Table 2 Mean annual growth rate AGR myear and relative growth rate RGR of bole, crown, marketable heights and respective
volumes and diameter at breast height, in 6–8- and 19–21-year-old mono-cultures of E. tereticornis and D. sissoo plantations
a
Parameters 19–21-year-old plantations
6–8-year-old plantations E. tereticornis
D. sissoo E. tereticornis
D. sissoo 0.436
c
Bole height 0.798
c
1.060
b
1.701
b
0.140
b
0.114
b
0.070
c
0.168
b
Crown height 1.348
b
1.158
b
0.979
c
2.094
b
0.229
b
0.085
c
0.185
b
0.194
b
0.986
c
0.996
c
Marketable height 1.582
b
1.996
b
0.159
b
0.062
c
0.227
b
0.117
b
0.031
b
Bole volume 0.012
c
0.041
c
0.099
b
0.587
b
0.152
c
0.467
c
0.282
b
2.397
c
Crown volume 24.21
b
4.749
c
35.367
b
0.158
c
0.308
b
0.176
c
0.356
b
0.021
c
0.045
c
0.030
b
0.107
b
Marketable volume
0.647
b
0.179
c
0.291
b
0.488
c
0.097
b
0.043
c
0.069
c
0.058
b
Diameter at breast height
0.247
b
0.171
c
0.066
c
0.079
b a
Simple figures represent the values of annual growth rate AGR for the respective parameters. Figures in bold represent the respective values in terms of relative growth rate RGR. Similar superscripts in a row represent the insignificant values at P = 0.
05 level, after applying Student’s t-test.
The widely accepted 8-year rotation cycle of E. tereticornis
Thapliyal, 1986;
Rajan, 1987;
Niskanen et al., 1993; Saxena, 1994 led us to examine its monetary value from 8 to 21 years of
age, the latter being the minimum maturation age of D. sissoo. Foresters generally base their deci-
sions upon growth as well as monetary gain for these two tree species over a short period of time.
So, comparative analysis has been done in terms of growth performance and total returns in both
age groups of each plantation type.
3. Ecological viability of growth performance in E. tereticornis and D. sissoo plantations
3
.
1
.
6
–
8
-year-old plantations The annual growth rate myear in terms of
bole and marketable height and volume were observed more in E. tereticornis compared with
D. sissoo plantations. However, no significant dif- ference existed between the crown heights of the
two tree types. In contrast the crown volume was over ten times larger in D. sissoo than E. tereti-
cornis. The annual growth rate myear of di- ameter at breast height was 1.4 times greater for
D. sissoo than E. tereticornis Table 2.
Simple cumulativeannual growth rate models based on the initial biomass production, have
usually been considered for growth expression and have therefore reflected better tree height
and girth measurements in E. tereticornis than D. sissoo
Upadhyaya, 1996;
Dutta, 1997;
Nadagouda et al., 1997; Nayak and Senapati, 1997. However, growth analysis in terms of rela-
tive growth rate, which is a more reliable statisti- cal approach, presents a different scenario. In
fact, growth follows the law of compound inter- est and relative growth rate considers the loga-
rithmic function of growth and incorporates the increment with respect to time interval Kramer
and Kozlowski, 1979.
The relative growth rate of bole, crown and marketable heights did not show any significant
difference between the two plantation types, while favouring the D. sissoo plantations in terms
of volume and diameter at breast height.
3
.
2
.
19
–
21
-year-old plantations The annual growth rates myear of bole,
crown and marketable heights as well as their respective volumes were significantly higher in D.
sissoo than E. tereticornis plantations. The annual growth rate of diameter at breast height was also
1.34 times greater for D. sissoo compared with E. tereticornis Table 2.
The better growth performance of D. sissoo plantations over E. tereticornis was further statis-
tically proven by relative growth rate. The values of bole, crown and marketable heights in terms of
relative growth rate were, respectively, 2.4, 2.28 and 1.88 times greater in D. sissoo than E. tereti-
cornis. Further, the relative growth rates of bole, crown and marketable volumes in D. sissoo plan-
tations were 1.85, 2.02 and 1.62 times greater than the respective values measured in E. tereticornis.
The D. sissoo plantations also showed 1.19 times greater relative growth rate in diameter at breast
height than E. tereticornis sites Table 2. The annual growth rate as well as the relative growth
rate of all the studied parameters in D. sissoo were much better for the older plantations compared
with the younger ones. Shiva 1993 reported bet- ter mean annual increment in case of D. sissoo
compared with E. tereticornis at 11 years of age. The cumulative growth rate revealed that after
10 – 12 years of growth, D. sissoo performs very well. The short-term approach for quick monetary
gain and seemingly fast growth has shifted the scenario in favour of E. tereticornis, however, in
the long term D. sissoo seems to be better for sustainable growth performance.
To estimate the overall tree performance, the data of annual growth as well as relative growth
rate for various parameters were subjected to discriminant analysis. The values of lambda
Table 3 strongly favoured D. sissoo plantations at 19 – 21 years of growth. On the other hand, at
6 – 8 years of growth, D. sissoo was more favoured in terms of relative growth rate, followed by
annual growth rate, compared with E. tereticornis plantations of similar age Table 3.
4. Economic viability of E. tereticornis and D. sissoo plantations
