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A report byFRANCIS R. HERMANPacific Northwest Forest andRange Experiment StationU. S. Forest ServicePortland, Ore.

PULPPAPER

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PULPWOOD world

Shelterwoodcuttingstudied to see if young-growth hemlock can be

regenerated by series of successive cuttings

—Portland, Ore.A STUDY NOW UNDERWAY at the Hemlock Experimental Forest near GraysHarbor in western Washington is de-signed to test shelterwood cuttings asa means of regenerating coastal west-ern hemlock. Hemlock Experimental

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FOREST WITH CLOSED CANOPY PRIOR TO CUTTING

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SELECTED TREES RETAINED TO SEED CUTOVER AREA

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LEAVE TREES AFTER SECOND CUT

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SHELTERWOOD MANAGEMENT SYSTEM, showing successive stages of regen-eration in western hemlock forest.

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Forest is owned by St. Regis PaperCo. and leased to the U.S. ForestService under a cooperative agree-ment to conduct research aimed atsecuring the greatest possible con-tinuous yield. Logging on the experi-mental forest is done by St. Regis andresearch is conducted by the PacificNorthwest Forest and Range Experi-ment Station, Portland, Ore.

In the U.S. Forest Service report,"Timber Resources for America's Fu-ture," we are told that more than 18%of the national pulpwood output isproduced in the Pacific Northwest. Tocontinue to furnish this proportion ofAmerica's pulpwood requirements inthe year 2000, Pacific Northwest for-ests must produce perhaps as muchas three and one-half times the pres-ent output. Even so, an estimated na-tional demand for 89 million cords ofpulpwood may require the UnitedStates to import nearly 15 millioncords. Successful methods of obtain-ing quick regeneration and maintain-ing optimum stocking on all forestlands will assist in preventing possibleshortages in wood products.

The wood of western hemlock isadmirably suited for producing goodpulp and lumber. Many mills in thePacific Northwest look to hemlock tofurnish at least a portion of theircordwood and sawlogs. Some millsin western Washington are currentlyutilizing hemlock in preference toother species. Western hemlock isblessed with many attributes thatmake it a good candidate for man-

Reprinted from PULP & PAPER, June 11, 1962Purchased by the U.S. Forest Service for official use

. . . shelterwood cutting

SEED TRAP makes it possible to estimate amount, viabilityand distribution of hemlock seed for any of several shel-terwood cutting intensities.

TRACTOR AND SULKY used for skidding tree-length logsfrom shelterwood compartment to roadside landing forbucking into pulpwood or sawlogs.

agement. It is a prolific producer ofseed and, when provided with itsproper environmental condition,grows rapidly, tall, and straight.

Clear cutting of old-growthhemlock commonly has been acceptedas the only method that will provideconditions conducive to reestablish-ment of hemlock. Is it certain, how-ever, that clear-cutting managementof young-growth western hemlock willprovide the best conditions for standregeneration? Examination of recentlycutover young-growth hemlock forestland reveals an abundance of weedsand brush but only a sparse cover ofnew hemlock seedlings. Would someform of partial cutting, such as theshelterwood system, prove more suc-cessful than clear cutting in providing

quick and abundant regeneration?Early in this century, logging, for-

est fires, and windstorms in westernWashington left some scattered oldhemlock trees and provided environ-mental conditions suitable for the es-tablishment of extensive, even-agedstands of nearly pure young-growthhemlock. The exact nature of theseenvironmental conditions is unknown.These older trees provided seed andsome degree of shelterwood protec-tion for the young forest. We cannotturn back the pages of history andconveniently look in upon acciden-tally created growing conditions.However, we can artificially createvaried sets of conditions and measureresulting environmental influencesconducive to establishment of a newforest

shelterwood cutting systemis being tested on the Hemlock Ex-perimental Forest, 15 miles north ofHoquiam, Wash.—an "experimentalisland" within a large area of young-growth western hemlock. The originalforest was logged near the turn of thecentury, and the bulk of the presentstand is now about 60 years old. Afew scattered, older western hemlocksthat escaped the early logging arefound throughout the area. The standaverages 270 stems per acre in trees6 to 30 in. in diameter, and volumesexceed 43,000 bd. ft. per acre. Hereon 68 acres in this nearly pure standof young-growth western hemlock, ef-fects of a wide range of shelterwoodcuttings on regeneration are beingstudied.

Comparison of 12 cutting intensi-

RESIDUAL SHELTERWOOD stand after initial cutting has23 trees per acre. Research will show if this is lightershelterwood stand than is desirable.

AFTER INITIAL CUTTING this stand has 54 trees per acre.Second cut in 5 years will leave half these trees to pro-vide seed and soil protection.

ties is being made in residual standsof 20 to 200 trees per acre. Loggingon cutting compartments of from 5 to7 acres each began in 1960. After in-terruption by winter weather, initialcuts on all 12 compartments werecompleted according to prescribedplan in the late summer of 1961.Nearly 2,000 cords of pulpwood and370,000 bd. ft. of sawlogs were re-moved in this first cut. According tothe shelterwood management plan,second and third cuttings on all com-partments at intervals of 5 years willcomplete the cutting schedule.

Shelterwood management differsfrom clear cutting in that it delaysthe time when the forest is completelycut over. Seed-bearing trees are re-moved by two or more successive fell-ings instead of by single cutting. Thusa new crop establishes itself from thesurviving seed trees. As the term sig-nifies, shelterwood also provides shel-ter or protection. Crowns of retainedtrees shade the forest floor and pro-tect new seedlings from bright sun-light and detrimental temperatureextremes. The limited intensity of sun-light also controls the development ofundesirable brush and weeds thatmight delay the establishment of ayoung forest.

Shelterwood cutting permits for-esters to select and retain certaintrees for their seed-bearing abilityand growth potential. In addition toproviding an abundant supply ofseed, the released trees will increasetheir rate of wood production—bothin quantity and quality. Shortenedrotations, improved yield volumes,and selected quality all may be ob-tained through careful shelterwoodmanagement.

Unlike the claims made for manyhealth tonic elixirs that purportedlycure all ailments, shelterwood manage-ment is not said to be perfect. Thereundoubtedly will be problems asso-ciated with the application of theshelterwood system. One of the pur-poses of the study is to evaluate these.Foremost is the possibility of loggingdamage to established seedlings dur-ing successive cuttings. Young growthestablished after a first cut may bedamaged by felling and skidding insubsequent cuts. Amount of damagesho. 1,1 be associated with the amountof timber cut each time. The finalmeasure of success will be the rela-tive abundance of healthy hemlockseedlings.

Factors contributing to an abun-dance of well-distributed and high-quality western hemlock seedlingsneed to be known and evaluated ifthey are to be encouraged in large-scale operations. These include en-vironmental influences such as compe-

tition from other plant species, lightintensity, aspect, slope, and seedbedas well as the factors of seed fall,germinative capacity, and seedlingsurvival.

In an effort to discover the quantityof seed that falls under each intensityof cutting, simple but effective seedtraps made of wire screen fitted intoa wood frame are placed within eachshelterwood-cutting compartment. Anumber of these traps scattered overa known area give an estimate of theavailable seed supply per acre. Con-tents of the traps are collected andexamined several times a year.

Logging costs and returnsfor the entire shelterwood manage-ment cutting period are being kept.Because work is less concentratedunder shelterwood than under clear-cutting management, logging costsmay be somewhat higher. Even extracost may be justified if healthy re-generation can be obtained morequickly under one than under an-other cutting treatment.

On other portions of the HemlockExperimental Forest, periodic thin-nings have been carried out since1950. These thinnings are designedto remove the least desirable mem-bers of the stand and promote de-velopment of the better members ofthe crop. The thinnings are stimulat-ing good crown development that willproduce good seed crops later on.These stands are being groomed forapplication of the best management—be it shelterwood or some other re-generation cutting method.

It is from thinning experiments thatwe get an inkling of the growth ca-pacity of young-growth western hem-lock. The net mean annual incrementto date has been 158 cu. ft. or 828bd. ft. per acre. The experimental for-est is growing rapidly, however, andthe thinned stands show a current netperiodic yearly increment of 179 cu.ft. or 1,490 bd. ft. per acre.

Time is not far off when young-growth western hemlock stands willbe called upon to bear a major por-tion of the rapidly increasing demandfor cellulose. Some of these stands,though only 40 to 60 years old, evennow furnish pulpwood to the ever-increasing capacity of pulp and papermills. Foresters must learn to man-age this young crop of wood to main-tain wood growth at least equal tothat of demand. Studies at HemlockExperimental Forest are designed toprovide foresters with managementguides. If shelterwood managementprovides the key to quick, adequateregeneration of western hemlock, ashelterwood cutting guide will beavailable for application by the endof the study period. ■