INTRODUCTION

Theoretical Basis

Contents

Forestry Literature ...........................................

MODELING PROCEDURES ...................................

StandModel .................................................

Species ...................................................

Tree Volumes ..............................................

Stand Characteristics .......................................

Stand Distribution ..........................................

Factor Productivity ...........................................

Factor Costs .................................................

Machines ..................................................

Labor .....................................................

Entrepreneur Profit .........................................

Stumpage .................................................

Harvest Systems .............................................

Harvest Simulation ............................................

Simulation Inputs ..........................................

Haul Costs .......................... ; .....................

Move Cost ..................................................

Move Times ...............................................

Alternative Costing Methods .................................

Comparative System Costs ..................................

Model Verification ............................................

DATA ANALYSIS .............................................

Cost Curve Derivation ........................................

Short Run Average Cost Curves ...............................

Long Run Average Cost Curve ..............................

Comparing Harvest Systems ...................................

Numerical Techniques ......................................

Graphical Techniques .......................................

Statistical Tests ............................................

Overall Differences .........................................

Sensitivity Analyses ..........................................

Parameter Changes .........................................

Results ..................................................

CONCLUSIONS ...............................................

Harvest System Trends .......................................

Shortwood ................................................

Manual Tree-Length ................................. . .....

Highly Mechanized Full-Tree ...............................

mole-Tree Chip ..........................................

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Tract Size Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Policy Implications . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . 19

LITERATURE CITED . . . . . . . . . . . . . .., . . . . . . . . . . . . . . . . . . . . . . . . . 20

APPENDIX:

Tables for Production Information, Input Costs, and

Simulation Inputs for Harvest Systems . . . . . . . . . . . . . . : . . . . . . . . 23

i

Economies of Forest Tract Size in Southern Pine Harvesting

Fred Cubbage

INTRODUCTION

Economies of forest tract size are crucial in

determining the economically available wood supply

in the United States. High average costs for forestry

operations on small tracts-diseconomies of sizeusually stem from high move and set-up costs for

heavily mechanized activities. The most capital intensive operations, such as regeneration and harvesting,

exhibit the highest average costs on small tracts.

Growing reliance on capital-intensive operations is

increasing concerns about economies of tract size.

Economies of size in forest harvesting create the

most immediate impacts on profitability and wood

supply. If harvest costs promise to exceed revenues,

the timber on a tract will not be cut. Regeneration

and timber stand improvement affect future wood

availability, while harvesting costs and revenues determine present supplies. Therefore, this research

focused on tract size economies in forest harvesting.

Theoretical Basis

Economies of size refer to the variation in average

unit costs possible by varying the size of the operation (Gregersen and Contreras 1979). Economies of

size are achieved when per unit costs decline as the

size of the plant changes; diseconomies occur when

unit costs increase (Heady 1952). Studies of economies of size rest on the determination and interpretation of the firm’s long run average cost curve,

which is in turn composed of many short run average

cost curves (fig. 1).

Empirical evidence suggests that the long run

average cost curve for most industries is “L-shaped”,

indicating economies of size up to a point, but beyond

that output level, average costs neither rise nor fall

when size is increased. The point at which average

costs cease to fall is known as the point of minimum

optimum scale (Bain 1969, Pratten 1971).

In forest land operations, both short run and

long run average cost curves are likely to be Lshaped since diseconomies are unlikely until very

large acreage sizes are reached. Concern over diseconomies of small tract size is more relevant in

forestry.

Better utilization of technology and mechanization, specialization of workers and equipment, reduction of resource indivisibilities, and other factors

create economies of large size (Chamberlain 1948,

Doll and Qrazem 1978, Heady 1952, Pratten 1971).

Most economies of large size in forestry are achieved

by spreading the initial fixed costs for capitalization

and transport of machinery over a larger output.

Extensive specialization of workers and equipment

offers little advantage in forestry because very few

land areas or harvesting crews are large enough to

take advantage of these economies. Better utilization

of large-scale technology and mechanization may provide some economies of size, but it is much less

important than spreading of initial fixed costs.

The economic-engineering or synthetic firm approach for estimating economies of size is the best

available method to examine the effect that tract

size alone has on production costs, so it was used

in this study. It is also the only method for estimating the potential average costs which firms could

achieve using modern technologies (French 1977,

Madden 1967).

Forestry Literature

Forestry literature on economies of size is sparse.

Some authors have examined economies of size in

forest manufacturing (Buford 1974, Buongiorno and

Gilless 1980, Dobie 1971, Granskog 1978, Mead

1966) and logging (Berndt et al. 1979). Only a few

studies, most of which are foreign, have examined

economies of forest tract size.

Sutton (1968, 1969, 1973) determined that per

acre overhead costs in New Zealand for relatively

small forests (2,000 acres) were about five times

those of a very large forest (292,000 acres). In

Norway, Noer (1975) found that, compared to 50

hectare tracts, 5 hectare parcels had per hectare

forest management costs almost twice as high. Even

20 hectare tracts had overall forest management costs

about 25 percent greater than 50 hectare parcels. In

Sweden, Andersson (1965) compared highly mechanized methods to conventional forestry. Tracts less

than 30 to 40 hectares had rapidly increasing costs,

especially in highly mechanized operations.

Fred Cubbage was Research Forester, Southern Forest Experiment Station, Forest Service-USDA, New Orleans, La. Currently

Assistant Professor, University of Georgia, School of Forest Resources, Athens, Ga.

1
SHORT RUN AVERAOE COST CURVES

AVERAGE COST

CURVE

1

UNITS OF OUTPUT

Figure l.-The long run average cost curve.

Row (1973, 1974, 1977, 1978) examined economies of size and the profitability of southern pine

growing. Fixed costs were reportedly the piimary

determinant of average costs for forestry operations

and the size of the fixed costs was directly related

to the level of mechanization.

Row concluded that most economies of large size

could be obtained in 80 acre tracts. For smaller

tracts, fewer management regimes had rates of return

which would be greater than an owner’s alternative

rate of return. At 20 acres, only intensive management of natural stands yielded positive returns. For

10 acre tracts, no management regimes offered an

acceptable investment opportunity.

Statistical cost research performed by Wikstrom

and Alley (1967) on National Forests revealed that,

for most forest management practices, costs per acre

increased rapidly with decreases in size of area, particularly for areas smaller than 40 to 50 acres. Gardner (1981) also found economies of size in forest

regeneration. However, acceptable rates of return

could be achieved on tracts as small as 10 acres, assuming no stumpage discounts were received. Thienpont (1976) concluded that tract size was not critical

in harvesting as long as labor-intensive bobtail operations were available for cutting small tracts.

MODELING PROCEDURES

The modeling procedures used in this study were

aimed at estimating short, run average cost curves

for harvesting timber on different sized tracts using

a range of harvest system mechanization levels. The

process entailed developing a stand model, gathering harvesting productivity and cost information,

2

assembling a range of harvest systems and d&term&

ing their overhead costs, simulating the harvesting

process, developing short run average cost curves,

and analyzing the results (fig. 2).

Stand Model

Most studies have found that harvesting productivity varies proportionately with tree size class

(Hypes 1979, Hypes and Stuart 1979, Plummer

1977, Tufts 1977) and have accordingly published

diameter-based productivity tables. Therefore, a

flexible stand model was used to account for productivity variations corresponding to diameter class

distributions.

Species.-Average harvest cost estimates were

based on a model stand of loblolly pine. It is the

most common and widely spread southern species,

the most valuable for pulpwood and timber products,

and the subject of most productivity studies. Productivity and cost estimates for all southern species

should be somewhat interchangeable.

Tree Volumes.-The loblolly tree volumes by

diameter breast height (dbh) used for this study

(fig. 3) were adopted from Hypes and Stuart (1979)

and Plummer (1977)) who based them on regression

equations developed during the American Pulpwood

Association Harvesting Research Project (HRP) .

These publications represent the most reliable data

available for use without modification. The remaining productivity studies were adapted to fit their

model trees. The average height and merchantable

height for loblolly trees were also taken from HRP

literature (Lanford and Cunia 1971).

Stand Characteristics.-Stand characteristics were

deveioped by working backward from an average
Stand Model

I

Develop model forest stand with average characteristics to be harvested in the simulation

Factor Productivity

Determine productivity of manual and machine operations to be used in a variety of harvest systems

”

Factor Costs I

Determine the factor costs for all inputs used in

harvesting operations

harvest systems for range of mechanization levels

Overhead Costs

Estimate the overhead costs for moving a harvest

system into a new forest tract

for range of tract size and mechanization levels

I

Model Verification

Check simulation results with data from real operations to determine validity of results

I

Analysis and Interpretation

Develop cost curves, analyze curves by tract size

and mechanization level, do sensitivity analysis

Figure 2.--Modeling steps in estimating economies of forest

tract size in Southern Pine harvesting.

Table b--Typical stand description

_ISpecies: Loblolly pine, unthinned natural stands

Age: 25 years

Site index: 70 feet at 50 years

Basal area: 80 square feet per acre

Total cubic feet yield of wood and bark: 1,897 fts per acre

Cubic feet yield of wood and bark to 4” top: 1,591 fts per acre

Standard cord yield of wood and bark to 4” top: 17 2/3 cords

per acre (cubic feet yield divided by 90 cubic feet per cord)

volume per acre to be cut in the stand. Conversations with forest industry employees and current

forest survey data in the South indicate that typical

yields for loblolly pine range from 10 to 20 cords per

acre, with an average in the upper teens. Most industrial stands in the South are being clearcut at an

average age of 25 to 30 years old. Using this information as a guide, a “typical” stand was chosen from

natural stand loblolly yield tables developed by Burkhart et al. (1972).

Selected stand characteristics at harvest are listed

in table 1. Stands were assumed to be clearcut for

pulpwood only on flat to gently sloping terrain. Oneway haul distances to the mill were assumed to be

30 miles for all harvest systems.

Stand Distribution.-The stand distribution in

figure 4 was used as the basis for subsequent productivity rate distributions developed for the study.

It is based roughly on tables by Plummer (1977)

and Feduccia et al. (1979) for natural and planted

loblolly pine, respectively. Figure 5 charts the volume

per acre by diameter class.

Factor Productivity

Productivity of harvest systems is the basis underlying harvest costs. Likewise, productivity rates for

individual manual or machine operations are the

basis for this research.

Productivity estimates were measured in or converted to production of cubic foot output of wood

per operating hour, as opposed to scheduled hour.

The operating hour basis is more useful since its

ratio to scheduled hours (commonly referred to as

availability) may vary widely depending on the

machine, the operator, the maintenance, the harvest

species, or other factors.

Availability or utilization figures for various machines and harvest operations were obtained from

company interviews and literature sources, such as

Hypes and Stuart (19’79), Plummer (1977, 1979,

1980)) and Warren (1977). Technically, availability

3
4 5 6 7 8 9 IO II 12 13 14 15-16

D.B. H. (INCHES)

Figure X-Pine tree volumes at each diameter laverage dbhx9.4 inches).

16,

4 5 6 7 8 9 IO II 12 13 I4 15-16

0.8. H. (INCHES)

Figure 4.--Model pine stand distribution.

300

I

Y

2 250

s 200

:

2 I50

5

q 100

s

=, 5 0

P

0

4-5 6 7 9 9 I O II I2 I3 1 4 1 5 I6

D. 8. H. (INCHES)

Figure S.-Volume per acre by dbh class (total crolmoe/acre=1.591 cu. ft.)
is defined as the percentage of scheduled hours a

machine is not broken down and is capable of performing work. Utilization means the percentage of

scheduled hours a machine or man is actually operating or productive. In practice, the terms are used

rather loosely. Both generally indicate operating

hours as a percent of scheduled hours. Appendix

table A2 includes the utilization figures for machines.

Several methods were used to determine productivity estimates by dbh class. Productivity by stem

size class for loblolly pine was often given directly

in tables or graphs. Data on a large number of harvest functions were available in this form. Examples

include chainsaw felling, limbing, bucking, and topping (Hypes and Stuart 1979, Plummer 1977, Tufts

1977); forwarding (Tufts 1977); and limited-area

feller-bunchers and whole-tree chippers (Plummer

1977).

Data which appear to have more statistical reliability can be generated from regression equations for

predicting productivity rates by tree size and/or

skid distance. Clair (1977) developed such equations

for knuckleboom loaders and rubber-tired cable skidders and worked with Matthes et al. (1977) in

developing regression equations for chainsaw felling.

Unpublished forest industry records also provided

information on productivity rates.

The productivity rates which were selected for use

in this research are summarized in appendix table

Al. Skidding and forwarding travel rates, load sizes,

and fixed load and unload times, used by the simulation program to estimate function productivity

rates, are summarized in appendix tables A8 to All.

A complete summary of all the productivity information gathered on harvesting southern pines is

also available (Cubbage 1981a).

Factor Costs

Current factor costs for harvesting equipment,

labor, entrepreneurship, and stumpage were used in

the analysis. Costs were indexed to 1980 prices, and

most of the data were collected in early 1980.

Machines-Several methods could be used to calculate the costs of machines used in harvesting.

These include the capital recovery method, a cash

flow basis, or machine rate calculations. The latter

were used because they are widely accepted in the

forest industry, are easy to work with and understand, and provide good average cost estimates for

the life of the machine. The machine rates are the

total of the overhead (fixed) costs and operating

(variabIe) costs per operating hour, excluding the

cost of the operator. Machine rates were calculated

using procedures described by the American Pulpwood Association (1965)) Matthews (1942)) Miyata

(1980) and Warren (1977).

Appendix table A2 summarizes the machine rate

costs for harvesting equipment commonly used in

the South. Again, more complete calculations are

summarized by Cubbage (1981a, 1981b).

Much of the operating cost information comes from

data published by Hypes and Stuart (1979) or Plummer (1979, 1980). Some operating costs for bulldozers, road graders, cable skidders, and grapple

skidders were obtained from cost tables in the Cost

Reference Guide (1980). Much current operating

cost data were gathered from southern forest industries with logging crews. For the machine rate calculations, gasoline and diesel fuel were assumed to

average $1.00 to $1.10 per gallon, engine oil 75$ per

quart, and hydraulic oil $2.80 per gallon.

Purchase price information for harvesting machines

was usually determined by informal discussions with

forest equipment dealers in the South. University and

industry personnel familiar with purchase prices were

consulted for corroboration and for price estimates

not provided by dealers. Delivered prices for individual machines were aggregated by class to determine

an average price for a type of machine.

Salvage values for equipment and trucks were

taken often from tables published by Hypes and

Stuart (1979). Green Guide (1980) estimates of

average resale values for construction equipment and

log skidders also were used for salvage values. Equipment having no published salvage value usually was

assumed to be salvaged for 20 percent of the purchase price. Expected life spans and yearly use rates

were taken from Hypes and Stuart (1979)) Plummer

(1979)) Tufts (1977)) and Warren (1977).

The informal survey of equipment dealers was also

used to determine the average insurance rates for

logging equipment. In-woods logging equipment, such

as bulldozers, skidders, and feller-bunchers, had

average insurance rates of about $4 per $100 of

purchase price for the life of the machine. Equipment used at the deck, such as loaders, slashers, or

chippers, had an insurance rate of about $1.25 per

$100 of the purchase price.

Insurance rates for logging trucks and trailers are

south-wide averages for physica damage insurance

and 100/300/100 liability coverage. The information

was obtained on a state-by-state basis from the Fred

S. James Company in South Carolina which insures

Iogging equipment throughout the South. Corroborating rate quotes were obtained from Transportation Associates Inc. and Carver General Insurance

Company in Louisiana.

Annual license, tags, and taxes costs are based on

the sum of local, state, and federal taxes and any

licenses required for operation. While the distribu5
tion of costs between tags and taxes varies from

state to state, the totals are usually similar. A telephone sampling of several states in the South was

used to determine average state tags and taxes costs

for use in the machine rate calculations. The machine rate taxes figure also includes federal highway

taxes calculated per IRS Publication 349 (Internal

Revenue Service 1979).

Average interest costs were computed based on a

12 percent annual interest rate per year levied

against the Average Annual Investment. Calculating

interest costs as a percent of Average Annual Investment is a standard procedure used by forest harvesting engineers (Kurelek 1976, Matthews 1942, Miyata

1980, Warren 1977). Deciding on the appropriate

interest rate was another matter.

Conversations with southern industry personnel

and equipment dealers indicated no uniform interest

rate in 1980. Dealer rates ranged from 7 to 12 percent add-on. Add-on rates from 7 to 9 percent for

company-backed or established customers were possible at the dealers. However, many dealers said

that established loggers could get considerably

cheaper loans through local banks. Annual interest

rates as low as 9 to 11 percent were still common

and rates seldom rose above 13 to 14 percent.

Given the range of rates existing in 1980, a reasonable choice was flexible. For the machine rate

calculations, 12 percent annual interest was optimistically chosen as appropriate. This is rather low compared to the inflationary rates experienced in late

1980 and 1981. However, few people were buying

equipment at the inflectionary levels; they tried to

finance equipment at lower rates or to defer purchases.

The machine rate calculations should reflect 1980

calendar year costs. They have been reviewed by

academic and industrial forest harvesting specialists.

The machine rate average costs must be used with

caution. Actual cash expenses for fixed costs, such as

interest payments and insurance, will be higher than

average in early years and lower in later years. Conversely, operating costs tend to be low when a

machine is new but increase with age.

Labor.-Labor costs (table A3) were based on

estimates by forest industry personnel of the contractor wage rates in their area and an American Pulpwood Association survey summarized by Hypes and

Stuart (1979). Wages were calculated on a scheduled

hour basis rather than a production hour or production incentive basis.

Fringe benefits such as vacation pay, health insurance, or bonus pay are not paid currently by most

southern independent contractors. Therefore, they

were excluded from the analysis. Current federal law

exempts overtime pay for crews of eight or less. Independent owner/operators who employ more than

6

eight persons must pay overtime and include it in

their cost calculations, although it was omitted for

simplicity in this paper.

Worker’s compensation payments were calculated

at their mean level for the South based on an American Pulpwood Association (1979) survey. A similar

1980 survey (American Pulpwood Association 1980)

indicates that rates declined slightly, but the 1979 figures were considered more representative. Unemployment compensation payments in the South average

about three percent of payroll for state and federal

contributions and were included as such. All employers and employees must pay social security taxes on

their salaries, so cost were levied accordingly. Logging

owner/operators need not pay worker’s compensation

on their own salaries; therefore none was included

as a cost for them.

Total social legislation costs by type of system are

summarized in table A4. All shortwood systems pay

rates according to the pulpwood only class. Treelength or full-tree operations which could sort out

sawtimber or other products were charged at the

pulpwood and sawtimber classification rates.

Entrepreneur Profit.-As Madden (1967) stressed,

the calculation of profit for an owner/operator firm

is crucial in cost calculations. Profit was assumed to

equal the salary of the owner/operator. Profits for

logging operations vary widely depending on, for

example, the owner, the operation, and the cost

accounting method. Most logging firms are averse to

revealing their profit. These problems led to standardized profit (salary) assumptions being made

(table A5). Small, less capital-intensive operations

were assumed to make less profit than large ones.

Profit assumptions were graduated by size of operation, so the relative levels probably reflect reality.

Stumpage.-The use of stumpage and delivered to

mill prices in the analysis created several problems.

Prices vary considerably from month to month and

year to year. Choosing the appropriate stumpage and

F.O.B. mill price can be somewhat arbitrary. Timber

Mart South (1979,198O) provides an excellent source

of average prices. Table A6 lists the reported average

southern pine price ranges from July 1979 to July

1980 for stumpage and products delivered to the mill

and prices which were used as “typical.” Late 1980

prices were not considered because they were depressed below “normal” levels. Mill prices were determined also for use in discussions of harvest system

profitability.

Harvest Systems

Various harvest systems were modeled to determine the effects of mechanization on average harvest

costs. The study analyzed shortwood, long log, tree-
length, full-tree, and whole-tree harvest operations

by combining productivity and cost data for individual operations into complete systems (table 2). Harvest systems currently prevalent in the South were

examined. Systems declining in use or experimental

equipment were not. The general descriptions of systems modeled provided the basis for balanced equipment and manpower spreads (tables 3 and 4). Table 5

displays the total 1980 investment required for each

harvest system.

Harvest Simulation

Mathematical calculations, linear programming, or

computer simulation can be used to estimate average

costs by tract size. Simulation was chosen since it

should be faster and more accurate in performing

numerous harvest cost calculations. Also, it is superior at modeling the actual harvesting process and

all its interactions.

After reviewing the harvest simulation programs

available, the Harvest System Simulator (HSS) program (Stuart 1980, 1981) was selected to simulate

the productivity and estimate costs of the modeled

harvest systems. The program requires that the input

productivity rates implicitly include stand features.

Harvest system balances depend on volume controls

used as program inputs which regulate harvest inventories for each harvest function. Poor program inputs

will generate poor results. This analysis attempts to

avoid both.

Simulation Inputs.-To clarify the modeling procedures used, a brief summary of the important simulation inputs follows. Each harvest system required

the harvest function productivity rates, equipment

and manpower spreads, equipment costs, and wages

to be used as inputs. Stumpage and overhead costs

for owner/operator profit were also needed.

All systems were assumed to operate 5 days per

week, 9 hours per day, and 32 to 44 weeks per year,

depending on the system. Each system’s harvests

were simulated for the range of tract sizes which

seemed practical for its mechanization level, varying

from 0 to 360 acres. Non-productive times, such as

breaks (2 per day), lunch, and machine breakdowns

and idle time (varied according to machine utilization

rates), were used as inputs to convert scheduled time

to productive time. Volume inventory controls were

also needed for each harvest function (i.e. felling,

skidding, loading) to prevent excessive build-ups of

wood. Apendix tables A8 through All summarize the

relevant simulation inputs.

H’auZ Costs.-The HSS program could simulate

haul time and costs directly, but it was more convenient to calculate them by hand and put them into

the program as pre-calculated costs (table A7). Using

the machine rate calculations and a 30 mile haul distance for all systems, the machine costs equaled the

cost per mile multiplied by the number of miles and

divided by the load in cords. Labor costs equaled the

wage per hour multiplied by the roundtrip time and

divided by the load.

Table 2.-Southern pine harvesting operations examined

A. Stump bobtail. Chainsaw fell, limb, top, and buck into 5’3” bolts; hand load with bigstick (boom and

cable) loader onto 4 cord tandem straight truck; haul

B . Bobtail and tractor. Chainsaw fell, top, and limb; farm tractor skid to roadside; buck into 5’3” bolts;

load onto 5 cord tandem straight truck with bigstick loader; haul

C . Skidder and truck. Chainsaw fell, top, and limb; choker skid to landing; load onto 5 cord tandem

straight truck with small hydraulic loader; haul

D. Semi-mechanized shortwood. Shear with tree shear; limb and top with chainsaw; skid with medium

size choker skidder; buck with chainsaw at deck; load with small knuckleboom loader onto

tractor-trailer truck; haul

E. Highly mechanized shortwood. Fell and bunch with rubber-tire feller-buncher; skid with medium

to large size grapple skidder; delimb with iron gate delimber; buck into 5’3” wood with hydraulic

slasher; load with medium knuckleboom loader onto tractor-trailer truck; haul

F . Shortwood prehauler. Fell, delimb, top, and buck with chainsaw; Ioad with attached knuckleboom

onto forwarder; forward to landing; load onto tractor-trailer truck; haul

G . Skidder long log. Fell, limb, and top with chainsaw; skid with small to medium size choker skidder;

buck at landing into long logs with chainsaw; load with large knuckleboom loader onto tractortrailer rig; haul

H. Manual tree-length. Fell, limb, and top with chainsaw; skid with medium size choker skidders;

load with large knuckleboom loader onto tractor-trailer truck; haul

I. Highly mechanized full-tree. Fell and bunch with rubber-tire feller-buncher; skid with large grapple

skidder; delimb with iron gate delimber: load with large knuckleboom onto tractor-trailer truck;

haul

. . J. Limited-area full-tree. Fell and bunch with tracked, limited-area feller-buncher; skid with large

grapple skidder; delimb with iron gate delimber; load with large knuckleboom loader onto

tractor-trailer truck; haul

K. Whole-tree chipping. Fell and bunch with rubber-tire feller-buncher; skid with large grapple

skidders; chip with large whole-tree chipper and blow into chip van; haul with tractor-trailer truck
Table 3.-Harvest system equipment

A. Stump bobtail

B. Bobtail and tractor

C. Skidder and truck

D. Semi-mech. shortwood

E. Highly mech. shortwood

F. Shortwood prehauler

G. Skidder long log

H. Manual tree-length

I. Highly mech. full-tree

J. Lmtd.-area full-tree

K. Whole-tree chip

--

t

r 7

2

3

sc

8

I I :

-

2

2

3

2 I

1

3

2

5

1

1

1

-

Table 4.-Harvest system manpower

System

Equipment Truck

Supervisor Saw hand operator driver Mechanic Total

A. Stump bobtail I/3 2 l/3 l/3 3

B . Bobtail and tractor l/3 l-1/3 1 l/3 3

C. Skidder and truck l/2 2-l/2 l-1/2 l-1/2 6

D. Semi-mech. shortwood l/3 2 2-l/3 2 l/3 7

E. Highly mech. shortwd. l/2 3 2 l/2 6

F. Shortwood prehatder I/3 3 1 2/3 5

G. Skidder long log l/2 l-1/2 l-1/2 l-1/2 5

H. Manual tree-length 1 3 2-I/2 2 l/2 9

I. Highly mech. full-tree 1 4-l/2 3 l/2 9

J . Lmtd.-area full-tree 1 3-l/2 3 l/2 8

K. Whole-tree chip I 5 3 1 1 0

Table 5.-Total harvest system investment costs, 1980 purchase prices

Harvest system

Equipment Hauling and

in-woods support eqpt. Total

A. Stump bobtail

B. Bobtail and tractor

C. Skidder and truck

D. Semi-mech. shortwood

E. Highly mech. shortwood

F. Shortwood prehauler

G. Skidder long log

H. Manual tree-length

I. Highly mech. full-tree

J. Limited-area full-tree

K. Whole-tree chip

_______-_____..__-. dollars _ _ _ _ _ . _ _ _ _ __--__.

2,700 13,500 16,200

30,600 27,000 57,600

74,500 47,000 121,500

146,500 146,000 292,500

197,700 170,600 367,700

41,500 61,000 102,500

eo,ooo 76,600 156,600

156,500 170,600 327,100

321,700 231,400 553,100

301,700 231,400 533,100

456,000 259,500 715,500
TabIe 6.-Average time spent in moving a logging operation to a new job site

Percent Avg. no.

Average of moves Avg. time employees Avg. time

No. skidders number made required to used to required

intbe o f during move during move on to move

operation employees work week week weekend on weekend

0 1.50 20

1 3.45 55

2 4.67 67

3 13.00 0

4 12.75 67

over 4 11.00 72

hours

1.0

3.4

4.3

6.0

6.7

2.0

1.8

2.8

2.0

3.0

7.0

hours

2.0

4.1

5.6

6.0

6.0

8.0

overall 6.30 60 4.4 2.8 4.8

Source: Watts and Watson 1978.

Move Cost

Fixed or overhead costs of harvesting tracts of

timber are the critical elements creating economies

of size. Sale administration and layout, moving into

a tract, and fixed charges for idle equipment cause

high average costs for small tracts. High fixed costs

require large outputs in order to minimize their contribution to average costs. Of all the overhead costs

in harvesting, the move costs for transportation and

idle equipment are the most important in determining economies of size (Walbridge 1967, Thienpont

et al. 1976). Therefore these costs were examined in

this study. Sale and administration costs may also be

significant (Kronrad et al. 1980), but they are likely

to be similar for all harvest systems. Systems with different mechanization levels are likely to have greatly

different move costs, owing to the fixed costs for idle

equipment and wages for non-productive employees.

Little literature is available on the cost of moving

harvest operations. McDermid (1969) found that

highly mechanized tree-length operations are by far

the most expensive to move. Bobtail operations were

the cheapest to move. He found that highly mechanized shortwood, partially mechanized shortwood,

and partially mechanized longwood system had similar move costs.

Move Times.-An American Pulpwood Association

report prepared by Watts and Watson (1978) provided a basis for estimating the cost of moving harvest operations. Their survey of 32 independent

Mississippi loggers and pulpwood producers determined the average time required for logging operators

to plan and execute a move. They found that large

operations usually move during the week, with the

move taking one-half to three-quarters of a work

day (table 6).

Alternative Costing Methods.-The best method

of estimating the costs of moving from tract to tract

is moot. Costs for transporting the equipment from

one site to the next and wages paid to employees who

are not productive during the move should be included. Similarly, a charge for the fired costs of

non-productive equipment should be included as a

cost item also. Employee wages and equipment fixed

costs would constitute a system rate cost for the

move.

The value of production foregone during the move

might also be included as an expense in addition to

the system rate cost. The total of the system rate

costs and foregone production costs were estimated

by the HSS computer program. Move time and transportation costs for each harvest system were used as

inputs into the simulation program, which then calculated the total cost to harvest the first piece of

wood-a proxy for move cost. This cost was used in

the harvest cost estimates by tract size.

Comparative System Cost.-Table 7 summarizes

the relevant move cost calculations by harvest system. Obviously, small systems cost less to move than

large systems. They require less time to move and

have lower fixed costs to be borne during the move.

The stump-to-stump bobtail system has virtually

no move costs. Small partially mechanized systems

(B,C,F,G) cost $200 to $500 to move. Large partially

mechanized systems (D,H) take $600 to $800 to

move and highly mechanized systems (E,I,J,K) require $1000 to $2400 to move.

Model Verification

The results of the modeling process and harvest

simulation were checked to determine whether they

were acceptable. Table 8 summarizes some comparisons between the simulation results and actual logging productivities and costs.

Generally, the simulation results appear reasonable. Weekly production estimates developed by the

9
Table 7.-Harvest system move costs

Total move costs

Sytem rate

Harvest Move Transport Payroll System rate expenses Foregone Manual Simulation

system time costs costs per hour1 per move” production calculations3

program*

hours --_---------_-_-----. dollars ._ _ ___ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ cords _-------I. dollars - - _ _ _ _ _ _ -.

A 2.0 0 0 3 5 0 0 0 8

B 4.0 8 5 2 4 5 0 152 4 237 1’78

C 4.0 85 24 112 320 8 405 403

D 4.3 3 3 191 161 474 15 507 600

E 6.0 141 211 18’7 837 2 5 978 993

F 4.3 8 5 105 7 9 267 11 352 332

G 4.3 8 1 104 108 311 10 419 502

H 4.3 7 6 259 I86 549 2 8 625 759

I 6.0 154 322 269 1103 6 2 1256 1237

J 12.0 225 542 254 2069 119 2294 2399

K 12.0 241 817 311 2599 155 2840 2382

‘Total of wages per hour, machine fixed and operating costs per hour, overhead equipment costs, and owner/operator salary per

hour.

sSame as 1, minus fixed and operating costs of operating haul trucks and operating costs of non-productive haul trucks and

harvest equipment, times the hours to move. ‘>,

Vystem rate expenses per move plus transport costs, manually calculated.

4System rate expenses per move plus transport costs, as calculated by the Harvest System Simulator computer program.

HSS program tend to be high because each week was

set up having five full days and crews working only

32 to 44 weeks per year to approximate the appropriate number of operable days in a year. In reality,

many work weeks consist of fewer than five days

because of bad weather and the logging crew works

all year. Simulated yearly production is somewhat

closer to reported average system productivity rates.

System costs are not affected by the number days per

week as long as the total number of days per year

remain the same.

The simulated harvest costs per cord indicate that

most systems are unprofitable. This is misleading

because all the systems have 1980 equipment costs.

Logging crews are actually using some older equipment purchased for lower prices, so they could still

make a profit at prevailing mill prices. The 1980 cost

data indicate that either mill prices or logging productivity must be increased for logging operations to

remain profitable in the future.

One may also examine the validity of the simulation results by comparing relative productivity and

costs among systems. The relative differences seem

reasonable, with more mechanized systems being

more productive. Relative system costs are close to

those calculated by Tufts (1979) in a thinning study.

He found bobtail and prehauler operations quite

economical, with tree-length operations being less

expensive only on stands averaging more than nine

inches dbh. Mechanized full-tree harvest systems were

the least expensive roundwood harvesting method.

Costs for whole-tree chipping were somewhat higher,

1 0

but the system had modeled one skidder and one

feller-buncher, which suggestions underutilization of

the chipper.

Overall, the synthetic logging firm modeling process

and simulation results seem valid. Productivities and

costs fall within realistic ranges and comparative

system differences are reasonable.

DATA ANALYSIS

The HSS program was used to estimate the average

cost per cord for tracts of various sizes, ranging from

0 to 360 acres. Replications were used in the cost estimates because they were easier and cheaper to run

on the computer than numerous individual estimates

and allowed more statistical tests.

Cost Curve Derivation

Short run average cost curves were determined for

each system using linear regression with tranformations of the simulated cost data. Harvest cost per

cord was the dependent variable and acres the independent variable. Quadratic, cubic, log, and inverse

transformations were tried in order to find the best

functional form for each harvest system.

The multiple linear regression package BMDPlR

(Biomedical Computer Programs 1977) was used to

perform the analysis. The coefficient of determination (R”), significance of the regression (F ratio),
significance of the coefficients (t tests), and standard

error (se) of the estimate were examined to select the

best form of the short run average cost curves. Also,

residual and normal plots were examined according

to accepted techniques to eliminate undesirable functions (Daniel and Wood 1971, Draper and Smith

1966, Johnston 1972, Truong 1980, Wonnacott and

Wonnacott 1979).

Short Run Average Cost Curves.-Inverse function

short run average cost curves were developed for all

harvest systems except A and B. A’s best form was a

linear function and B’s was a quadratic. Dummy

variables were used to account for a cost data idiosyncrasy of some tract sizes-multiples of 25 or 30

acres having lower average costs than mutiples of

40 acres. The dummy variables were considered significant at alpha equal to 0.10. Regressions with

non-significant dummy variables were recalculated

without the dummies in the regression. Table 9

presents the relevant statistical parameters for the

final cost equations selected, including the dummy

variables.

The dummy variables account for variation in

tracts of 25- or 30-acre multiples and merely lower

the intercept for cost estimates at those points. Since

the lower costs were merely an idiosyncrasy of the

computer-simulated cost data and not a real world

difference, the dummy variables and coefficients were

dropped entirely from the equations, providing the

most realistic estimates of harvest costs per cord.

The final harvest cost equations are summarized in

table 10.

Long Run Average Cost Curve.-Economic theory

dictates that an envelope curve below and tangent to

the short run average cost curves is, by definition,

the long run average cost curve. Derivation of an

envelope curve for the harvest systems modeled

proved to be quite difficult, however.

Figure 6 graphs the short run average cost curves

for systems A through K. Drawing a continuous curve

under all the harvest system cost curves is not possible, primarily because system A has virtually no

overhead costs. A kinked freehand envelope curve can

be drawn under the cost curves or the lowest cost

segments can be combined into a scalloped long run

average cost curve. However, statistiscal estimation

of the envelope curve was not possible. Attempts were

unsatisfactory because a regression including data

from A at small acreages raised the cost curve far

above what it was determined to be by system I at

large acreages. Therefore, the conclusions regarding

economies of tract size were drawn from the comparison and analysis of important harvest system short

run average cost curves and trends in system selection.

Comparing Harvest Systems

With short run average cost curves derived for all

systems, comparisons in relative system costs can be

made. Systems may differ in overhead costs, costs at

minimum optimum size, or both. Numerical, graphical, and statistical procedures may be used for comparisons among harvest systems.

Numerical Techniques.-The cost equations in

table 10 permit ranking of the harvest systems by

minimum cost level or by size of logging chance at

which they reach that cost. Table 11 ranks the 11

Table &-Productivity and cost of simulated and actual operations

System

Simulated

weeks

worked

per year

Simulated productivity

cords per

Week Year

Reported average

literature productivity

cords per

Week 50 wk. yr.

Simulated Southern

minimum average

cost/cd. FOB mill

FOB mill price/cd.

_ - - - - - - - dollars -------

A. Stump bobtail 3 2 5 0 1600 2 6 1300 40.97 38.00

B. Bobtail and tractor 3 6 4 0 1440 3 0 1500 49.11 38.00

C . Skidder and truck 4 0 9 0 3600 9 0 4500 57.04 38.00

D. Semi-mech. shortwood 4 0 160 6400 150 7500 46.92 38.00

E. Highly mech. shortwood 4 4 190 8360 150 7500 44.79 38.00

F. Shortwood prehauler 4 2 110 4620 8 0 4000 41.30 38.00

G. Skidder long log 4 0 105 4200 120 6000 45.50 38.00

H. Manual tree-length 4 4 290 12,760 250 12,500 41.88 38.00

I. Highly mech. full-tree 4 4 465 20,460 350 17,500 37.66 38.00

J . Lmtd.-area full-tree 4 4 445 19,580 350 17,500 37.54 38.00

K. Whole-tree chipping 4 2 580 24,360 350 17,500 33.96 31.68

Sources: Simulated Productivity-Harvest System Simulator.

Literature Productivity-Systems A-H Watson et al. 1978; Systems I-K Glenn Plummer, Georgia Kraft Co., personal

communication.

Southern Average F.O.B. MiII Price-Timber Mart South 1979, 1980.

1 1
Table S.-Regression statistics for the final harvest system cost curves

Student’s t

Bl B2*

(acres) (dummy or acres?)

Coefficient of Standard F Significance Significance

Harvest system determination error ratio Value level Value level

A. Stump bobtail .95 .071 7 0 8.3 .OOl

B . Bobtail and tractor .96 .1416 230 -1.4 .189 5.687 .OOOl

C. Skidder and truck .99 .0885 2371 65.3 .OOOl -2.1 .034

D. Semi-mech. shrtwd. .94 .2747 356 25.4 .OOOl -2.13 ,038

E. Highly mech. shrtwd. .96 .3643 1374 37.1 .OOOl

F. Shortwood prehauler .68 .4025 3 5 6.8 .OOOl -3169 .003

G. Skidder long log .90 .3873 193 18.5 .OOOl -1.717 .093

H. Manual tree-length .94 .4791 457 29.1 .OOOl -3.399 .OOl

I. Highly mech. full-tree .96 .6418 925 41.3 .OOOl -5.7 .OOOl

J . Lmtd. area full-tree .98 .7693 3007 54.8 .OOOl

K. Whole-tree chip .99 .7402 2269 65.8 .OOOl -3.516 .OOl

*Square acres for system B; dummy variable for remaining systems when found significant at alphaz.10.

Table IO.-Final cost curves selected

Harvest system Final cost curve equation

A. Stumn bobtail

B. Bobtail and farm tractor

C. Skidder and truck

D. Semi-mechanized shortwood

E. Highly mechanized shortwood

F. Shortwood prehauler

G. Skidder long log

H. Manual tree-length

I. Highly mechanized full-tree

J. Limited-area full-tree

K. Whole-tree chipping

where: Yzharvest cost (dollars per cord)

X = tract size harvested (acres)

Y r=40.97$0.02 (X)

Y =r49.17’7-0.016(X) +O.OOl (X2)

Y=56.88+17.92O(l/X)

Y=46.682+20.835(1/X)

Y=44.369+38.891(l/X)

Y=41.125+9.894(1/X)

Y=45.261+21.75(1/X)

Y=41.418+39.941 (l/X)

Y=37.089+74.506(1/X)

Y=37.230+119.389(1/X)

Y=33.092+139.67(1/X)

Table IL-Rank of harvest systems by minimum acreage size required to reach minimum cost level

Bank System

Acres required to reach minimum cost

507, slope 1% slope

level level

HSS

simulated

move cost

1 A. Stump bobtail 0 0

2 B. Bobtail and tractor 8 8

3 F. Shortwood prehauler 14 3 1

4 C . Skidder and truck 19 4 2

5 D. Semi-mech. shortwood 2 0 4 6

6 G. Skidder long log 21 4 7

7 E. Highly mech. shortwood 2 8 6 2

8 H. Manual tree-iength 2 8 6 3

9 I. Highly mech. full-tree 39 8 6

10 J. Lmtd.-area full-tree 4 9 109

11 K. Whole-tree chipping 53 118

dollars

8

178

403

600

993

332

502

759

1237

2399

2382

12
351 t I I I I I I

0 5 IO 15 2 0 2 5 3 0 3 5 4 0

TRACT SIZE (ACRES)

Figure C-Harvest system short run average cost curves by acres, graph from 0

acres to depict intersections.

systems according to the average size at which they

approach their minimum cost. System A is minimum

at the intercept. System B, a quadratic function, has

a minimum point at 8 acres. The remaining systems

(inverse functions) are assumed to approach their

minimum cost (horizontal level) when the first derivative of the cost function equals 0.01 (the crook

of the 1;). The 0.05 level is also included.

Similarly, the harvest systems are ranked according to the level of their minimum cost in table 12.

System A has a minimum cost at zero acres, system B

at eight acres, and systems C through K at infinity.

Graphical Techniques.-Graphs of the equations

in table 10 facilitate viewing cost curve intersections

and differences in levels. Two forms of graphical relationships are appropriate. First, plots of harvest cost

per cord versus acres allows comparison of the actual

cost curves for different systems by tract size (figs. 6

and 7). Second, linearized transformations of cost

per cord versus l/acres are useful (fig. 8). Linearized

plots aid inspections for differences in slope and level

among harvest systems. Lines which cross in the

linearized plot indicate that systems probably have

different slopes (overhead costs). Parallel lines indicate that systems seem to have similar overhead

costs; different levels of parallel lines suggest that

the average minimum costs are different. Statistical

tests among systems were performed to test the significance of the visual differences.

Since the plots of 11 harvest systems on one graph

tend to be quite crowded, bar chart comparisons

to 40

(fig. 9) may be preferred for inspections of costs

at different tract sizes.

Statistical Tests.-Two tests were used to insure

that the apparent differences among harvest systems

were statistically significant. The two bobtail systems

had different functional forms, so were different by

definition, The method of group regressions (Freese

1964, 1967; Snedecor and Cochran 1967) was used

to test for differences in slope and level among the

nine linearized inverse cost functions. Different slopes

indicated significantly different overhead costs and

different levels (intercepts) indicated significantly

different minimum average costs.

Harvest systems with overhead cost differences of

about $200 or less usually had similar slopes. Systems

with differences of $300 or more always had different

slopes, as would be expected. Also, systems J and K,

which had similar overhead costs but widely different

ultimate cost levels, had significantly different slopes.

The Bonferroni Significant Difference‘Test (Miller

1966) was used on the data in the cost curve tails

(table 13) of the nine inverse functions to determine

whether their mean ultimate average cost levels were

significantly different. The test determined that at

the one percent alpha level, differences of 64 cents or

more were statistically significant. Therefore, only

the harvest system pairs of full-tree systems I and J

and prehauler system F and tree-length system H

were not significantly different. The statistical tests

confirm the apparent rank order differences among

harvest system average costs.

13
Overall Differences.-The rankings, graphs, and

statistical tests support conclusions about differences

among harvest systems. Highly mechanized full-tree

systems (I and J) have the lowest average cost for

harvesting roundwood, about $37.50 per cord. System I is the lowest cost roundwood system on tracts

17 acres and larger and system J is second from 27

acres and up. However, they require about 85 and

110 acres respectively to reach their minimum optimum tract size according to the cost equations. This

corresponds to the minimum tract sizes these systems

actually seem to require in practice. Tract sizes of

60 acres for system J and 40 acres for system I would

incur average costs at least $1 per cord more, which

most operators would surely try to avoid.

Bobtail truck system A, shortwood prehauler system F, and manual tree-length system H fall at the

next roundwood average cost level of about $41.50

per cord. Each requires considerably different acreages to reach the minimum optimum tract sizeabout 1 acre for A, 30 for F, and 60 for H. Again,

these acreage guides seem reasonable compared with

actual experience. The bobtail system has the lowest

average costs of all systems up to 17 acres, followed

closely by the prehauler system. Average cost for the

bobtail system increase only slightly throughout its

range up to 40 acres. The prehauler system average

costs increase only slightly down to 10 to 15 acres,

and the tree-length system down to 30 to 40 acres,

Beyond their lowest limits, costs rise appreciably.

Table 12.-Rank of harvest systems by minimum cost levels

Bank Harvest system Cost per cord

at minimum

1 K. Whole-tree chip

2 I. Highly mechanized full-tree

3 J . Limited-area full-tree

4 H. Manual tree-length

5 A. Stump bobtail

6 F. Shortwood prehauler

7 E. Highly mechanized shortwood

8 G. Skidder long log

9 D. Semi-mechanized shortwood

10 B . Bobtail and tractor

11 C . Skidder and truck

dollars

33.09

37.09

37.23

39.94

40.97

41.13

44.37

45.26

46.88

49.11

56.88

Whole-tree chipping system K has the lowest average cost for harvesting pulpwood ($34 per cord).

However, it receives a lower revenue ($31.68 per cord

versus $38 per cord) resulting from a less desirable

product. Therefore, the whole-tree chip system probably falls between the efficient full-tree systems and

tree-length systems in profitability. In addition, it

requires 120 acres to reach its minimum optimum

tract size. Tracts less than 80 acres have average

harvest costs over $1 per cord more.

Partially mechanized shortwood (D) , highly mechanized shortwood (E) and long log (G) systems were

generally not cost competitive in average southern

6 0

2; C

rt 56-

P

4

3 2 I I I I I I I I

0 4 0 I30 120 160 200 240 280 320 ?

TRACT SIZE (ACRES)

Figure 7.-Harvest system short run average cost curves by acres, graph for complete

range of data simulated for all systems.

14
pine pulpwood harvesting conditions, with costs averaging $45 to $49 per cord. They had both high move

costs and high average costs-the worst combination for all tract sizes. Small scale operations using

straight trucks and farm tractors (B) or small skidders (C) had excessive average costs ($49 and $57

per cord) on all tracts.

Sensitivity Analyses

Sensitivity analyses tested the effects of changes

in assumptions on the cost curves for selected harvest

systems. Only system H and I were analyzed. They

are low-cost systems currently employed in the South.

Tree-length systems similar to H are the most common and may be considered as primarily manual systems. Systems similar to I, a highly mechanized

full-tree system, are becoming more popular and may

be considered primarily mechanized systems. Sensitivity analyses using these two sy‘stems provides

information for the most popular systems in the

South, as well as insights regarding comparative

effects of parameter changes on manual versus mechanized systems.

Parameter Changes.-Effects of changes in tract

shape, stand volume, input productivity rates, overhead costs, and fuel costs were tested. The cost curves

were estimated for a limited acreage in the sensitivity

analyses (0 to 120 acres at the most). They were

compared with new cost curves derived for the same

range from the original data. Therefore, differences in

curves were due only to differences in the data, not

computational methods.

The limited data sets generated in the sensitivity

analyses prohibited statistical hypothesis testing, so

only numerical and graphical comparisons were made.

Earlier comparison tests among harvest systems indicated that numerical and visual differences were usually statistically significant. A similar pattern would

probably emerge in the sensitivity analyses if enough

data points could be simulated.

Results.-Table 14 summarizes the average cost

equations derived for the sensitivity analyses. Numerical interpretation of the equations or means is

straightforward. For inverse functions, the intercept

represents the minimum cost level at infinity. Regressions with lower intercepts ultimately have lower

average harvest costs per cord. The slope of the regression is a proxy for the number of acres required

to approach the minimum cost. Lower slope coefficients indicate that the minimum cost level is reached

more quickly than high coefficients.

The seasitivity analyses reveal that highly mechanized harvest system I always retained its minimum

average cost advantage over manual tree-length system H, even with the changes in assumptions. When

Table 13.~Mean cost per cord in cost curve tails by harvest

system

Mean cost

Rank System per cord Observations Data range

1 K

2 J

3 I

4 F

5 H

6 E

7 G

8 D

9 C

dollars

33.96

37.541

37.661

41.302

41.882

44.79

45.40

46.92

57.04

number acres

18 160-360

18 160-360

2 6 120-360

13 go-280

21 120-360

19 80-280

15 80-280

17 . 80-280

12 80-280

*Average costs for systems J and I not significantly different,

alpha=.01 (64Q).

2Average costs for systems F and H not significantly different, alpha=.01 (646); are significantly different at alpha

= .05 (54&).

Note: all other system costs are significantly different at

alpha=I.Ol.

the tract size was changed from square to rectangular,

the highly mechanized system became only slightly

better than the manual tree-length system.

However, in all other sensitivity analyses, the

highly mechanized full-tree system actually improved

its competitive position. When productivity rates are

reduced similar percentages in each, manual systems’

costs increased more than mechanized systems’. Even

at input rates only 75 percent as productive, the

mechanized system retained its cost advantage over

the manual system operating at full productivity

rates.

The stand model in the research had a volume of

17.67 cord per acre. Sensitivity of costs to low volumes (10 cords per acre) and high volumes (27.2

cords per acre) was tested. High volumes provided

no cost advantage for the tree-length system but

reduced average costs about $2.50 per cord for the

mechanized system. Low volumes increased minimum

average costs a modest $4 per cord for the mechanized system and a hefty $14 per cord for the

manual system.

In the modeling, only move costs were used as

estimates of initial overhead costs for harvesting a

new tract. In practice, there are additional, unquantified overhead costs for sale administration, purchase

by the logger, and harvesting layout. In a Massachusetts study, Kronrad et al. (1980) found that consulting forester charges averaged $30 per acre for

administering cordwood sales, or $2400 for an 80 acre

tract. Gregersen et al. (1980) calculated an average

administrative cost of $4 per acre for cost-share programs. For 80 acres, this would be $320. Watts and

Watson (1978) found that checking out a job site

15
3 3

0 .02 .04 .06 .OS .I0 .I2 .I4 .I6 .I8 .20

I/ACRES

Figure &-Harvest system short run average cost curves by I/acres, systems C-K.

usually took about four hours, although they did not

estimate the cost.

The range of costs for harvest administration, purchase, and layout indicates their importance. Since

precise estimates of these costs are not available,

overhead costs of $500 and $2000 were added in the

sensitivity analysis to test the effects on the cost

curves.

On the whole, it appears that added overhead costs

will not affect the ultimate average cost level for a

system, but will make small tracts less profitable by

increasing the optimal tract size considerably-one

and one-half to two times the original acreage size

for $500 and $2000 in added costs, respectively. Also,

added overhead costs will increase the point at which

manual systems reach their minimum economic size

until any advantages from in lower move costs is

negated.

Increases in fuel and lubrication costs increased

average harvest costs for manual tree-length system

H more than for highly mechanized system I. Apparently, chainsaw and choker skidders use more fuel

per unit of output than the highly efficient fellerbunchers, grappel skidders, and gate delimbers when

both systems are operating at their full production

levels.

CONCLUSIONS

Tract size is important in determining average

harvest costs. The spreading of the initial fixed costs

for moving and setting up a harvest system are the

primary causes for economies of size. Large mechanized systems have higher move and set-up costs

than small systems; therefore, they require a larger

acreage size in order to minimize the effect of overhead costs on average costs. The implications for

economies of tract size depend on the trends in harvest system selection and forest policies.

Harvest System Trends

Harvest equipment and system adoption in the

United States has generally followed an evolutionary, rather than revolutionary, path. This trend is

likely to continue, with the systems producing wood

for the lowest cost tending to dominate harvesting as

producers pursue a Darwinian equipment selection

process. Current trends in labor availability and

factor costs favor some systems over others.

Shortwood.-Two factors are contributing to the

decline in use of shortwood systems. First, the most

economical shortwood systems-the stump-to-stump

bobtail truck and shortwood prehauler-rely heavily

on manual labor to fell, limb, top, and buck trees with

a chainsaw and to hand-pile bolts in the woods. The

number of men willing to perform such strenuous

work has been declining for decades. In addition,

bobtail systems have traditionally relied on minimum

wage labor which is increasingly hard to hire. Therefore the two labor-intensive operations, although

cost-effective, are likely to continue declining in

numbers.

Second, shortwood systems will decline in use because increasing mechanization proves to increase,

16
m IO ACRES 40 ACRES w

120 ACRES

Figure 9.-Comparative system minimum average costs.

not decrease, average harvest costs. Mechanized systems which use tree-length or full-tree skidding and

manual or mechanized bucking at the deck are significantly more costly than other shortwood, treelength, or full-tree systems. Bucking is an extra

function which generates no financial return, penalizing mechanized shortwood systems. Shortwood harvesting also prevents sorting and selling high-value

products.

Manual Tree-Length.-Many loggers in the South

have adopted tree-length logging and trucking operations. The harvesting simulation results confirm the

wisdom of this practice. On tracts larger than 40

acres, manual tree-length operations compare favorably in cost with the labor-intensive stump bobtail

system and shortwood prehauler system. The treelength systems maintain low costs but eliminate over

one-half the hand labor required in the low-cost

shortwood systems, increasing chances for system

survival.

Tree-length systems also enable a producer to

move from a low-volume operation to a high-volume

operation with correspondingly larger gross profits.

Low cost shortwood systems usually do not produce

more than 100 cords per week. Tree-length operations

may increase weekly production per crew up to 250

to 300 cords per week.

Tree-length logging is currently the most popular

system in the South and will continue to supplant

shortwood operations. Despite the cost advantage

of highly mechanized full-tree systems, tree-length

systems should remain popular through the 1980s.

Compared with highly mechanized systems, chainsaw

and choker skidder systems are a less costly step in

mechanization and have lower fixed costs to be borne

when economic conditions are depressed and mills

limit wood purchases. Also, they have lower move

costs, are more adaptable to rough or wet land, and

are useful in irregular stands with large timber or for

such jobs as pulling trucks.

Highly Mechanized Full-Tree.-Highly mechanized full-tree harvest systems have the lowest average

harvest costs per cord for roundwood products. The

rubber-tired feller-buncher grapple skidder system

and the tracked limited-area feller-buncher system

had similarly low ultimate average harvest costs per

cord. Both were cheaper than manual tree-length systems on average sites, although the limited-area

feller-buncher system required larger tracts to reach

its cost minimum. The highly mechanized full-tree

system proved to be better yet on sites with low or

high volumes, for increases in fossil fuel costs, or in

increased overhead costs. It is also advantageous for

multiple-product operations.

The cost advantages suggest that highly mechanized feller-buncher grapple skidder operations will

continue to increase in number and dominate pine

roundwood harvesting wherever terrain and institutional considerations permit. Rough or swampy

terrain may limit their use and they may not have

comparative cost advantages in thinnings, hardwood

cutting, or sawtimber harvesting.

Institutional factors inhibiting rapid adoption of

highly mechanized systems include high investment

costs and high interest rates. Forest industry policies

will also affect their adoption. Before loggers i vest

in high-priced mechanized systems, they need a% surante that they can harvest and sell wood in high

volumes. Imposition of quotas in soft markets or

closing of mills due to strikes could quickly bankrupt

17
Table 14.~h’ensitivity analysis costs for comparisons

System Acreage size Parameter of interest Regression (ave.) cost

H O-40 base data

50% productivity rates

75% productivity rates

poor shape

H O-100 base data

low volume

high volume

$500 added overhead

$2090 added overhead

I O-100 base data

50% productivity rates

75% productivity rates

poor shape

low volume

high volume

$500 added overhead

$2000 added overhead

H 4 0 base data

1.5 X fuel costs

2.0 X fuel costs

I 100 base data

1.5 X fuel costs

2.0 x fuel costs

Where: YEharvest cost (dollars per cord)

X=tract size harvested (acres)

Y =40.353+48.556 (l/X)

Y=58.288+65.292(1/X)

Y =46.347+49.318 (l/X)

Y =41.223+49.808 (l/X)

Y =40.869+44.595 (l/X)

Y=54.599+46.343(1/X)

Y=42.508+20.613(1/X)

Y=41.322+85.441(1/X)

Y--40.937+269.128(1/X)

Y=36.272+80.641(1/X)

Y=43.649+118.97O(l/X)

Yr=37.902+83.879(1/X)

Y =40.914+41.394( l/X)

Y=40.251+148.634(1/X)

Y=33.744+56.064(1/X)

Y =35.082+ 135.624 (l/X)

Yr=35.265+296.878(1/X)

yz41.98 sz.12

Yz43.49 SZ.12

??=44.61 s-.18

P~37.46 sz.18

y~37.60 sz.09

P=39.01 sz.08

capital-intensive operations dependent on high production to make payments on equipment.

The sensitivity analyses and recent productivity studies indicate’ that the cost advantages arising in the simulations may even be understated.

Highly mechanized full-tree systems seem certain to

increase in popularity. Highly mechanized systems

may not approach their minimum cost level until

tract sizes reach 80 to 120 acres, but are, costcompetitive with manual tree-length systems on

tracts as small as 10 acres. Adaptations such as low

ground pressure tires or tracks may make the fellerbunchers and skidders more suited to less idealterrain conditions.

Whole-TreeGhip .-Pulpwood production using the

whole-treechipping system was the lowest cost opera-

,tion ‘by a wide margin. However, the whole-tree chip

simulation assumed that the model stand would be

purchased for the same price that prevails for conventional products and receive a 25 percent overrun without any additional stumpage cost. Sophisticated

sellers realize that chipping systems harvest greater

volumes and may demand greater stumpage prices. _

Also, lower revenues per cord make the systems less

profitable than the highly mechanized full-tree systems. In addition, the chipper is a large consumer

of energy.

The whole-tree chip system is probably more profitable than tree-length systems on average stands,

even if a bonus were paid for volume overruns. When

the dirty chips can be mixed with other mill roundwood or used to make special products, whole-tree

chipping may be the most profitable harvesting

method. If any economical method is adopted for

cleaning the chips, it may rival the highly mechanized

full-tree systems in popularity. Also, sorting out highvalue butt portions for veneer or lumber could make

“whole-tree” chipping more competitive.

Tract Size Effects

\

Harvest system trends indicate that future movements along the long run average cost curve will
consist of shifts to tree-length and highly mechanized

full-tree systems. Bobtail operations will persist due

to ease of entry and exit for small operators, low capital investment, and cost competitiveness. However,

their use is decreasing and their share of roundwood

harvest is likely to be less than 5 to 10 percent of the

volume in the near future. Consequently, bobtail

operations will be insufficient to harvest all the small

tract offerings.

The situation is smiliar with the shortwood prehauler system. It is economical on small tracts but

waning in numbers. Except in Louisiana, very few

shortwood forwarders are used in the South, probably

due to lack of available manual labor. The shifts to

more capital-intensive harvest systems with high

moving costs are causing concern for economies of

tract size.

Determining the point of minimum optimum size

on the dominant tree-length and full-tree systems

influences the conclusions regarding tract size problems. For L-shaped cost curves, the cost function

slope and concomitant acreage sizes and costs at

various intervals is useful in defining the minimum

optimum size level (table 15). Judgement seems to

indicate that the two percent slope level is an optimistic break for determining the point at which economies of tract size are reached. Indeed, the one

percent level may be a defensible choice.

Using the 2 percent slope level as a criterion,

there are serious cost problems on small tracts. The

manual tree-length system incurred excessive harvest

costs on tracts less than 45 acres. The highly mechanized full-tree system required at least 62 acres to

reach its minimum optimum size.

In timber harvesting, as in all productive activities,

equilibrium prices move toward the lowest cost incurred by the most efficient firms. As efficient shortwood operations decrease in number and contribute

less to total roundwood harvests, only the very efficient highly mechanized full-tree harvest systems and

less efficient tree-length systems are likely to remain.

In order to maximize their profits, loggers will tend

to move to more efficient short run average cost

curves, moving downward and right on those curves.

Forest industry pricing will reflect the productivity

increases and movements along the long run average

cost curve. They will pay comparatively lower mill

prices or contract prices to equilibrate their prices

with the minimum cost point on the logger’s long run

average cost curve and eliminate excessive profits

gleaned by efficient loggers. This is the crux of the

economies of size issue in forestry. If loggers mechanize to achieve high production and concomitant low

average harvest costs, small acreages become uneconomical to harvest at equilibrium prices.

Even if a variable rate were allowed, tracts less

than 20 to 30 acres probably would not be worth the

increased harvest costs per cord. Acreages less than

20 acres will be exceedingly expensive to harvest and

even tracts less than 50 acres will be significantly

more costly. Other forest harvesting and forest management literature suggests that 50 acres is the minimum size for avoiding high average costs as well.

These acreage guidelines are flexible, depending on

the volume per acre. High volume stands will be more

economical at smaller acreages and low volume stands

or thinnings will require larger acreages.

Policy Implications

High costs on small tracts suggest that forest management should be concentrated on tracts 40 acres

or more in size. Tracts less than 40 to 60 acres are

likely to receive such a penalty in harvesting costs

alone that they would not be very economic.

For cost efficiency, sawtimber harvests may require smaller acreages than pulpwood harvests.

However, sawtimber harvests imply that pulpwood

thinnings may be required, especially in plantations.

The lower volumes removed in thinnings will require

Table 15.-Acres required to obtain a given percent slope level and associated harvest

costs per cord, Systems H and I

Slope level

H. manual tree-length

Tract size Cost per cord

I. highly mechanized full-tree

Tract size Cost per cord

percent acres dollars acres dollars

50.0 9 45.86 1 2 43.30

25.0 1 3 44.49 1 7 41.47

10.0 20 43.42 2 7 39.85

5.0 28 42.84 39 38.71

2.0 45 42.31 62 37.99

1.0 64 42.04 87 37.64

0.1 203 41.61 276 37.04

19
even larger acreages for economical operation than

those found in this research, exacerbating the tract

size problem. On the whole, the literature and this

research support the conclusion that large tracts (50

to 125 acres) have, significant economic advantages

over small tracts (less than 50 acres). Average costs

increase rapidly on tracts below 50 acres and are

prohibitive on tracts below 10 to 20 acres.

To maximize economic efficiency, forest policies

should encourage pulpwood and timber production on

large tracts. Timber growing assistance, such as the

Forestry Incentive Program and Agricultural Conservation Program, should have minimum acreage

requirements of at least ‘20 to 40 acres. The Forest

Service and forest industries should mandate pulpwood pine harvests of at least 40 to 80 acres, rather

than having regulations favoring small maximum

clearcut sizes. Cooperative forest management and

industrial forestry assistance programs should also be

slanted toward large acreages.

Forest policies which favor large tract sizes seem

inequitable to small forest owners. Consequently, the

policies might run aground on the basis of political

considerations. Harvesting small areas may be preferable for environmental reasons. The wisdom of sacrificing economic efficiency in favor of equity or

environmental criteria must be debated and decided

by forest policy makers.

The net effect of increased timber harvest costs on

small tracts depends on the policies pursued by forest

industry and the federal and state governments. If a

market solution is accepted, prices and contractor

rates would remain at equilibrium (minimum cost)

levels and small tracts would become uneconomical

to harvest. Economic roundwood supplies would be

reduced, shifting supplies on small tracts to the

future, and causing pulpwood prices to increase in

real terms. Increased prices might in turn bring forth

increased pulpwood production.

Forest industries could deal with high average costs

on small tracts by incorporating the differences into

their pricing structure and accepting some high-cost

wood. They still would have to determine the minimum tract size for paying the added average harvest

costs, but variable pricing would make fewer acres

unprofitable to harvest than would flat rate equilibrium pricing.

If variable pricing and market pricing alternatives

are deemed unacceptable, government could act to

reduce effects of increased harvest costs on small

tracts. Costs to the landowner could be decreased via

incentive programs or tax advantages, offsetting

higher harvest costs. Direct payments to loggers

could be used also to make up the difference between

large and small tract average costs, and might be

more efficient.

Given the relatively low size at which most economies of size are reached (about 100 acres), efforts

to aggregate tracts might be successful in reducing

average harvest costs. However, costs of aggregation

must not exceed the harvest cost savings. Intermediate technology, the often proposed solution for high

costs on small tracts, is not likely to reduce average

costs. Small-scale equipment suffers from high fixed

costs for development and assembling, making it

inherently more expensive than more productive

larger equipment.

Forest planners and policy makers must consider

the costs and benefits of the alternatives for overcoming diseconomies of size. Environmental or equity

criteria or negative public opinions of large tract harvesting may outweigh the benefits of economic efficiency alone. The optimal solutions to the problem

depend on the objectives, values, and criteria used in

decision-making. Optimal solutions may also vary by

geographic region, depending on the institutions and

forest types in existence.

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Appendix Tables for Production Information, Input Costs, and

Simulation Inputs for Harvest Systems

Table Al.-Averages of production rate distributions used*

Harvest machine function

Average production

(fts per productive hour) Literature bases

Chainsaw fell, limb, top, and buck

Chainsaw fell, limb, and top

Chainsaw limb and top

Tree shear fell

Rubber-tire feller-buncher fell

Limited-area tracked feller-buncher fell

Hand pile 5’3” bolts

Chainsaw buck 5’3” bolts at deck

Chainsaw buck long logs

Bobtail forward

Hydraulic slash and load 5’3” bolts

Bigstick load at stump

Bigstick load at deck

Small knuckleboom load-shortwood

Medium knuckleboom load-tree length

Whole-tree chip

222 Plummer 1977

382 Hypes and Stuart 1979

792 Hypes and Stuart 1979, Plummer 1977

1,179 Curtin and Bunker 1972, White 1969

1,072 American Pulpwood Association 1977

1,479 Fowler 1972

307 Plummer 1977

493 Hypes and Stuart 1979

526 Hypes and Stuart 1979

4,815 manual calculations

602 Plummer 1977

138 Hypes and Stuart 1979

190 Hypes and Stuart 1979

945 Hypes and Stuart 1979

1,848 Clair 1977

2,830 Plummer 1977

*Actual productivity rates used were put in the simulation program as frequency distributions based on stand diameter distributions; see Cubbage 1981b for details.

23
Table AS.-Machine costs, utilization, and life (1980)

Equipment

Purchase Salvage

price value

Cost per operating hr (mi)s

Life Op hrs (mis)* Utilizations

yrs per year Fixed Operating Total (availability)

Chainsaw-straight blade

Dozer with shear

Small feller-buneher

Medium rubber-tire f.b.

Lmtd.-area fir.-bnchr.

500 0 1 1200 .47 3.00 3.47 5 0

65,500 32,750 5 1200 12.88 9.00 21.88 6 5

55,000 11,000 3 1300 16.69 12.45 29.14 6 5

70,000 13,500 4 1300 17.53 10.25 27.78 6 5

120,000 18,000 5 1200 28.92 16.54 45.46 6 0

70 h.p. cable skidder 40,000 8,000 4 1300 9.96 8.20 18.16 6 7

90 h.p. cable skidder 46,000 10,000 4 1300 11.34 10.08 21.42 6 7

110 h.p. cable skidder 47,000 5,500 5 1200 11.52 11.11 22.63 6 7

120 h.p. cable skidder 60,000 6,000 5 1200 14.84 12.43 27.27 6 7

70-90 h.p. grapple skidder 48,000 10,000 4 1200 12.90 9.73 22.63 6 7

110 h.p. grapple skidder 62,000 16,500 5 1200 14.12 11.76 25.88 6 7

High-speed tracked g.s. 180,000 22,000 5 1200 44.01 31.98 75.99 6 5

Farm tractor skidder 27,000 5,400 5 1OOG 7.60 7.40 15.00 6 5

Shortwood forwarder

Longwood forwarder

Bigstick loader

Small knuckleboom

Medium knuckleboom

Used truck for loaders

40,000 8,000 4 1300 9.96 7.74 17.70 6 4

55,000 11,000 4 1300 13.70 10.00 23.70 6 4

2,600 260 5 720 .95 2.14 3.09 (90)

27,000 8,000 5 1000 6.47 12.00 18.47 6 5

42,000 13,700 5 1000 9.86 12.00 21.86 6 5

6,000 600 3 1000 3.20 3.00 6.20 6 5

Hydraulic slasher 8,000 0 4 1000 2.70 .70 3.40

Gate delimber 1,700 340 5 1500 .27 .12 .39

Medium chipper

Large chipper

Small used bulldozer

Medium new bulldozer

Road grader

82,000 16,400 5 1500 13.89 15.07 28.26

174,000 27,000 5 1500 30.27 24.04 54.31

(&

80

80

24,500

75,320

65,000

5 500 13.80 8.04 21.84 6 5

5 1200 14.00 13.00 27.00 6 5

5 1200 10.50 14.97 25.47 6 5

Bob truck dead tandem

Bob truck live tandem

13,000

20,000

4,900

44,000

40,000

3,000

9,000

3 24,000 .26 .53 .79

4 24,000 .28 .55 .83

r/s ton pickup 7,000

Service/crew truck 25,000

3 25,000 .13 .12 .25

3 25,000 .42 .lQ .61

Diesel truck-tractor 45,000

Shortwood trailer 9,000

Bundle-bucker trailer 9,000

Pole trailer 7,800

Chip van 10,000

Lowboy-25 ton 12,500

1,500

5,000

10,000

2,000

2,000

2,000

4,300

4,000

5 60,000 .24 .64

6 66,666 .03

6 66,666 .03

6 66,666 .03

8 37,500 .05

10 5,000 .39

.40

.07

.07

.05

.07

.05

.lO

.lO

.08

.12

.44

,___ _ _ . dollars I_ _ - - - ----------dollars ------ percent

‘Operating hours (miles) per year: number of hours (miles) equipment is actually being used each year; woods equipment

(i.e. feller-buncher, skidder, loader, grader, dozer) in hours, road equipment (i.e. truck, trailer) in miles.

*Cost per operating hour: fixed cost includes depreciation, interest, taxes, and insurance; operating cost includes fuel and lubrication, tire or track costs, and repair and maintenance (including labor).

Wtilization is percent of scheduled time machine is actually used. Availability for bigstick loader and gate delimber is percent of

scheduled time they are not broken down-available to be used.

24
Table A3.-Labor rates and approximate weekly hours by

labor class

Position

Wage Approximate

per hour hours per week

dollars

Unskilled general labor:

bobtail truck system 3.50 4 5

Unskilled general labor: small

mechanized operations 5.00 4 0

Saw hands: medium to large

operations 6.00 4 5

General equipment operators:

small skidders, chippers 6.00 4 5

Special equipment operators:

skidders, loaders,

feller-bunchers 6.50 4 5

Truck driver: straight truck 6.00 40

Truck driver: tractor-trailer 7.00 5 0

Mechanics 8.00 5 0

Table A4.-Social legislation costs-percent paid per dollar of base pay

Cost item Worker’s compensation classification

Social Security

Worker’s Compensation

Unemployment Compensation

Total

Pulpwood only Pulywood and sawtimber

2705 2701

-__-_- ____ percent - ____ -___

6.13 6.13

30.00 22.00

3.00 3.00

39.13 31.13

Table AS-Profit or salary of the entrepreneur by system

Annual profit

Description of logging operations Systems 8 or salary

Stump bobtail A

Bobtail and farm tractor B

Small mechanized operations C,D,G

Prehauler system F

Large operations E,H,I

Highly mechanized operations JX

dollars

9,000

10,000

14,000

16,000

24,000

30.000

Table A6.-Average southern pine stumpage and F.O.B. mill

prices July 1979-Jul.y 1980

Range

Product High Low Typical

._------ dollars--------

Pulpwood stumpage (standard cord) 11.97‘ 10.90 11.70

Pulpwood FOB mill (standard cord) 39.72 36.65 38.00

Sawtimber stumpage

(MBF Scribner) 154.45 107.77 142.00

Sawlops FOB mill (MBF Scribner) 192.64 157.92 180.00

Dirty Chips FOB mill (green ton) 12.38 9.18 12.00

Source: Timber Mart South 1979, 1980.

25
Table A’7.-Haul harvest,system--JO mile haul

System(s) and

transportation equipment

Cords

per

load

Labor costs

Machine costs

Wages Total

Cost/mile cost Hours cost cost

per Hrly. per per per

Truck Trailer cord rate Fringe load cord cord

A Dead tandem bobtail

B Live tandem bobtail

C Live tandem bobtail

D,E,F Tractor-trailer

truck, pulpwood trailer

G,H,I,J Tractor-trailer

truck, pole trailer, or

bundle-bucker trailer

K Tractor-trailer truck.

chip van

4

5

5

10

8

10

----I- dollars...---...........-.--....-..- percent .---- dollars.----

.79 11.85 owner/operator 4 0.00 11.85

.83 9.96 owner/operator 4 0.00 9.96

.83 9.96 6.00 39 4 6.67 16.63

.64 .iO 4.44 7.00 39 4.5 4.38 8.82

.64 .09 5.48 7.00 31 4 4.58 10.06

.64 .lO 4.56 7.00 31 4.5 4.13 8.69

Table AS.-Operating days per year and tract sizes simulated by operation

Harvest system

Yearly operating times Tract sizes simulated (acres)

Days/year Weeks/year1 5-402 5-2803 5-3604

A. Stump bobtail 160 3 2

B. Bobtail and tractor 180 3 6

C. Skidder and truck 200 4 0

D. Semi-mechanized shortwood 200 4 0

E. Highly mechanized shortwood 220 4 4

F. Shortwood prehauler 210 4 2

G. Long log 200 4 0

H. Manual tree-length 220 4 4

I. Highly mechanized full-tree 220 4 4

J. Limited-area full-tree 220 4 4

K. Whole-tree chip 210 4 2

X

X

X

X

X

X

X

X

X

X

X

15 days per week, 5 shifts per week, 9 scheduled hours per day.

%,10,15,20,30, and 40 acre tracts.

~5,10,15,20,30,40,50,60,70,80,90,100,120,160,200,240, and 280 acre tracts.

~5,10,15,20,30,40,50,60,70,80,90,100~120,160,200,240,280,320, and 360 acre tracts

26
Table AS.-Travel rates for in-woods machines or activities Table Al&-Load capacities for skidders or forwarders

Machine or activity Travel rate Machine Load capacity

Man with chainsaw

Man piling wood

Tracked dozer with tree shear

Rubber-tired feller-buncher

Limited-area feller-buncher

Farm tractor

Choker skidder-70 horsepower

Choker skidder-90 horsepower

Choker skidder-110 horsepower

Choker skidder-120 horsepower

Grapple skidder-110 horsepower

Shortwood forwarder

Bobtail truck in woods

feet per minute

88

176

164

264

176

264

350

350

350

350

350

453

88

Farm tractor

Choker skidder-70 horsepower

Choker skidder-90 horsepower

Choker skidder-l 10 horsepower

Choker skidder-120 horsepower

Grapple skidder-110 horsepower

Shortwood forwarder

cubic feet

23

60

68

9 0

112

110

180

Source: personal discussions with industrial and academic

harvesting experts and manufacturer’s equipment specification sheets.

Source: personal discussions with industrial and academic

harvesting experts and manufacturer’s equipment specification sheets.

Table AX-Fired times and productivity rates used for loading and unloading skidders

or prehaulers

Machine

Fixed time to Loading & unloadload & unload ing production

(minutes) (fts/produc. hr.)

Farm tractor

Choker skidder-70 horsepower

Choker skidder-90 horsepower

Choker skidder-110 horsepower

Choker skidder-120 horsepower

Grapple skidder-110 horsepower

Gate delimber (110 hp grp. skid.)

Grapple skidder-110 horsepower

plus gate delimb fixed time

2.46 561

4.7 766

4.7 862

4.7 1150

4.7 1404

3.3 1818

1.4 4285

4.7 1395

Calculations to convert time into cubic feet of production:

(1) 1 hour/fixed time per loadzloads per hour

(2) loads per hourxload capacity (fts) = production (ft”/hr.)

Source: personal discussions with industrial and academic harvesting experts and various

unpublished literature.

“7

~0,s. ~ov~~#MEMT PRINTING OFFICE: 1982- 66’+-0R5/1(1

CUBBAGE, FRED.

1982. Economies of forest tract size in southern pine harvesting, U.S. Dep. Agric., For. Serv., Res. Pap. SO-184,

27 p., South. For. Exp. Stn. New Orleans, La.

This pub&cation provides model and data analyses for determining optimum tract sizes for forest harvests.