connect the drop line to a bundle. After a short flight to the landing zone, the helicopter releases the load and returns to the woods. Sirois and Stokes (1986) and Jackson and Morris (1986) observed a helicopter crew operating in cypress swamps in coastal South Carolina. The operation required a crew of 14, plus a front-end loader and a knuckleboom loader. At extraction distances of 900 to 2,900 ft, cycle times ranged from 1.74 to 5.35 min. Average production was about 3,100 ft3 per scheduled hour of operation. Willingham (1989) described the initial configurations of helicopter logging with Scott Paper Co. in the Mobile Delta. Their system consisted of manual felling followed by helicopter extraction to a riverbank, where logs were loaded on a barge. The system evolved to include tracked feller-bunchers and a purpose-built helicopter to maximize efficiency.
Another application of helicopters is in steep terrain, where roadbuilding costs are high and ground-based extraction is difficult. Sloan and others (1994) reported on the use of a K-MAX logging helicopter for a shelterwood harvest in the mountains of Virginia. Working at an average extraction distance of 1,900 ft, the operation was estimated to produce 1,300 ft3 per hour.
Helicopters are not limited by ground conditions, but they are limited by weather, altitude, and piece size. In order to accumulate full loads, helicopter logging requires a particular minimum volume per acre. Hourly costs are very high. The reported operating costs in 1986 were about $2,000 per hour, including support but not felling. To avoid delays, the landing zone must be large enough to safely handle the loading of 15-20 trucks per day. The primary advantages of helicopter logging are the reduction of soil disturbance associated with roads and skidtrails and the reduction in roadbuilding costs. With the fast cycle times, helicopters are also able to operate economically at longer extraction distances than most ground-based systems.
A key component in forest operations technology is the skill and expertise of loggers. The Sustainable Forestry Initiative adopted in 1994 by the American Forest and Paper Association provided an incentive to promote logger training. Member companies support programs through financial contributions and by performance expectations established for their suppliers. A second key factor was the development of new OSHA logging safety regulations in 1996. In response, all but one Southern State developed some form of logger training and education (Forest Resource Association 2000). Oklahoma sends its people to courses in Arkansas. Curricula vary, but generally include safety and first aid, business management, best management practices (BMP's), environmental considerations, and forest management. Some courses are for supervisors, while others are for workers. Graduates receive formal recognition and may be required to remain current through continuing education. In 1999, 8,254 contractors and employees completed some form of a logger training and education course.
The 1990 Census (U.S. Census Bureau 2000a) reports 51,525 workers engaged in logging (Occupational Codes 494 and 496). Figure 1 shows the distribution of these logging workers across the South. Note that significant numbers of timber cutters are in counties with no forest products output. This is particularly apparent in Texas, Oklahoma, and Florida, where there are concentrations of workers in metropolitan areas. These likely represent urban treecutters who clear land and perform arborist services. It is probable that other metropolitan areas have similar numbers of nonforest timber cutters. The ES-202 Covered Employment data suggest a 1999 southern logging workforce of 43,234, approximately a 15 percent increase over the last decade (Figure 2).
A number of studies document characteristics of these southern loggers. The Southern Technical Divisions of the American Pulpwood Association conducted a series of pulpwood producer surveys periodically from 1976 to 1993. The most recent report from the 1993 data (Munn and others 1998) located 8,700 contractors with 46,580 employees, operating in 11 Southern States (not including KY or OK). Based on workforce estimates and pulpwood production reported, the survey sample was a nearly complete census of pulpwood producers. The most common harvesting configuration was a rubber-tired feller-buncher working with grapple skidders to extract wood for tree-length transport. Most delimbing and topping were done with chainsaws, but delimbing gates were used in about half of the operations. Less than 3 percent of crews used in-woods chippers. From the receiving mills' perspective, about 78 percent of the wood volume was produced by only 28 percent of the crews. Almost half of the pulpwood logging crews sampled produced less than 70 tons per week. The periodic sampling of pulpwood producers shows a clear increase in crew productivity over the last 20 years (Figure 3).
In their analysis of successful logging contractors, Stuart and Grace (1999) reported that productivity increased by about 12 percent between 1994 and 1997. In the sample of the upper quartile of loggers, productivity averaged about 60,000 tons per year. Greene and others (2001) found that weekly production of Georgia loggers nearly doubled from 1987 to 1997. Capital investment per cord remained nearly constant over the decade, while labor productivity increased by 79 percent.
Combining the logging population data with TPO production figures provides an overview of logging productivity variations across the South (Figure 4). Productivity was negatively related to percent hardwood production. Productivity was highest on the Coastal Plains and decreased through the Piedmont to the Appalachians and Interior Highlands.
The various assessments of the logging workforce show a diverse range of forest operations in the southern forest. The majority of fiber is produced with high-production ground-based systems. However, the majority of forest operators are small contractors with relatively low productivity. Technology has been developed to meet most conceivable forest conditions in the South. However economic viability limits the options of loggers and landowners.
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content: Bob Rummer |
created: 21-NOV-2001 |