nds ca
ile abo
used t
1 basis
om sta
re appli
ive nat
d anal
l area a
TlNG GROWTH AND YIELD
91
25
8
20
7
6
15
Z
E
::l
c:
0
~
s:
4
u
c:::
:§.
~
I~
10
5
4
8
12
16
Age (years)
20
24
28
Figure 4.2 Ouadratic mean diameter (D q ) over age for
6 stems-per-acre planting densities (s.p.a.) of slash pine
in the Transvaal, South Africa. (After Pienaar, 1965.)
r of trees per acre as predictor variables, have obviated the normality
ch (Nelson and Bennett, 1965). The following sections develop variable
. growth and yield prediction methods in some detail. Particular emphasis
d on techniques applicable to plantations.
prediction models can be categorized by the complexity of the mathe­
approach involved:
Models in tabular form
, Models as equations and systems of equations
1. Direct prediction of unit-area values
'2. Unit-area values obtained by summation
(a) Equations for classes of trees
(b) Equations for individual trees