This document discusses the concept of a normal forest, which is defined as an ideally constituted forest that can sustain yields indefinitely through balanced age distributions, growing stock, and annual increment removal. A normal forest is characterized by: [1] a normal series of age classes distributed appropriately across the forest; [2] a maximum normal increment given the forest type and site conditions; and [3] a normal growing stock volume indicated by yield tables. The concept of a normal forest provides an ideal standard for comparison to evaluate the condition of an existing forest and ensure maximum sustained benefits from management.

1. Normal Forest – growing
stock and increment
Muhammed Iqbal A
Dept. of Forest Management and
Utilization
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2. Definition
“A Forest which, for a given site and given
objects of management, is ideally constituted
as regards growing stock, age-class
distribution and increment , and from which
the annual or periodic removal of produce
equal to the increment can be continued
indefinitely without endangering future yields.
A forest which by reason of normalcy in these
aspects serves as a standard of comparison for
sustained yield management.” (Glossary)
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3. Characteristics of Normality
• Three main attributes of an ideal forest
managed for sustained yields in perpetuity
2.A normal series of age-classes or age-
gradations
3.A normal increment and
4.A normal growing stock
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4. Normal Age gradation
• Trees of all ages from one year old to rotation
age in appropriate quantity
• When trees of certain age limits occur mixed
together on the same area forms an age-class
• In a very irregular forest there may neither be
age-gradations nor age-classes; in such cases
the sign of normality is the proper distribution
of trees of all ages
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5. Normal Increment
• Maximum increment attainable by a given
species and for a given rotation, per unit area
on a given site
• Abnormality may be due to faulty formation,
faulty treatment, injurious external influences
and also unequal distribution of age-classses
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6. Normal Growing Stock
• Volumes of stands in a forest with normal age
classes and a normal increment
• In practice this taken to be the volume
indicated in Yield Tables for each classes
• NGS doesn’t necessarily imply a normal forest
• Example a forest of low density
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7. An Ideal Standard
• Normal forest is an Ideal model
• Nothing as absolute normality
• Concept is related to both rotation and system
of management
• To compare the existing condition of the
forest and to get the maximum benefit
• Necessary for proper appreciation of the
principles of Yield Regulation
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8. Abnormality
1. Over stocking
2. Under stocking
3. NGS volume but abnormal distribution of age
classes or age gradations
4. Subnormal increment
5. Normal Increment Volume in a abnormal
forest
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9. Silvicultural system on Normality
• Normal Even aged Forest
• Normal Un evenaged Forest
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10. Normal Even aged Forest
• The clear-felling system, in which all age
gradations from one year to Rotation age are
present, each occupying equi-extensive/equi-
productive areas, in which the rotation-age
coupe is felled and regenerated every year,
offers the simplest example of a conventional
Normal forest, capable of giving annual
sustained yield
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11. • Test of normality is the presence of all age-
gradations/classes, occupying equi-extensive/
equi-productive areas, fully stocked and
putting on normal increment . Strictly
speaking, occupation of equal areas by class is
not essential, but the proportion of different
ages should be correct
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12. Normal Un evenaged Forest
• In an entierly uneven-aged forest worked
under Selection System, trees of all ages (and
sizes) are found mixed together on every unit
of area, even as small as half an hectare
• Large, mature trees are felled when they
reach exploitable size or their increment falls
below the acceptable level
• Age and rotation are meaningless concepts
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13. DE LIOCOURT’S LAW
• F. DE LIOCOURT discovered that in a fully
stocked Selection Forest, the number of stems
falls off from one diameter class to the next in
geometrical progression, which means that
the percentage reduction in the stem number
from one diameter class to the next is
constant .
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14. References
• Forest Management by Ram Prakash, IBD,
Dehradun.
• Google
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15. THANK YOU
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