214
H . KLOMP
TABLE I
Data of 6 Twig Samples Taken in the Summer of 1954 to
Estimate Larval Density
1
2
3
Sample Sack
Date
90
91
92
92a
93
94
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
1
2
3
9 Aug.
10
11
8 Sept.
9
10
4
5
6
7
of
of
Number Number
Number of larvae
shoots larvae
per shoot
per ma
2 336
2 529
2 552
2 036
2 012
2 418
2 280
2 401
2 608
2 046
2 720
2 274
2 786
1 9 8 6
2 163
1 9 5 9
2 741
2 828
55
64
59
32
90
53
77
22
74
54
61
85
74
56
56
37
66
49
0.0236
0.0253
0.0231
0.0157 -
b" =
0.0251
w, = 11.6
0.0219 /
J
0.0338
0-0092
0.0282
\
0.0264
0.0224
0.0374
0.0189
0.0241
0.0173
& on the other hand is very variable as a result of an extreme variability of tree size. Moreover, only a limited number of trees can be cut
down to count the number of shoots present. To avoid this difficulty
we looked for a relation between the number of shoots per tree (St) and
the size of the tree, expressed in the circumference of the trunk (C).
This relation proved to be:
log St = a + b log C
(3)
The parameters a and b vary year by year, and therefore have to be
estimated annually. To achieve this about 46 trees whose trunk
memurements were known, were felled each year to count the number
of shoots present in the crowns (see Fig. 4). The values of a and b are
estimated by a linear regression calculation.