A unique aspect of mation about the use of nontimber goods is privately held this situation is the fact that a single entity manages a large by Aboriginal people, and this information on wildlife har- landscape with the objective to supply mills with different vesting, for example, will not be freely released because of fiber requirements.
Furthermore, the Meadow Lake Tribal its value to hunters and its sensitive nature. Information may Council[1] owns the NorSask sawmill to which Mistik also be withheld because of the cultural importance of Management supplies fiber. Thus, concerns regarding the certain sites or activities. The firm has information on nontimber harvest activities. Given the cul- also put considerable effort into developing co-management tural significance of these resources, and that different reg- boards with Aboriginal communities in the region and pro- ulations apply to Aboriginal harvesters, information from viding mechanisms for Aboriginal people to benefit from recreational hunting licenses and related wildlife harvest statistics that are routinely gathered from non-Aboriginal the employment opportunities created in the region.
These This article begins with a description of a data collection issues suggest that data gathering techniques used in typical effort that focused on building trust and developing the studies of recreational hunting demand are not useful in an research program in cooperation with the communities. This Aboriginal hunting context. First, monetary valu- members of the Aboriginal community was collected. The ation may imply property rights that are rejected by the community members expected the researchers to pass in- Aboriginal people.
A contingent valuation approach that these sites, though no cessation of forestry activity was requests a willingness to pay for improved quality of non- promised by the researchers or Mistik. This information timber goods would likely be rejected as it implies that the included identification of areas with high moose popula- Aboriginal people do not have the rights to the resource. An tions, cabins, salt licks, and other attributes of the land.
The collection of this revealed preference some segments of the Aboriginal population. In cases where RP information is described below. Study Area and Sample After describing the data collection process, the article The study area for this project is the Millar Western- continues with a description of the modeling process com- NorSask FMA area in northwestern Saskatchewan, which bining RP and SP data and the simulation of hunting extends along the Alberta-Saskatchewan border, comprising behavior following forest harvesting plans.
The impacts of 3. The current population forest harvesting on hunting are examined using monetary of the FMA area is about 25, spread over about 22 welfare measures as well as a form of resource compensa- communities in and around the FMA area. This population tion.
Although NorSask utilizes the softwood and Millar explored. Western utilizes the hardwood in the region, the landscape The results suggest that modeling actual behavior can be planning for the region as a whole is undertaken by Mistik used as a method of capturing some of the value of non- Management Ltd.
However, substan- Management Information Booklet. Furthermore, challenges in identifying the Data Collection Process opportunity cost of time make the monetary valuation of Initial contacts with the communities and the forest man- nontimber resources difficult.
Use of resource compensation agement agency identified that even though Aboriginal peo- methods, however, appears to be promising. The methods pre- ple are engaged in collection and use of many different sented in this article provide insights into the potential for resource nontimber forest products, large game harvesting in partic- compensation as a practical way to incorporate the values of ular moose; deer and caribou to a lesser extent was con- Aboriginal people into forest management.
The analysis of zon- sidered the most important. The community members them- ing, or concentrated forest harvesting versus dispersed harvesting, selves were interested in participating in a study of hunting also suggests potential for this as an approach that incorporates as this activity is important culturally as food for hunters Aboriginal values into forest management.
The article concludes and other members of the community, and as an activity that with a discussion of some of the limitations of the study and could be significantly affected by forest management ac- challenges associated with incorporating Aboriginal values into tions.
Thus, the initial contacts with the communities to forest management planning. An approach that engages the community in defining Hunting trip information for the past hunting season was the research program is emerging as a requirement in con- collected in two complementary formats.
The first was a ducting research with Aboriginal communities. It also included information on the from previous hunting research in the economic literature.
While the design of the survey harvested by the individual being interviewed and by the was to be a straightforward question and answer session, the group.
Further information on location of the trips recorded in the trip log. Trust was an important factor in the entire process. Both the map and the trip log were used simultaneously Community members were apprehensive about discussing in collecting information. Some of the more traditional hunting and trapping activities with a stranger, especially a hunters would require significant interpretation of the map non-Aboriginal person.
In response, we employed one pri- because they were not accustomed to seeing two-dimen- mary interviewer who became known in the communities sional representations of the land base. Once this was ac- and developed relationships with the local people. We also complished, the use of a map as a visual tool worked to employed a community resident who socially and culturally make the respondents feel more at ease with the process.
This person helped to arrange Many informants preferred to talk in stories and they would point out the sites and then begin to remember the rest of the interviews, attended them to ease the participants, and trans- trip details that were needed to complete the trip log.
Mistik Man- development of trust between the interviewer and commu- agement provided digital files for the region including nity members. The fact that the interviewer lived and par- lakes, rivers, roads, trails, FMA, and other planning unit ticipated in the community was fundamental to the research boundaries.
This information was used as geographic refer- process. Although individual trips were digitized, to en- ships with the respondents. Reciprocity for participation in sure confidentiality, the data were aggregated for each com- the study was offered at several levels.
First, the research munity. Aggregating the individual general hunting areas by group made a commitment to report back the findings to community also helped determine the geographical extent each of the communities. Each hunter was asked during the of hunting trips for each community.
General hunting areas mapping exercise to identify special sites such as nesting for several communities overlapped, but for the most part areas, calving areas, burial sites, cabins, or historical sites.
A they followed the boundaries of Fur Conservation Areas, map of special sites was created for each community and which are based on traditional trapping areas. Third, in such as salt licks, cabins, areas of exceptional moose hab- interviews with First Nations elders an offering of tobacco itat, burial sites, and avian nesting areas on the maps. This offering is These maps are similar to those generated in traditional a sign of respect and helps to formalize the relationship land-use mapping exercises and reflect the traditional eco- between the interviewer and the elder.
We employ some of this information in devel- oping measures of the attributes of hunting sites. We extend existing studies on Aboriginal hunting e. We used a choice facilitate investigating the influence of better access to experiment approach to investigate how Aboriginal people larger commercial centers on harvesting behavior.
During the development of the sur- ments designed to capture preferences of southern hunters vey tool, we were informed that it would be culturally for hunting sites in central and northern Saskatchewan. This inappropriate for us to ask respondents to report their annual list of potential hunting site characteristics was presented to income. The appropriateness of each they worked. However, it became evident during the inter- attribute was discussed, and culturally appropriate levels views that over the course of a year many respondents were were determined.
This set of attributes was further vetted employed in a series of jobs that last for a few days to through an elder hunter who after some discussion approved several weeks or months in many different industries rang- the list.
From these approved attributes a choice experiment ing from forest firefighting to road construction to forestry was designed.
A much more detailed employment record for the The attributes themselves did not differ radically from year would be needed to be able to impute individual earlier designs used in studying non-Aboriginal hunters income levels.
These features have significant implications for the ac- However, the levels of the attributes did see Table 1. In curacy of value of time calculations derived from travel particular, the levels for the distance traveled and the mode distances using standard economic approaches i.
Because many individuals in our sample from earlier surveys reflecting the fact that Aboriginal hunt- changed their employment-related activities over the year, ers live in their hunting regions and that past cultural prac- we use the average male income for the region in our tices influence the mode of transportation for some of them.
We attained average male The prototype choice experiment was initially text based, income levels from the national Aboriginal census Statis- similar to choice experiments used in mail surveys of li- tics Canada One elder informant, who was conversant in English Methods but had difficulty reading, found that reading the survey and Descriptions of the behavior of boreal Aboriginal hunters discerning the specifics of the choice experiments was dif- in the anthropological literature suggest that they have con- ficult.
It was decided that an illustrative approach would be siderable knowledge of moose biology and that their hunt- more appropriate in this setting. Photographs were used for ing behavior represents decisions that optimally provide attributes for which a picture would easily illustrate its opportunities for harvest. For example, Winterhalder meaning, such as time since harvest and access to the describes frequent use by hunters of areas in proximity to hunting site.
More detail on the choice experiment can be water and forest areas recently disturbed by fire, and that found in Dosman et al. Feit Table 1. Definition of hunting site attributes for the choice experiment administered to the Aboriginal hunters. This information to previous timber harvest operations. Usually aerial Our modeling framework is illustrated in Figure 2. We survey transects are used by biologists to estimate moose employ hunter knowledge and forest characteristics to de- abundance, but these had not been completed in the study velop a model of moose population or abundance.
This region. To overcome this gap in the data, and following the model provides measures of one of the most important research by Feit , information provided by the hunt- attributes of the sites. In addition to information on moose ers was used to develop a moose abundance indicator for populations, forest landscape and road network characteris- each OA. To create this indicator, OAs were identified in tics are directly used as explanatory variables in a RP which respondents indicated there were exceptional areas model.
We then employ a combination of RP and SP data to for moose. The information on moose populations and for- generate a joint model of hunter preferences. Each of these est landscape attributes were used to construct a model of components will be outlined below.
Given the discrete nature of this vari- able exceptional habitat or not , a logit model was used to Spatial Resolution estimate the probability that any OA in the FMA had Because our objective was to develop a hunting site exceptional moose habitat. For this spatial scale, the operating model e.
These included the density of rivers, areas of dis- used to plan forest harvest operations in the FMA. Hunters turbance from fire or previous timber harvests, the area of in our sample took trips to most of the OAs in the FMA, standing water, the area of muskeg, and the area of forest as well as some outside the FMA.
Other From the digital files provided by Mistik Management, variables were chosen that were related to human use and the following variables for each OA were developed: lake perception such as the number of cabins within 10 km of an area ha , length of rivers km , length of road km by class OA and the presence of a salt lick within 10 km of the OA.
For the OAs in the The independent variables in the model are reported in FMA, the following forest landscape characteristics were Table 2. The crown closure and river density variables were harvests, the area burned in forest fires, nonforest area e. This model was used to esti- mate the probability that each OA in the FMA would contain exceptional moose habitat. Choice Model Development The interest in this article is in developing a model to explain why hunters visit certain OAs over others and how their choices might be affected by timber harvesting.
This information represents discrete choice data, which can be analyzed using econometric methods based on random util- ity theory Louviere et al. This theory maintains that the utility an individual derives from visiting an alternative site, i, is considered to be associated with the attributes of that alternative. Vi can be characterized by its attributes. A summary of the strategy used in modeling Aborig- bel, the conditional probability of selecting alternative i inal hunting trips in the NorSask FMA.
Parameter signs and significance levels for a logit model used to estimate the probability that an OA contains high moose populations. Variable Description Parameter sign P-value Constant — 0. However, this is not the case for the RP data. However, in models in which multiple data size was reduced to 30 OAs by randomly selecting a subset sources are merged to estimate the parameter vector, the of the relevant OAs for each trip from the full choice set. In part this arises because data for some important attributes were The landscape attributes used in the models and their not available e.
In addition, the RP coding are described in Table 3. Because we combined the attributes are likely correlated and confound effects. For RP and SP data in a joint model, several variables from the example, the effect of forest harvesting on the esthetics and RP and SP data were transformed so that their coding was appearance of a site would be confounded with the impact commensurate. Note that there is not complete overlap on moose populations.
The encounters variable, models can outperform RP models in predicting actual for example, exists only in the SP data. The variables behavior when the SP data are carefully collected Haener et common to both models are travel cost, moose abundance, al. Therefore, both data types are employed in two variables for time since forest harvest, and water access. The joint model combines data for the attributes common to Table 3. The wage rate was determined by dividing the average attributes unique to the RP and SP data to be estimated.
The male income in each community by the total number of model we use for simulation is based only on the attributes work hours in a year assuming a hour workweek. We common to both models and one variable unique to the RP recognize that this method of valuing time may be inappro- data i. Because the SP data are based on an priate for this context and suggest that tradeoffs associated orthogonal design, we can employ a subset of the attributes with pursuing subsistence activities need to be further in estimation and simulation without significant concern investigated.
The combined variables and their resulting codes are listed in rows 2—7 of Table 3. The parameter estimates for the joint RP-SP model and In modeling hunting site choice, travel cost is commonly the corresponding RP and SP models are reported in Table used as proxy for the cost of visiting areas e. The RP model only has parameters for those attributes et al. Following the stan- that could be related to the spatial information provided by dard procedures in the travel cost literature, it was assumed the hunters and Mistik Management.
For the SP model, that travel cost is a function of out-of-pocket expenses parameters displayed are only for those attributes used in related to travel distance and the time costs of traveling the choice experiment. The joint model contains parameters e. Travel distance was included in for all of the characteristics in the RP and SP models, but the design of the SP choice experiment. However, it was recall that these parameters are constrained to be equal necessary to calculate travel distances for the RP data.
To across the two sets of data. Because the joint model provides the most In several parts of the FMA, the road network is sparse, complete information on attributes, it is discussed in detail therefore travel distances include the distance by road and below.
The operating costs associated with the nonroad In the joint model, the travel cost and the encounter portion of the distance was assumed to be three times this parameters are negative and significant. This suggests that figure, as supported by information suggesting that the fuel the hunters prefer to hunt closer to their communities and mileage of off-road vehicles and snowmobiles is about that they would prefer fewer encounters with other hunters one-third that of a car or truck.
The cabins, water access, and the moose The standard means of incorporating the value of travel abundance indicator variables are positive and significant. We assumed an average speed of 90 kph These findings suggest that the hunters prefer to hunt in and use one-third the estimated wage rate for each commu- OAs with or near cabins, that have good water access, Table 4. Note, however, ment Vincent and Binkely We consider an analo- that the access variables, while positive, are statistically gous strategy here; however, the zoning considered is a insignificant.
Because moose abundance is also harvest is used for comparison with the dispersed harvesting related to forest disturbance patterns see the new cut vari- plan. The 3, ha of dispersed harvesting planned for the able in Table 2 , the choice model parameters suggest a general hunting area of community 1 is reallocated into 3 complex pattern of preferences for forest age and distur- OAs, and the 6, ha of harvesting planned for the general bance.
It appears that there are amenity effects for the forest hunting area of community 2 is reallocated into 4 OAs. These changes result from impacts on moose abundance.
An advantage of using choice models to examine pref- Figure 3 shows those OAs that experience relatively erences over attributes is that the model can be used to significant changes in the predicted distribution of trips examine changes in choice behavior when attributes of one following the dispersed and concentrated timber harvests.
This can be The change in trips is measured by the percentage change in done in a probabilistic framework using Equation 1 above. The response to the dis- model, monetary measures of economic welfare can also be persed forest harvesting plan shows that the most significant associated with these changes in attributes see Hanemann impact arises in OAs that have not been previously har- These features were used to simulate the effects of vested.
Because most of the forest harvesting in the area hunting trips in the general hunting areas of two communi- of community 2 occurs on such lands, the impacts are more ties in the study and the associated economic impacts. Simulation of Timber Harvesting Employing a concentrated forest harvesting plan signif- To determine the influence of timber harvesting on hunt- icantly reduces the impact on hunters.
In part this is because ing behavior, two harvesting scenarios for two communities of the decreased number of OAs affected, but it is also were imposed on the current distribution of trips in the because most of the sites selected for concentrated harvests relevant general hunting areas. The first scenario uses Mis- had already experienced some degree of timber harvesting.
According to this plan, about 3, ha of forest, improved overall outcome. The harvesting effects are more pronounced in community A strategy that has been receiving significant attention in 2 and are very small in community 1. As mentioned above, forest management recently is the zoning of land areas and the reason for this difference is that timber harvesting has the concentration of activities within zones.
Rather than occurred near community 1 for a number of years. This zoning strategy area. In community 2, however, most areas visited by hunt- is often referred to as the TRIAD a three zone strategy ers in the community have never been subjected to forestry involving an-intensive forest management zone, a protected operations.
This rotation yields largest volume per unit area, per annum, and is an important rotation which is adopted frequently. It is suitable where the total quantity of woody material is important and not the size and specification, like firewood, raw material for paper pulp, fibre and particle board industries based on disintegration processes of wood. Rotation of Highest Income: It is the rotation that yields highest average annual gross or net revenue irrespective of the capital value of the forests; also known as rotation of highest revenue or forest rental.
It is calculated without interest and irrespective of the times when the items of income or expenditure occur. Land value is also not considered in this case. This rotation is fixed under the assumption that the wood has same value whatever its size, and annual expenses do not vary with alterations in the rotation. This rotation is important from the over all national point of view, as attainment of highest gross revenue is more important than that of net income because larger expenditure and investment generates several social benefits, and indirect advantages to the trade and industry.
Private owners are interested in maximum net revenue by keeping the rotation period as short as possible. Financial Rotation: It is the rotation which yields the highest net return on the invested capital. It is a rotation determined on financial considerations, i. In this rotation all items of revenue and expenditure are calculated with compound interest at an assumed rate, usually the rate at which the Government is able to borrow money.
It may be defined as, - The rotation which gives the highest discount profit, usually at its commencement. This rotation is not applicable to natural forests because of lack of data regarding age, growth rate, mortality, etc. This is easily fitted to the management of man-made forests especially industrial plantations. The economic principles are applied in this case and this rotation gives the highest net profit over and above a certain fixed percent, after allowing compound interest on all expenditure and income.
Trees are the capital and growth increment is interest; both are indistinguishable. Increment is the increase in growth of a tree or crop with age. It may be in term of wood content, or any of the factors which increase with age-diameter, height, basal area, volume, quality price or value.
It is determined for any given period, by measuring it at the beginning and at the end of the period. Definition: The increase in girth, diameter, basal area, height, volume, quality, price of individual trees or crops during a given period. In Forest Management, the term increment refers usually to only volume increment, and that too of crops rather than of individual trees.
It is intimately connected with the volume and age of the crops. Usually taken as the periodic annual increment over a short preceding period. Periodic Annual Increment P. Since annual measurements are very difficult in forest and impossible in practice, only P. If the period is short, P. Mean Annual Increment M. The total increment upto a given age divided by that age is M. The volume of a tree is built up of successive C.
The C. The mean of all C. Final Mean Annual Increment F. Curves: The study of C. In case of light demanders and moderate shade bearers, the maximum is reached when the height growth culminates. In case of shade bearers, maximum is attained several years after the culmination of height growth, and after attaining maximum, C. The curves drawn for different species conform to the same pattern as show in Fig. Keeps below C.
It is an expression of the relation between increment and volume. It is the ratio of increment and volume expressed percentage. Current annual increment percent: It is the relation between the annual increase of increment during a given year and the volume at the beginning of the year expressed as percentage. Period increment percent: This is the percentage ratio between the increment during a given period to a basic volume i.
Mean annual increment percent: It is the percent ratio which the M. The decrease in I. This allows the removal of greatest possible volume of wood capital with reduction of smallest possible amount of increment.
In effect it transforms the forest capital from low to increased I. Increment percent I. It affords in an inexperience officer the opportunity to know the work done, the procedure and the relative cost.
It is particularly useful as a guide for planning future schemes for projects. It also brings into view the financial commitments involved. Occasionally a compartment may be sub divided into sub- compartment temporarily. A compartment register is precisely a book for recording the time, cost and different type of operations carried out in the compartment. The costs of operation are expressed in mandays. However the cost of a manday at the time of operation is also stated so that the cost can be evaluated in cash.
The silvicultural system in operation time and cost of thinning, climber cutting, Reasoning are clearly stated. These are some examples of operations to be recorded in a compartment register. For example the ratio of different component of the Rotting mixture e. It shows the net profit or loss of the nursery. These percentages are indicated in a circular design drawn to scale.
Control form is a form of completion report, stating the amount of work expected to be done, work done and reasons for excess or deficit.
Control form is not used for nursery alone; it is also applied to plantation programme. For example a state may decide to plant up 1, acres of land yearly but it may happen that in a particular year they planted only acres and so having a deficit of 50 acres.
It may also happen that they plant say In this programme the control form is used as a sort of guidance. The management procedure leading to this result is called yield regulation. The very essence of Y. There is no single formula for the solution of cut-determination.
Thus Y. Generally the main objectives why timber production and telling of trees should be regulated can be broadly discussed under 4 headings namely: 1. Silvicultural 2. Labour 3. Industries Object of Yield Regulation 4.
Economic Reasons. Cutting more than required or cutting more than can be replaced. This may cause determination of the soil, introduction of unwanted species. The dense shade of an over-matured tree will make it difficult for young plant on forest floor to survive due to lack of light.
LABOUR The employer needs skilled labour to carry out his work and this can only be got by regular employment intermittent employment leads to forced employment of casual labour with consequent lack of skill and responsibility. Similarly an employee will not stay in a job or trade hthat offers only intermittent employment. It means then that both parties employer and employee suffer when the work is intermittent.
These capital investments is made up of two things — the trees themselves and the money expended in operations in that forest. Although the owner of the forest may make a profit by waiting 60 years or more for the trees to mature before selling them, yet he has nothing to line on in the meantime.
Whereas he can get better returns on this money by merely putting it in a saving bank. We must consider the capital tied up in the forest to be an investment upon it every sensible petran expects a return or profit. Not as a final profit but as a steady interest on the money invested. This can only be got by regular periodic Preferably Annual yield from the forest. Several methods have been tried particularly in Europe to regulate yield and attain those objectives.
Some methods have been move successful than others. The type of method to be adapted depends on the type of forest and the degree of accuracy required. The methods used so far can be divided into 4 major groups: 1.
Methods based on area only. Methods based on area and volume control. Methods based on volume or volume and increment of growing stock 4. Methods based on number and size of trees. Annual Coupe Method. The methods consist of dividing the whole forest into equal areas, equal in number to the rotation. Each part is cut and regenerated sequentially every year. Since there will be site difference or micro site variation; each area will produce at different yield. It follows therefore that the longer the Rotation the greater the differences will be.
Hence this method is assumed to be best suited for short rotation crops. The method also assumes an evenness in ages of crop. In general this method is best suited for plantations grown on short rotation e. It is this the quickest way of attaining a sustain yield from the forest. The method tries to decide ahead the allowable cut and its location for the whole rotation. Due to the fact that the tropical high forest is compared of many different species, it means that the yield from each annual coupe is likely to be vastly different in the first rotation.
This difference is further aggravated by the facts that some species are economic while some are not. And it is only the economic ones that are exploited several attempts have been made to overcome these vast difference in annual yield. This include: 1. Reservation of some rotation of the forest.
A part of the forest is set aside as a reserved area and is not considered as part o the yield. This reserve is intended to be used as a BUFFER against large fluctuations in yield and will be used to replace or supplement any areas of very low yield.
In this case area of annual coupe is equal to the area of the whole forest misuse area of reserve divided by the rotation. Rotation 2. Free choice of coupe by contractors In this case, the contractor is allowed to choose the order in which he takes the annual coupes. Normally the contractor enumerates the forest and from his data he can nominate which coupe he wants to take next.
He can then select his yield to sait the market demand. For instance if the contractor wants obese, he will nominate or choose the coupe with a large proportion of obeche while on the other hand if he wants mahogany, he will opt for a coupe with a large proportion of mahogany.
By so doing it is hoped that by the time he eventually gets to the coupe with a lower yield, it is likely the number of economic species taken to the market should have increased considerably so that they are which was thought to be of low yield earlier on will now be considered as high yielding area.
Fixing of minium felling girth. The third method for adjusting the yield of a coupe is also practiced in high forest. By this method a mnim fell girth is set for each species below which the contractor is not allowed to fell.
The method of annual coupe is more suitable for the crop that is clear felled at rotation age and for system of direct planfix or artificial regeneration. In this method however it can be applied suitably to a high forest system i. The shelter wood system demands a gradual removal of the trees in the area to encourage natural regeneration.
The periodic block is therefore that part of the forest allocated fir regeneration or other treatment during a specific period. When all the periodic blocks are allocated and maintain their territorial identity or a working plan they are termed fixed or permanent periodic blocks.
To avoid the vigidity and reduce the sacrifices of the permanent periodic block method, the obvious remedy is to abandon fixed periodic blocks and realot then according to circumstances at each revision of the work plan namely at the end of each period. Such blocks that di bit retain their territorial identities at a W. Generally we call the period over which the fellings are completed as the regeneration period P. The whole forest has to be divided ino a number of equal areas known as periodic blocks equal in number to rotation over regeneration period.
Within each P. Hence it is impossible to calculate yield by area but it has to be calculated by volume. If the trees were not growing, then the yearly volume yield would be their present volume v divided by the period P.
But they do grow. Now the trees cut at the beginning of the period have no time to grow but those cut at the end of the period can grow for the whole period. So on average the trees put on half the increment I they would have put on if they have been left untouched. So the volume available for cutting annually in the regeneration block is the present volume v plus half the increment I that the untouched stands would have put on in the period.
The volume of cut can be determined indirectly through area control methods or directly through volume control method. The mgority of methods of Y. It is always necessary to check up whether the presumed conditions have been fulfilled otherwise these formulae would be misleading. Advantages: 1. Applicable to all types of silvicultural system.
Useful as an overall guide to appropriate cut. Useful in bringing an unmanaged forest under some degree regulation. Being derived from a mathematical model of the grow stock, it allows for the quick estimation of the allowable cut often from a limited amount of data.
Disadvantages: 1. Even though more accurate than area method, it could be more expensive in the sence that regular or constant enumeration will be required and this is time and money consuming and labour demanding. Increment which is regard in most volume formulae tend to be a weak figure. If volume or increment data are incurrect, there is no assurance that the forest is constituted as desired. Therefore for safe application of V. Von Mantel assumed the concept of a normal forest i. S is equal to the annual yield multiplied by Rn all upon 2.
If the G. However in practice, trees are not enumerated or mmed below a certain girth limit. Another disadvantage is that the formula is wrongly applied to all forest irrespective of their normality. If there is no normal distribution of trees of all age classes then the annual yield will be very wrong.
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