North Central Research Station

North Central Research StationForest Service—U.S. Department of Agriculture

1992 Folwell AvenueSt. Paul, Minnesota 55108

Manuscript approved for publication September 1, 19981998

FOREWORD

Forest Inventory and Analysis (FIA) is a continuing endeavor asmandated by the Renewable Forest and Rangeland Resources Plan-ning Act of 1974. Prior inventories were mandated by theMcSweeney-McNary Forest Research Act of 1928. The objective ofFIA is to periodically inventory the Nation’s forest land to determineits extent, condition, volume of timber, growth, and removals. USDAForest Service regional experiment stations are responsible for con-ducting these inventories and publishing summary reports for indi-vidual States. The North Central Research Station is responsible forforest resource evaluation in Illinois, Indiana, Iowa, Kansas, Michi-gan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota,and Wisconsin.

CONTENTS

Page

Procedural Changes ..........................................................................1Regional Composite Database ............................................................4Conceptual Model ..............................................................................5Model Application ..............................................................................5Moving Average .................................................................................6Conclusions ......................................................................................7Literature Cited .................................................................................7Appendix ...........................................................................................7 Definition of Terms .........................................................................7 Table Titles ....................................................................................9 Tables ..........................................................................................10

The North Central Forest Inventory and AnalysisTimber Product Output Database—

A Regional Composite Approach

Dennis M. May

The Forest Inventory and Analysis (FIA) Pro-gram at the North Central Research Station isresponsible for inventorying over 80 millionacres of forest land spread across 11 States inthe North-Central Region of the United States(fig. 1). As part of this ongoing effort to main-tain comprehensive statistics on the currentstatus, past changes, and future potential ofthe region’s forests, FIA also conducts specialstudies to estimate and track regional timberharvests and their consequential impacts onthe forests and economies of the region. Thesetimber product output (TPO) studies quantifytimber harvests and timber processing in theregion by periodically canvassing all knownusers of roundwood products (saw logs, veneerlogs, pulpwood, firewood, etc.) in each State.Procedures for conducting these studies havebeen well documented by Smith (1991), butgenerally two types of TPO studies are con-ducted: industrial and nonindustrial. Indus-trial TPO studies are used to determine round-wood harvests for primary wood-using mills(sawmills, veneer mills, pulpmills, etc.). Be-cause pulpmills and composite product mills(OSB, particleboard, chipboard mills, etc.) arerelatively few in number and make up such alarge portion of total roundwood use in theregion, FIA canvasses these mills annually(Piva 1996). All other primary wood-using mills(sawmills, veneer mills, cooperage mills, etc.)are canvassed in cooperation with State for-estry agencies at intervals that range frombiennial to decennial or longer depending onthe State (Hackett and Pilon 1997). Stateforestry agencies also collaborate with FIA inperiodically conducting nonindustrial TPO

Dennis M. May, Research Forester, received aB.S. in forest management from the Universityof Maine and an M.S. in forest resources fromthe University of Idaho. He joined the USDAForest Service in December 1983 and has beenworking with the North Central Station’s ForestInventory and Analysis unit since May 1992.

North Dakota

South Dakota

Nebraska

Kansas

Minnesota

Iowa

Missouri

Wisconsin

Michigan

IndianaIllinois

Figure 1.—The 11 States in the North-CentralRegion.

studies to determine residential uses of round-wood for fuel and posts (May et al. 1997).Together, the industrial and nonindustrialstudies provide a complete picture of a State’stimber product output for a given year.

In 1992, the established procedures for con-ducting these studies were reevaluated toaddress the possibility of combining TPOstudies into a regional composite that could bemanaged within the framework of a relationaldatabase. The ensuing procedural changes,the reasoning behind those changes, and thedevelopment and structure of the resultingregional composite database are outlined inthis publication. Examples from industrialTPO studies are used to illustrate the develop-ment of the regional database, conceptualizethe composite approach, and demonstrate itsapplication in addressing everyday TPO infor-mation needs.

PROCEDURAL CHANGES

In the past, each industrial TPO study wasconsidered an independent assessment of aState’s production and consumption of round-wood (fig. 2). Considerable effort was expended

on estimating a State’s production of round-wood. All primary wood-using mills in thetarget State would be canvassed to determinethe volume of roundwood harvested and pro-cessed within the State (internal use). Thencertain out-of-State mills, those that hadpreviously used roundwood from the targetState and those within some predetermineddistance of the target State’s border (50 miles,3 counties, etc.), would be canvassed to ascer-tain roundwood exports from the target State.Depending on the number of out-of-State millscanvassed in this export zone (fig. 3), theworkload could increase substantially relativeto the generally small portion of a State’s total

IAinternal

use

IAexports

IAimports

IA Roundwood Production = IA Internal Use + IA ExportsIA Roundwood Consumption = IA Internal Use + IA Imports

Figure 2.—Roundwood production versusroundwood consumption.

production that was captured. And invariably,the list of out-of-State mills would be incom-plete or the export zone too small, and millsthat should have been canvassed would bemissed, resulting in an underestimate ofexports and consequently of roundwood pro-duction. To complete the estimate of round-wood consumption, an estimate of roundwoodimports would be collected from the targetState’s mills as well. This production-focusedprocess would be repeated from State to State,resulting in independent assessments of eachtarget State’s timber product output. As aresult, mills in the overlapping export zones ofneighboring States would receive multiplecanvasses asking redundant questions (fig. 4).Aside from being inefficient and burdensome tothe receiving mills, the redundant canvassingcaused duplication problems (individual milldata entered more than once) when the inde-pendent State TPO studies were merged intomulti-State or regional summaries.

Although sufficient in the past, this indepen-dent approach to TPO studies with its inherentproblems and shortcomings was negativelyimpacting data collection and data manage-ment in a time of increasing frequencies of TPOstudies and calls for more regional assess-ments. What the old procedures failed torecognize, and failed to take advantage of, wasthe duplicity in the data collected in the inde-pendent TPO studies. When viewed from aregional perspective rather than from a State-specific perspective, it is apparent that oneState’s roundwood exports are another State’s

Iowa Export Zone

Figure 3.—Focus on target State’s productionestimate. Canvass all mills within targetState and all mills within export zone.

1990

1983

1988

Figure 4.—Overlapping export zones created byfocusing on each target State’s productionestimate.

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roundwood imports (fig. 5). Therefore, much ofthe redundancy and inefficiencies of the pastprocedures can be eliminated by focusing datacollection efforts on consumption estimationrather than production estimation, and thenletting the import data collected provide theexport data for estimating roundwood produc-tion in other States. When we shift to con-sumption-oriented TPO studies (fig. 6), thecanvass zone becomes limited and known(State boundaries define the extent of thecanvass zone, and imports, hence exports, arederived from a 100-percent canvass), the millsare canvassed only once during the TPO studyfor their State (no redundant canvassing), andthe import data are shared to provide theexport data for other States’ production esti-mates (eliminating the duplicate mill problemswhen compiling regional or multi-State sum-maries).

Although the shift to consumption-orientedTPO studies eliminated the problems of thepast, it did cause minor dating differences inthe data used to estimate production becausenot all of the State consumption studies thatsupply the roundwood export data are con-ducted in the same year. Fortunately, exportvolume is generally a relatively small propor-tion of the region’s or a State’s total production,and the time and effort once expended onredundant export zone canvassing is now usedto minimize these dating differences by short-ening the interval between TPO studies in eachState. To eliminate the need to do export-zonecanvassing of mills outside the North-CentralRegion and repeat the problems of the past at a

IA Imports

WI Exp

orts1990

1983

1988

Figure 5.—One State’s roundwood exports areanother State’s roundwood imports.

Figure 6.—Focus on target State’s roundwoodconsumption estimate. Only canvass millswithin the target State.

regional level, FIA conducts cooperative TPOdata exchanges with other FIA units, Stateforestry agencies, and other governmentalagencies, swapping information on the volumeof roundwood imported into the North-CentralRegion from neighboring regions for informa-tion on the volume of North-Central roundwoodexported to those neighboring regions. Essen-tially then, under this new consumption-oriented approach, industrial TPO studies areno longer independent, but are dependentupon one another for the export portion of theirproduction estimate, and as such, each be-comes an integral component of a regionalcomposite (fig. 7).

1993...1993...

1993...1993...

19901992...

19881994...

19911994...

19831996...

199019921994...

199019921994...

19901995...

Figure 7.—Regional composite database ofconsumption canvasses.

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REGIONAL COMPOSITE DATABASE

The consumption studies for each State arepieced together into a regional compositewithin a relational database managementsystem. Through the power and flexibility ofthe relational database management system,we can take full advantage of the interdepen-dencies of the studies to address a wide rangeof TPO information needs across scales thatvary from local to regional. Each TPO studycollects the same basic data: information

MAIN DATA DEPOSITORY

INTERPRETIVE VIEWS

TPO REPORTSTPO ANALYSIS

TPO DATA REQUESTS

MILLRESIDUE

SUMMARIES

INVENTORYREMOVAL

SUMMARIES

TPOSUMMARIES

SUPPORT TABLES

SPECIESNamesCodesGroups

UNITOF MEASURE

CONVERSIONS

UTILIZATIONCONVERSIONS

FIPCODES

StateUnit

County

TPOSpeciesProductVolume

Unit of measure...

MILL RESIDUESpecies

TypeDisposition

Disposition percent...

MILLStateUnit

CountySizeType...

about the wood-using industry itself (location,type, size, etc.), that industry’s use of round-wood (geographic source, species, product,etc.), and its generation and disposition of millresidues. All of these data are stored in tablesthat have been organized into a multi-tieredstructure comprised of a central data deposi-tory, support tables, and interpretive views (fig.8). The structure of the database is centeredaround the main data depository, which con-sists of three relationally joined tables thatcontain all of the data collected about the mills,

Figure 8.—Structure of the regional composite database.

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their roundwood use, and their residues.Generally, these basic data need further pro-cessing to facilitate their use and interpreta-tion, while at the same time protecting againstthe disclosure of individual mill data. Thetransformation of these basic data into aninterpretable and meaningful form is accom-plished by relationally joining the three tablesin the main data depository to a secondarylevel of tables, called support tables. Thesesupport tables contain all of the conversions,factors, descriptive names, etc. for transform-ing the basic data into interpretable form.Views, a database feature that allows theresults of the underlying query of the basicdata as modified by the support tables to inturn be displayed and queried, are used tologically organize the interpretable data intoeasily understood summaries that facilitateinformation reporting and dissemination.

CONCEPTUAL MODEL

The regional database can be conceptuallyrepresented as an initial composite of the latestTPO consumption studies for any State whosemills consumed roundwood harvested from theNorth-Central Region, and whose data wereavailable at the time of the database’s estab-lishment (table 1). Because the data in thesestudies were deemed to be the best availableestimates at the time, some TPO study data,like that for Nebraska 1993, were back filled,while others, like those for Illinois 1983 or Iowa1988, were carried forward to provide a com-plete regional composite for calendar year1990. In each year thereafter, some data fromthe previous year’s regional composite wereupdated with data from new TPO studies, whilethe remaining data were carried forward fromthe previous year to provide a complete re-gional composite for each calendar year. Theextent to which the regional composite isupdated in any one year depends on the inter-val between successive TPO studies for a Stateand the quantity of roundwood consumed in aState. For example, the annual pulpwoodsurvey accounts for (updates) over half of theregion’s consumption and production of indus-trial roundwood in any 1 year, while the inter-val between the periodic canvasses of all otherprimary wood-using mills using roundwoodother than pulpwood varies considerably byState as evident in table 1. Because each newTPO study partially updates the region’s con-sumption estimate and its imports (other

State’s exports) can update the productionestimate for several States as well, the regionalcomposite progressively and dynamically movesthrough time, providing a continual time seriesof the latest available timber production andconsumption data for any State in the region,the region as a whole, or any part thereof.

MODEL APPLICATION

Tables 2-7 display a progressive time series ofTPO data for the North-Central Region derivedfrom applying the conceptual model to theassessment of industrial roundwood produc-tion, consumption, and interstate movementpatterns. In 1990, the year of the initial com-posite estimate, 1,204.1 million cubic feet ofindustrial roundwood were produced from theregion’s forests (table 2). Most of this volume(98.2 percent) was retained within the regionfor processing into a variety of primary woodproducts (pulp, lumber, veneer, etc.). Theremainder was exported out of the region forprocessing. Canada, Wyoming, and Kentuckywere the largest recipients of this exportedroundwood. Of the volume of roundwood thatwas used within the region, 91.5 percent wasprocessed into primary products in the sameStates from which it was cut. The other 8.5percent moved between North Central Statesbefore being processed. The States of Wiscon-sin, Michigan, and Indiana were some of thebig recipients of the wood, while Michigan,Wisconsin, Minnesota, and Illinois were someof the largest providers of the wood that movedinternally. All totaled, the region consumed1,196.9 million cubic feet of industrial round-wood in 1990, 1.2 percent of which was im-ported from outside the region. Kentucky,Wyoming, Ohio, and Arkansas supplied most ofthe roundwood imported for processing in1990.

From 1990 to 1994, there were progressivelylarger increases in the region’s annual produc-tion and consumption of industrial roundwood.In 1995, industrial roundwood production fellslightly from 1994 levels to 1,312.8 millioncubic feet, but was still 9 percent higher thanin 1990 (table 7). Just over 98 percent of theregion’s production continued to be internallyprocessed into primary products in 1995,evidence of a concurrent buildup in the region’sroundwood processing capacity since 1990. Asfurther testimony to this buildup, imports ofroundwood more than doubled, due mostly to

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the increased use of Canadian roundwood,while exports remained fairly constant, hover-ing around 20 million cubic feet over the 6-yearperiod. All totaled, regional consumptionreached 1,322.6 million cubic feet in 1995,slightly lower than in 1994 but still 10.5 per-cent more than in 1990. Minnesota exhibited,by far, the biggest gains in industrial round-wood consumption and production during theperiod, followed by Wisconsin, Missouri, andMichigan. Indiana was the only State posting asignificant decline in roundwood use andharvest over the period. Overall, the regionwent from being a net producer of industrialroundwood (production greater than consump-tion) in 1990 to being a net consumer of indus-trial roundwood (consumption greater thanproduction) in 1995, with the switch occurringin 1993 (table 5).

Each year newly completed TPO studies par-tially updated the initial composite estimate,allowing the time series of annual compositeestimates to be made. In some years, like 1991(table 3), only the annual pulpwood survey wascompleted, but it still updated 52 percent ofthat year’s composite estimate. The updatingimpact of this study does, however, vary con-siderably from State to State, ranging fromupdating three-quarters of Minnesota’s annualproduction and consumption of industrialroundwood to having no impact in a State likeNebraska that lacks an established pulp andcomposite products industry. In other years,like 1994 (table 4) when TPO studies of theother primary wood-using industries in Iowa,Michigan, Missouri, and Wisconsin were com-pleted along with the annual pulpwood survey,85 percent of that year’s composite estimatewas made up of new data. The new studies notonly update the consumption estimate for theirState and the region, but their import datapartially update the production estimate forother North Central States. For example, notonly did the 1992 TPO consumption study inMichigan update one-quarter of the region’sconsumption estimate, but its import datapartially updated the production estimate offour other North Central States (Illinois, Indi-ana, Minnesota, and Wisconsin) and throughcooperative data exchanges the productionestimates of Kentucky, New York, Ohio, Penn-sylvania, Tennessee, West Virginia, and Canadaas well (table 4).

MOVING AVERAGE

This updating effect is also evident in thesteady increment of the average volume-weighted date of the annual production esti-mates for each North Central State and theregion over the 6-year time series (calculated byaveraging the date of each consumption surveycontributing to the production estimate afterweighting each survey’s date by the volumecontributed). A good example of this updatingeffect is exhibited in the average volume-weighted dates of Illinois’ production estimates.At the time of the database’s establishment, thelatest consumption study for Illinois was dated1983. Therefore, Illinois’ internal use volumealso carried the 1983 date. But, becauseIllinois’ export volume was gathered from theimport data of several other States that weresurveyed in later years, the resulting averagevolume-weighted date of the Illinois productionestimate for calendar year 1990 was actually1985.6. And because of the periodic updatingof these other States’ consumption studies overthe 6-year period, the average volume-weighteddate for the Illinois production estimate in-creased to 1987.3 by calendar year 1995without there ever having been a new Illinoisconsumption study. The annual pulpwoodsurvey has a similar updating effect on theaverage volume-weighted date of the consump-tion surveys for States with pulp and compositeproduct mills. This is evidenced by the non-integer (fractional) dates for some of the con-sumption studies in the time series. Goodexamples of this are the fractional averagevolume-weighted dates of Wisconsin’s con-sumption surveys in the odd-numbered calen-dar years of the time series, the years in whichonly the consumption data of the pulp andcomposite product mills were updated. Overthe time series, the average volume-weighteddates of the region’s production and consump-tion estimates increased from 1990.0 in calen-dar year 1990 to about 1994.2 in calendar year1995 as a consequence of from 52 to 85 per-cent of the region’s TPO data being replaced(updated) each calendar year. Ongoing con-sumption studies in 1996 for Arkansas, Illinois,Michigan, Minnesota, and Wisconsin, and thatyear’s pulpwood survey, will ensure that theregional composite continues to advancethrough time (table 1).

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CONCLUSIONS

In this example, the regional composite data-base was used to assess the production, con-sumption, and movement patterns of industrialroundwood in the North-Central Region in aprogressive time series. With minor modifica-tions to the database query, information couldhave just as easily been retrieved for specificproducts (saw logs, veneer logs, etc.), species(red pine, cottonwood, etc.), geographic areas(States, counties, etc.), sources of roundwood(growing stock/cull, live/dead, sawtimber/poletimber/sapling, etc.), segments of thewood-using industry (industrial, nonindustrial,or both), or any group or combination of theseor any other of the data attributes collected inthe TPO surveys. Or, if we modify the underly-ing assumptions of how the individual studiesare pieced together and related to one another,alternative conceptual models of the regionaldatabase could be constructed (regressive timeseries, point in time, latest available, etc.) toprovide the most appropriate information.Such flexibility is one of the benefits of theregional composite approach to TPO datamanagement. The other great benefit of thisapproach is the dynamic nature of the data-base, which is continually moving forward intime as each new TPO study partially updatesthe regional composite, while building a his-toric archive of data that can be pieced togetherand manipulated as seen fit to address a wholehost of TPO-related questions.

LITERATURE CITED

Hackett, Ronald L.; Pilon, John. 1997. Michi-gan timber industry—an assessment oftimber product output and use, 1994.Resour. Bull. NC-189. St. Paul, MN: U.S.Department of Agriculture, Forest Service,North Central Forest Experiment Station.66 p.

May, Dennis M.; Settle, Jeff; Benjamin,Tamara. 1997. Residential fuelwoodconsumption and production in Indiana,1996. Resour. Bull. NC-188. St. Paul,MN: U.S. Department of Agriculture, ForestService, North Central Forest ExperimentStation. 29 p.

Piva, Ronald J. 1996. Pulpwood production inthe North-Central region, 1995. Resour.Bull. NC-180. St. Paul, MN: U.S. Depart-ment of Agriculture, Forest Service, NorthCentral Forest Experiment Station. 39 p.

Smith, W. Brad. 1991. Assessing removals forNorth Central forest inventories. Res.Pap. NC-299. St. Paul, MN: U.S. Depart-ment of Agriculture, Forest Service,North Central Forest Experiment Station.48 p.

APPENDIX

DEFINITION OF TERMS

Bolts.—Roundwood products that are less than8 feet in length.

Byproducts.—Mill residues (slabs, edgings,trimmings, shavings, sawdust, veneer coresand clippings, etc.) that are used for prod-ucts such as pulp chips, fuel, charcoal,mulch, etc.

Central stem.—The portion of a tree between a1-foot stump and the minimum 4.0-inchtop diameter outside bark, or point wherethe central stem breaks into limbs.

Coarse mill residue.—Wood residue suitablefor chipping such as slabs, edgings, andveneer cores.

Commercial species.—Tree species presentlyor prospectively suitable for industrial woodproducts. (Note: Excludes species oftypically small size, poor form, or inferiorquality such as hophornbeam, Osage-orange, and redbud.)

Cull.—Rough and rotten trees plus sections ofthe central stem of growing-stock trees thatdo not meet regional merchantabilitystandards.

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Diameter at breast height (d.b.h.).—Theoutside bark diameter at 4.5 feet above theforest floor on the uphill side of the tree.For determining breast height, the forestfloor includes the duff layer that may bepresent, but does not include unincorpo-rated woody debris that may rise above theground line.

Fine mill residue.—Wood residue not suitablefor chipping such as sawdust and veneerclippings.

Forest land.—Land at least 16.7 percentstocked by forest trees of any size, orformerly having had such tree cover, andnot currently developed for nonforest use.(Note: Stocking is measured by comparingspecified standards with basal area and/ornumber of trees, age or size, and spacing.)The minimum area for classification offorest land is 1 acre. Roadside, streamside,and shelterbelt strips of timber must have acrown width of at least 120 feet to qualifyas forest land. Unimproved roads andtrails, streams, or other bodies of water orclearings in forest areas shall be classed asforest if less than 120 feet wide.

Growing-stock tree.—A live timberland tree ofcommercial species that meets specifiedstandards of size, quality, and merchant-ability. (Note: Excludes rough, rotten, anddead trees.)

Hardwoods.—Dicotyledonous trees, usuallybroad-leaved and deciduous.

Industrial roundwood products.—Logs, bolts,and other round sections of trees (includingchips from roundwood) cut for processingat primary wood-using mills (includes sawlogs, veneer logs and bolts, cooperage logsand bolts, pulpwood, fuelwood, posts,poles, pilings, shaving/excelsior bolts, minetimbers, etc.).

Internal use roundwood.—(See Roundwoodretained).

Merchantable sections.—Refers to sections ofthe central stem of growing-stock trees thatmeet either pulpwood or saw-log specifica-tions.

Mill residue.—Wood materials (coarse and fine)and bark generated at primary wood-usingmills from roundwood processed intoprimary products (lumber, veneer, pulp,etc.). These residues include wood prod-ucts (byproducts) obtained incidental toproduction of principal products and woodmaterials not utilized for some product.

Noncommercial species.—Tree species oftypically small size, poor form, or inferiorquality that normally do not develop intotrees suitable for industrial roundwoodproducts. Classified in volume tables asrough trees.

Nonforest land.—Land that has never sup-ported forests, and land formerly forestedwhere use for timber management is pre-cluded by development for other uses.(Note: Includes areas used for crops,orchards, Christmas trees, improved pas-ture, residential areas, city parks, improvedroads of any width and adjoining clearings,powerline clearings of any width, and 1- to39.9-acre areas of water classified by theBureau of the Census as land. If inter-mingled in forest areas, improved roads andnonforest strips must be more than 120feet wide and more than 1 acre to qualify asnonforest land.)

Nonindustrial roundwood products.—Logs,bolts, and other round sections of trees cutfor direct residential use and not for pro-cessing at primary wood-using mills (in-cludes fuelwood, posts, etc.).

Poletimber.—A growing-stock tree at least 5.0inches d.b.h. but smaller than sawtimbersize (9.0 inches d.b.h. for softwoods, 11.0inches d.b.h. for hardwoods).

Primary wood-using mills.—Mills receivingroundwood products or chips from round-wood for processing into primary products(lumber, veneer, pulp, etc.).

Rotten tree.—A tree that does not meet re-gional merchantability standards becauseof excessive unsound cull.

Rough tree.—A tree that does not meet re-gional merchantability standards becauseof excessive sound cull. Includes noncom-mercial tree species.

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Roundwood consumption.—The quantity ofroundwood products processed in a givengeographic area (includes internal use(retained) roundwood and roundwoodimports).

Roundwood exports.—The quantity of round-wood products harvested in a given geo-graphic area and then transported toanother geographic area for processing.

Roundwood imports.—The quantity of round-wood products processed in a given geo-graphic area after being transported in fromanother geographic area.

Roundwood products.—Logs, bolts, or otherround sections of trees (including chipsfrom roundwood) cut for industrial ornonindustrial uses.

Roundwood production.—The quantity ofroundwood products harvested in a givengeographic area (includes internal use(retained) roundwood and roundwoodexports).

Roundwood retained.—The quantity of round-wood products harvested in a given geo-graphic area and processed in the samegeographic area.

Sapling.—A live tree between 1.0 and 5.0inches d.b.h.

Sawtimber tree.—A growing-stock tree con-taining at least a 12-foot saw log or twononcontiguous saw logs 8 feet or longer,and meeting regional specifications forfreedom from defect. Softwoods must be atleast 9.0 inches d.b.h. and hardwoods mustbe at least 11.0 inches d.b.h.

Softwoods.—Coniferous trees, usually ever-green, having needles or scale-like leaves.

Timber product output.—The production andconsumption of roundwood in a geographicarea plus the volume of mill residuesgenerated by primary wood-using mills inthe geographic area.

Timberland.—Forest land that is producing, oris capable of producing, in excess of 20cubic feet per acre per year of industrialroundwood products under natural condi-tions, is not withdrawn from timber utiliza-

tion by statute or administrative regulation,and is not associated with urban or ruraldevelopment.

Tree.—A woody plant usually having one ormore perennial stems, a more or lessdefinitely formed crown of foliage, and aheight of at least 12 feet at maturity.

TABLE TITLES

Table 1.—Conceptual model of individualconsumption studies making up theregional composite of industrialroundwood use by calendar year,North-Central Region

Table 2.—Composite estimate of industrialroundwood consumption, produc-tion, and interstate movement,North-Central Region, 1990






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10

11

12

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15

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May, Dennis M.1998. The North Central Forest Inventory and Analysis

timber product output database—a regional compositeapproach. Gen. Tech. Rep. NC-200. St. Paul, MN: U.S. De-partment of Agriculture, Forest Service, North Central Re-search Station. 16 p.

Discusses a regional composite approach to managingtimber product output data in a relational database. De-scribes the development and structure of the regional com-posite database and demonstrates its use in addressingeveryday timber product output information needs.

KEY WORDS: Consumption, exports, imports, production,roundwood.

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North Central Research Station