This article was submitted by Don Gasper

Whole-tree logging, the removal of the entire tree including all the branches and crown, is both a relatively new form of logging and "the extreme in (forest) management" (Coates, 1982). In some areas of the northeastern United States and Canada, whole-tree logging is becoming the practice of choice.

Today, on two of the five ranger districts on the White Mountain National Forest (WMNF) 60-75% of the timber logged is by whole-tree logging (US Forest Service, 1993). It is common on industrial lands in Maine and New Hampshire, and takes place on some public lands including the White and Green Mountain National Forests. Despite the lack of research, some 1050 biomass plants are now operating in the United States (Johnson, 1993). Wood-to-energy plants in New Hampshire alone burn approximately 1.2 million tons of wood chips (equal to approximately 480,000 cords of wood) a year. Supplying these wood-to-energy plants with wood chips could have major impacts on New England forests.

Whole-tree logging uses large, mechanical equipment. This equipment has increased the amount of soil disturbance in the areas being logged. In a study of four whole tree clearcutting (WTC) sites, 92% of the soil surface was disturbed on two of the sites, 98% on one site, and 71% on the last site because the rest of the area was too steep and rocky for the operation of heavy machines (Pierce, et al., 1993).

Soil disturbance can range from destroying soil structure, reducing or eliminating regrowth for several years , to scarification. This is exposure of mineral soil without a canopy. If rain drops do not erode it, soil can become crusted and compacted solely by rainfall impact, to the point where seedling roots may have trouble penetrating the soil (Pierce, et.al.,1993).

Pierce, et al. (1993) found that at three WTC sites, 48-81% of the areas were compacted. Compacted soil inhibits "root penetration, aeration, and infiltration capacity, which may lead to soil saturation, erosion, and reduced seedling growth"(ibid.). Indeed, Martin (1988) found that logging equipment can cause compaction on more than 90% of a site. "The evidence seems clear that compaction, however slight, reduces seedling germination and growth to some degree" (ibid.).

Organic matter on the ground conserves forest nutrients, natural fertilizers, soil conditions, water stabilizing elements, and other life supporting requirements (Coates, 1982). Humus, organic debris including dead plants, leaves, twigs, tree trunks, and roots in various stages of decomposition, is an important source of nutrients. Hans Jenny of the College of Natural Resources at the University of California, Berkeley, stated:

"For soil to function effectively in plant production it must possess substantial water-holding and ion-exchange capacities, good physical structure, and thriving populations of bacteria, fungi, and invertebrates. These attributes are highly correlated with humus substances, which are dark-brown organic macro-molecules rich in phenolic compounds and are derived from plant remains and microbial synthesis. Humus has high absorptive capacity for toxic metals, and its buffering power mitigates the impact of acid rain. Humus maintenance requires a steady influx of plant biomass from root decay and aboveground organic residues" (1980, emphasis added).

Biomass operations remove almost all of the above-ground organic residues. According to Pierce, et al. (1993), clearcutting of northern hardwoods leads to a decrease in thickness, organic content, and nutrient content of humus. "Within 3 to 15 years after cutting, the ‘O’ horizon (humus) is reduced by about one-half."

Little research has been conducted to determine the amount of residue needed to maintain soil conditions for regeneration and growth (Cramer, 1974). Despite this lack of knowledge and understanding of the impacts of whole-tree logging, some foresters continue to promote it.

Whole-tree clearcutting dramatically changes the vegetative characteristics of the logged area. Species present at the site before logging usually regenerate, but in very different proportions. According to Pierce, et al. (1993):

"We expect that 75-100 years will be required on each site to establish precutting levels of basal area, biomass and density."

WTC imposed a distinct even-aged structure, likely to persist for 75-100 years, on the forest. Mechanical activity of skidders over most of each site crushed or damaged existing seedlings."

In many cases, economic pressure will cause logging to occur long before the 75-100 years required to restore structural diversity to the site. Essentially, 75-100 years in the evolutionary succession of the forest are irretrievably lost for it will never be allowed to develop.

Whole-tree thinning can change the entire structure of a forest. Eastern forests are complex in structure, having multiple layers of canopy. The many different kinds and ages of trees and other vegetation mean multiple layers of leaves. The more foliage layers, or the greater the vertical complexity of forest vegetation, the more breeding birds generally found in the forest (Willson, 1974). Whole-tree thinning removes the economically less valuable trees, thereby eliminating the multi-layer canopy. Whole-tree thinning is the foresters’ version of ethnic cleansing.

Whole-tree clearcutting removes over 90% of the above-ground biomass, or approximately 20-25% more of the original biomass than a stem-only clearcut (Pierce, 1993). Also, nutrients such as nitrogen, calcium and potassium are removed. Indeed, Pierce, et al. (1993) found that "WTC removes from 1.2 to over 3 times the nutrients removed with conventional stem-only clearcutting."

In New Hampshire, many biomass operations are thinning "junk" or economically low-quality wood. Yet, this young low quality wood has a high amount of nutrients in the branches and crown. According to Pierce, et al.(1993),

"The difference in nutrient removals between whole-tree and stem-only clearcutting is greater in young stands than in older stands, because a greater proportion of stand biomass is contained in the nutrient-rich crowns of young stands."

According to R.H. Waring of the Department of Forest Ecology at Oregon State University (1980):

"The annual growth of a forest peaks when the forest canopy first closes. A policy to thin or harvest at this time is not uncommon. Unfortunately, the forest's use of nutrients is also highest at this time, so complete tree harvesting results in a major loss of the available nutrients, exceeding 50% of the pool for some minerals such as potassium."

Pierce, et al. (1993) found that "a single WTC removed 4-6% of the total N, 5-13% of the Ca, and 2-3% of the K."

Over a 100-year rotation, nitrate is usually fully replaced due to the amount of nitrate in air pollution. Potassium input and output is basically balanced in an undisturbed forest, so any logging causes a depletion. Magnesium depletion is similar to that of potassium.

Presently, acidic precipitation is depleting calcium in the soils of New England. Logging leads to increased leaching of nutrients, and can double the rate of Ca loss.

"With WTC, the loss of Ca is 13-33% in 100 years for one harvest and 21-58% for three harvests at the four sites examined. Acid precipitation and WTC harvest removal contribute about equally to Ca depletion...Calcium depletion already may contribute to Red Spruce mortality at high elevations." (Pierce, 1993).

One of the summary conclusions from the Canadian Forest Service’s National Forestry Institute on whole tree removal states:

"Harvesting whole trees means the removal of twig and leaf tissues which contain high nutrient concentrations, and account for 28 to 92 percent of the nitrogen, 20 to 83 percent of the phosphorus, 6 to 85 percent of the potassium, and 5 to 87 percent of the calcium in the above ground components" (Coates, et al., 1982).

Coates, J.F., H.H. Hitchcock, L. Heinz (1982). Environmental Consequences of Wood and Other Biomass Sources of Energy. Office of Strategic Assessments and Special Studies, U.S. EPA.Washington, DC.

Cramer, Owen P., ed. (1974). Environmental Effects of Forest Residues Management in the Pacific Northwest. USDA Forest Service General Technical Report PNW-24. Portland, Oregon.

Federer, C.A., J.W. Hornbeck, L.M. Tritton, C.W. Martin, R.S. Pierce, C.Tatersall Smith. (1989) "Long-Term Depletion of Calcium and Other Nutrients in Eastern US Forests." Environmental Management. Vol. 13, #5:593-601.

Jenny, H. (1980) "Letters." Science. Vol. 209, June 20, 1980.

Johnson, Robert. (1993). "Electric Utilities Study An Old, New Source of Fuel: Firewood." The Wall Street Journal. Dec.2, 1993.

Martin, C. Wayne. (1988). "Soil Disturbance by Logging in New England -- Review and Management Recommendations." Northern Journal of Applied Forestry. Vol. 5, #1.

Nickols, Hank. (1993). "Utility’s plan loses sight of forest and the trees." The Boston Sunday Globe. November 28, 1993.

Pierce, R.S., J.W. Hornbeck, C.W. Martin, L.M. Tritton, C.T. Smith, C.A. Federer, H.W. Yaeney. (1993). Whole-tree Clearcutting in New England: Manager’s Guide to Impacts on Soils, Streams, and Regeneration. USDA Forest Service General Technical Report NE-172.

Staebler, G.R. (1979). "Rationalization of Biomass Harvest and Use." Proceedings: Impact of Intensive Harvesting on Forest Nutrient Cycling. Broomall, PA: Northeast Forest Experimental Station, U.S. Department of Agriculture, Forest Service.

U.S. Forest Service. (1993) White Mountain National Forest Monitoring Report. Laconia, NH.

Waring, R.H. (1980) "Opportunities and Constraints on Forests Imposed by Their Nature as Ecological Systems." Forest Land Use Symposium #1: Discussion Papers. The Conservation Foundation, Washington, DC.

Willson, M.R. (1974) "Avian Community Organization and Habitat Structure." Ecology. 55:1017-1029.