A review of dipterocarps - Center for International Forestry Research

Management of Natural Forests
0.82 cm/yr; logged forest, 0.93 cm/yr; plantation, 1.22
cm/yr) (Primack et al. 1989). In any case, among the
commercial species, dipterocarps grow much more
vigourously than non-dipterocarps, by at least 25-35%
(e.g. periodic diameter mean annual increment for Labis
F. R., Peninsular Malaysia: dipterocarps, 0.85 cm/yr;
non-dipterocarp commercials, 0.66 cm/yr) (Tang and
Wan Razali 1981). Among the dipterocarps the light
hardwoods grow faster than the heavy ones (growth rates
in Peninsular Malaysia sample plantation plots: light
hardwood Shorea macrophylla, 2.23 cm/yr; heavy
hardwood Shorea sumatrana, 0.86 cm/yr) (Appanah and
Weinland 1993). Growth rate, expressed in diameter
increment, is lowest with smaller individuals, and
culminates usually in the 50-60 cm diameter classes,
and declines in bigger trees. This pattern of diameter
increment has been seen in the Philippines (Weidelt and
Banaag 1982), Sabah (Nicholson 1965), and Peninsular
Malaysia (Tang and Wan Razali 1981). A sample from
the Mindanao concessions in the Philippines illustrates
the point:
Following logging or liberation thinning, the
residuals are known to respond to the release by
increasing their growth rates. In general the increments
were highest in the first years after logging, and declined
slowly, and after about the fifth year the benefits of
release seem to cease (Tang and Wadley 1976).
Site\ Age Year 1 Year 2 Year 3 Year 4 Year 5
Peninsular
Malaysia-
Tekam F.R.
Peninsular
Malaysia-
Labis F.R.
dbh class (cm) cm/yr
10
20
30
40
50
60
70
80
90
0.72
0.63
0.57
0.79
0.68
0.71
0.44
0.58
0.69
0.78
0.83
0.86
0.86
0.85
0.79
0.67
0.63
0.57
Besides, the above, the trees grew faster (mean annual
diameter increment) in plots where more timber was
harvested (plot residual basal area) after logging (Tang
and Wadley 1976):
n/a
Residual basal area
(m 2 /ha)
10-16
16-22
>22
140
A peculiar behaviour of all tropical trees, including
that of dipterocarps, is the extremely wide range of
growth rates of individual trees even within the same
diameter class. The variation coefficient may reach 70-
100%. This is illustrated in the mean annual diameter
increment for the minimal, maximal and median growth
rates (cm/yr) of Shorea species in primary, liberationtreated,
and plantation forests in Sarawak (Primack et
al. 1989):
Mean annual
diameter
increment (cm)
Primary
Forest
Mean annual diameter
increment (cm/yr)
Liberation
Felling
0.44
0.45
0.55
Plantation
Minimum 0.13 0.16 0.80
Maximum 0.82 0.93 1.22
Median 0.30 0.43 0.86
Next is the variation in the growth rates within one
region, and between regions. Studies of the annual
diameter increment (cm/yr) of dipterocarps in the
Philippine (Weidelt 1996) and Sarawak forests (Primack
et al. 1989) illustrate these points:
Location Mean annual diameter
increment (cm)
Sarawak:
Mersing
Bako
Philippines:
Mindanao
Visayas
Luzon
0.41
0.30
0.73
0.48
0.52
It should be noted that dipterocarps on fertile sites
in the high rainfall area of eastern Mindanao have high
annual increments. The growth rates are consistently
better in the Philippines than Sarawak, indicating regional
differences. The forests in the Philippines should
generally have better yields. Even within Sarawak, there
are differences between the two forests, which can be
ascribed mainly to better soil fertility at Mersing.
Despite the existence of some good information on
the growth of dipterocarp trees, there is a tendency to
exaggerate their growth rates. For example, in Peninsular
Malaysia, the generally accepted standard for growth of
trees in logged forests is above 0.8 cm/yr diameter