Biological Productivity of Renewable Resources Used as Industrial Materials (1976) / Chapter Skim
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UNITED STATES TIMBER POTENTIAL
UNITED STATES TIMBER POTENTIAL
Pages 27-62
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From page 27... ...
, Marty assayed some generalized estimates of the net mean annual growth that might be anticipated for various softwood timber types, and multiplied these values by the area in each site class for each softwood forest type. By this simple method, he estimated that the United States could grow 17 billion cubic feet of softwoods per year, 77 percent more than the 1970 supply of 10.7 billion cubic feet, but less than the - 27
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From page 28... ...
In addition, the allowable cut on these National Forest lands would be raised under present sustained yield computational practices because of the "allowable cut effect," the increase in computed permissible harvest of existing oldgrowth resulting from taking into account the anticipated higher yields from the managed stands. The miscellaneous private lands considered in the Outlook Study of intensive management potentials occur primarily in the southern states.
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From page 29... ...
Drainage has been employed successfully to improve the growth of spruce and other lowland forest types in northern Europe for many years. Some three million acres have been drained in Finland and nearly one million acres have been similarly treated in Sweden.
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From page 30... ...
Several million acres fall in this category, a high percentage of which have phosphate-deficient soils. On these, a combination of drainage plus fertilization with phosphate would improve the growth of pine forests substantially.
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From page 31... ...
The net effect of an extensive program of fertilization and drainage would be to raise the site quality of a portion of the forest land in the United States. Assuming for the sake of simplification that such efforts are confined to nitrogen fertilization of 4.7 million acres in the Douglasfir and related mesophytic conifer types of the Pacific Coast, and to phosphate fertilization and drainage of 5.8 million acres in moist loblolly and slash pine types in the South, and assuming that the total acreages of these types remain essentially unchanged, we may tentatively modify the acreages of the different site classes as indicated in Table 5.
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From page 32... ...
Conversion of Forest Type In the Outlook Study, forest site guality is estimated on the basis of the vegetation currently occupying the area at the time of the forest survey. Since some of our commercial forest land is currently unstocked, and since an even greater amount of it is stocked with tree species that are growing more slowly than others that are equally well adapted to grow on the same sites, the net effect is that the Outlook Study substantially underestimates the growth potential of United States commercial forests in these respects.
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From page 33... ...
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From page 34... ...
Improving Stocking Through Reforestation Probably the single most important factor in maintaining the productivity of the forests of the United States is the development and maintenance of full stocking through a nationwide program of seeding and planting where and when necessary. The Outlook Study reports a total of 20.7 million acres of non-stocked commercial forest land, or 4.2 percent of our commercial forest land: 4.8 million are in the South, 3.7 million are in the Pacific Coast region, 9.6 million are in the North, and 2.7 million are in the Rocky Mountains.
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From page 35... ...
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From page 36... ...
For southern pines, we estimate a potential acreage of 68 million acres of Site IV or tetter (more than 50 cubic feet per acre per year)
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From page 37... ...
It may well be that a plantation of genetically superior trees that is regularly thinned will produce more usable timber volume than would be predicted by adding the growth improvement expected from thinning alone to that expected from genetic improvement alone. For areas actually planted, the potential increases in yield may be greater than indicated above because of gains from disease resistance.
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From page 38... ...
reconstructed the annual mortality and gross growth of a fast-growing Monterey pine plantation in New Zealand. At age 35, the gross annual increment was 516 cubic feet per acre per year or 55 percent greater than the net annual increment of 332 cubic feet per acre per year.
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From page 39... ...
By comparing these with older normal yield tables that predict net growth, we can estimate the amount of mortality that might be salvaged through thinnings. Ostrom and Gibbs (1973)
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From page 40... ...
30 50 70 2,194 4,563 6,932 3,768 6,975 10,182 1,574 2,412 3,250 72 53 47 Western white pine (Watt 1960) Ponderosa pine (Meyer 1961)
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From page 41... ...
In the absence of badly-needed growth data in the form of managed-stand yield tables on a gross growth basis for all major forest types in the United States, we may assume that normal yield table values can be increased by 25 percent if silvicultural management in the form of regular thinnings can be applied. However, southern pines and other fast-growing species on short rotations should be considered exceptions to this generalization.
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From page 42... ...
On the positive side, prescribed burning has long been an important component of forest management, especially in the southern pine forests. Burning every 3 to 5 years reduces the buildup of natural fuels, forestalls damage from possible wildfires, kills invading hardwood trees, maintains subclimax conifer stands in a healthy growing condition, and may enhance tree growth.
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From page 43... ...
again has an allowable cut effect in increasing the productivity of the whole management unit and permitting an immediate increased harvest. In still another situation, many acres in the Rocky Mountains and Pacific Coast are occupied by overmature timber stands with little or no net growth.
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From page 44... ...
The amount lost is relatively small in the case of managed even-aged stands of commercial species harvested at rotation age for pulp as well as for lumber, and relatively great in the case of unmanaged oldgrowth stands that are highly defective and harvested primarily for lumber. The former situation is frequently encountered on industrial forest lands in the southern pine
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From page 45... ...
volume of two billion cubic feet of logging residues, plus an additional 1.7 billion cubic feet from primary manufacturing residues. At 35 pounds per cubic foot, this represents a total of 65 million tons of unused residues.
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From page 46... ...
. The literature on complete tree use has been summarized by Keays (1971)
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From page 47... ...
Whittaker's estimate is, therefore, comparable with the 74 cubic feet per acre per year estimated by the Outlook Study as the potential growth of the commercial forests in the United States. Intensive Biomass Management Over and above a more complete use of the merchantable boles in the forest ecosystem lies the intriguing possibility of increasing total biomass production of the forest ecosystem through the selection of highly efficient photosynthesizers and growing them under intense cultivation over short rotations.
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From page 49... ...
conclude that logging residue is and will continue to be too expensive for use as fuel only, but it is a potentially attractive source of material for products. While research should be continued on the possibility of greatly increasing the total biomass potential of the forest through intensive management of genetically superior species on rotations of two to four years, it would be unrealistic at present to assume that such techniques will have any widespread application in the near future.
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From page 50... ...
In the Outlook Study, some five million acres of forest in the Rocky Mountain area are excluded for one or more of the reasons cited, wikstrom and Hutchison (1971) found that 22 percent of the classified commercial forest land in six western national forests was not currently available for timber management and harvest.
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From page 51... ...
Pacific Coast: Alaska, Washington, Oregon, and California.
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From page 52... ...
In the Pacific Northwest and southern pine regions, the economic value of timber growing should, to some extent, counter pressures to withdraw commercial forest land for recreational use or to convert high quality forest land into lower quality agricultural land. The commercial forest area of the United States will continue to decline in the future.
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From page 53... ...
It seems appropriate, therefore, to discount the possibility of a downgrading in forest practices and to join with the Forest Service in its Outlook Study by taking the continuation of 1970 levels of management as our base line. Summarizing the projections of the Outlook Study to 1985 and 2000, we find that the United States, with an annual harvest of 14 billion cubic feet of wood (225 million tons of wood and bark)
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From page 54... ...
Forest Type Site Classes I,II III IV V Total Softwoods Oak-pine Upland-Hardwoods Lowland-Hardwoods Non-stocked Total 13,478 53,452 89,626 35,984 192,542 Source: The Outlook for Timber in the United States, U.S. Department of Agriculture Forest Service (1974)
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From page 55... ...
Forest type Site Classes I,II III IV Total Fir- spruce 2,348 2,004 2,948 727 8,029 Western Hardwoods 4,184 1,946 1,980 434 8,545 Non- stocked 1,470 680 1,113 442 3,707 Total 23,628 15,572 22,904 5,518 67,622 Douglas-fir 13,728 Hemlock-Sitka spruce Redwood Ponderosa pine 1,895 Lodgepole pine Larch-pine 6,458 8,245 4,482 8,616 1,194 29,627 2,719 17,712 Source: The Outlook for Timber in the United States. o.S Department of Agriculture Forest Service (1974)
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From page 56... ...
Department of Agriculture Forest Service (1974)
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From page 57... ...
Projected Forest Areas The projected acreage of commercial forest land in the United States for each broad site productivity class and for softwood and hardwood types separately is summarized in Table 13. In developing this projection, the following assumptions were made.
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From page 58... ...
Table 13 Projected Changes in Area of Commercial Forest Land under Intensive Management by Site Class and Species Group Softwoods 1970 Projected, 2020 Hardwoods 1970 Projected, 2020 Non-stocked 1970 Projected, 2020 Total 1970 Projected, 2020 I,II Site Productivity Class III IV V Total (million acres)
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From page 59... ...
Under these assumptions, and rounding off each category to the nearest million acres, it will be seen that the acreage of softwoods would be increased from 242 million to 261 million acres despite the overall loss of 20 million acres of commercial forest land, and that most of this increase would be on the better sites. The assumptions are optimistic but technically feasible and economically well within reality.
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From page 60... ...
Just as it is highly improbable that all forest lands can be kept fully stocked so as to produce the full yields predicted by normal yield tables, it is equally improbable that intensive thinning and tree-improvement regimes can be applied to all forest lands. In the latter case, it is likely that the main applications will be on the better forest sites in the commercially important and already wellmanaged Douglas-fir and southern pine regions.
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From page 61... ...
S Added Douglas fir Added Southern pine Total Hardwoods Total U
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From page 62... ...
Applying the potential gain in growth from thinning and genetic improvement, we predict an increase in productive potential of 760 million cubic feet annually in the Douglasfir region and 1,119 million cubic feet from southern pine. Adding these two gains to the earlier estimate, we predict a total biological productive potential of 19 billion cubic feet (290 million tens of wood and bark)
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