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Forestry
Metric Measurement in Forestry. Obtainable from the Agricultural, Horticultural and Forestry Industry Training Board, Bourne House, 32/34
Beckenham Road, Beckenham, Kent. Pp. 91, 21 X 14-5 cm. Price 4op (8s.)
including postage. 1
Review by R. H. WATSON
WE learn on the first page that this booklet was compiled by the Programme Instruction Centre for Industry, University of Sheffield, with co-operation from the Forestry
Commission and the Agricultural, Horticultural, and Forestry Industry Training
Board. We then read that this is a programmed learning book and that when we have
completed the programme we will be able to measure and carry out calculations using
metric units.
Part I deals with Metric Linear Dimension and we are carefully introduced to
metres, kilometres, millimetres, and centimetres. As soon as we start dealing with
metric measurement in forestry, however, the difficulties start. Between pages 12 and
19 there are a number of ambiguities, e.g. it is never obvious whether felled or standing
trees are being measured; and why no mention of saw-log length conventions ? Part II.
Calculations Using Decimals should prove very useful to any forester whose arithmetic
has become rusty. The fencing examples on page 41 are nicely worded. Part III. Area
is straightforward, using nursery beds, football pitches, and stacking areas as examples.
Part IV. Metric Units of Volume and Mass deals with liquid volumes and weights,
and the examples are made realistic by relating to herbicides and fertilizers. Examples
of the Use of Decimal Currency and Metric Units in Forestry in Part V appear to have
been carefully compiled although Decimal Currency is slipped in without any prior
mention. The examples are all sound, relating as they do to materials required for
practical tasks, to planting costs, and wage packets. Part VI. Temperature is very
brief. We are not told how to convert and the only temperatures mentioned are
boiling-point and freezing-point. This is followed by a comprehensive self-test which
makes an extremely useful contribution to the booklet. In question 2(a) the wrong
unit has been used.
We reach the last page programmed to measure and calculate in metric units, but
without knowing whether the booklet was intended for us or not. It seems a great
pity that nowhere is it stated at whom the booklet is aimed, or that it is intended
for use in conjunction with short courses on metrication. All practising foresters
should have a copy of this booklet and should work through it at their own pace.
They will find it unusual and their attitude to it will reflect their aptitude for figures
and their adaptability to new educational methods.
G. F. SCHREUDER. Optimal Forest Investment Decisions through Dynamic
Programming. Yale University School of Forestry Bulletin No. 72. New
Haven, 1968. Pp. 70, 23 X 15 cm. Price $2-00.
Review by
ANNE TUPHOLME
IN recent years a number of mathematical models representing each of the various
stages in the wood-based activities of a region have been published. These have
usually been constructed for studying either forest management or the primary and
secondary wood processing industries, but have not given an integrated approach to
the subject.
1
Payment should be made at the time of order and envelopes should be marked
'Forestry Metric Booklet'.
Reviews
107
The purpose of this paper is to develop a model to optimize the discounted present
value of the net benefits of alternative possible investments that could be undertaken
in a particular region when all the stages from the planting to the primary manufacturing sections of the forestry operations are considered. The author claims that this is
a major development, since foresters have continued to base their decision-making
on the theory that the maximum value of the discounted present value of the net
benefits of the combined system is the sum of the discounted present value of each
part where each part is evaluated with respect to market prices. He emphasizes that
foresters have known this to be a wrong approach when conditions of pure competition
are non-existent, a feature of the economy of many countries, especially developing
countries, but that they have continued to use the method in the absence of the
availability of any of complete generality.
An explanation is given for choosing a dynamic programming technique for a
model which spans a finite number of planning periods. It is interesting to see the
use of a forward recursive approach, which requires values that describe the state of
the system initially, as opposed to the much-used backward approach. The model
is complex yet each stage of the iterative procedure is described clearly and in detail.
Five special cases of the model are discussed in analytic terms, illustrating the wide
potential of the basic model. It is also suggested how the model could be generalized
for planning on the national level.
An example is presented to show how a typical problem can be solved by the
model. It seems a pity that additional space was not allocated to further details of the
calculations involved in presenting the example, since there seems to be some confusion between the presentation and explanations of the symbols in the formula for
the discounted present value of the forestry sector on page 15. For example, it is
stated on page 22 that 'with the exception of cn(S), Cn'41 and cn(9), all the functions
depend on the variable Yn, on the variable Vn or on both', yet on page 15 rn<4) is
defined as a function of Yn and Vn). It is not at present clear to the reviewer how the
apparent inconsistency can be explained. Unfortunately there were other oversights
in the proof-reading. In particular, on page 13, r n and c n should be defined as functions, not vectors. A more serious error is that in the formulae on pages 13 and 15,
the factor (i + Kn)n should be replaced by ( I + K J ) (i + K,) . . . (i+K n ), which can be
m
written more concisely as /7(i + K,).
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However, despite these reservations the paper is concisely and clearly written and
should stimulate interest in the use of dynamic programming techniques in forestry.
Economics and the Folklore of Forestry. Thesis, Syracuse
University. University Microfilms, High Wycombe, 1970. Price $11-50.
JOHN BENNETT.
Review by A. J.
GRAYSON
IN the current climate of uncertainty about the direction which British forest policy
should take, it is salutary to read a work which reveals with such striking clarity how
little the themes of the debate have changed over the past few decades. Dr. Bennett
has chosen to consider the development of forestry thinking in the United States
between 1902, the year of formation of the Society of American Foresters, and 10.30.He illustrates and analyses the course of the debate by identifying four rules which
incorporate the main themes of economic thought in American forestry. These are:
(1) the rule of timber primacy—wood regarded as an absolute necessity, (2) the rule
of sustained yield—the ethic that each generation should hand over its natural
resource heritage intact to the following generation, (3) the rule of the long-run—