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