Cost is important to all industry. Costs can be divided into two general classes; absolute costs and relative costs. Absolute cost measures the loss in value of assets. Relative cost involves a comparison between the chosen course of action and the course of action that was rejected. This cost of the alternative action - the action not taken - is often called the "opportunity cost".
The accountant is primarily concerned with the absolute cost. However, the forest engineer, the planner, the manager needs to be concerned with the alternative cost - the cost of the lost opportunity. Management has to be able to make comparisons between the policy that should be chosen and the policy that should be rejected. Such comparisons require the ability to predict costs, rather than merely record costs.
Cost data are, of course, essential to the technique of cost prediction. However, the form in which much cost data are recorded limits accurate cost prediction to the field of comparable situations only. This limitation of accurate cost prediction may not be serious in industries where the production environment changes little from month to month or year to year. In harvesting, however, identical production situations are the exception rather than the rule. Unless the cost data are broken down and recorded as unit costs, and correlated with the factors that control their values, they are of little use in deciding between alternative procedures. Here, the approach to the problem of useful cost data is that of identification, isolation, and control of the factors affecting cost.
1.2 Basic Classification of Costs
Costs are divided into two types: variable costs, and fixed costs. Variable costs vary per unit of production. For example, they may be the cost per cubic meter of wood yarded, per cubic meter of dirt excavated, etc. Fixed costs, on the other hand, are incurred only once and as additional units of production are produced, the unit costs fall. Examples of fixed costs would be equipment move-in costs and road access costs.
1.3 Total Cost and Unit-Cost Formulas
As harvesting operations become more complicated and involve both fixed and variable costs, there usually is more than one way to accomplish a given task. It may be possible to change the quantity of one or both types of cost, and thus to arrive at a minimum total cost. Mathematically, the relationship existing between volume of production and costs can be expressed by the following equations:
1.4 Breakeven Analysis
A breakeven analysis determines the point at which one method becomes superior to another method of accomplishing some task or objective. Breakeven analysis is a common and important part of cost control.
One illustration of a breakeven analysis would be to compare two methods of road construction for a road that involves a limited amount of cut-and-fill earthwork. It would be possible to do the earthwork by hand or by bulldozer. If the manual method were adopted, the fixed costs would be low or non-existent. Payment would be done on a daily basis and would call for direct supervision by a foreman. The cost would be calculated by estimating the time required and multiplying this time by the average wages of the men employed. The men could also be paid on a piece-work basis. Alternatively, this work could be done by a bulldozer which would have to be moved in from another site. Let us assume that the cost of the hand labor would be $0.60 per cubic meter and the bulldozer would cost $0.40 per cubic meter and would require $100 to move in from another site. The move-in cost for the bulldozer is a fixed cost, and is independent of the quantity of the earthwork handled. If the bulldozer is used, no economy will result unless the amount of earthwork is sufficient to carry the fixed cost plus the direct cost of the bulldozer operation.
1.5 Minimum Cost Analyses
A similar, but different problem is the determination of the point of minimum total cost. Instead of balancing two methods with different fixed and variable costs, the aim is to bring the sum of two costs to a minimum. We will assume a clearing crew of 20 men is clearing road right-of-way and the following facts are available:
1. Men are paid at the rate of $0.40 per hour.
2. Time is measured from the time of leaving camp to the time of return.
3. Total walking time per man is increasing at the rate of 15 minutes per day.
4. The cost to move the camp is $50.
If the camp is moved each day, no time is lost walking, but the camp cost is $50 per day. If the camp is not moved, on the second day 15 crew-minutes are lost or $2.00. On the third day, the total walking time has increased 30 minutes, the fourth day, 45 minutes, and so on. How often should the camp be moved assuming all other things are equal? We could derive an algebraic expression using the sum of an arithmetic series if we wanted to solve this problem a number of times, but for demonstration purposes we can simply calculate the average total camp cost. The average total camp cost is the sum of the average daily cost of walking time plus the average daily cost of moving camp. If we moved camp each day, then average daily cost of walking time would be zero and the cost of moving camp would be $50.00. If we moved the camp every other day, the cost of walking time is $2.00 lost the second day, or an average of $1.00 per day. The average daily cost of moving camp is $50 divided by 2 or $25.00. The average total camp cost is then $26.00. If we continued this process for various numbers of days the camp remains in location, we would obtain the results in Table 1.1.
TABLE 1.1 Average daily total camp cost as the sum of the cost of walking time plus the cost of moving camp.
|Days camp remained in location||Average daily cost of walking time||Average daily cost of moving camp||Average total camp cost|
We see the average daily cost of walking time increasing linearly and the average cost of moving camp decreasing as the number of days the camp remains in one location increases. The minimum cost is obtained for leaving the camp in location 7 days (Figure 1.2). This minimum cost point should only be used as a guideline as all other things are rarely equal. An important output of the analysis is the sensitivity of the total cost to deviations from the minimum cost point. In this example, the total cost changes slowly between 5 and 10 days. Often, other considerations which may be difficult to quantify will affect the decision. In Section 2, we discuss balancing road costs against skidding costs. Sometimes roads are spaced more closely together than that indicated by the point of minimum total cost if excess road construction capacity is available. In this case the goal may be to reduce the risk of disrupting skidding production because of poor weather or equipment availability. Alternatively, we may choose to space roads farther apart to reduce environmental impacts. Due to the usually flat nature of the total cost curve, the increase in total cost is often small over a wide range of road spacings.
2. UNIT COST AND COST EQUATIONS
The use of breakeven and minimum-cost-point formulas require the collection of unit costs. Unit costs can be divided into subunits, each of which measures the cost of a certain part of the total. A typical unit cost formula might be
X = a + b + c
where X is the cost per unit volume such as dollars per cubic meter and the subunits a, b, c will deal with distance, volume, area, or weight. Careful selection of the subunits to express the factors controlling costs is the key to success in all cost studies.
2.2 Example of Cost Equations
Let us suppose the cost of harvesting from felling to loading on trucks is being studied. If X is the cost per cubic meter of wood loaded on the truck, we could represent the total cost per unit as
X = A + B + Q + L
where A would be the cost per unit of felling, B the cost of bucking, Q the cost of skidding, and L the cost of loading.
To determine the cost per subunit for felling, bucking, skidding, and loading, the factors which determine production and cost must be specified. Functional forms for production in road construction and harvesting are discussed in Sections 4 and 5. Examples for felling and skidding follow.
For felling, tree diameter may be an important explanatory variable. For a given felling method, the time required to fell the tree might be expressed as
T = a + b D2
where T is the time to fell the tree, b is the felling time required per cm of diameter, D is the tree diameter and "a" represents the felling time not explained by tree diameter-such as for walking between trees. The production rate is equal to the tree volume divided by the time per tree. The unit cost of felling is equal to the cost per hour of the felling operation divided by the hourly production or
A = C/P = C/(V/T) = C (a + B D2)/V
where C is the cost per hour for the felling method being used, P is the production per hour, V is the volume per tree, and T is the time per tree. The hourly cost of operation is referred to as the machine rate and is the combined cost of labor and equipment required for production. (Machine rates are discussed in Section 3.)
Determine the felling unit cost for a 60 cm tree if the cost per hour of a man with power saw is $5.00, the tree volume is 3 cubic meters, and the time to fell the tree is 3 minutes plus 0.005 times the square of the diameter.
T = 3 + .005 (60) (60) = 21 min = .35 hr
P = V/T = 3.0/.35 = 8.57 m3/hr
A = C/P = 5.00/8.57 = $0.58/m3
In skidding, for example, if logs were being skidded directly to a road (Figure 2.1), then the distance skidded is an important factor and the stump to truck unit cost might be written as
X = A + B + Q + L
X = A + B + F + C(D/2) + L
where the skidding subunit Q has been replaced by symbol F representing fixed costs of skidding such as hooking, unhooking and decking and C(D/2) represents that part of the skidding cost that varies with distance. C is the cost of skidding a unit distance such as one meter and D/2 represents the average skidding distance in similar units. It is important to note that the average skidding cost occurs at the average skidding distance only when the skidding cost, C does not vary with distance. If C varies with distance, as for example, with animal skidding where the animal can become increasingly tired with distance, the average skidding cost does not occur at the average skidding distance and substantial errors in unit cost calculations can occur if the average skidding distance is used.
If logs were being skidded to a series of secondary roads (Figure 2.1) running into a primary road, then the expression C(D/2) would be replaced by the expression C(S/4) and the cost of truck haul on the secondary roads would appear as a separate item. In the expression C(S/4), the symbol S represents the spacing of the secondary roads and the distance S/4 is the average skidding distance if skidding could take place in both directions. Therefore, the expression C(S/4) would define the variable skidding cost in terms of spacing of the secondary roads.
A formula for the cost of logs on trucks at the primary road under these circumstances would be
X = A + B + F + C(S/4) + L + H(D/2)
where D/2 is the average hauling distance along the secondary road and H is the variable cost of hauling per unit distance.
The formula can be extended still further to include the cost of the secondary road system by defining the road construction cost per meter R, and the volume per square meter, V. Then, the formula becomes
X = A + B + F + C(S/4) + L + H(D/2) + R/(VS)
2.3 Applications of Cost Equations
In the preceding equation, we have a situation where as the spacing between skidding roads increases, skidding unit costs increase, while road unit costs decrease. With the total cost equation, we can look at the cost tradeoffs between skidding distance and road spacing. Calculus can be used to derive the formula for road spacing which minimizes costs as follows:
dX/dS = C/4 - R/(VS2) = 0
S = (4R/CV).5
An alternative method is to compare total costs for various road spacings. The total cost method has become less laborious with the use of programmable calculators and microcomputers. It provides information on the sensitivity of total unit cost to road spacing without having to evaluate the derivative of the cost function.
Given the following table of unit costs, what is the effect of alternative spur road spacings on the total cost of wood delivered to the main road if 50 m3 per hectare is being cut and the average length of the spur road is 2 km. The cost of spur roads includes landings.
TABLE 2.1 Table of costs by activity for the road spacing example.
|Skid||$/m3||2.00 (fixed cost)|
|Skid||$/m3-km||2.50 (variable cost)|
Since only the skidding costs and spur road costs are affected by the road spacing, the total unit cost can be expressed as
X = A + B + F + C(S/4) + L + H(D/2) + R/(VS)
X + 0.50 + 0.20 + 2.00 + C(S/4) + 0.80 + .15 (1) + R/(VS)
X = 3.65 + C(S/4) + R/(VS)
To evaluate different road spacings, we vary the spur road spacing S and calculate the total unit costs (Table 2.2). It is important to use dimensionally consistent units. That is, if the left side of the equation is in $/m3, the right side of the equation must be in $/m3. This is most easily done if all volumes, costs and distances are expressed in meters; such as volume cut per m2, skidding cost per m3 per meter, and road cost per meter. For example, the total cost for a spur road spacing of 200 meters is 3.65 + (2.5/1000) (200/4) + (2000/1000)/[(50/10000) (200)] or $5.78 per m3.
TABLE 2.2 Total unit cost as a function of road spacing.
|Spur Road Spacing, m||Total Unit Cost, $/m3|
The road spacing which minimized total cost could be interpolated from the table or calculated from the formula
S = (4R/CV) .5
S = 800 m.
When costs have been collected in a form which permits unit costs to be developed from them, not only is it possible to predict costs, it is also possible to adjust conditions so that minimum cost can be achieved. Too often, recorded costs are only "experience figures". They are usually made available in a form which can be used to predict costs only under conditions that closely conform to those existing where and when the recorded costs were collected. This is not true of unit costs, which can be fitted into the framework of many different harvesting situations and can be made to tell the story of the future as well as that of the past.
A wide range of cost control formulas can be derived. Typical problems include:
1. The economic location of roads and landings. - The calculation of the optimal spacing between spur roads and landings subject to one-way skidding, two-way skidding, skidding on slopes, linear and nonlinear skidding cost functions.
2. The economic service standard for roads. - The comparison of the benefits of lower haul costs and road maintenance costs as a function of increased initial investment. The calculation of the optimal length of swing roads as a function of the tributary volume.
3. The economic selection of equipment for road systems fixed by topography or other factors. - The identification of the breakeven points between alternative skidding methods which have different fixed and variable operating costs.
4. The economic spacing of roads which will be served by two types of skidding machines. - For example, machines used to skid sawtimber and to relog for fuelwood.
5. The economic spacing of roads which will be reused in future time periods.
Another important application of unit costs is in choosing between alternative harvesting systems.
A forest manager is developing an area and is trying to decide between harvesting methods. He has two choices of skidding systems (small or large), two choices of road standards (high or low), and two choices of trucks (small or large). If larger skidding equipment is selected to bring the logs to the landing, he can still choose to buck them into smaller logs on the landing. We assume that bucking on the landing will not affect log quality or yield.
The managers staff has developed the relevant unit costs, which are summarized in Table 2.3 and Table 2.4. What should he do?
TABLE 2.3 Unit costs for options of using small equipment and large equipment.
1/See Table 2.4 for transport costs as a function of road standard. Wood for large system could be bucked on landing for $0.15/m3 and loaded on small trucks.
2/Large logs must be bucked at mill.
TABLE 2.4 Unit costs for road and transport options using small and large equipment.
These choices can be viewed as a network (Figure 2.2). You can verify that the least cost path is obtained by using the larger skidding equipment and trucks and constructing the higher standard road. The total unit cost will be $8.50 per m3. A key point is the ease at which these problems can be analyzed, once the unit costs have been derived. In turn, the derivation of the unit costs is facilitated by having machine rates available (Section 3).
The unit cost of logging or road construction is essentially derived by dividing cost by production. In its simplest case, if you rented a tractor with operator for $60 per hour - including all fuel and other costs - and you excavated 100 cubic meters per hour, your unit cost for excavation would be $0.60 per cubic meter. The hourly cost of the tractor with operator is called the machine rate. In cases where the machine and the elements of production are not rented, a calculation of the owning and operating costs is necessary to derive the machine rate. The objective in developing a machine rate should be to arrive at a figure that, as nearly as possible, represents the cost of the work done under the operating conditions encountered and the accounting system in use. Most manufacturers of machinery supply data for the cost of owning and operating their equipment that will serve as the basis of machine rates. However, such data usually need modification to meet specific conditions of operation, and many owners of equipment will prefer to prepare their own rates.
3.2 Classification of Costs
The machine rate is usually, but not always, divided into fixed costs, operating costs, and labor costs. For certain cash flow analyses only items which represent a cash flow are included. Certain fixed costs, including depreciation and sometimes interest charges, are omitted if they do not represent a cash payment. In this manual, all fixed costs discussed below are included. For some analyses, labor costs are not included in the machine rate. Instead, fixed and operating costs are calculated. Labor costs are then added separately. This is sometimes done in situations where the labor associated with the equipment works a different number of hours from the equipment. In this paper, labor is included in the calculation of the machine rate.
3.2.1 Fixed Costs
Fixed costs are those which can be predetermined as accumulating with the passage of time, rather than with the rate of work (Figure 3.1). They do not stop when the work stops and must be spread over the hours of work during the year. Commonly included in fixed costs are equipment depreciation, interest on investment, taxes, and storage, and insurance.
3.2.2 Operating Costs
Operating costs vary directly with the rate of work (Figure 3.1). These costs include the costs of fuel, lubricants, tires, equipment maintenance and repairs.
3.2.3 Labor Costs
Labor costs are those costs associated with employing labor including direct wages, food contributions, transport, and social costs, including payments for health and retirement. The cost of supervision may also be spread over the labor costs.
The machine rate is the sum of the fixed plus operating plus labor costs. The division of costs in these classifications is arbitrary although accounting rules suggest a rigid classification. The key point is to separate the costs in such a way as to make the most sense in explaining the cost of operating the men and equipment. For example, if a major determinant of equipment salvage value is the rate of obsolescence such as in the computer industry, the depreciation cost is largely dependent on the passage of time, not the hours worked. For a truck, tractor, or power saw, a major determinant may be the actual hours of equipment use. The tractor's life could be viewed as the sand in an hour glass which is only permitted to flow during the hours the equipment is working.
3.3.1 Purchase Price (P)
This is the actual equipment purchase cost including the standard attachments, optional attachments, sales taxes, and delivery costs. Prices are usually quoted at the factory or delivered at the site. The factory price applies if the buyer takes title to the equipment at the factory and is responsible for shipment. On the other hand, delivered price applies if the buyer takes title to the equipment after it is delivered. The delivered price usually includes freight, packing, and insurance. Other costs such as for installation should be included in the initial investment cost. Special attachments may sometimes have a separate machine rate if their lives differ from the main equipment and form an important part of the equipment cost.
3.3.2 Economic Life (N)
This is the period over which the equipment can operate at an acceptable operating cost and productivity. The economic life is generally measured in terms of years, hours, or in the case of trucks and trailers in terms of kilometers. It depends upon a variety of factors, including physical deterioration, technological obsolescence or changing economic conditions. Physical deterioration can arise from factors such as corrosion, chemical decomposition, or by wear and tear due to abrasion, shock and impact. These may result from normal and proper usage, abusive and improper usage, age, inadequate or lack of maintenance, or severe environmental conditions. Changing economic conditions such as fuel prices, tax investment incentives, and the rate of interest can also affect the economic life of equipment. Examples of ownership periods for some types of skidding and road construction equipment, based upon application and operating conditions, are shown in Table 3.1. Since the lives are given in terms of operating hours, the life in years is obtained by working backwards by defining the number of working days per year and the estimated number of working hours per day. For equipment that works very few hours per day, the derived equipment lives may be very long and local conditions should be checked for the reasonableness of the estimate.
3.3.3 Salvage Value (S)
This is defined as the price that equipment can be sold for at the time of its disposal. Used equipment rates vary widely throughout the world. However, in any given used equipment market, factors which have the greatest effect on resale or trade-in value are the number of hours on the machine at the time of resale or trade-in, the type of jobs and operating conditions under which it worked, and the physical condition of the machine. Whatever the variables, however, the decline in value is greater in the first year than the second, greater the second year than the third, etc. The shorter the work life of the machine, the higher the percentage of value lost in a year. In agricultural tractors for example, as a general rule 40 to 50 percent of the value of the machine will be lost in the first quarter of the machine's life and by the halfway point of lifetime, from 70 to 75 percent of the value will be lost. The salvage value is often estimated as 10 to 20 percent of the initial purchase price.
3.4 Fixed Costs
The objective of the depreciation charge is to recognize the decline of value of the machine as it is working at a specific task. This may differ from the accountant's depreciation schedule-which is chosen to maximize profit through the advantages of various types of tax laws and follows accounting convention. A common example of this difference is seen where equipment is still working many years after it was "written off" or has zero "book value".
Depreciation schedules vary from the simplest approach, which is a straight line decline in value, to more sophisticated techniques which recognize the changing rate of value loss over time. The formula for the annual depreciation charge using the assumption of straight line decline in value is
D = (P' - S)/N
where P' is the initial purchase price less the cost of tires, wire rope, or other parts which are subjected to the greatest rate of wear and can be easily replaced without effect upon the general mechanical condition of the machine.
Interest is the cost of using funds over a period of time. Investment funds may be borrowed or taken from savings or equity. If borrowed, the interest rate is established by the lender and varies by locality and lending institution. If the money comes from savings, then opportunity cost or the rate this money would earn if invested elsewhere is used as the interest rate. The accounting practice of private firms may ignore interest on equipment on the ground that interest is a part of profits and, therefore, not a proper charge against operating equipment. Although this is sound from the point of view of the business as a whole, the exclusion of such charges may lead to the development of unrealistic comparative rates between machines of low and high initial cost. This may lead to erroneous decisions in the selection of equipment.
Interest can be calculated by using one of two methods. The first method is to multiply the interest rate by the actual value of the remaining life of the equipment. The second simpler method is to multiply the interest rate times the average annual investment.
For straight-line depreciation, the average annual investment, AAI, is calculated as
AAI = (P - S) (N + 1)/(2N) + S
Sometimes a factor of 0.6 times the delivered cost is used as an approximation of the average annual investment.
Many equipment owners must pay property taxes or some type of usage tax on equipment. Taxes, like interest, can be calculated by either using the estimated tax rate multiplied by the actual value of the equipment or by multiplying the tax rate by the average annual investment.
Most private equipment owners will have one or more insurance policies against damage, fire, and other destructive events. Public owners and some large owners may be self-insured. It could be argued that the cost of insurance is a real cost that reflects the risk to all owners and some allowance for destructive events should be allowed. Not anticipating the risk of destructive events is similar to not recognizing the risk of fire or insect damage in planning the returns from managing a forest. Insurance calculations are handled in the same way as interest and taxes.
3.4.5 Storage and Protection
Costs for equipment storage and off-duty protection are fixed costs, largely independent of the hours of use. Costs of storage and protection must be spread over the total hours of equipment use.
3.5 Operating Costs
Operating costs, unlike fixed costs, change in proportion to hours of operation or use. They depend upon a variety of factors, many of which are, to some extent, under the control of the operator or equipment owner.
3.5.1 Maintenance and Repair
This category includes everything from simple maintenance to the periodic overhaul of engine, transmission, clutch, brakes and other major equipment components, for which wear primarily occurs on a basis proportional to use. Operator use or abuse of equipment, the severity of the working conditions, maintenance and repair policies, and the basic equipment design and quality all affect maintenance and repair costs.
The cost of periodically overhauling major components may be estimated from the owner's manual and the local cost of parts and labor, or by getting advice from the manufacturer. Another owner's experience with similar equipment and cost records under typical working conditions is a valuable source. If experienced owners or cost records are not available, the hourly maintenance and repair cost can be estimated as a percentage of hourly depreciation
3.6 Labor Costs
Labor costs include direct and indirect payments such as taxes, insurance payments, food, housing subsidy, etc. Labor costs need to be carefully considered when calculating machine rates since the hours the labor works often differs from the hours the associated equipment works. What is important is that the user define his convention and then to use it consistently. For example, in felling, the power saw rarely works more than 4 hours per day, even though the cutter may work 6 or more hours and may be paid for 8 hours, including travel. If felling production rates are based upon a six-hour working day, with two hours of travel, the machine rate for an operator with power saw should consider 4 hours power saw use and eight hours labor for six hours production.
3.7 Variable Effort Cycles
The concept that men or equipment work at constant rates is an abstraction that facilitates measurements, record keeping, payments and analysis. However, there are some work cycles which require such variable effort that it is more useful to construct machine rates for parts of the cycle. One important case is the calculation of the machine rate for a truck. When a log truck is waiting to be loaded, is being loaded, and is being unloaded, its fuel consumption, tire wear, and other running costs are not being incurred. Or, if these costs are incurred, they are at a much reduced rate. For the standing truck, a different machine rate is often constructed using only the fixed cost and the labor cost for this part of the cycle. Part or all of the truck depreciation may be included.
If a single machine rate were used to estimate the unit cost for truck transport and this value was converted to a ton-km cost or $/m3-km cost without removing the "fixed" cost of loading and unloading then the "variable" cost of transport would be overestimated. This could lead to erroneous results when choosing between road standards or haul routes.
3.8 Animal Rates
The calculation of the animal rate is similar to the machine rate, but the types of costs differ and merit additional discussion.
3.8.1 Fixed Cost
The fixed cost includes the investment cost of the animal or team, harness, yoke, cart, logging chains and any other investments with a life more than one year. Other fixed costs include the upkeep of the animals.
The purchase price of the animal may include spare animals if the working conditions require that the animal receive rest more than overnight, such as every other day. To allow for the possibility of permanent injury, the animal purchase price may be increased to include extra animals. In other cases, accidents can be allowed for in the insurance premium. The salvage cost for the animal has the same definition as for a machine rate but in the case of the animal, the salvage value is often determined by its selling value for meat. Average annual investment, interest on investment, and any taxes or licenses are treated the same as for equipment. To find the total fixed costs for the animals, the fixed costs for the animal, cart, harness, and miscellaneous investments can be calculated separately since they usually have unequal length lives and the hourly costs added together.
Animal support costs which do not vary directly with hours worked include pasture rental, food supplements, medicine, vaccinations, veterinarian services, shoes, ferrier services and any after-hours care such as feeding, washing or guarding. It could be argued that food and care requirements are related to hours worked and some part of these costs could be included in operating costs. Pasture area (ha/animal) can be estimated by dividing the animal consumption rate (kg/animal/month) by the forage production rate (kg/ha/month). Food supplements, medicine, vaccinations, and veterinarian schedules can be obtained from local sources such as agricultural extension agents.
3.8.2 Operating Costs
Operating costs include repair and maintenance costs for harnesses, carts, and miscellaneous equipment.
3.8.3 Labor Costs
The labor cost in the animal rate is for the animal driver (and any helpers). For full year operations it is calculated as the labor cost per year including social costs divided by the average number of working days or hours for the driver (and any helpers).
4. ESTIMATING ROAD CONSTRUCTION UNIT COSTS
The unit cost of road construction in dollars per kilometer is the sum of the subunit costs of the road construction activities. Road construction unit costs are estimated by dividing the machine rates by the production rates for the various activities involved in road construction. The road construction activities considered here are surveying, clearing and grubbing, excavation, surfacing, and drainage.
Surveying and staking costs vary considerably depending on type and size of the job, access, terrain, and job location. One method of estimating production is to estimate the number of stakes which can be set per hour and the number of stakes which must be set per kilometer. For example, assume about 15 stakes can be set per hour with a two-man crew with the preliminary survey line already in place. A typical five-point section consists of two reference stakes, two slope stakes, and one final centerline stake.
The surveying production rate in km per hour is equal to the number of stakes the crew sets per hour divided by the number of stakes required per km.
A survey crew is setting 300 stakes per km at a rate of 15 stakes per hour. The cost of a survey crew including transport is $10 per hr.
P = 15/300 = .05 km/hr
UC = 10/.05 = $200/km
4.3 Clearing and Piling
The clearing and piling cost can be calculated by estimating the number of hectares of right-of way to be cleared and piled per kilometer of road. The clearing and piling production rate in km/hr is the hectares per hour which can be cleared and piled per hour divided by the number of hectares per km to be cleared and piled. Clearing can be accomplished in a number of ways, including men with axes or power saws. Merchantable logs may be removed by skidder or tractor and the remainder piled by tractor for burning or decay. Felling rates and skidding rates for logging can be used for determining the cost of the removal of merchantable logs.
On gentle terrain, if a wide right-of-way is being cleared to permit sunlight to dry the road surface after frequent rains, the project might be estimated as a land clearing project. A method for estimating the total time per hectare required to clear, grub, and pile on gentle terrain with a tractor and shearing blade is shown below. Additional details can be found in the Caterpillar Performance Handbook No. 21, Caterpillar, Inc.
4.3.1 Mechanized Clearing
The clearing time will depend upon the size of tractor and the number and size of the trees. The clearing time, Tc, in machine hours per hectare is
Tc = (X/60) (AB + M1N1 + M2N2 + M3N3 + M4N4 + DF)
where X is the hardwood density factor, A is the vine density factor, B is the base minutes per hectare, M is the minutes per tree in each diameter range, N is the number of trees per hectare in each diameter range, D is the sum of the diameters of all trees per hectare larger than 180 cm, and F is the minutes per cm of diameter to cut trees with diameters greater than 180 cm.
The earthwork cost is calculated by estimating the number of cubic meters of common material and rock which must be moved to construct the road. The earthwork production rate is calculated as the cubic meters per hour which can be excavated and placed divided by the number of cubic meters per km to be excavated.
Road construction superintendents can often estimate the number of meters per hour that their equipment can build road based upon local experience after looking at the topography. The engineer's method is to calculate the number of cubic meters to be excavated using formulas or tables for calculating earthwork quantities as a function of sideslope, road width, cut and fill slope ratios. Production rates for bulldozers and hydraulic excavators are available.
For example, a 6.0 meter subgrade on a 30 percent slope with a 1.5:1 fill slope and 0.5:1 cut slope with a one foot ditch and a 20 percent shrinkage factor would be approximately 2100 bank cubic meters per km for a balanced section.
An average production rate in common material (no rock) from an equipment performance handbook might be 150 bank cubic meters per hour for a 300 hp power-shift tractor with ripper. The tractor cost is $80/hr. The rate of excavation would be
P = (150 m3/hr)/(2100 m3/km) = .07 km/hr
UC = 80/.07 = $1143/km
If the earthwork is not being placed or sidecast within 50 meters of the cut, the production rate for pushing the material to the placement location must be made. Scrapers or excavators and dump trucks may be used.
Excavation rates in rock vary with the size of job, hardness of rock and other local conditions. Often there is a local market price for blasting. Estimates of blasting production can be made by knowing the size of equipment and the type of job. For example, a 10 cm track-mounted drill and 25 cubic meter per minute air-compressor may prepare 40 cubic meters per hour for small, shallow blasts and 140 cubic meters per hour for larger, deeper blasts including quarry development to produce rock surfacing. A major cost will be explosives. For example, 0.8 kg of explosive such as Tovex might be used per cubic meter of rock at a cost of approximately $2 per kg.
4.5 Finish Grading
Finish grading of the subgrade can be estimated by determining the number of passes a grader must make for a certain width subgrade and the speed of the grader. This number can be converted to the number of hours per hectare of subgrade. For example, a 120 hp grader may require about 10 hours of productive machine time without delays per hectare of subgrade or 0.1 hectares per hour. The production rate for final grading of a 6.0 meter subgrade would then be,
P = (0.1 ha/hr)/(0.6 ha/km) = .17 km/hr
If the grader cost is $30/hr, the unit cost of grading is
UC = 30/.17 = $176/km
Similarly, the rate of pulling ditches per kilometer can be estimated.
Surfacing costs are a function of the type of surfacing material, the quantity of surfacing material per square meter, and the length of haul. Local information is the best guide in constructing surfacing costs due to the wide range of conditions that can be encountered.
Natural gravel from streams may require only loading with front-end loaders directly to dump trucks, transporting, spreading, and may or may not be compacted.
Laterite may be ripped by crawler tractor, loaded by front-end loader, transported, spread and grid-rolled with a sheeps-foot roller to produce a sealed running surface.
Rock may have to be blasted, loaded into one or more crusher(s), stockpiled, reloaded, transported, spread, and compacted.
The costs for each of these operations can be developed by estimating the equipment production rates and machine rates.
Drainage costs vary widely with the type of drainage being installed. The costs of drainage dips (water bars), culverts, and bridges are often expressed as a cost per lineal foot which can then be easily applied in road estimating. Local values for cost per lineal foot for culverts and different types of bridges are generally available. If not, constructed costs can be made by using time study data.
ESTIMATING LOGGING UNIT COSTS
Logging unit costs are estimated by dividing machine rates by the production rates for the various logging activities. Logging components considered here are felling, bucking, skidding, loading, and transport.
5.2 Felling and Bucking
The major variables in felling and bucking are the tree diameter and the number of bucking cuts after felling. An example of a formula for the time to fell and buck a tree is
T = a + b D2 + c B
where T is the time per tree in minutes, b is the minutes per unit diameter and the D is the diameter, c is the time per bucking cut and B is the number of bucking cuts. The coefficient a is the time per tree that is not related to diameter such as walking between trees or preparing to cut. Sometimes terrain and brush are taken into account by using equations of the form
T' = (1 + f) T
where f is an adjustment factor for terrain or brush. The production rate, P, in cubic meters per hour is
P = V/T
where V is the volume per tree, m3, and T is the time per tree, hr. The unit cost of felling is
UC = C/P
where C is the machine rate for felling and bucking and P is the production rate.
A power saw and operator cost $5.00 per hour and the time to fall and buck a tree is
T = 4.0 + .005 D2 + 2.0 B
For a tree with volume 6 m3, dbh of 80 cm and 1 bucking cut
T = 4.0 + .005 (80)(80) + 2.0 (1) = 38.0 min = 0.63 hr
P = V/T = 6/0.63 = 9.5 m3 per hr
UC = 5/9.5 = $0.52 per m3
For a tree with volume 1.25 m3, dbh of 40 cm and 1 bucking cut
T = 4.0 + .005 (40) (40) + 2.0 (1) = 14.0 min = 0.23 hr
P = V/T = 1.25/.23 = 5.4 m3 per hr
UC = 5/5.4 = $0.93 per m3
Skidding production is estimated by dividing the volume per load by the time per round trip. The round trip time, T, is the sum of the times for travel unloaded, hooking, travel loaded, and unhooking.
T = a N + b1 x1 + b2 x2
where a is the combined time for hooking and unhooking per log, b1 is the minutes per meter for unloaded travel, b2 is the minutes per meter for loaded travel, x1 is the distance from the landing to load pickup point and x2 is the distance from the load pickup point to the landing. If the outhaul distance and inhaul distance are the same, the roundtrip time can be expressed as
T = a N + b x
where b is the minutes per roundtrip distance and x is the one-way distance. The coefficient b is calculated as
where v1 is the travel speed unloaded and v2 is the travel speed loaded.
A skidder is bringing in 3 logs with a volume of 4 m3. The unloaded speed is 200 meters per minute and the loaded speed is 100 meters per minute. The hook time is 1.5 minutes per log and the unhook and decking time is 1.1 minutes per log. The skidding distance is 300 m. The machine rate for the skidder and crew is $40 per hour.
T = (2.6) (3) + 300/200 + 300/100 = 12.3 min = .21 hr
P = 4/.21 = 19.5 m3 per hour
UC = 40/19.5 = $2.05 per m3
b = (200 + 100)/[(200) (100)] = .015 min/m
T = (2.6) (3) + .015 (300) = 12.3 min
The cost of hooking, unhooking and decking is
UCF = (C/60) (aN)/V
UCF = (40/60) (2.6) (3)/4 = $1.30 per m3
The cost per cubic meter of wood per unit distance (measured one-way), UCV, is
UCV = (C/60) (b)/V
UCV = (40/60) (.015)/4 = $0.0025/m3-m
At a skidding distance of 300 meters
UC = UCF + UCV = 1.3 + (.0025) (300) = $2.05 per m3
The same method can be used to estimate the skidding costs with agricultural tractors and trailers, animals, or with cable systems.
A team of oxen brings in one log with a volume of 0.8 m3. The unloaded speed is 30 meters per minute and the loaded speed is 30 meters per minute. The hook time is 2 minutes and the unhooking and watering time is 5 minutes. The skidding distance is 100 meters. The rate for the oxen and driver is $3.00 per hour.
T = (7) + 100/30 + 100/30 = 13.7 min = .23 hr
P = .8/.23 = 3.48 m3 per hour
UC =3/3.48 = $0.86 per m3
Loading production is estimated by dividing the volume per cycle by the minutes per cycle. The time per log for loading single logs is often as simple as
T = a
where a is the time per cycle.
A truck is being loaded by hydraulic knuckleboom loader. It is loading 1.0 m3 logs individually at an average rate of 2 per minute. To prepare for loading trucks, however, the loader spends 30 minutes per hour sorting logs. What is the loading production rate and cost?
When the loader is actually loading logs, the production rate is
P = (1.0)/.5 = 2.0 m3/min = 120 m3/hr
but the loading production per machine hour is 60 m3/hr.
The cost of log sorting can either be shown as a reduced effective rate of log loading or as a separate subunit cost of the total logging unit cost. If the sorting cost is included in the loading cost, the unit cost of loading is then
UC = 40/60 = $0.67 per m3
5.5 Truck Transport
The method of estimating truck production depends upon the purpose of the analysis. If truck production is being calculated for the purpose of determining the number of trucks needed for truck haul, then the average truck load is divided by the total roundtrip time including unloaded travel time, loading time, loaded travel time, and unloading time. The calculation is similar to that for skidding with the roundtrip travel time, T expressed as
T = a + b1 x1 + b2 x2
where a is the combined time for loading and unloading, b1 is the hours per km for unloaded travel, b2 is the hours per km for loaded travel, x1 is the distance from the landing to load pickup point and x2 is the distance from the load pickup point to the landing. If the outhaul distance and inhaul distance are the same, the roundtrip time can be expressed as
T = a + b x
where b is the hours per roundtrip km and x is the one-way distance. The coefficient b is calculated as
where v1 is the travel speed unloaded and v2 is the travel speed loaded.
A 22-ton truck carries an average of 30 m3 per trip. The haul route is 35 km. The unloaded truck travels 40 km per hour and the loaded truck travels 25 km per hour. The combined waiting and loading time is 30 min per load and the combined waiting and unloading time is 20 min per load. The cost per truck standing hour is $20 and the cost per truck running hour is $30. What is the production per hour?
T = (30 + 20)/60 + 35/40 + 35/25 = 3.11 hrs
P = 30/3.1 = 9.65 m3/hr
The "fixed" unit cost of truck standby for loading and unloading is:
UFC = ($20/hr) (30 + 20 min)/60 min/hr/30 m3 = $0.56 per m3
The "variable" unit cost of truck travel is:
UVC = ($30/hr) (35/40 hr + 35/25 hr)/30 m3 = $2.28 per m3
or expressed on a ton-km basis:
UVC = ($30/hr) (35/40 hr + 35/25 hr)/22 t/35 km = $.089 t-km
The total unit cost of truck haul is:
UC = UFC + UVC = 0.56 + 2.28 = 2.84 per m3
5.6 Typical Stump to Mill Logging Systems
To illustrate the use of machine rates (Section 3) and the production relationships discussed in this section, stump to mill logging costs for three typical logging systems are shown. In each of these examples, the stump to mill or water harvesting activities are listed along with assumed machine rates and production data. The production data are then converted into production per hour with the conversion method depending on the form of the data. Unit costs for each activity and a stump to mill or water cost is calculated.
5.6.1 Plantation Large Wood
Assume clear felling of a pine plantation is being planned. An estimate is being made of the stump-to-mill harvesting costs for one possible alternative for the operation. The roads are already in place. The activities are:
1. Fell, delimb, and cross cut with power saw.
2. Skid to roadside using a rubber-tired skidder.
3. Load truck trailer using a self-loading truck.
4. Transport by truck to the mill.
Machine rates (col 2) and production data (col 7) for this example are shown in Table 5.1. The machine rates for the various labor-equipment combinations of cutter with power saw, rubber-tired skidder with operator and helper, and truck driver with self-loading truck are developed using the techniques from Chapter 3. Production estimates are made from experience, available formulas or tables, or short time studies (Appendix B). A good source of felling, skidding and loading production for large plantation wood can be found in Planning Roads and Harvesting Systems by FAO, 1977.
The formula used for the hourly production calculation (Table 5.2, col 8) depends upon the information available. On the following pages production calculations are shown for various harvesting activities. For the felling, delimbing and cross cutting:
P = 4 trees/hr × 1.1 m3 per tree = 4.4 m3 per hour.
For skidding the logs to the landing by rubber tired skidder:
T = 5 + 200 m/(60 m/min) + 200 m/(100 m/min) = 10.33 min
Assume we have observed about 10 min per hour are involved in unplanned delays so we can either increase the average time per trip to
T = 10.33 min × (60/50) = 12.4 min per trip including delays
or we can reduce the effective hour from 60 minutes per hour to 50 minutes per hour:
P = 2.2 m3/load × 50 min/10.33 min per trip = 10.6 m3/hr
For loading the truck trailers a short time study indicates the time per log is 30 sec with an average log size of 0.55 m3. The loader only spends about 30 minutes per hour loading trucks and the remainder of the time decking and sorting logs. We have two choices here. We could reduce the loading rate to create a "sorting and loading production" rate or we could keep the two production rates separate. A combined sorting and loading rate.
P (loading only) = .55 m3/log × 2 log/min × 60 min/hr = 66 m3/hr
P (sorting and loading) = 66 m3/hr/2 = 33 m3 per hr
For truck transport to the mill yard:
T (standing) = 45 min per trip = .75 hr
P (standing) = 20 m3/load/.75 hr = 26.7 m3/hr
T (traveling) = 25 km/20 km/hr + 25 km/25 km/hr = 2.25 hr
P (traveling) = 20 m3/load/2.25 hr = 8.9 m3/hr
After the machine rates and production rates have been derived, the individual unit costs can be calculated (Table 5.1, col 9). The stump-to-mill cost for this harvesting alternative is $9.58 per m3. Road reconstruction or road maintenance costs should be added, if appropriate, using the techniques from Chapter 4.
PACE - A COMPUTER PROGRAM FOR COST CALCULATIONS
The computer program, PACE (Production and Cost Evaluation), was developed to assist in calculating machine rates, road construction costs, and harvesting costs. It can be used to evaluate tradeoffs between road costs and harvesting costs. This section will describe the PACE program and can be used as a user guide. A computer disk with the PACE program for IBM PC/XT/AT and compatibles are provided with this manual. See Section 6.7 for installation instructions.
PACE is divided into three parts: (1) machine rate calculations, (2) road construction calculations, and (3) harvesting production and unit cost calculations. Analysis begins with the preparation of machine rates for combinations of equipment and labor which will be used in road construction and harvesting. Next, road construction costs are developed using the machine rates from (1). And last, machine rates, road costs, and harvesting production rates are combined to develop production and unit cost estimates
PACE is easily learned through a tutorial example. The tutorial includes calculation of a machine rate, a road construction cost, and a harvesting production and cost estimate Copies of the computer monitor displays are included along with the formulas used to make the calculations.
6.2 Starting PACE
PACE consists of six programs linked together by an executive program with the main menu. Type PACE and press <enter>. The monitor will display the main menu (Figure 6.2). You are now ready to begin.
6.3 Machine Rate Calculations
Let's begin by preparing a machine rate for an operator with a power saw. To reach the machine rate program menu (Figure 6.3), use the cursor control arrows to highlight the machine rate program, MAC-COST.EXE and press <enter>. The MAC-COST menu (Figure 6.3) will appear.
ADVANCED APPLICATIONS OF PACE
The standard applications of PACE were discussed in Chapter 6. Occasionally, you may want to model other situations. In this section we present several advanced applications of PACE. These applications will assist you in thinking up additional ways to model situations you are interested in studying.
The PACE program is designed to build upon machine rates so that the analyst can trace back a harvesting cost-road cost analysis to the set of underlying assumptions. Occasionally you might want to get unit costs quickly without making a number of machine rate files and road cost files. In this situation, it may be useful to keep a .UCD file on your disk. You only need to build this file once and save it. When you recall this dummy file, it satisfies the input requirements for PACE. You can then change machine costs in the various screens. The only thing you need to remember is that PACE uses the proportions derived in the original machine rate files to divide any revised machine rates between ownership, operating, and labor costs. If all you are interested in is the total unit cost for any activity, it does not matter.
7.3 Combining Road Sections
Often the road from the landing to the mill may have two or more road standards or other factors which affect the travel speed of the truck. PACE only permits entry of one truck speed.
If you want to calculate a truck transport cost which includes the total route you will need to derive the average loaded and average unloaded speed outside of PACE and use these average speeds in PACE. The example below shows how to do this for a road divided into three sections.
The speed on section 1 is V1, on section 2 is V2 and on section is V3. The length of the sections are L1, L2, and L3 respectively.
7.4 Combining Skidding Systems
In some cases, PACE can be used to combine two skidding systems. The Unit Cost program can then be used to solve for the optimal skidding distance for each system simultaneously. For example, consider a situation where oxen are being used to skid along trails perpendicular to tractor skid trails, and the tractors swing the wood to truck roads. If we consider the oxen to be the "lateral skidding cycle" for the tractor skidding system we can model this system in PACE by deriving an equivalent lateral skidding speed and equivalent hook and unhook time which takes into account the difference in machine rates for the oxen relative to the tractor
FAO TECHNICAL PAPERS
1. Forest utilization contracts on public land, 1977 (E* F* S*)
2. Planning of forest roads and harvesting systems, 1977 (E* F* S*)
3. World list of forestry schools, 1977 (E/F/S*)
3 Rev. 1. - World list of forestry schools, 1981 (E/F/S*)
3 Rev. 2. - World list of forestry schools, 1986 (E/F/S*)
4. World pulp and paper demand, supply and trade
Vol. 1, 1977 (E* F* S*)
Vol. 2, 1978 (E* F* S*)
5. The marketing of tropical wood in South America, 1978 (E* S*)
6. National parks planning, 1978 (E* F* S***)
7. Forestry for local community development, 1978 (E* F* S*)
8. Establishment techniques for forest plantations, 1978 (Ar*** C* E** F* S*)
9. Wood chips, 1978 (C* E* S*)
10. Assessment of logging costs from forest inventories in the tropics, 1978
1. Principles and methodology (E* F* S*)
2. Data collection and calculations (E* F* S*)
11. Savanna afforestation in Africa, 1978 (E* F*)
12. China: forestry support for agriculture, 1978 (E*)
13. Forest products prices, 1979 (E/F/S*)
14. Mountain forest roads and harvesting, 1979 (E*)
14 Rev. 1. - Logging and transport in steep terrain, 1985 (E*)
15. AGRIS forestry: world catalogue of information and documentation services, 1979 (E/F/S*)
16. China: integrated wood processing industries, 1979 (E* F* S***)
17. Economic analysis of forestry projects, 1979 (E* F* S*)
17 Sup. 1. - Economic analysis of forestry projects: case studies, 1979 (E* S*)
17 Sup. 2. - Economic analysis of forestry projects: readings, 1980 (E*)
18. Forest products prices 1960-1978, 1980 (E/F/S*)
19. Pulping and paper-making properties of fast-growing plantation wood species
Vol. 1, 1980 (E*)
Vol. 2, 1980 (E*)
20/1. Forest tree improvement, 1985 (E* F* S*)
20/2. A guide to forest seed handling, 1985 (E* S*)
21. Impact on soils of fast-growing species in lowland humid tropics, 1980 (E* F* S*)
22/1. Forest volume estimation and yield prediction, 1980
Vol. 1 - Volume estimation (E* F* S*)
22/2. Forest volume estimation and yield prediction, 1980
Vol. 2 - Yield prediction (E* F* S*)
23. Forest products prices 1961-1980, 1981 (E/F/S*)
24. Cable logging systems, 1981 (E*)
25. Public forestry administration in Latin America, 1981 (E*)
26. Forestry and rural development, 1981 (E* F* S*)
27. Manual of forest inventory, 1981 (E* F*)
28. Small and medium sawmills in developing countries, 1981 (E* S*)
29. World forest products, demand and supply 1990 and 2000, 1982 (E* F* S*)
30. Tropical forest resources, 1982 (E/F/S*)
31. Appropriate technology in forestry, 1982 (E*)
32. Classification and definitions of forest products, 1982 (Ar/E/F/S*)
33. Logging of mountain forests, 1982 (E* F* S*)
34. Fruit-bearing forest trees, 1982 (E* F* S*)
35. Forestry in China, 1982 (E*)
36. Basic technology in forest operations, 1982 (E* F* S*)
37. Conservation and development of tropical forest resources, 1982 (E* F* S*)
38. Forest products prices, 1962-1981,1982 (E/F/S*)
39. Frame saw manual, 1982 (E*)
40. Circular saw manual, 1983 (E*)
41. Simple technologies for charcoal making, 1983 (E* F* S*)
42. Fuelwood supplies in the developing countries, 1983 (Ar* E* F* S*)
43. Forest revenue systems in developing countries, 1983 (E* F* S*)
44/1. Food and fruit-bearing forest species, 1983 (E* F* S*)
44/2. Food and fruit-bearing forest species, 1984 (E* F* S*)
44/3. Food and fruit-bearing forest species, 1986 (E* S*)
45. Establishing pulp and paper mills, 1983 (E*)
46. Forest products prices 1963-1982, 1983 (E/F/S*)
47. Technical forestry education design and implementation, 1984 (E* F*)
48. Land evaluation for forestry, 1984 (E* F* S*)
49. Wood extraction with oxen and agricultural tractors, 1986 (E* F* S*)
50. Changes in shifting cultivation in Africa, 1984 (E* F*)
50/1. Changes in shifting cultivation in Africa - seven case-studies, 1985 (E*)
51/1. Studies on the volume and yield of tropical forest stands
1. Dry forest formations, 1989 (A* F*)
52/1. Cost estimating in sawmilling industries: guidelines, 1984 (E*)
52/2. Field manual on cost estimation in sawmilling industries, 1985 (E*)
53. Intensive multiple-use forest management in Kerala (India), 1984 (E* F*)
54. Planificación del desarrollo forestal, 1985 (S*)
55. Intensive multiple-use forest management in the tropics, 1985 (E* F* S*)
56. Breeding poplars for disease resistance, 1985 (E*)
57. Coconut wood, 1985 (E* S*)
58. Sawdoctoring manual, 1985 (E*)
59. The ecological effects of eucalyptus, 1985 (E* F* S*)
60. Monitoring and evaluation of participatory forestry projects, 1985 (E*)
61. Forest products prices 1965-1984, 1985 (E/F/S*)
62. World list of institutions engaged in forestry and forest products research, 1985 (E/F/S*)
63. Industrial charcoal making, 1985 (E*)
64. Tree growing by rural people, 1985 (E* F* S*)
65. Forest legislation in selected African countries, 1986 (E* F*)
66. Forestry extension organization, 1986 (E*)
67. Some medicinal forest plants of Africa and Latin America, 1986 (E*)
68. Appropriate forest industries, 1986 (E*)
69. Management of forest industries, 1986 (E*)
70. Wildland fire management terminology, 1985 (E/F/S*)
71. World compendium of forestry and forest products research institutions, 1986 (E/F/S*)
72. Wood gas as engine fuel, 1986 (E*)
73. Forest products: world outlook projections, 1986 (E/F/S*)
74. Guidelines for forestry information processing, 1986 (E*)
75. An operational guide to the monitoring and evaluation of social forestry in India, 1986 (E*)
76. Wood preservation manual, 1986 (E*)
77. Databook on endangered tree and shrub species and provenances, 1986 (E*)
78. Appropriate wood harvesting in plantation forests, 1987 (E*)
79. Small-scale forest-based processing enterprises, 1987 (E* F* S*)
80. Forestry extension methods, 1987 (E*)
81. Guidelines for forest policy formulation, 1987 (E*)
82. Forest products prices 1967-1986, 1988 (E/F/S*)
83. Trade in forest products: a study of the barriers faced by the developing countries, 1988 (E*)
84. Forest products: world outlook projections (Products and country tables), 1988 (E/F/S*)
85. Forestry extension curricula 1988 (E*)
86. Forestry policies in Europe, 1988 (E*)
87. Small-scale harvesting operations of wood and non-wood forest products involving rural people, 1988 (E* F*)
88. Management of tropical moist forests in Africa, 1989 (E* F* P*)
89. Review of forest management systems of tropical Asia, 1989 (E*)
90. Forestry and food security, 1989 (E*)
91. Design manual on basic wood harvesting technology, 1989 (E*). The above publication has been issued as No. 18 in the FAO Training Series
92. Forestry policies in Europe, 1989 (E*)
93. Energy conservation in the mechanical forest industries, 1990 (E*)
94. Manual on sawmill operational maintenance, 1990 (E*)
95. Forest products prices 1969-1988,1990 (E/F/S*)
96. Planning and managing forestry research: guidelines for managers, 1990 (E*)
97. Non-wood forest products: the way ahead, 1991 (E*)
98. Les plantations à vocation de bois d'oeuvre en Afrique intertropicale humide, 1991 (F*)
99. Cost control in forest harvesting and road construction, 1992 (E*)
Availability: April 1992
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