3.2. Regeneration Methods: Clearcut

Description

A method of regenerating an even aged stand in which a new age class develops in a fully exposed microclimate after removal, in a single cutting, of all trees in the previous stand. Regeneration is from natural seeding, direct seeding, planted seedlings, and/or advance reproduction. The management unit or stand in which regeneration, growth, and yield are regulated consists of the individual clearcut stand (Adams et al. 1994).

Extent

Clearcutting is the most common regeneration method used in North America today, particularly in the US South. It is well-suited to plantation forests and many naturally regenerated stands.

Cuts Involved

Clearcutting is so commonly applied in part due to its simplicity. Clearcutting involves only a single cut that removes all merchantable timber to regenerate the stand. Following this cut, the stand is either artificially (e.g. planting or direct seeding) or naturally regenerated with trees of a single age class.

Common Variations

A commercial clearcut is the most typical variation of the clearcut regeneration method. This involves the removal of all merchantable timber. A clearcut may thus still have standing live trees remaining following harvest. These are usually not intentionally retained (as in a two age regen method), but rather are simply not cut. There are a variety of reasons trees may not be cut.

• They may be too small to be merchantable.
• Poor stem form may limit merchantability, particularly in locations with weak pulpwood markets.
• Heart rot may make otherwise suitable trees unmerchantable.
• Some species are not useful for producing forest products.
• There may be no market at the time of harvest for trees that would usually be merchantable.

Trees left after a commercial clearcut may either be left, or treated during site preparation. During site prep trees may be deadened with herbicides or by girdling and left standing. They may also be felled with a chainsaw or shear, and then treated with the rest of the slash. When deciding what to do with unmerchantable stems, both their effect on the new cohort and the cost of handling them should be considered.

A biological clearcut is a harvest where all trees are removed, regardless of size class or merchantability. Biological clearcuts are used for research purposes, but are rarely, if ever, prescribed in operational forests.

A cleancut is a clearcut in which both merchantable and smaller unmerchantable trees are cut down to some minimum size limit. Cleancutting is prescribed for species where shade created by a midstory will prevent adequate regeneration. For example, southern bottomland hardwoods being managed for oaks are often cleancut, with all stems more than 2 inches dbh removed to prevent shading the new cohort (Hodges 1995).

The spatial arrangement of clearcutting can also be varied. Strip clearcuts are used when the species being regenerated are not windfirm, or when natural seeding is required for regeneration but seed dispersal distances are limited. Strip clearcuts are often done in a series. Once a clearcut strip has regenerated, the adjacent strip is then cut. Considering prevailing wind directions and orienting strips appropriately is important for either reason that strips are being utilized.

Another commonly utilized method of clearcutting is the patch clearcut. Patch clearcuts are the same as clearcutting, but are conducted on a smaller spatial scale. Patch clearcuts may be no more than a few acres in size. This subject will be covered in greater detail in the selection section.

Ecological Considerations (Silvics)

Clearcutting results in the most fully exposed microclimate of any regeneration method. It is best suited to shade intolerant species. Many pioneer species are appropriate for regenerating via clearcutting.

While clearcuts result in more light reaching ground-level, the amount and quality of light varies across a clearcut. Along with light, air temperature, soil temperature, relative humidity, and soil moisture all also vary. In the northern hemisphere, the sun is generally found in the southern portion of the sky throughout the day. Thus, the south edge of a clearcut in an area with level topography will be shaded by the adjacent stand, while the center and north edge of a clearcut will receive more light. Eastern edges are shaded in the morning when it is relatively cool, and are fully exposed to the sun in the afternoon, when it is warmer. The opposite trend applies to western edges. Edge environments are often more variable in their microclimate than the interior of a clearcut, or even an uncut stand (Chen et al. 1993). So although a clearcut may appear relatively homogenous, this spatial variability in the light environment may create patches suitable to the regeneration of species with varying shade tolerances.

The size, geometry, and orientation of clearcut patches will also influence the light environment. Larger clearcuts tend to receive more direct light rather than diffuse light, which can result in hotter daytime temperatures and cooler nighttime temperatures (Carlson and Groot 1997).

Beyond light, newly establishing seedlings are also affected by belowground processes, including competition for soil resources with the roots of adjacent stands and non-crop vegetation. In general, increasing root biomass of herbaceous and weedy species results in reduced growth of desirable species (Lockaby et al. 1988). Despite this effect, light often remains the most limiting resource for young seedlings compared to nutrient or water availability (Ricard et al. 2003). Because seedlings are small, their nutrient and water demands are low compared to larger trees. This is coupled with greater nutrient and water availability following clearcutting as slash decomposes, releasing nutrients and the evapotranspirative demand of the harvested stand is greatly reduced (Fox et al. 2007).

As with any regeneration method, it is important to consider how the new cohort will establish on the site following clearcutting. If planting or direct seeding of a shade intolerant pioneer species is planned, then clearcut size and shape are not constrained by the need to ensure adequate regeneration. If natural regeneration from seed is desired, then the natural patterns of seed dispersal must be taken into account. For species with wind-dispersed seed, it is necessary to know the distance that seed will be distributed from surrounding stands and the prevailing wind direction. If clearcuts are too large, seed of desirable species may not reach all the harvested area, resulting in a regeneration failure.

In some species it may be possible to rely on stump or root sprouting as a source of regeneration following clearcutting. Sprouting potential varies with species, tree size, and age (Dey and Jensen 2002). If sprouting is desired, then any available data on sprouting for the species in question should be used to determine if regeneration will be sufficient following harvest.

Protection of the soil resource is critical if silviculture is to be a sustainable practice. Many forests in the US South were established on previously eroded lands that were degraded through unsustainable agricultural practices. While topsoil may be very thin in these stands, it is not the result of past silvicultural practices. In more mountainous regions, such as the western US, the potential for erosion is higher. Mass wasting, or the bulk movement of soil as in a landslide, generally increases in both soil volume lost and frequency of slides as slopes become increasingly steep (Amaranthus et al. 1985). In general, the vast majority of erosion associated with clearcutting occurs on forest roads and skid trails, not on the harvested matrix (Aust and Blinn 2004). Erosion from the harvested matrix may be higher for several years following clearcutting before vegetation can become established enough to retain the soil (Swank et al. 2001). Streamside management zones, or buffers of unharvested trees maintained around streams, are an effective means of preventing eroded sediment from entering streams (McBroom et al. 2008, Ward and Jackson 2004).

Clearcutting has been found to have mixed effects on various species of wildlife and their habitat. For example, clearcutting in boreal forests was found to vary in its effect on wildlife depending on the size of their home ranges (Potvin et al. 1999). In this study, animals with large home ranges (> 2 sq. miles) continued to utilize suitable areas of clearcuts and surrounding vegetated areas. Animals with medium-sized home ranges (< 60 acres) no longer used the clearcut patches. Those with the smallest home ranges (< 2.5 acres) either remained in the clearcut area, or relocated to surrounding intact stands. Effects of clearcutting on wildlife also vary by species. For instance, clearcutting resulted in reduced abundance of some salamander species, but had no effect on others in the Pacific Northwest (Grialou et al. 2000). Some species, such as white-tailed deer, prefer recently clearcut areas as a source of abundant browse (Ford et al. 1993). If management for wildlife habitat is a silvicultural objective, an understanding of the effects of clearcutting on the specific species under management is necessary.

Suitable Species

• US South
  • Loblolly pine (Pinus taeda)
  • Slash pine (Pinus elliottii)
  • Longleaf pine (Pinus palustris)
  • Shortleaf pine (Pinus echinata)
  • Eastern cottonwood (Populus deltoides)
  • Baldcypress (Taxodium distichum)
  • Sycamore (Platanus occidentalis)
  • Tupelos (Nyssa spp.)
  • Pecan (Carya illinoinensis)
  • Green ash (Fraxinus pennsylvanica)
  • Cherrybark oak (Quercus pagoda)
  • Nuttall oak (Quercus texana)
  • Willow oak (Quercus phellos)
  • Laurel oak (Quercus laurifolia)
  • Water oak (Quercus nigra)
  • Sweetgum (Liquidambar styraciflua)
• US North
  • Jack pine (Pinus banksiana)
  • Red pine (Pinus resinosa)
  • Black spruce (Picea mariana)
  • Black cherry (Prunus serotina)
  • Balsam poplar (Populus balsamifera ssp. balsamifera)
  • Paper birch (Betula papyrifera)
• US West
  • Douglas-fir (Psuedotsuga menziesii)
  • Ponderosa pine (Pinus ponderosa)
  • Sitka spruce (Picea sitchensis)
  • Western hemlock (Tsuga heterophylla)
• Interregional
  • Yellow-poplar (Liriodendron tulipifera) S,N
  • Trembling aspen (Populus tremuloides) N,W

Economic Considerations

Because clearcutting results in the removal of all merchantable timber in a stand with a single entry, it usually yields the greatest profit at a single time of any regeneration method. Stands managed for timber via clearcutting can be placed on the shorter rotations than those regenerated by other methods, also giving clearcutting an economic advantage. Because of the simplicity, stand uniformity, and operational efficiency of clearcutting it also tends to be the most economically efficient regeneration method, yielding the highest value per ton harvested.

Clearcutting does have some economic disadvantages as well. In regions where rotations are longer, it may be 50 years or more between clearcut harvests with little income from a stand. In such situations selection silvicultural systems may have greater net present values than clearcutting since timber can be harvested at more frequent intervals. This disadvantage can be offset to some extent through the application of well-planned thinnings. It is also important to consider the costs of any necessary site preparation and artificial regeneration that may be necessary with clearcutting, as these costs will essentially be carried for the entire length of the rotation, or at least until they can be offset through income from thinning operations.

Taking steps to minimize the amount of slash left in a clearcut harvest will reduce subsequent site preparation costs. This can be encouraged by using a lump-sum timber sale, rather than a pay-as-cut sale, to encourage greater utilization by logging contractors. Pay-as-cut sales compensate a logger for the volume actually cut and the unit price, and thus do not provide as much incentive to remove lower-value products such as pulpwood. With lump-sum sales, the sale price is not a function of the volume cut. This encourages the logger to remove all material that may be merchantable, even if it is of lesser value, thus reducing the amount of slash that will be left following harvest.

Societal Considerations

Clearcutting more than any other silvicultural practice requires an awareness and sensitivity to the societal effects of silvicultural decisions. This is particularly true for foresters working on federal or state lands, where public input and collaboration is often a legally required step in the management process. Even when clearcutting is an ecologically and economically sound practice, it may not be a viable management option due to societal constraints. The extent to which societal constraints are a factor depends on the ownership status of the land. Small private landowners may be much less concerned if at all with public perceptions than are large timberland management corporations. Corporations in turn are not required to directly involve the public in management decisions, while federal agencies are legally obligated. On numerous occasions lawsuits have blocked economically and ecologically sound forest management plans on National Forests because the foresters involved did not fully consider the societal aspects of their silvicultural decisions.

Misinformation relating to clearcutting abounds. As of the 2000 US Census, only 21% of Americans lived in rural areas (US Census Bureau 2000). Many individuals in urban areas may have little knowledge of forestry or silviculture, and may believe that clearcutting is synonymous with deforestation, the death of a forest, or the creation of a biological desert (Belt and Campbell 1999). None of these outcomes is in fact true, as can be seen from the content presented in this section. Certain pro-environmental non-governmental organizations are responsible for actively spreading misinformation about clearcutting, usually as a tactic to achieve policy goals. Such misinformation is often either simplified to the point of being incorrect, or is advertised as a universal truth despite actually being applicable in only certain situations. For example, the Sierra Club suggests on one of its websites (http://sierraclub.org/clearcutting/, accessed 23 July 2012) that: "Clearcutting is an extreme form of logging that replaces natural forests with tree plantations." Not all clearcuts are artificially regenerated, and many of the ecosystem services they go on to state are threatened by plantations (clean water, clean air, habitat, fire protection) are in fact services provided by both plantations and natural stands alike. The truth is far more complex than indicated. It is the foresters task to correct such misinformation when possible.

One unavoidable aspect of clearcuts is that they are ugly. This fact alone may have led to much of the misinformation just described. A field of stumps surrounded by slash is not as visually appealing as an intact forest stand to almost anyone. There are a number of modifications to clearcut systems that can be made to improve aesthetics, although their efficacy depends largely on the topography of the region.

• A. Aesthetic management zone (AMZ), or a buffer of trees, can be left along major roads.
• B. Streamside management zones (SMZ) can also be used to improve aesthetic quality and limit the visual impact of harvest areas as seen from major roads.
• C. Dog-leg logging roads can limit the distance visible into a clearcut area.
• D. Patches of trees retained within the clearcut matrix minimizes visual impact and makes clearcut areas appear smaller and more heterogeneous.
• E. Locating log decks away from highly visible areas leaves the often small, unregenerated patches they create with large amounts of slash out of sight.
• F. Irregular harvest boundaries better blend clearcuts with the surrounding landscape at the time of harvest and long after.

Silvicultural System Considerations

Sites with sensitive soils may not be suitable for regeneration by clearcutting. Sensitive soils include those that are easily erodible, such as deep, sandy soils on hilly sites. Shelterwood systems may be more appropriate to these sites to preserve the soil. Soils sensitive to rutting or compaction may vary in their sensitivity depending on the time of year or weather. Rutting can be avoided on most soils by ceasing harvest operations when conditions are too wet. In low-lying areas of the coastal plain, drier upland sites become more valuable from a logistical perspective, as they can be harvested when it is not possible to traffic on wetter sites. Compaction also tends to be worse during wet-weather logging, as water in the soil reduces soil strength by acting as a lubricant and allowing soil particles to more easily move against one another and into macropore spaces (Greacen and Sands 1980). In general, soils with more organic matter and more active soil fauna tend to be less susceptible to compaction (Greacen and Sands 1980). In regions with cold winters, operating when the ground is frozen will also prevent compaction and rutting.

Timber marking is often minimal in clearcut systems. It is usually necessary to mark property boundaries, harvest boundaries, streamside management zones, and aesthetic management zones. In some situations it may also be advisable to mark log roads, landing locations, and skid trails, although this is often unnecessary when working with well-trained and experienced loggers.

Establishment Treatments

Many clearcuts require some degree of site preparation. This is usually necessitated by the need to manage slash. The degree to which slash needs to be managed depends on:

1. the amount of slash present,
2. the degree of access necessary for subsequent operations, and
3. the need to protect the new cohort from insects, disease, or fire.

For example, if it is desirable to machine plant rather than hand plant a stand, then much of the large slash needs to be removed or compacted to the point that a tractor or dozer can operate on the site.

Chemical competition control is commonly prescribed in plantations to allow the planted seedlings to outcompete grasses, shrubs, and non-crop tree species. Mechanical site preparation is not always required but is sometimes necessary to ameliorate rutting or compaction that occurred during harvest operations. All these options are covered in greater detail in the site prep section.

Following site preparation, the stand may be either planted or direct seeded, as is covered in greater detail in the corresponding sections.

Intermediate Treatments

Subsequent intermediate treatments are dependent largely upon stocking at establishment. If clearcuts are naturally regenerated, or direct seeded they may establish at high densities, requiring precommercial thinning. Planted stands with appropriate competition control usually do not require a precommercial thinning. The timing and intensity of thinnings can be controlled to some extent by planting density, as lower density stands will reach minimum merchantable diameters more quickly.

Clearcut Pros

• Planting allows use of genetically improved stock.
• Planting allows the best control of stocking and spacing.
• Clearcutting produces the most uniform stands.
• Clearcutting allows for the shortest possible rotation.
• There is high economic efficiency and returns.
• High timber value obtained in a single harvest.
• Clearcutting is easy to prescribe and implement, and involves the least marking.
• Precommercial thinning is not usually required with planting.

Clearcut Cons

• Clearcutting may regenerate structurally simple stands with less habitat value.
• There may be greater establishment costs.
• Planting often requires more labor and machinery to establish a new stand.
• With artificial regeneration the provenance may not be locally adapted.
• Poorly executed planting results in unacceptably low survival and growth
• Clearcutting risks of soil degradation due to compaction, rutting, or erosion.
• Clearcut size is limited by some certification systems.
• Clearcutting adjacent stands requires a green-up period in some certification systems.
• Aesthetics are often poor immediately following harvest.
• Misinformation abounds relating to clearcutting.
• Large clearcut areas without adequate provisions for regeneration often remain understocked.

Examples

References

Adams, D. L., J. D. Hodges, D. L. Loftis, J. N. Long, R. S. Seymour, and J. A. Helms. 1994. Silviculture Terminology with Appendix of Draft Ecosystem Management Terms. Silviculture Instructors Subgroup of the Silviculture Working Group of the Society of American Foresters. https://www.bugwood.org/silviculture/terminology.html

Amaranthus, M. P., R. M. Rice, N. R. Barr, and R. R. Ziemer. 1985. Logging and forest roads related to increased debris slides in southwestern Oregon. Journal of Forestry 83:229-233. https://www.fs.fed.us/psw/publications/ziemer/Ziemer85.pdf

Aust, W. M. and C. R. Blinn. 2004. Forestry best management practices for timber harvesting and site preparation in the eastern United States: An overview of water quality and productivity research during the past 20 years (1982–2002). Water, Air, & Soil Pollution: Focus 4:5-36. http://dx.doi.org/10.1023/B:WAFO.0000012828.33069.f6

Belt, K. and R. Campbell. 1999. The clearcutting controversy - Myths and Facts. West Virginia University Extension Service. http://ahc.caf.wvu.edu/joomla/index.php?option=com_remository&Itemid=148&func=fileinfo&id=247 (Broken link, last accessed 23 July 2012)

Burns, R. M. and B. H. Honkala, editors. 1990. Silvics of North America. U.S. Department of Agriculture, Forest Service, Washington, DC. https://www.srs.fs.usda.gov/pubs/misc/ag_654/table_of_contents.htm

Carlson, D. W. and A. Groot. 1997. Microclimate of clear-cut, forest interior, and small openings in trembling aspen forest. Agricultural and Forest Meteorology 87:313-329. http://dx.doi.org/10.1016/S0168-1923(95)02305-4

Chen, J., J. F. Franklin, and T. A. Spies. 1993. Contrasting microclimates among clearcut, edge, and interior of old-growth Douglas-fir forest. Agricultural and Forest Meteorology 63:219-237. http://dx.doi.org/10.1016/0168-1923(93)90061-L

Dey, D. C. and R. G. Jensen. 2002. Stump sprouting potential of oaks in Missouri Ozark forests managed by even- and uneven-aged silviculture. in Proceedings of the Second Missouri Ozark Forest Ecosystem Project Symposium: Post-treatment Results of the Landscape Experiment. General Technical Report NC-227. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. http://www.treesearch.fs.fed.us/pubs/19044

Ford, W. M., A. S. Johnson, P. E. Hale, and J. M. Wentworth. 1993. Availability and use of spring and summer woody browse by deer in clearcut and uncut forests of the Southern Appalachians. Southern Journal of Applied Forestry 17:116-119. https://doi.org/10.1093/sjaf/17.3.116

Fox, T. R., H. L. Allen, T. J. Albaugh, R. Rubilar, and C. A. Carlson. 2007. Tree nutrition and forest fertilization of pine plantations in the southern United States. Southern Journal of Applied Forestry 31:5-11. https://doi.org/10.1093/sjaf/31.1.5

Greacen, E. and R. Sands. 1980. Compaction of forest soils. A review. Soil Research 18:163-189. http://dx.doi.org/10.1071/SR9800163

Grialou, J. A., S. D. West, and R. N. Wilkins. 2000. The effects of forest clearcut harvesting and thinning on terrestrial salamanders. Journal of Wildlife Management 64:105-113. http://dx.doi.org/10.2307%2F3802979

Hodges, J. D. 1995. The southern bottomland hardwood region and brown loam bluffs subregion. Pages 227-270 in J. W. Barrett, editor. Regional Silviculture of the United States. John Wiley & Sons, Inc., New York, NY. ISSN: 0471598178

Lockaby, B. G., J. M. Slay, J. C. Adams, and C. G. Vidrine. 1988. Site preparation influences on below ground competing vegetation and loblolly pine seedling growth. New Forests 2:131-138. http://dx.doi.org/10.1007/BF00027764

McBroom, M. W., R. S. Beasley, M. Chang, and G. G. Ice. 2008. Storm runoff and sediment losses from forest clearcutting and stand re-establishment with best management practices in East Texas, USA. Hydrological Processes 22:1509-1522. http://dx.doi.org/10.1002/hyp.6703

Potvin, F., R. Courtois, and L. Bélanger. 1999. Short-term response of wildlife to clear-cutting in Quebec boreal forest: Multiscale effects and management implications. Canadian Journal of Forest Research 29:1120-1127. http://dx.doi.org/10.1139/x99-040

Ricard, J.-P., C. Messier, S. Delagrange, and M. Beaudet. 2003. Do understory sapling respond to both light and below-ground competition? A field experiment in a north-eastern American hardwood forest and a literature review. Annals of Forest Science 60:749-756. http://dx.doi.org/10.1051/forest:2003069

Swank, W. T., J. M. Vose, and K. J. Elliott. 2001. Long-term hydrologic and water quality responses following commercial clearcutting of mixed hardwoods on a southern Appalachian catchment. Forest Ecology and Management 143:163-178. http://dx.doi.org/10.1016/S0378-1127(00)00515-6

U.S. Census Bureau; 2000 Census Summary File 1; Table GCT-P1; generated by Jeremy Stovall; using American FactFinder; (23 July 2012). http://factfinder2.census.gov (Broken link)

Ward, J. M. and C. R. Jackson. 2004. Sediment trapping within forestry streamside management zones: Georgia Piedmont, USA. JAWRA Journal of the American Water Resources Association 40:1421-1431.
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