Technodiversity Glossary

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

Every worker has his individual abilities and strengths. The same job that is easy for somebody can be difficult for another person; we say that the first person is more talented for this job than the other one.

 (See more under TDiv PR1-E04)

Additional costs are a part of the cost calculation. They occur when the work is necessary for the production, but is not productive in a sense that there is an output of any products.

Very often it happens that workers are working hard, but do not produce any single product.

As an extreme example, take the work with a cable yarder. Before the yarder can be installed, an engineer must explore the terrain and trace a ground profile with distance and inclination. Based on that profile, he can select the best path for the cable corridor, selecting suitable spar trees, anchors and intermediate supports. Then he’ll go back to the forest and mark the corridor. Now a troop of specialists installs the yarding system. The end-mast and the intermediate supports must be prepared: they are stabilized with guylines, some pulleys are fixed, saddles are mounted…

Finally, the skyline is laid out, lifted and tightened. This takes the work of several persons and the basic machine over hours. Now the productive work begins.

When all logs in the area have been extracted, the yarder system needs to be dismantled. Also here, a troop of persons takes down the skyline, frees the end-mast and the intermediate supports, collects all materials (cables, pulleys, strops etc.) and stores all, ready for transport to the next site.

All these additional costs must be regarded when the costs per m³ are calculated. With yarder systems, they can be so high that the extraction with yarders will be achievable only under conditions of small clear-cuts.

(See more at TDiv PR1-C04)

The term mechanized work describes the degree of mechanization of a technical operation. Other degrees are manual work and motor-manual work. Mechanized work can further be divided into simple, advanced and automatic work.

When the machine takes over the auxiliary function to handle the object with means of a crane or a grapple, e.g., we call it advanced mechanized work.

A typical example is a tractor or forwarder equipped with a loader.

In this case the driver can control all important functions of the system without “feet on the ground or hand on the tree” (Lövgren, Swedish scientist). Given the hazards of forest work, this can be an important improvement in terms of safety and ergonomics – not just production efficiency.

This is one method to find the best option. Other methods are minimax rule, monetarization, utility analysis, and optimality curves, for example.

In 1990 Saaty proposed a new solution based on paired comparisons. Under each criterion we ask which one of two options is better. At the end we count the relations of the options. The option with the highest sum of “wins” is the best.

Using the same example as with the other methods, we can come to following tables:

With so few options it is easy to find the relations and to calculate the “wins”. In fact, Saaty’s method is more sophisticated than just that, but for us it is enough to use the same weights as before.

We see, that under this method the advantage of option 3 is more visible. All other options are comparably bad. This is a result that can be seen often: the method tends to exaggerate relationships because it does not discriminate between small and large differences.

AHP is widely used in sciences – but only there. For practice life it covers too many hidden effects.

(See more at PR1-F04)

See mechanized method

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

The attributes of workers are different like gender, age, height, weight, power… In practical life, these attributes are regarded to be invariable.

(See more under TDiv PR1-E04)

The term mechanized work describes the degree of mechanization of a technical operation. Other degrees are manual work and motor-manual work. Mechanized work can further be divided into simple, advanced and automatic work.

Automatic work can be subdivided into different degrees of automation.:

In forestry, the cut-to-length harvester is an example for a machine with partly automatic work (at level i3). Some prototypes try to operate driverless (i4). 

An axe is a tool used for the cutting of objects. It is composed of a shaft and a steel wedge, which is sharpened on the narrow side.

The axe is one of the oldest tools used for felling trees (buffer 10 to 11). Furthermore, it can be exploited for delimbing (buffer 11 to 12) and wood splitting (buffer 12 to 13).

Because human force is needed to cut with an axe, the work with an axe is assigned to the manual work. Other harvesting tools, the use of which is assigned to manual work, are the machete, the bush knife, and the hand saw.

(See PR1-B03)

If the strain of a worker overruns the permanent work load, it may increase the danger of an acute or chronic damage. Therefor breaks for recovery are necessary and should actively be provided by the employer.

The minimal duration of this break should correspond with the strain over the permanent work load to bring enough compensation to the overrunning strain. We call it “shortest break”, because it should not be shorter than the given duration in order to fulfil its requirement. In the figure below, we have three working situations:

-       The green line shows a work, where the strain (here indicated with the heart beat) during the working time does not run over the permanent work load. So, the shortest break is zero, no compensation is required.

-       With the yellow line, the permanent work load is reached but not overrun. Also here, we don’t need any break.

-       At the red line, the heart beat is for a long time over the permanent work load. Here a debit increases that needs to be compensated. This debit can be interpreted by the area A₁. In the first seconds of the break the heart beats are higher than the permanent work load; so, though they are decreasing, the heart beats (A₂) are counted as overrunning strain, too. The break is long enough, when the area A3 between heart beats and permanent work load is as large as the sum of A₁ and A₂. Now the compensating effect is enough.

There are three other types of breaks that have other effects:

-       organic breaks allow some organs to be unloaded while the load is taken over by other organs; one example is to move a heavy load from one hand into the other hand

-       short breaks of five minutes are for personal belongings and to recover the mind from concentration

-       longer breaks with 15 to 30 minutes allow to take lunch and to communicate with other colleagues

(See more under TDiv PR1-E04)

A term that is often used in system analysis. A buffer interrupts a flow and opens a space for contents that can be stored and loaded again. It is the link between two elements in a chain. 

In Technodiversity, we take this concept to describe interruptions in a harvesting process, which divide the process into two sub-processes. Since the buffer allows to store the logs, the connected sub-processes must not wait one for each other and can develop their full productivities. 

In the functiogram, the buffers are represented by a button while the cub-processes are shown by arrows. In order to concatenate the sub-processes, they must meet at a buffer. So, the buffers have a key role for building and optimizing harvesting processes. 

In lecture PR1-B07 they are named by numbers. 

(See PR1-B07)  

The cable skidder is a machine used for the extraction of trees. Driving on rubber tires or caterpillars it is specialized to off-road conditions.

The cable skidder extracts full trees and tree length from the trail (buffer 21 & 22) to the forest road (buffer 31 & 32).

Instead of a cable, trees can be dragged by a grapple skidder, clam-bunk skidder, or loaded with a loading crane to a forwarding trailer, forwarder. Another possibility for extraction on un-accessible terrain is the cable yarder or the helicopter.

It contains a single or double winch with reeling functions. With the cable given by the winch the load can be compiled and hold.

The extraction of the load takes places in a dragging movement. Since the cable skidder is a self-propelled machine, the work with the cable skidder is declared as simple mechanized work.

The cable yarder is a machine used for the extraction of trees. Other machines that can be used for this sub-process are the cable skidder, grapple skidder, clam-bunk skidder, skidder with a loading crane, farm tractor equipped with a forwarding trailer, and forwarder.

The cable yarder extracts full trees and tree lengths from the stand (buffer 11 & 31) to the forest road (buffer 12 & 32).

The extraction takes place in a carrying movement. Therefore, a cable is stretched between the tower of the cable yarder, and a standing tree or a second, mobile tower. On this cable a carriage is riding which lifts the load into the air and carries it along the cable line. To have an undisturbed transportation of the load the cable yarding system is erected on corridors, which are free from trees.

The extraction with a cable yarder is soil friendly because the cable yarder does not move itself during the extraction process and the load is in the air during the transit. So, the corridor underneath the cable line does not experience any load. The negative aspect of the cable yarder is the time-consuming assembly and dismantling, which makes this extraction option expensive.

The cable yarder is primarily used in the mountains and in other rough terrain. Working with the cable yarder is considered as simple mechanized work.

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

The capability of a person is a combination of attributes, abilities, and skills. If the capability fits the demands of the standard method, the strain is low. If not, strain will keep accumulating… Thus, the strain can differ from person to person, though the job is the same.

(See more under TDiv PR1-E04)

A chainsaw is a motorized tool that it used to saw off a complete tree from its roots (buffer 10 to 11). Furthermore, it can be used for delimbing (buffer 11 to 12) and to cross-cut trees into logs (buffer 12 to 13).

The alternative commonly used in forestry for the felling sub-process is the feller and for the felling - pre-skidding - delimbing sub-processes the harvester.

The sawing movement is performed by a saw chain, which runs over a chainsaw bar. Due to the motor of the chainsaw, the user does not need to apply force for the movement of the saw itself. Therefore, working with the chainsaw is by far easier than working with an axe or a hand saw.

Since the chainsaw is mechanically driven but must be held in position by a human being, the work with the chainsaw is classified as motor-manual work.

 (See PR1-B03 and B07)

The chip method is one of four different functional groups of harvesting methods. The others are fulltree, tree length and cut-to-length method.

With chip methods, the wood is chipped before it reaches the forest road.

The two most common alternatives are:

An integrated feller-chipper (a) fells the trees and chips them in a single pass. Chips are blown into a container, carried by the feller-chipper or by an auxiliary vehicle. Or the trees are felled, moved to the trail and chipped there (b).

(See more at TDiv PR1-B07)

The clam-bunk skidder is a rubber-tired or tracked machine used for the extraction of trees. Other machines that can be used for this sub-process are the cable skidder, grapple skidder, skidder with a loading crane, farm tractor equipped with a forwarding trailer, forwarder, and cable yarder.

The cable skidder extracts full trees and tree length from the trail (buffer 21 & 22) to the forest road (buffer 31 & 32). Therefore, the clam-bunk skidder is equipped with an integrated loader that lifts one end of the tree lengths into an inverted clam. The clam holds the load during the extraction process, resulting into a dragging movement of the load.

Like all skidders, the work with the grapple skidder is declared as advanced mechanized work.

(See PR1-B03 and B07)

Compatibility, ecological see ecological compatibility

Compatibility, societal see societal compatibility

In Technodiversity, the compatibility of a working method is expressed with the help of an ecogram.

But since the working method in nearly all cases is a composition of two or more sub-processes, the ecogram of the method must be composed by the ecograms of the sub-processes, too.

For example, we have a fully mechanized ctl-method with harvester and forwarder. Since the reach of the harvester is limited by the length of its crane, it needs to drive near to each harvest tree. As long as the harvester may drive offroad (=P1), this is no problem. But when we demand that the machine remains on trails that also will be used in future (say permanently), the trails should not be spaced further than twice the length of the crane, normally 20 m (=P2). The assessment is very good on dry soil and less with increasing humidity.

Before the forwarder comes, short logs are stored alongside the trail. So directly, the distance of the trails doesn’t matter for this machine (but indirectly it does: the wider the distance the higher the volume that must be transported on one trail and therefore the higher the impact to the soil there). The compatibility concerning soil moisture is the same as with the harvester.

To combine these two ecograms, we introduce the “bottle-neck-rule”: For each field in the ecogram, the worst assessment of all procedural steps is used as final assessment for the total method. Both, harvester and forwarder are assessed in a similar way for the T-classes, but the harvester goes only for P1 and P2. So, the total method also is only compatible for P1 (driving without binding at permanent lines) and P2 (trails with 20 m distance). We see that this method does not fulfil the demands of the forest owner that are expressed in the technogram.

In another example, a working method is composed by three sub-processes: felling with the chainsaw, processing by machine and extraction by a forwarder fitted with bogie tracks. Each sub-process has its own suitability that can be expressed by a typical ecogram. Thus, first we must look at the ecograms of each sub-process.

The worker with his chainsaw is compatible nearly everywhere. The ecogram shows mostly star symbols, only under very wet conditions the walking can be limited.

The processor (here a harvester that is working on the trail), is mainly limited by the moisture; since the trees are pre-skidded to the trail it can be used under all P-classes (except P5).

Both sub-processes together only make sense at a trail distance of 40 m. Therefore, the processing of this method is only reasonable at P-class 3 (=40 m). The assessment whether the process is very good, good or limited compatible, depends on the worst case; here the processor (again following the bottle-neck principle).

The forwarder drives on the trails, too. Since the logs are pre-skid, it can be used under all P-classes P1-P4 (except P5).

The common ecogram of the total method again is a combination of the ecograms of processing and extraction under observing the bottle-neck principle. When – like in this example – the technogram of the stand demands for the fields P3-T2, -T3, and -T4, this method is well compatible under normal and dry conditions.

(See more at TDiv PR1-D05)

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health.

If the strain overruns the permanent work load, it may have two consequences: On one hand the body is pushed to improve its capacities. We use this effect for active training and conditioning. But on the other hand, acute or chronic damage can occur. Therefor breaks for recovery are necessary and should actively be provided by the employer.

Controlling is one of the auxiliary functions of harvesting. It does not directly change the state of the working object or its position, but steers these operations and deals with the data (logistics). In Technodiversity, controlling is not mentioned intensively; but nevertheless here a great potential for innovations and efficiency is covered.

Before a decision maker decides to buy a machine, e. g., he should estimate the probable costs and earnings and calculate the net income.

The earnings normally depend on the market and cannot be influenced. So, the cost side is that one, where the decision maker can ‘earn or burn money’.

In some cases, the cost of any future operation can be assessed very easily, because the decision maker has his own experience.But very often, he must estimate the costs based on very foggy data. They are unclear, because the costs will occur in future, for example in the next 6 years.

We sub-divide cost calculations due to the time when we make them: pre-calculation, interim-calculation and post-calculation.

(See more at TDiv PR1-C01 and PR1-C02)

See engineering formula

Economic effectiveness asks whether the result of an action fulfils the objective, in this case the economic goal. Sometimes, when it is not possible to measure the grade of fulfilment, it must be estimated. But sometime the fulfilment can be measured - like with coverage.

Imagine that you have a forest stand, which is opened-up with trails that have a distance of 40 meters. One option that you have selected is the standard combination of harvester and forwarder. The problem is that the crane outreach is only 10 m and only 50 % of the stand can be harvested. So, the effectiveness of this solution is 50 %.

You might add a worker with chainsaw, who fells those trees, which are outside the crane reach, towards the trail. Now, all trees can be reached and harvested. The effectiveness climbs up to 100 %.It often happens, that some technical options cover less than 100 %. Therefore, coverage is one attribute to measure the effectiveness.

(See more at TDiv PR1-C01)

The cut-to-length (ctl) method is one of four different functional groups of harvesting methods. The others are fulltree, tree length and chip method.

The character of ctl-methods is that the trees are brought to the forest road in form of short logs.

There are several ways to do it: (a) Trees are converted into logs directly in the stand (i.e., felling-delimbing-crosscutting in a smooth single pass). Or (b) trees can be delimbed inside the stand right after felling, but they are crosscut into logs after the stem lengths have been pre-skidded to the trail. Or (c) one may pre-skid full trees to the trail and perform there the delimbing and cross-cutting – so they are extracted as logs. After extraction (d), the logs can be transported directly to the factory as such or turned into chips before transport.

(See more at TDiv PR1-B07)

See plastic and elasticdeformation of soil

The term "degree of mechanization" is commonly used, but the content of this term varies extremely. After a long discussion, the authors of "Technodiversity" have agreed to the following, complex definition:

In case of one single subprocess 

It can have three degrees:

• Manual work: Everything is done by human or animal, as a maximum a hand tool is used.    
• Motor-manual work: The energy is coming from a machine that is handled by  a human. Thus, the weight is limited. Typical examples are the work with a chainsaw or with a brush-cutter. 
• Mechanized work: When the machine is self-propelled, the limitation of the weight is much lower. As a consequence the machine can have more power and can be optimized for the task. Mechanized work can be subdivided into several steps:

  • Simple mechanized work offers increased power and mobility, but all auxiliary functions are done by humans. Example: a cable skidder can move larger loads than a human can, and does that at a higher speed. But the attachment of the logs must be done manually by the operator.

  • When the machine also takes over the auxiliary function to handle the object by means of a crane or a grapple, e.g., but all actions must be steered by the operator, we call it advanced mechanized work. A typical example is a tractor or forwarder equipped with a loader.

  • Actually, mechanized work is developing more and more towards automatic work. We like to subdivide 4 steps of automation:

    • information assistance (by sensors)
    • control assistance (by electro-hydraulic control, e.g.)
    • automation of sub-processes
    • driverless operations

    In forestry, the cut-to-length harvester is an example of a machine that reaches the level automation of sub-processes. Some prototypes try to operate driverless.

  • 

In case of two sub-processes:

Normally, a total harvesting process is a combination of two or more sub-processes. Since each sub-process has its degree of mechanization,  we want to characterize the total process by a degree of mechanization, too. 

This is easy, if the degrees are equal. Then we have a fully manual, a fully motor-manual, or a fully mechanized method. 

If the degrees differ, we take the name of the highest degree and add the adjective "partly". 

"Almost fully mechanized":

In some cases, we need a more differentiated description. Let's explain it with an example: When the distance between trails is wider than 20 m, the harvester that is instructed to stay on the trail cannot fell all trees, because its crane is not long enough. In that case a worker with his chainsaw fells those trees beyond harvester reach towards the trail. Later, the harvester picks the full trees up and processes them.

Here, the most important machines are harvester and forwarder, forming a fully mechanized method. But due to the felling with chainsaw as an additional sub-process, the degree of the total process would turn to partly mechanized. We have the feeling that does not well represent the reality. Consequently, if the sub-process with the lower degree of mechanization is only necessary for a smaller subset of working objects, we can express it with “almost fully mechanized”.

Depreciation is a part of the cost calculation with the engineering formula. It considers the loss of value of a working system during its life span.

Imagine you plan to buy a machine. It is very expensive, so the decision should be made carefully.  If you intend to get a loan from the bank, you need a plan to pay the money back within a certain time. That means: Hour by hour you must put aside a certain sum, which you will transfer to your bank at the end of the month.We call this depreciation.

The lifetime of a tool or machine is limited. There are several reasons for decay:

•       Technical decay (obsolescence) depends on technical progress: when new and better machines appear, your old machine may be no longer competitive.

•       Technical aging (wear) happens when parts of the machine become thin, stiff, inflexible, and break, i.e.

•       In some situations, we have only limited use of a machine, afterwards we will not need it any longer.

•       Or the machine suffers from a “fashion change”, when your technology will become unfashionable, and nobody will be interested in this technology any longer.

Depreciation is the response to the progressive loss of value of your machine. During this time, we must pay back the initial investment.

If we did not borrow the money from the bank, we have taken it from the “investment pool” of our company. We have only changed money into a machine with the same value. When the value of the machine decreases, we must pay back into this pool in order to stay as “rich” as before.

A third argument for depreciation deals with taxes:

Since the taxes are based on the win, we should not forget the hidden costs by the daily devaluation of our equipment.

How do we calculate depreciation?

•       First, we decide how many years the machine will be used.

•       Then we ask, whether it will be possible to sell the old machine at the end of the utilization time. But be careful there! Normally there is some residual value, but we may want to assume that it is 0 and use it as a silent reserve to compensate the higher price for a new machine – due to inflation and technical development.

•       The annual depreciation now is calculated as the initial investment minus the assumed residual value divided by the number of years.

This is called linear depreciation. In fact, real devaluation is not linear (here implied with red or green) but in practical term a linear solution is good enough and it is easier to calculate.

(See more at TDiv PR1-C02)

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

We know that there are days when the same job feels hard, and days when it feels much easier. So, for the same individual the strain can differ. This partly depends on the health, conditioning, tiredness, hunger and time of the day. We call these organic reasons disposition.

(See more under TDiv PR1-E04)

For Technodiversity, we introduce an E-class to specify the complex influence of the standard working method on the strain of work.

The question is, are there any categories that correspond with the special capabilities of the persons? Concerning physical stress, we can deduce them from the degree of mechanization.

These categories correspond with the risk of an accident, too. In general, work safety improves as we progress through the various degrees of mechanization.

Eco-efficiency is a partial objective for decision-making. It asks for the minimal ecological input to reach a certain effect or – with other words – for the maximal effect under a given ecological input. In the technical context the ecological input is the energy consumption and grey energy (for construction, maintenance and final recycling purposes of the machines and sites); for forest technology, the impact to the forest soil by compaction and erosion must be regarded, too.  

Together with its twin ecological compatibility we can assess the ecological suitability that is one sub-objective to find the optimal option. Parallel to the ecological suitability we also should look at the economic and the social suitability. For more information about systematics of decision-making, look at objectives and three-step model of optimization.

(See more under TDiv PR1-A03 and PR1-D02 – D04)

With the ecogram, Technodiversity indicates under which forest conditions a harvesting method can be used. It has the same basic structure like the technogram of the stand. When both graphs, technogram and ecogram, match well, then the method is suitable under these conditions.

Every method has its limitations. Concerning the structure of the ecogram, the following rules will help to find them:

The upper limit is defined by technical restrictions. A harvester, e.g., has its limits because of the length of its crane. Other methods are limited by the maximum length of the pre-skidding devices. And all methods, where machines must drive on the soil, cannot work at P5.

To the right side (towards wet soils), the damage on the ground limits any acceptance. Heavy machines are perfect for dry soils, good on fresh soils, and come to their limits with moist soils. If there are aids like bogie tracks or traction chains on the wheels, compatibility moves one column to the right.

The left and lower limits are given by competing methods, that are better for those conditions. No one who can take these alternatives would decide to take the option in dispute, because it is too expensive, too cumbersome or just not necessary for those conditions.

In the figure, the functiogram of an almost fully mechanized method with bogie-tracks for 40 m distance of the trails is shown together with its corresponding ecogram. By the chainsaw, this method is specialized for P3 (= 40 m trail distance), not less and not more. For a fresh soil (T2), the suitability is assessed as very good (star symbol), for moist soils it is good (plus symbol), and for wet conditions it is only limited (minus symbol). Also for dry conditions we decided to give a minus symbol, because there a method without bogie-tracks is better.

Matching the technogram of the stand and the ecogram of harvesting methods, those methods can be found that are best under the given conditions.

The problem is, that the ecogram of a working method must be composed by the ecograms of the sub-processes. Here, some rules must be regarded.

(See more at TDiv PR1-D04 and D05)

Ecological compatibility is a partial objective for decision-making. It looks for the disturbances in nature and environment, which will not be regenerated in reasonable times, and wants to minimize them.

Since not all effects will occur at every action, but the likelihood is high that any damage will happen, we have to think about risks and side-effects. 

Together with its twin eco-efficiency we can assess the ecological suitability that is one sub-objective to find the optimal option. Parallel to the ecological suitability we also should look at the economic and the social suitability. For more information about systematics of decision-making, look at objectives and three-step model of optimization.

(See more under TDiv PR1-A03 and PR1-D01)

Ecological efficiency see eco-efficiency

In a study from 2009, Kleinhückelkotten et al. have found five different groups of people who use the forests for recreation. One of them are the ecological forest romantics, the others are holistic forest friends, pragmatical distant persons, self-centered forest users, and indifferent persons.

The ecological forest romantics represented 16% of the sample. They regard forests as highly organized natural organisms that require our full care. They believe that conventional forest operations are a threat and should be modified for additional sustainability.

This group of visitors has very little interest and acceptance for modern forest technology and is often vocal about it. 

(See more under TDiv PR1-E02)

Ecological suitability is one sub-objective of the decision-making process. It corresponds with the ecological objective of the company in a means-end-relationship: The means should be developed in a way that it fulfills the end that is given by the objective of the company.

The ecological suitability is subdivided into eco-efficiency and ecological compatibility. On the same level are two competing sub-objectives: the economic and the social suitability. The relationships between them can be organized by the general concept for technical operations that is given by the company.

(See more under TDiv PR1-A03 and -D01)

Economic effectiveness is a partial objective for decision-making. It assesses the effect of any action against the background of what is intended to reach. So, other words for effectiveness can be functionality or coverage.

Together with its twin economic efficiency we can assess the economic suitability that is one sub-objective to find the optimal option. Parallel to the economic suitability we also should look at the ecological and the social suitability. For more information about systematics of decision-making, look at objectives and three-step model of optimization.

(See more under TDiv PR1-A03 and PR1-C01)

Economic efficiency is a partial objective for decision-making. It asks for the minimal input to reach a certain effect or – with other words – for the maximal effect under a given input.

Together with its twin economic effectiveness we can assess the economic suitability that is one sub-objective to find the optimal option. Parallel to the economic suitability we also should look at the ecological and the social suitability. For more information about systematics of decision-making, look at objectives and three-step model of optimization.

For any real process, after finishing and collecting all costs the efficiency of the process can be measured. But in advanced, we must calculate the costs with a lot of uncertainties. To do this, the engineer formula is a method to calculate the costs as likely as possible.   

(See more under TDiv PR1-A03 and PR1-C01)

Economic suitability is one sub-objective of the decision-making process. It corresponds with the economic objective of the company in a means-end-relationship: The means should be developed in a way that it fulfils the end that is given by the objective of the company.

The economic suitability is subdivided into economic efficiency and economic effectiveness. On the same level are two competing sub-objectives: the ecological and the social suitability. The relationships between them can be organized by the general concept for technical operations that is given by the company.

(See more under TDiv PR1-A03)

Effectiveness is one of thepartial objectives when we look for the suitability of any option to find the optimal option. It explains in which extent the effect of any option fulfils the demands that are given by the corresponding sub-objective. For example, when we want to fell and extract trees from any harvesting site, the effectiveness is 100 % if we can extract all trees. If not, it will be worst.

Effectiveness in the decision-making model for forest harvesting operations appears under three different contexts:

·       The economic effectiveness asks whether the operation fulfils the economic demands. Like in the example above, the effectiveness describes whether everything that we want to reach will be reached. So, economic effectiveness means functionality, technical coverage…

·       The ecological effectiveness deals with the ecological risks and side-effects of the operations. The drift is towards the optimal solution without any risks or side-effects. We call it ecological compatibility.

·       Also the social effectiveness deals with risks and site-effects, but in this case they are measured against the societal needs. Here we see the disturbance of people who want to recreate in the forest, who look for cultural demands and so on. We call it societal compatibility.

(See more under TDiv PR1-A03)

Effectiveness, economic see economic effectiveness

Efficiency is one of thepartial objectives when we look for the suitability of any option to find the optimal option. If more than one option leads to a comparable effect, the decision maker looks for that one that promises the lowest input. Or when he wants to invest a certain input, he hopes to receive an output that is as high as possible. These are two opposite poles of efficiency; between them all combinations are possible.

In the decision-making model for forest harvesting operations, efficiency occurs under tree contexts:

·       Economic efficiency (or simply efficiency) demands to spare money. The cheapest option is the best under point of view of efficiency. It can be calculated by machine cost calculation.

·       With the ecological efficiency, the ecological input is the crucial “currency”. For example, energy consumption and grey energy can be seen as important criteria. In case of forest operations, the forest soil, which is compacted by the machines, can be seen as the most important input variable. We call it eco-efficiency.

·       The word social efficiency sound hard and somehow anti-social. But it means that the social resource, the workers, are treated with care so that they don't suffer from the operations. Therefore, we prefer the word ergonomics, which means the health care and safety from accidents during the work. 

(See more under TDiv PR1-A03)

Efficiency, ecological see eco-efficiency

see economic efficiency

Efficiency, social see ergonomics

See natural regeneration of soil

Depending on local economy, underemployment can be an issue of societal compatibility. In that case, forestry may offer an opportunity to unskilled workers and therefore it represents an asset for the local society. For that reason, decision makers may favor labour-intensive logging systems that do not require specialized workers as mechanized systems do.

A good attribute to measure this is the degree of mechanization:

As a tendency, fully manual methods achieve very low productivities but offer employment to workers with low qualifications.

Partly motor-manual methods demand for better skills but achieve a relatively low productivity, too.

Fully motor-manual and partly mechanized methods need well educated and skilled workers, so that not every job-seeker is viable.

Fully mechanized work has the lowest employment potential, since it relies on very few but highly educated operators.

The engineering formula covers all different sorts of costs that a working system has during its life span. It calculates the costs per hour. Since in real life during this hour some short interruptions can happen, the calculation is made for PMH₁₅, which means one hour including short breaks until 15 minutes.

The cost components are depreciation, interest costs, repair and maintenance costs, variable costs and labor costs.

(See more at TDiv PR1-C02)

Ergonomics is a partial objective for decision-making. It tries to lower the stress and strain that derives from the working site and to minimize the danger to be hurt by accidents or any occupational disease (it does not cover the option to spare a working site at all, when the reason is to spare the labor costs).

Together with its twin societal compatibility we can assess the social suitability that is one sub-objective to find the optimal option. Parallel to the social suitability we also should look at the economic and the ecological suitability. For more information about systematics of decision-making, look at objectives and three-step model of optimization.

(See more under TDiv PR1-A03 and PR1-E04)

Extraction is one of the main functions of harvesting and means the change of the position of the working object. In forest operations we differentiate three steps

-       from the felling site to the next facility that is provided for transport purposes like a strip road, trail or corridor; we call this first step pre-skidding or in case of a yarder lateral yarding; if the machines are allowed to drive on the forest floor without limitation to any trails, this step of pre-skidding is obsolete

-       alongside the trail to the landing where the logs can be handed over to the long-distance transport; we have different words for this step like skidding, forwarding and yarding

-       from the landing or storage in the forest to the customer; this long-distance transport uses public roads, waterways, railways etc.; in Technodiversty it is not elaborated as well, because the project concentrates to the processes inside the forest.

The feller is a self-propelled machine which is designed to fell trees (buffer 10 to 21). Alternatives, which are commonly used in forestry for the sub-process of felling, are the chainsaw as a tool, and the harvester as a machine.

The feller itself can only take over the function of felling and pre-skidding over the distance of the crane length, further steps must be performed by other forest machines e.g., the processor.

A shear or saw device, which is attached to the end of the feller´s hydraulic arm, cuts the tree off from its roots and bunches the full trees.

Since all the steps of felling are executed by the feller and the human only needs to control the movements, the work with the feller is classified as advanced mechanized work.

(See PR1-B03 and B07)

see solutions for felling

A felling damage happens by the felling and processing of a tree to the tree itself and to neighboring trees and values.

With motor-manual felling (a), the tree falls down forming a quadrant.

The axis of this movement originates at the aptly, called “hinge”. As it falls, the tree develops a high dynamic force.Any obstacle in its way is in serious danger. If another tree is hit, it will be broken or wounded. If that occurs, a damage has been inflicted on the environment - not to the human being itself. Very often, this devaluation is not important: yet, if the injured tree is particularly valuable, then an important financial damage has also occurred.

With machine felling (b) – using a feller or a harvester – , the tree is cut from its root, lifted a little bit and pulled towards the machine position. As a result, the wide tree crown falls mostly in the void left by the cut tree – where now there is little that could be damaged.

Experience shows that by this procedure, the risk of inflicting felling damage to the remaining stand has turned nearly to zero.

If the machine is strong enough to lift the tree upright (c), it can move it out of the stand and lay it down where there is no risk of damaging anything. This procedure is applied when the driver wants to spare clumps of regeneration developing under the cut tree.

This proves that machines are able to reduce site damage, opposite to the common feeling of public, provided that the driver is sufficiently competent and careful.

(See more at PR1-D01)

See rosette

The forwarder is a rubber-tired or tracked machine used for the extraction of trees. Other machines that can be used for this sub-process are the cable skidder, grapple skidder, clam-bunk skidder, farm tractor equipped with a forwarding trailer, and cable yarder.

The forwarder is mainly utilized for the extraction of short logs with a maximum length of 6 m (so called crane length).

An integrated grapple loader lifts the logs onto the forwarder, where the logs are held by stanchions. Since the load does not touch the ground during the transportation process from the trail (buffer 32) to the forest road (buffer 33), this type of extractions is assigned to the carrying extraction.

The forwarder is commonly used in combination with a harvester. The combination of both machines is called “fully mechanized cut to length method” or short “cut to length method”.

A farm tractor equipped with a forwarding trailer is also used in some cases as a substitute for the forwarder.

The work with the forwarder is described as advanced mechanized work.

(See PR1-B03 and B07)

The full tree method is one of four different functional groups of harvesting methods. The others are tree length, cut-to-length and chip method.

With the full tree method, trees are cut down and then taken as full trees to the forest road.

There (a) they can be loaded on special trailers and transported as full trees to the factory. Otherwise (b), once at the forest road, trees are delimbed and topped and transported to the factory as tree lengths. Or (c) they could also be crosscut at pre-defined lengths and transported to the factory as logs. Or finally (d), the logger opts for chipping the whole trees rather than delimbing and crosscutting them.

(See more at TDiv PR1-B07)

See manual method

See mechanized method

See motor-manual method

The functiogram is one possibility to describe a harvesting method in forestry. In Technodiversity, it is used as standard visualization for processes and methods.

From LÖFFLER et al. we have adopted the columns, where the location of the action is visualized:

•       Stand

•       Strip road, trail, corridor

•       Forest road

•       Factory

From top to down we added the steps leading to state change:

• Complete tree
• Full tree
• Tree length
• Log
• Chips

In combination of both, we get a ‘road map’ of different paths, through which we can step forward from the top left corner (the complete tree) to the comfortable right end (i.e., the desired product).

Technical operations are expressed by colored arrows. Each sub-process ends up with a buffer that is expressed by a dark button. Normally a process is a combination of two or more sub-processes that are concatenated. Each sub-process can be named by a pictogram of the most important actor like a machine, an animal or a hand-tool. If necessary, additional information can be made by pictures or words.

As one example, the fully mechanized method with harvester and forwarder is shown here.  

The harvester performs the following tasks: fells the tree, moves the full tree to the trail (pre-skidding), delimbs the tree and cross-cuts it into shorter logs. Finally, the logs are stored alongside the trail as a small pile – i.e., a buffer (dark button). Later on, the forwarder loads the logs, carries them along the trail to the landing at the forest road and unloads the logs. Here again a buffer is formed (second dark button). The truck loads the logs and delivers them to the user plant.

On the basis of a functiogram, the harvesting method can be subsumed under one of the following functional groups: full-tree method, tree-length method, cut-to-length method or chip method. The combination of the degrees of mechanization of each sub-process gives the degree of mechanization of the total method. In our example, we have a fully mechanized cut-to-length method.

(See more at TDiv PR1-B06)

Due to the confusing number of different harvesting methods, there is a need to define functional groups of them where some crucial attributes are the same. One possibility that is often used in practice is to subdivide the methods by the form in which the tree arrives at the forest road:

-       as a full tree = full tree method

-       as a tree length = tree length method

-       as a short log = short wood or cut-to-length method

-       or as chips = chip method.

(See more at TDiv PR1-B07)

Functionality describes whether any systems functions in a way that it fulfils the demands. In our technical context, it may be seen as synonym for economic effectiveness.

Functionalize see functionalizing

Functionalizing is the first step of the three-step-model of decision-making in forest technology. The second step is localizing and the third one is individualizing.

The first step aims at finding and designing all harvesting processes that can work under local conditions and technical constraints of the stand. Here, machines that are available and operators, who are available, are combined to working methods that can be assumed to do the demanded job. In order to expand the search space as large as possible, several options should be selected that differ greatly from one another (different machines, different degrees of mechanization etc.). And one option should never be forgotten: the option to do nothing, the so-called zero-option.

(See more under TDiv PR1-A04 and TDiv PR1-B01 to B07)

Functions can be divided into two groups: Main functions and auxiliary functions.

Main functions influence directly the working object. Again, we have two sub-groups: those that change the state of the object and those that change its position.

Auxiliary functions help to manage the process, but don’t have a direct input to the working object. On to highest level, we have two auxiliary functions: the handling that is a more physical sub-process and the steering that operates the process and deals with data.

In tree harvesting operations, the main functions are the harvesting and the extraction. Though the auxiliary functions are important, too, in Technodiversity they will not be treated further.

General concept is a guideline for a company that gives a certain drive to the operations in a field. For example, a forest company may have different general concepts for silviculture, for hunting, for nature conservation activities, e.g. For technical operations, it should also formulate a general concept.

Like the ultimate goal for the total company, the general concept has two dimensions:

·      For internal decision-making situations it clarifies priorities or preferences between the sub-objectives or partial objectives. Thus, it improves the transparency and operationality of the decision-making process in this field.

·      For external use it should explain with simple words the focus how this company sees its operations. It can be regarded like a motto that explains the typical behavior of the company.

(See more at PR1-A03)

The grapple skidder is a rubber-tired or tracked machine used for the extraction of trees. Other machines that can be used for this sub-process are the cable skidder, clam-bunk skidder, farm tractor equipped with a forwarding trailer, forwarder, and cable yarder.

The grapple skidder is mainly used to extract full trees from the trail (buffer 21) to the forest road (buffer 31).

In contrast to the clam-bunk skidder, the grapple skidder assembles and holds its load with a hydraulic grapple, that opens downwards. 

Like all skidders, the work with the grapple skidder is declared as advanced mechanized work.

(See PR1-B03 and B07)

The hand saw is used as a tool for dividing an object by sawing it. Characteristic for the hand saw used in forestry are the bar handles at each side of the saw blade. As an alternative to the axe the hand saw is operated by two people, each standing at a handle. By alternately pulling the hand saw a kerf is formed in the complete tree which leads to the felling of the tree at a certain point (buffer 10 to 11).

Since only human force is needed to saw with the hand saw, it is assigned to the manual work.

Other harvesting tools, the use of which is assigned to manual work, are the axe, the machete, and the bush knife.

(See PR1-B03)

Handling is one of the auxiliary functions of harvesting. It does not directly change the state of the working object or its position, but brings the tools, machines and objectives together. A very effective tool for handling is a crane with a hydraulic grip that allows the operator to stay apart from the object and therefore out of the risk zone. Though handling is a very effective and efficient area for improving the working site, it is not mentioned intensively in Technodiversity.

The harvester is a self-propelled machine that takes over all partial steps of the timber harvest, which are felling, delimbing, measuring, cross-cutting and bunching (buffer 10 to 21, 22 or 23). There is no other machine that combines all these sub-processes. Along the crane it takes over a short pre-skidding as well (buffer 21 to 22).

The harvester is a widely used instrument in wood harvesting.

(Photo BOKU)

Depending on whether the harvester is having the same felling and processing unit (all functions can be performed with one grab of the tree), or the processing unit is separate from the felling unit (functions need to be performed with more than one grab of the tree), the harvester is called one- or two-grip-harvester. Since today most machines on the market are one-grip-harvesters, this differentiation gets less important. 

Currently, other prototypes are being tested in addition to the classic harvester construction. They differ from the classic model in the way they move, which should enable these models to be used in very steep terrain or to minimize the soil compaction of the harvester (See lecture B06: Harvester Highlander (Konrad, Austria), Prototype walking machine (Plustech Oy, Finland) or Prototype Portalharvester (TU Dresden, Germany)).

(Photos PLUSTECH and TUD)

Since every step of timber harvest is executed by the harvester and the operator only needs to control the movements, the work with the harvester is classified as mechanized work.

Harvesting is one of the main functions of harvesting. The term has two meanings: As a general term it includes felling of trees, processing to a transportable product and the extraction from the forest to the customer. As a more precise term it only points to the change of state of the product, while the extraction is not included.

In this narrow sense the harvesting includes the sub-functions felling, delimbing, topping, cross-cutting or bucking and chipping. All other sub-functions except the felling is called processing as well.

Different sub-processes can be assembled into a full chain, when the end of the foregoing sub-process matches the needs of the following sub-process. In the functiogram, such a so-called ‘buffer’ is symbolized by a dark button.

In real life, when we plan any job, we know where it begins and where it should end. Between these two poles we have a lot of options to reach this aim. But as soon as we define one specific sub-process, the list of viable sub-processes becomes much shorter.

For example, we want to fell trees and process them into short logs, which are stored at the forest road. This means that we start with buffer 10 and end up at buffer 33. Here we have more than 5 options to reach this goal. But when we decide to use a forwarder for the extraction tasks, the degree of freedom decreases, because the forwarder is specialized for extraction from 23 to 33 (it is good for short logs). To finalize the method, we only need to fill the gap between buffers 10 and 23. Then, out of our initial more than 5 options, only 3 are left.

(See more at TDiv PR1-B07)

In Technodiversity, we prefer to visualize harvesting methods by a functiogram. For naming we have found following convention:

The noun describes the functional group of harvesting like full tree method, tree length method, cut-to-length (ctl) method or chip method.

An adjective declares the degree of mechanization like (fully) manual method, partly motor-manual method, (fully) motor-manual method, partly mechanized method, and fully mechanized method.

As an example, the functiogram shows the fully mechanized ctl-method.

(See more at TDiv PR1-B06 and B07)

In a study from 2009, Kleinhückelkotten et al. have found five different groups of people who use the forests for recreation. One of them are the holistic forest friends, the others are ecological forest romantics, pragmatical distant persons, self-centered forest users, and indifferent persons.

About 22% of the sample was classified as holistic forest friends. These people like natural forest structures and believe that modern forestry will assure sustainable yield of products and sustainable forest functions. This group is relatively comfortable with forest technology.

(See more under TDiv PR1-E02)

The horse or mule is a tool being used for the pre-skidding of full trees (buffer 11 to 21) and tree length (buffer 12 to 22) and for the pre-skidding and skidding of logs (buffer 13 to 23 or 33).

Horses work on more or less flat terrain and drag the load, while mules are used in steep terrain and prefer to carry the logs. The work with the horse or mule is classified as manual work.

A classic combination in which the horse/ mule is being used is the “Tree length method using chainsaw, horse, and tractor” also known as “Partly mechanized tree length method”.

In a study from 2009, Kleinhückelkotten et al. have found five different groups of people who use the forests for recreation. One of them are the indifferent persons, the others are holistic forest friends, ecological forest romantics, pragmatical distant persons, and self-centered forest users.

With 18% of the total, the indifferent persons form a relatively large group. They feel no emotional connection with forests at all. If they talk about forestry, they assume that forestry is too primitive for them. Often, they don’t accept that forestry earns money with forest products. Fortunately, members of this group will seldom visit a forest.

(See more under TDiv PR1-E02)

see individualizing

Individualizing is the third step of the three-step-model of decision-making in forest technology. The first step is functionalizing and the second one is localizing.

With the third step, one extracts from the remaining processes that option that offers the best fit with the individual aims of the decision-maker. It will be one of the technical processes, but it can also be that the zero-option is the best.

(See more under TDiv PR1-A04 and PR1-F01 to F05)

Interest costs are a part of the cost calculation with the engineering formula. They consider the costs that have to be paid back to the bank for borrowing the money. Normally, the interest is indicated as a percentage of the borrowed sum per year.

In reality, it is calculated monthly on the base of the actual residual debt. So, it becomes less from month to month. In the last month it is nearly zero. Taken as the grand average, interest is calculated over half of the borrowed sum.

Thus, we can approximately calculate the interest costs with

•       the price of the initial investment

•       divided by 2 (to reach the average)

•       times the interest rate in percent.

(See more at TDiv PR1-C02)

The interim calculation is a part of the cost calculations that a manager must do during the work life of a machine or working system.

The task of the interim calculation is to check whether the preliminary estimations of the system costs were realistic and can be approved by the real work of the system. If there are deviations, it is necessary to calculate newly and to correct the data for the further use of the system. In extreme situations it can be optimal to finish the utilization of the system earlier than planned and to sell it if possible, in order to limit the economic damage.

This seems to be simple, but it is not:

In contrast to the pre-calculation, where the costs are calculated as average over the total planned life span, now the real cost curves are observed. The experiences with the curves of repair and maintenance costs of written-off machines show that they vary extremely due to the age of the machine. So, in order to find a realistic view from the machine, the real costs must be compared with the an estimation how the cost curves normally will behave.

(See more at TDiv PR1-C01 and PR1-C05)

Labor costs are a part of the cost calculation with the engineering formula. They consider the wage costs of the operator plus all additional costs.

Here we should be careful:

If the operator only works with that machine, we can take the total costs of this worker (including assurance etc.) over the year and divide them by the same time of productive utilization “m” as we have for the machine.

However, a driver or worker often operates two or more machines, in which case it is easiest to calculate his/her costs per hour and then conduct all the machine cost calculation on an hourly basis.

As we stated before, labor costs have two main components:

•       w = gross wage

•       s = social costs thatmust be covered by the employer like insurance, wage costs during unproductive times due to holidays, traveling expenses etc. (but not his taxes). They are normally indicated as percentage of the gross wage.

The percentage of social costs is highly variable from country to country. In Germany, e. g., it depends mainly on the company:

•       in private forest companies it is about 80-110 %

•       in public forest administrations it often reaches 130 %. 

(See more at TDiv PR1-C02)

See rules and laws for forest operations

Levels of decision-making are normative, strategical, tactical, and operational. This follows a traditional differentiation in military (definitions by Carl v. Clausewitz 1780-1831), but today it has been taken over by management schools for civil purposes as well.   

On each level different types of decisions must be made. The levels are corresponding with each other and are organized in a hierarchical order. Persons on the next lower level need to be informed about the decisions that are made on the next higher level in order to do their jobs in a convenient way.

(See more under TDvi PR1-A05)

see localizing

Localizing is the second step of the three-step-model of decision-making in forest technology. The first step is functionalizing and the third one is individualizing.

The second step checks for any local constraints to their deployment and leads to the exclusion of non-compatible options. The criteria are the economic suitability for the company (effectiveness and efficiency), the ecological suitability for the local environment (ecological compatibility and eco-efficiency), and the social suitability for the local population (societal compatibility and ergonomics).

For any operational method, the tools and machines as well as the working steps are fixed. But sometimes the worker does not exactly what he is asked to do. Maybe he invents his own sequence of steps or he works in a way that conflicts with any safety rules – then we call it the manner of working.

Since the worker is the one who has the most experience with the working situations, it can happen that his manner of working leads to an improvement of the standard operational method. But if he breaks any legal limits or safety rules, then this manner cannot be accepted.  

(See more under TDiv PR1-E03)

In Technodiversity, the total harvesting process normally is seen as a combination of several sub-processes. Each sub-process has a certain degree of mechanization. The degree of mechanization of the total method is given by the combination of these single degrees. There are five degrees of mechanization: (fully) manual method, partly motor-manual method, (fully) motor-manual method, partly mechanized method, fully mechanized method.

If there is no power equipment in any sub-process, say both sub-processes are done by manual work, the method is a fully manual method.

Fully manual methods are not unusual in developing economies or in part-time work.

The word fully underlines the character of the process, but it can be missing.

(See more under TDiv PR1-B04 an d B05)

The term manual work describes the degree of mechanization of a technical operation. Other degrees are motor-manual work and mechanized work.

In Technodiversity, a graphical method to find the optimal harvesting method is supposed.

The technical conditions of the forest stand are represented by the technogram with the sides T-class (trafficability due to the moisture of the soil) and P-class (productivity of the stand). Each stand falls exactly into one field, in the example it is T3-P3; but under dry or wet conditions it can move to left (dryer, T2) or right (wet, T4).

As one possible harvesting method, the functiogram of a almost fully mechanized ctl-method with bogie-tracks is shown. In the ecogram, it has its optimum at T2-P3, but is good under T3-P3 and limited under T4-P3 and T1-P3.

Matching both graphs shows that the method is very good under dry conditions, but also good under normal conditions in this stand. In combination with the ecograms of other technical options, this may be a basis to select the optimal option.

(See more at TDiv PR1-D04)

In Technodiversity, the total harvesting process normally is seen as a combination of several sub-processes. Each sub-process has a certain degree of mechanization. The degree of mechanization of the total method is given by the combination of these single degrees. There are five degrees of mechanization: (fully) manual method, partly motor-manual method, (fully) motor-manual method, partly mechanized method, fully mechanized method.

If all sub processes are done with self-propelled machines, the method is a fully mechanized method or easier: mechanized method.

Typically, that occurs when the harvester-forwarder team or the feller-buncher and skidder team are employed.

(See more under TDiv PR1-B04 and B05)

When the engine is no longer portable but needs a carrier, we call that mechanized work. Because the weight of the machine is no longer limited by the weak carrying power of humans, the machine can be developed without any mass restrictions.

Currently we observe a steady increase of machine weight, in the pursuit of higher power and efficiency. But that does not go without any ecological consequences…

Mechanized work can be further subdivided into simple mechanized work, advanced mechanized work and automatic work.

(See more at TDiv PR1-B04)

See working method

This is one option to find the best option. Others are the monetarization, utility analysis, AHP, and optimality curves, for example. 

Next step is focusing on that single criterion that is the most important for the decision-maker. In real life, it often will be the monetary efficiency. If so, the decision-maker will select that one among the surviving options that offers the highest income.

Option 3 does not fulfill the ecological compatibility requirement because it needs a higher trail density than is considered acceptable. Options 1 and 2 score quite low in terms of societal compatibility due to the activities on the forest roads. And the income of the zero-option does not fulfill the economic expectations. At the end, no option is good enough.

The decision-maker  now has two possibilities: to look for better options or to lower his demands.

After that operation, the edge of option 1 (pT skidder) decreases, but it still remains the most profitable.

This is one option to find the best option. Others are the minimax-rule, utility analysis, AHP, and optimality curves, for example. 

Some economists point out, that evaluations deal with values. And values should be quantified in terms of currency, so that the easiest end is to add all values… That amounts to transfer any assessments to Euros or dollars. There are some models to do this in a fairly scientific way. 

Taking an example, we must invent some estimated figures. If those are accepted, then option 3 is best, and option 2 seems to be surprisingly good, too. But in some cases, we pass the limits of fairness and modesty. How to calculate the value of human health? …or of eco-efficiency? So, for as attractive this idea may sound, in practice it generates significant controversies.

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

We know that there are days when the same job feels hard, and days when it feels much easier. Besides the organic disposition, the motivation of the worker is crucial for the strain.

Motivated workers experience their work easier and suffer less from strain symptoms.

Disposition and motivation together form the readiness for work. While capability is the potential of any given person, readiness is the percentage of that potential actually activated.

(See more under TDiv PR1-E04)

In Technodiversity, the total harvesting process normally is seen as a combination of several sub-processes. Each sub-process has a certain degree of mechanization. The degree of mechanization of the total method is given by the combination of these single degrees. There are five degrees of mechanization: (fully) manual method, partly motor-manual method, (fully) motor-manual method, partly mechanized method, fully mechanized method.

If both sub-processes are done by motor-manual work, the total process is a fully motor-manual method (or simpler: motor-manual method).

Examples are seldom; in practice we sometimes see a chainsaw and a motor-manual winch.

(See more under TDiv PR1-B04 and B05)

The term machine work describes the level of mechanization of a technical operation. Other levels are manual work and mechanized work.

Because manual work is tiresome, people have always looked for some external source of power. In modern times, the obvious step is to use an engine to drive the tool – hence the appearance of portable machines.

In forestry we call that „motor-manual work“ (an original forest definition that describes the situation well).

Typical examples of motor-manual work are the work with a chainsaw or with a brush cutter.

(See more at TDiv PR1-B04)

see horse

See natural regeneration of soil

See natural regeneration of soil

Any compaction of a soil can be recovered by physical power (like frost or mechanical lifting) or by biological activities (roots, micro-organisms, worms…). Biological activities get their power by life processes that depend on breathing. Due to this reason, the measurement of carbon dioxide (CO₂) in the pores is a valid indicator for biological actions.

In biologically active soils the percentage (on volume) of CO₂ is about 0,3%, a bit higher than in the outside air.

Directly after traffic we observe a quick increment of CO₂ in the soil pores.But after a couple of hours the percentage of CO₂ can go down again. We believe that in this case the pores in the soil are opened again by biological activities from all directions.Thus, though the specific soil pressure may be high, when the affected volume of soil is small and the lateral area is large as we have it with human footprints or animal steps, then recovery happens very quickly.

When a light tractor (< 5 t) drives on the soil, the impact is higher. For the first few months, the percentage of CO₂ is significantly higher, but there is a tendency to recovering during the first year. Of course, much depends on the gross weight of the tractor, the number of passes, the soil type, the moisture… so, driving with tractors seems to approach the limits.

When a harvester, which has a gross weight > 15 tons, drives on the soil, the impact is so high, that the percentage of CO₂ increases in the first few months and may exceed the 1,0 %_vol threshold. Over several years there is no clear tendency towards recovery.

This tendency gets clear as soon as heavy forest machines drive on the soil several times. Here the soil shows no tendency for recovery.

(See more at PR1-D02)

On the normative level of decision-making, persons like the owner of the company, the forest owner or in case of a state forest the parliament defines the objectives of all actions. Since in most cases there are more than one objective, collaborators need a guideline how to deal with competing or contradicting objectives. Very often a general guideline is given for external advertisement as well as for the internal communication, where this guideline allows all decision-makers in the company to streamline their decisions with the wishes of the top-management.

(see more in TDiv PR1-A05)

Objectives of forest operations depend on the objectives of the decision-making body, which normally is the forest owner. He follows his individual set of objectives, only.

In a first glance we can assume that there will be an overarching task to maximize the income of the owner. But things should be differentiated a bit more:

·      The material objective of any forest and herewith also for every forest owner is to care about the forest and to deliver services and goods in a sustainable way. This defines the typical character of this branch, its restrictions and limitations.

·      The manager of the forest must regard all these limitations. But inside these restrictions and natural limitations, different options are given to optimize the success. Choosing the best option is the original job of the manager. But what is the best? Here the overarching task may be to maximize the income of the owner, but in some cases, there are diverging priorities. The success of the manager is measured on the background of this formal objective.

So, not only one objective is followed but a set of more than one. Normally we work with three objectives, economy, ecology and social aspect. The relationship between them can be fixed with an ultimate goal that is typical for the forest owner resp. company.

Since the objectives and the ultimate goal are valid for all actions of the company (like silviculture, hunting, nature conservation and harvesting, e.g.), they must be broken down for each field. For each objective we are looking for one corresponding sub-objective that defines the suitability of the means to reach the objective. So, the sub-objectives for forest operations are economic suitability, ecological suitability and social suitability.

Each sub-objective can further be subdivided into two partial objectives, the effectiveness and the efficiency. Thus, at the end we have exactly 6 partial objectives that in common describe the suitability of operational options. We call this step the assessment as the objective part of the decision-making process.

Like we have seen with the ultimate goal, also the sub-objectives can be brought to a relationship by the help of a general concept. A well-developed general concept for forest operations declares the priorities and preferences of sub-objectives and partial objectives in order to find a final evaluation of the best option.

(See more in TDiv PR1-A02 and A03).

Operational method describes a special aspect of a working method. While the working method gives an overview on machine, input and output of the method, the operational method concentrates on the work of the operator. It asks what he has to do, in which sequence he must go on, what he must look for…

But sometimes the worker does not exactly what he is asked to do. Maybe he invents his own sequence of steps or he works in a way that conflicts with any safety rules – then we call it the manner of working.

(See more under TDiv PR1-E03)

On the operative level of decision-making, persons fell a lot of daily decisions during the operation to reach the assigned tasks. This happens on all management levels. But concerning forest technology and its impact to forests, mostly the forest workers and operators with their machines make things happen. So, collaborators on this practical level have a high and direct influence to the technical effects and damage to products, forest stands and soils by their operative decisions. 

The term “operative” should not be confused with “operational” that means that an objective is defined with clear results, responsibilities and appointed days.

(see more in TDiv PR1-A05)

This is one method to find the best option. Other methods are minimax rule, monetarization, utility analysis, and AHP, for example.

This method that has been developed at Harvard University. With this method the efficiency and the effectiveness of each option are compared against each other. 

This works well when there is only one effectiveness and one efficiency. Since we have three criteria, we need to adapt it a bit: 

• We combine all efficiencies to one overall efficiency
• and all effectivenesses to one overall effectiveness.

Here, we use the the same example as with the other decision making methods and also the same weights.

Option 3 is located on the highest optimality curve, while option 1 is the worst option.

(See more under PR1-F04)

From the Saxonian technological map we know the idea to expand the distance between permanent trails when the soils has a high sensitivity.

In Technodiversity, the decision about the distance between skid trails is made by the forest owner. This socio-economic approach gives the full freedom to him, asking: How much of the site’s productive potential are you willing to sacrifice to the technical function?”

Depending on the answers, we introduce five so-called P-classes (for productivity, but it does not only depend on the productivity):

P1: At a stand with low value (rocks, pure sand), any possible damage of traffic is not as important for the owner. Here, traffic may happen.

P2: At a medium-value stand, where the advantages of fully mechanized methods are dominant, up to 20% of compacted soil is acceptable.

P3: At a high value forest stand, where the owner sees the biological needs prior to technical needs, compaction should stay under 10%.

P4: At a stand with a very high value, the technical considerations should be restricted to a minimum, say roundabout 5 %.

P5: Finally, at a stand with an extreme high value, no machine traffic on the floor is accepted.

When we assume that a trail has a width of 4 m, then this corresponds with following patterns of opening-up:

P1: driving is accepted without any permanent pattern = “unlimited”

P2: trails with “20 m” distance

P3: trails with “40 m” distance

P4: trails on old given routes, mostly >80 m distance = “uneven”

P5: no driving with machines outside constructed roads at all.

These P-classes form the Y-axis oft the technogram of a stand as well as the ecogram of harvesting methods.

(See more at TDiv PR1-D04)

In Technodiversity, the total harvesting process normally is seen as a combination of several sub-processes. Each sub-process has a certain level of mechanization. The degree of mechanization describes the combination of these levels. There are five degrees of mechanization: (fully) manual method, partly motor-manual method, (fully) motor-manual method, partly mechanized method, fully mechanized method.

If one sub-process is done by manual or motor-manual work and the other by mechanized work, then the method is a partly mechanized method.

Examples are: chainsaw and skidder, chainsaw and forwarder, or hand tool and tractor.

(See more under TDiv PR1-B04 and B05)

In Technodiversity, the total harvesting process normally is seen as a combination of several sub-processes. Each sub-process has a certain level of mechanization. The degree of mechanization describes the combination of these levels. There are five degrees of mechanization: (fully) manual method, partly motor-manual method, (fully) motor-manual method, partly mechanized method, fully mechanized method.

If one sub-process is done by manual work and the other by motor-manual work, then the method is a partly motor-manual method.

Examples are: chainsaw and horse or chainsaw and extraction by hand.

(See more under TDiv PR1-B04 and B05)

See system performance

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

When the worker can manage his workload independently, he can find the right pace to keep strain at an acceptable level.But there are situations when the strain exceeds that level. For example, when the worker is pushed to reach a certain performance that is beyond his long-term capacity… or when he is so motivated that he does not realize that he is overreaching.

If the actual strain momentarily exceeds this permanent load, it will not be a problem. In real life, this happens very often. It can even improve the training and exercise (conditioning). But at the end of the day there should be a balance between periods of excessive strain and periods of lower strain (recovery). Otherwise, overload will accumulate and result in damage.

(See more under TDiv PR1-E04)

What happens, when a vehicle drives on dry soil?

First compaction:The larger pores collapse, and the soil is compacted.

Relaxation:After the wheel has passed, the elastic component of the soil (roots, pores with compressed gas etc.) will push it back towards its original volume. But the former level is seldom reached.

Subsequent compaction (following passes):When the load is the same as with the former traffic, the compaction and relaxation are as high as before.

Finally, there remains a permanent rut.

(See more at PR1-D02)

The portable winch is used for pre-skidding tree length or single logs from the stand (buffer 12 or 13) to the trail (buffer 22 or 23). Other possibilities to pre-skid logs are by tractor winch, horse/ mule or a human carrying the logs. 

The portable winch is a powered tool that reels in or pays out a cable. To use the reeling function the portable winch gets tied to the base of a tree close to its location. From there the portable winch can fulfill its dragging function as soon as the cable has been fixed to the full tree, tree length or log, that should be dragged.

Because of its light weight, the portable winch causes negligible soil compaction and can be carried to its location by human. Since the portable winch needs to be carried into the stand/ trail by a human, the work with the portable winch is considered as motor-manual work.

(See PR1-B03 and B07)

The post calculation is a part of the cost calculations that a manager must do during the work life of a machine or working system.

The task of the post calculation is to collect all costs that have occurred with this system during its total life span. So, it is only pure statistics. But these statistics give important hints for further calculations, because they serve as experience data and reference numbers for calculations that concern with comparable machines or systems, respectively.

(See more at TDiv PR1-C01)

In a study from 2009, Kleinhückelkotten et al. have found five different groups of people who use the forests for recreation. One of them are thepragmatical distant persons, the others are holistic forest friends, ecological forest romantics, self-centered forest users, and indifferent persons.

In the study, the pragmatical distant persons represented 23% of the total and formed the biggest group. They see the forest primarily as a material resource. They believe that forestry performs well and like it when a forest looks organized and cleaned up. This group supports efficient forest technology and may complain when efficiency is sacrificed to nature conservation. 

(See more under TDiv PR1-E02)

Before we decide to invest into any machine or system, we should try to get a detailed insight to its cost structure. If we use the same scheme for calculation for different options, we can compare the costs of them. So, the calculation scheme is important. Traditionally, we use the engineering formula, which has fife cost elements: depreciation, interest costs, repair costs, variable costs and labor costs.

But before we start to calculate the costs of any sub-process, we need to get an overview over the cost structure of the total process. To do this, we must build up the tree of calculations.

(See more at TDiv PR1-C01)

see solutions for pre-skidding

On the base of the tree types of ruts on soil combined with the behavior of lumps of soil when they are thrown against any surface, the Bavarian State Forest BaySF has developed a practical reference sheet:

•       If you have the type 1 and the soil lump is stable, you may drive.

•       If you have the type 3, then stop driving immediately

•       If you have the type 2 and the soil lump can be formed easily, you should try to drive very carefully:

--      if the ruts stay at type 2, then go on driving

--      if they turn to type 3

---     reduce the load or the tire pressure and repeat the test

---    if they still turn to type 3, then stop!

(See more at TDiv PR1-D03)

The word derives from Latin „procedere“, meaning “to go on”. As a term, „process“  describes what happenswith details about tools and machines, working steps, time consumption, results etc.

As soon as there is any normative implication how the process should be, we talk about a method. When this method should normally be used, we call it standard method.

In detail, we can make a difference between the terms working method, operational method and manner of working.

(See more under TDiv PR1-E03)

Processing changes the state of the working product. In forest harvesting context, processing includes delimbing, topping, cross-cutting or bucking and chipping, but not felling. Felling and processing together are called harvesting (in a narrower sense).

(See more at TDiv PR1-B01)

The processor is a self-propelled machine which is designed to delimb and cut-cross felled trees into logs (buffer 31 to 33 or buffer 32 to 33). Alternatives which are commonly used in forestry for the sub-processes of delimbing and cross-cutting are the chainsaw as a tool, and the harvester as a machine.

The processor can handle multiple functions such as delimbing, measuring and cross-cutting or bunching, but the processor cannot fell trees. Therefore, the work of the processor follows the felling of the tree and is mainly performed on central places, where full trees are arriving, or on the forest road.

Processors were the technical stage before industry was able to build harvesters, Today the task of a harvester can be done by harvesters as well. Only in combination with cable yarders, we se specialized processors.  

The work with the processor is assigned to the mechanized (automatic) work.

See system performance

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

We know that there are days when the same job feels hard, and days when it feels much easier. This depends on the disposition (physical variance) on one hand and the motivation (mental variance) on the other hand. Both together form the readiness for work.

While capability is the potential of any given person, readiness is the percentage of that potential actually activated.

(See more under TDiv PR1-E04)

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health.

If the strain overruns the permanent work load, it may have two consequences: On one hand the body is pushed to improve its capacities. We use this effect for active training and conditioning. But on the other hand, acute or chronic damage can occur. Therefor breaks for recovery are necessary and should actively be provided by the employer.

(See more under TDiv PR1-E04)

One aspect of societal compatibility is the potential to get in conflict with people who seek recreation in the forests. This group of forest users is not homogenous and so their demands are diverse, too. This makes it difficult to fully meet their needs.

Some studies have tried to describe this population of forest users. As an example, we can quote the research work of Kleinhückelkotten, who correlated forest visitor’s characteristics with SINUS-milieus that are widely used in socio-economics. SINUS-milieus try to categorize people  based on the intersection of social class (defined by income as lower or upper class) and the main orientation like  traditional values, believe in modernization or reorientation and experimentation as shown in the figure.

Though these results are only representative for Germany at beginning of this century and cannot be transferred to other countries without adaptations, the basic information seems to be relevant in general. The groups are:

·      22% holistic forest friends

·      16% ecological forest romantics

·      23% pragmatical distant persons

·      22% self-centered forest users

·      18% indifferent persons.

But all forest visitors have one common need: they use the forest roads as their access to the forest and don’t want to be disturbed. consequently, if we keep the roads clear for people to move on them, this can help to improve the acceptance of forest techniques and operations. In Technodiversity, we have invented the S-class that describes the grade of disturbance on the forest road by harvesting operations.

(See more under TDiv PR1-E02)

Repair and maintenance (R&M) costs are a part of the cost calculation with the engineering formula. They consider the estimated costs for repairs and services during the life span of the machine.

Saving money in anticipation of breakdowns and regular planned maintenance has two effects:Have money available when maintenance is needed and to share those costs that occur irregularly with all customers.

From other machines we can get a feeling of how high the R&M costs would be. As a general rule of thumb based on experience, a forwarder needs the same sum for repairs and maintenance over its whole service life span as the initial price of the machine. A tractor takes a bit less, a harvester a bit more. This relationship can be expressed as a factor “r” for repairs.

Now it’s easy to calculate the costs of repair and maintenance:

•       Take the price of initial investment

•       multiply it with factor r

•       and divide it by the number of years that you expect the machine to run.

However, the trend is not linear. Normally, a machine will have very low R&M costs in the first years, then those costs will increase as the effect of wear develops. Therefore, this calculation accounts for the average costs per year over the whole machine lifetime.

Old machines that are written-off and don't cost for depreciation or interest, have a wide space for R&M costs. This is the reason that there is a market for written-off machines.

(See more at TDiv PR1-C02)

See natural regeneration of soil

Risks and side-effects are non-intended effects of our actions.

Side-effects happen, whether we like it or not. Normally this term is preferred for those that hurt us, not for the indifferent or desired ones. The task is to find a way to keep those undesirable side-effects within acceptable limits. To that end, we must improve our system or run a new system selection.

Contrary to side effects, risks may happen but are not inevitable. If they happen, they often cause heavy damage. If, e.g., we a damage that will cost 1000 € - if it happens. If we estimate that this damage will occur in 5 % of all cases, the risk is 1000 € x 0,05 = 50 €.

But be careful with the word damage, because not every change is a damage. To category any result as a damage is an anthropocentric decision:

To be a damage, the change must be is caused by a singular incident, that we can undoubtedly address.

But not all changes disturb the needs of human beings. So, the decision to be a damage is an anthropocentric one. A damage only happens to things that have a certain value for us. This may not be expressed in terms of money: it can also be ecological value, social value or emotional value… the fundamental thing is that value is being lost.

And of course, only those consequences that are not desirable from the human point of view are a damage.

The system, will it be able to reverse it in a reasonable time? If so, we can accept it. But if not, it really is a damage. But what is a reasonable time? In Technodiversity, as a practical approach we have defined reasonable time as the time span between two interventions – like “return time”. For example, for thinning operations 5-10 years, for systems with permanent cover (tropics) 25-40 years. If recovery needs longer than that time span, we may consider the damage as permanent.

When we want to know who is responsible for a damage, we should be careful. In forestry, very often people have the tendency to blame the machines if something goes wrong, because they look strange and aggressive in the nature. But a lot of negative changes have their root cause in a wrong decision. In such case, the machine is not to blame, but the manager, who has taken the decision. But in the case that the machine has caused the damage, we should address it clearly to avoid the same incident in the future.

Damage by forest operations is sub-divided into felling damage and skidding damage.

For decision making, we have several methods to find the best option. Examples are minimax rule, monetarization, utility analysis, AHP, and optimality curves (see PR1-F04). 

They all have in common that the decision is generally made in order to achieve a specific goal. But unfortunately, in real life the goal is not always clear. Therefore, with the rosette the argumentations is turned from head to feet: We ask which option will be the best when we modify the goal.

As an example, we take the same example as with the other decision making methods with the same “scores” as well. And – like with school grades – we accept to treat them like cardinal numbers. That way we can use the mathematical operations of addition and multiplication. Then we play with weighing in order to clarify the effect of changing priorities on option ranking.

When we take economy as the sole criterion (100% weight), we get the following optima:

• for efficiency #3 fC winch-assist
• for effectiveness #2 pT yarder
• for suitability #3 fC winch-assist

• for efficiency #0 zero-option and #1 pT skidder
• for effectiveness #0 zero-option and #3 fC winch-assist
• for suitability #0 zero-option

And finally, if we choose social aspects as the sole criterion (100% weight), we get the following optima:

• for efficiency, effectiveness, and suitability #0 zero-option and #3 fC winch-assist

Until now, it seems confusing. But by introducing some finer transitions, hopefully we shall find a pattern. We will calculate these transitions with the weights:

When we paint all 10 combinations and arrange them to a "rosette", we can put our winners the three poles:

• #0 Zero-option is the winner, when we don’t think at the economic dimension.
• #1 pT skidder wins, when we fade out the ergonomic disadvantages.
• #3 fC winch-assist is the best option under the economic and ergonomic views.

• #3 fC winch assist is nearly the overall winner.
• #0 zero-option is evaluated on a comparable level when economy is not considered.
• #2 pT yarder is the best option when we simply focus on effectiveness.

• #3 fC winch assist is the best option when economy and/or societal aspects play a role.
• #0 zero-option is better, when ecology comes to the fore.

Concerning the basic concept of Technodiversity, decision making should respect local societal needs to keep a certain societal compatibility. In some cases, the local society has developed a specific sensitivity against human impacts to nature in general, and forest land in particular. In other cases, people fear that forest activities can destroy historical sites, natural monuments etc.

In general, the correlations with harvesting activities are too specific for drawing general rules. When an issue arises, decision makers need to manage it individually.

Very often, restrictions are explicitly formulated as laws, landscape plans or other regulations. Obviously, official regulations must be heeded to and if any such regulations concern an operation, they must be considered since the beginning at the planning stage. When selecting the most suitable system, any option going against such regulations must be immediately excluded from the list.

(See more at TDiv PR1-E02)

See types of ruts on trails

See sectors under wheel

Public recreation can get in conflict with harvesting operations. Based on SINUS-milieus, different user groups are found that have very different needs and expectations to the forest owner. But all forest visitors have one common need: they use the forest roads as their access to the forest and don’t want to be disturbed. If we keep the roads clear for people to move on them, this can help to improve the acceptance of forest techniques and operations. Thus, the forest roads take over the role as a key factor for the acceptance of techniques by the forest visitors.

Based on the functiogram, we can define five S-classes for societal compatibility:

S1 chipping of wood on the forest road of storing of chips there with noise, dust, and trash on the ground = arrow ending at 34;

S2 processing round wood on the forest road with impact to the road = arrow down ending at 32 or 33;

S3 unloading and loading of tree lengths or full trees along the forest road with skidding on the floor = arrow from 22 to 32 or 21 to 31;

S4 unloading and loading of short wood along the forest road, only picking up of products = arrow from 23 to 33;

S5 perfect, no contact with forest roads.

(See more at TDiv PR1-E02)

Under a wheel, the load is covered by the soil. Inside the soil, zone of the same pressure (isobars) can be drawn like onion peels. Directly under the wheel the forces follow gravity and form a compaction. But to the left and right of the main vertical push, the soil can relax against the neighboring soil particles; the vectors turn around. The parts of the soil near the surface give way to the pressure and are lifted.

Thus, ruts are not only the result of compaction, but also of lateral lifting of the soils beneath the ruts.

(See more at PR1-D02)

In a study from 2009, Kleinhückelkotten et al. have found five different groups of people who use the forests for recreation. One of them are the self-centered forest users, the others are holistic forest friends, ecological forest romantics, pragmatical distant persons, and indifferent persons.

In the study, 22% have been characterized as self-centered forest users. For them, the forest is no more than a backdrop for their hedonistic activities, such as playing sports, picnicking etc. They regard any limitations as the unacceptable restriction of their freedom.

 As such, they are not amenable to restrictions caused by forest activities, regardless of harvesting methods and technology.

(See more under TDiv PR1-E02)

See risks and side-effects

The term mechanized work describes the level of mechanization of a technical operation. Other levels are manual work and motor-manual work. Mechanized work can further be divided into simple, advanced and automatic work.

Simple mechanized work offers increased power and mobility, but all auxiliary functions are done by humans.

Example: a cable skidder, which can move larger loads than a human can, and does that at a higher speed. But the attachment of the logs must be done manually by the operator.

(See more at TDiv PR1-B04)

see solutions for skidding

Skidding damage happens during the extraction. It can be caused by the machine or the skidded log.

Animals seldom bump into trees, because they fear to be wounded. Machines have no sensors to protect from damage, only the driver should have. Therefore, in dense stands the moving pattern of the machine has an influence to the likelihood of a damage:

Curves can be tricky, when the rear axle has a shorter turning radius than the front axle as it is common with Ackerman steering. Conventional machines like farm tractors and trucks have Ackerman steering.

Dedicated forestry machines often have an articulated frame, where the two half-frames are connected by a central hinge. In that case, the rear wheels follow exactly the same track as the front wheels. The risk to damage trees is much lower.

Another cause of damage is that the superstructure of a forest machine (like cabin, loading boom and basket) bumps against neighboring trees because of uneven floor. If the machine is fitted with bogies, the deflection of the chassis is only half as high then without bogies, so the danger of accident decreases.

Damage to the stand can be caused by long logs, too. The area of the danger zone depends on the length of the log and the angle 𝛂 between log axis and strip road.

This formula says that the length has the most important influence on the danger zone. Thus, Systems that transport short logs make less damage to the forest stands.

(See more at PR1-D01)

Ergonomics follows a very simple basic model that derives from physics: When you impact a body with a certain stress, the body will react with a corresponding strain. Since a standard method causes a stress that is typical for this standard method, the strain as a reaction to this typical stress situation should be typical, too.

The intensity of the strain, however, is not the same. It depends on the worker: his personal attributes, his abilities and his skills (together they form the capability for work). And it varies due to the actual disposition and motivation (together called readiness for work), and his health. If the strain overruns the permanent work load, breaks are necessary for his personal recovery to avoid acute or chronic damage.

Most jobs require a certain technique. Skilled persons can reach results that will never be possible for unskilled persons.

(See more under TDiv PR1-E04)

Social efficiency see ergonomics

Social suitability is one sub-objective of the decision-making process. It corresponds with the social objective of the company in a means-end-relationship: The means should be developed in a way that it fulfills the end that is given by the objective of the company.

The social suitability is subdivided into ergonomics and societal compatibility. On the same level are two competing sub-objectives: the economic and the ecological suitability. The relationships between them can be organized by the general concept for technical operations that is given by the company.

The societal compatibility deals with the needs of the local society, within which the forest company operates. It is achieved by matching the different demands for recreation, heritage, employment etc. In Technodiversity, we have invented the S-class.

Ergonomics, however, is focused on the wellbeing of the workers employed by the forest company, which is responsible for the working sites and methods. Employers must plan and conduct their operations in a way that minimizes the risk for the operators to suffer an accident or become ill. In Technodiversity, we have invented the E-class.

Now we combine the assessments for ergonomics and societal compatibility in a 5x5-table, on x-axis the E-class and on y-axis the S-class.

As an example, a fully mechanized CTL method with harvester and forwarder falls into the S-class S4 and E-classes E4 (forwarder) and E5 (harvester). Another option, a partly mechanized tree-length method with horse and tractor, falls in S-class 3 and E-classes E1 (horse), E2 (chainsaw), and E3 (tractor).

Now the decision maker can mark his individual preferences. Here we chose traffic light colors to represent green (okay), yellow (limited), red (not acceptable).

For example, one decision maker might feel uncomfortable with manual work due to safety concerns and prefer mechanized work, instead. Then he marks E1 with red, E2 with yellow, and the other columns with green (left table).

Concerning compatibility with recreational needs (in the middle), our decision-maker may want to avoid processing on the forest road. Loading operations, however, could be accepted without constrains. Consequently, S1 and S2 are not acceptable, but all other S-classes are okay for this decision maker.

When we combine those assessments (right table), at each intersection the less desirable color is dominant (comparable with the bottle-neck-rule). 

In our example we see, that the fully mechanized cut-to-length method with harvester and forwarder (fC) fits well to the societal assessment of this company. The partly mechanized method fails, due to the critical assessment of manual and motor-manual work.

(See more under TDiv PR1-A03, -E01, -E04, and E05)

Societal compatibility is a partial objective for decision-making. It wants to avoid disturbances that can occur in conflict with the needs and demands of the public. In forestry people enter the forests to recreate and enjoy their life and feel disturbed by forest operations. Cultural needs of the local population can be disturbed by technical activities, too. A third criterion may be the wish of local people to be employed by the forest company in order to earn money.

As criteria in Technodiversity, we use the S-classes for societal needs. 

Together with its twin ergonomics we can assess the social suitability that is one sub-objective to find the optimal option. Parallel to the social suitability we also should look at the economic and the ecological suitability. For more information about systematics of decision-making, look at objectives and three-step model of optimization.

(See more under TDiv PR1-A03, PR1-E02, and -E04)

See recreation

When a vehicle gets in contact with the forest floor, its weight bears on the ground. One part bears on the solid phase like stones, sand, clay, and roots. But the forces are transmitted to the soil pores, too, which can be filled with air or water. In case of water, this liquid cannot be compressed and transfers the load in all directions.

Directly on the surface two additional effects occur:

•       The cohesion describes the binding forces of a body, for example when the wheel is caught by a thorn vine.

•       And there is a certain adhesion that depends on the electromagnetical coherence between two units, here between wheel and soil surface (but this force is very week).

All these forces together form the resultant force.

The resultant force can be expressed by two components:

•       the normal force, which works perpendicular to the contact surface and

•       the shear force, which works rectangular to it parallel to the surface.

Together with the reaction of the ground, they form a power triangle: When the triangle is closed, the soil is stable enough to keep the wheel. But when the potential of the soil is lower, then the triangle is not closed and the soil will be compacted.

Since this compaction will make the soil stronger, the reaction force increases. When the reaction force is equal to the resultant force, the compaction stops. But a rut remains; we call it plastic deformation.

(See more at PR1-D02)

The model of soil damage of Technodiversity acts on the assumption of tree soil states:

A) Untouched forest soil: biologically healthy and productive

B) Trafficable trail: compacted by former traffic and strong enough for future traffic

C) Destroyed trail: impacted by former traffic in a way that is no longer usable.

By traffic, a soil moves from untouched soil (A) to trafficable trail (B). After traffic, maybe it has a chance to find back to state (A) by biological (worms, roots…) and physical (frost) influences. As long as this happens in a reasonable time, we call it elastic deformation. But very often the traffic with our heavy machines causes a plastic deformation, which means that no natural regeneration will happen in a reasonable time period.

This must not be regarded as damage as long as the technical function of the trail has priority for the owner. Because the compacted trail can be used for future harvesting operations, too, as long as it keeps its technical functionality. This has the advantage that next time the rate of compacted soil will not increase. To reach this, we demand for permanent trails as a central idea of eco-efficiency.

For the question, how much of the soil is allowed to be fixed for technical purposes, no absolute answer can be found. This depends on the decision of the owner.

Consequently, any further degradation of the soil towards destroyed trail (state C) must be avoided. There are two tactics: To stop the operation immediately when critical signs occur or to shape the harvesting system in a way that the likelihood of any damage is minimized. But sometimes the trail will be destroyed in a way that no more traffic can happen on it. Then it should be repaired by technical means (road construction) to recover the technical functionality.

(See more at PR1-D02)

One option which can only be executed by a special machine is the “harwarding” of short logs.

In this case a special machine, the harwarder, fells the tree, delimbs it, cross-cuts it into logs and skids the logs to the forest road (buffer 10 to 33). All these sub-processes are done in one step without a buffer to interrupt.

Since all the sub-processes are done by the harwarder, it is assigned to the mechanized work.

To produce chips (= chipping) at the forest road, full trees (buffer 31 to 34), tree lengths (buffer 32 to 34) or short logs (buffer 33 to 34) can be used.

The chipping is a mechanized work and can be executed by a chipper.

To produce chips (= chipping) on the trail, full trees (buffer 21 to 24), tree lengths (buffer 22 to 24) or residues (buffer 23 to 24) can be used.

The chipping is a mechanized work and can be executed by a chipper.

A specialized option is a biomass-harvester. This machine fells the tree and directly forms chips out of it (buffer 10 to 24).

The sub-process of cross-cutting describes the transformation from tree lengths or a full tree into short logs. It can be carried out either in combination with the delimbing of the tree or detached from the delimbing as a single function.

If the tree is delimbed and cross-cut in one step, this is usually done on the trail (buffer 21 to 23) or the forest road (buffer 31 to 33). The combination of delimbing and cross-cutting is executed mechanically with a processor ( can also be executed with a harvester) on the trail or the forest road.

If the tree length is cross-cut as a single function, it can be done either in the stand (buffer 12 to 13) or on the trail (buffer 22 to 23) or the forest road (buffer 32 to 33). Usually it is done motor-manually with a chainsaw.

During the sub-process of delimbing, a full tree is converted into a tree length by cutting of the top of the tree and the branches.

If the tree is only delimbed, this is usually done motor-manually with the chainsaw. Depending on where the full tree is located, delimbing can be performed either in the stand (buffer 11 to 12), on the trail (buffer 21 to 22) or the forest road (buffer 31 to 32).

The sub-process of delimbing can also be carried out in combination with the felling of the tree. This combined option of felling and delimbing can be executed mechanically by a harvester or motor-manually with a chainsaw. While the tree that is felled and delimbed motor-manually remains in the stand (buffer 10 to 12) after the process, the tree that is felled and delimbed mechanically is lifted onto the trail during the process (buffer 10 to 22).

During the sub-process of extracting/ skidding, the tree lengths are moved from the trail (buffer 22) to the forest road (buffer 32).

Usually, the extracting is executed mechanically. Often used machines are the cable skidder and clam-bunk skidder. In both cases, the transport of the tree lengths is carried out in a dragging movement. The cable skidder can also be used not only for the skidding of tree lengths but also for the combined sub-processes of pre-skidding and skidding (see “Solutions for pre-skidding and skidding of tree lengths”).

The extraction of short logs describes the transportation of the logs from the trail to the forest road (buffer 23 to 33).

It is a mechanized work, usually done by a forwarder or a tractor with a trailer.

For the subprocess of felling there are two options common. The complete tree can be either just felled or felled and then directly hauled.

If the tree is only felled, the subprocess normally is performed motor-manually with a chainsaw. After felling, the full tree remains in the stand (buffer 10 to 11).

If the tree is felled and hauled, the full tree does not stay in the stand after felling but is moved to the trail (buffer 10 to 21), where it will get hauled. These steps (felling and hauling) are executed by a feller and form the second option for the subprocess of felling. The work with the feller is described as mechanized work.

The felling and processing (= harvesting) of short logs can also be executed in one step. Without a buffer to interrupt the process, the complete tree is felled, branches are removed, and the tree is topped and cross-cut.

This process can be done motor-manually with a chainsaw or mechanically with a harvester. If the harvesting takes place motor-manually, the logs remain in the stand near the stump (buffer 10 to 13). If the harvesting is done mechanically, the stem is lifted onto the trail during the process (buffer 10 to 23).

In some cases, the sub-process of pre-skidding is not necessary and can be skipped. Then, the tree lengths are skidded directly from the stand (buffer 12) to the forest road (buffer 32).

This may be the case, if there are no regulations for the machines to stay on a permanent trail or if the technology of the machines makes the sub-process of pre-skidding unnecessary.

Machines which can skid tree lengths directly are for example the cable yarder or the cable skidder. While the cable yarder skids the tree lengths in a carrying movement to the forest road, the cable skidder needs to drag the tree lengths.

The pre-skidding of full trees can be performed either by animals (horse) or as mechanized work by machines.

As machines usually a tractor winch or a cable yarder are taken for the subprocess of pre-skidding.

While the tractor winch and horse can only drag the full tree from the stand (buffer 11) to the trail (buffer 21), the cable yarder is able to carry the full tree to the trail.

During the pre-skidding of short logs, the short logs are moved from the stand onto the trail (buffer 13 to 23). In special cases, the short logs can also be skidded directly from the stand to the forest road (buffer 13 to 33).

Due to the “light” weight of the short logs, there are a lot of options possible for pre-skidding them. They can either be carried manual by a person or a mule or dragged by a horse. Another option is to pre-skid the logs mechanically with a cable skidder.

The cable skidder and horse can also be used for the direct skidding of logs from the stand to the forest road.

The pre-skidding of tree lengths (stem without branches and crown) can be performed either manual by animals (horse) or as mechanized work by machines.

The most common options for the pre-skidding of tree lengths are the use of a horse, tractor winch or cable yarder.

While the tractor winch and horse can only drag the tree length from the stand (buffer 12) to the trail (buffer 22), the cable yarder is able to carry the tree length to the trail (buffer 22).

The skidding of full trees is commonly a mechanized sub-process. For the extraction of full trees several options are available.

The clam-bunk skidder and grapple skidder are normally used only for the skidding from the trail (buffer 21) to the forest road (buffer 31). Whereas the cable yarder and the cable skidder can be taken not only for the skidding but also for the pre-skidding of full trees (buffer 11 to 31).

The transportation of the full tree by cable skidder, grapple skidder or clam-bunk skidder is executed in a dragging movement, the transportation with the cable yarder in a carrying movement.

Cutting tree at the base with chainsaw and fell it in a predefined pattern.