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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Plantations 172<br />
diameter <strong>of</strong> 46.3 m and 75 cm respectively in 31 years. At<br />
the age <strong>of</strong> 29 years, Shorea platyclados stands in Pasir<br />
Hantap Experimental Forest in Indonesia have an average<br />
height <strong>of</strong> 29 m, bole length <strong>of</strong> 17 m and an average diameter<br />
<strong>of</strong> 41 cm. In Sarawak, trees <strong>of</strong> Shorea species <strong>of</strong> the pinanga<br />
group reached diameters between 34 cm and 75 cm between<br />
the age <strong>of</strong> 34 and 48 years (Primack et al. 1989). Shorea<br />
macrophylla showed the best growth per<strong>for</strong>mance, and S.<br />
splendida the poorest. A severe depression in growth<br />
occurred during flowering years. There is however, the<br />
danger in assuming the same growth rates in operational<br />
plantations and over the whole range <strong>of</strong> sites. Care has to be<br />
taken in economic calculations not to overestimate the<br />
per<strong>for</strong>mance.<br />
Shorea robusta is the most intensively researched<br />
species concerning growth and yield. Some yield tables<br />
exist (e.g., Howard 1925, Griffith and Bakshi Sant Ram<br />
1943). The species’ growth rate under different<br />
treatments has been reported by Mathauda (1953a). The<br />
growth rates <strong>of</strong> other dipterocarp species were reported<br />
by Mathauda (1953b) and Rai (1979, 1981a, b, 1989).<br />
More recently, the long-term research sites have been<br />
<strong>review</strong>ed and updated by Rai (1996). Under natural<br />
conditions the annual rate <strong>of</strong> diameter growth <strong>for</strong> most<br />
dipterocarp species is only 0.3 to 0.35 cm.<br />
Among the <strong>dipterocarps</strong>, the growth and yield <strong>of</strong><br />
Shorea robusta has been well investigated (Howard<br />
1925, Griffith and Bakshi Sant Ram 1943, Krishnaswamy<br />
1953, Mathauda 1953b, 1958, Chaturvedi 1975, Suri<br />
1975b, Raman 1976). The maximum biomass production<br />
was 14.62 tons/ha/year during the 18th year (Raman<br />
1976). In thinning trials, the results showed the<br />
superiority <strong>of</strong> the heavy and very heavy low thinning<br />
treatments (Krishnaswamy 1953). In India, research in<br />
thinning <strong>of</strong> plantations has been carried out, while this is<br />
not the case in other parts <strong>of</strong> the Indo-Malayan region.<br />
Dawkins (1963) introduced the crown diameter to bole<br />
diameter relation (also called growing space index) to<br />
estimate basal area density. This relation has been used<br />
<strong>for</strong> determining stand density regimes <strong>for</strong> Shorea<br />
robusta (Chaturvedi 1975). Suri (1975b) developed a<br />
quantitative thinning model <strong>for</strong> Shorea robusta which<br />
considers different types <strong>of</strong> crown disengagement<br />
regimes. Each <strong>of</strong> these crown disengagement regimes<br />
has a specific sequence <strong>of</strong> growing space index values.<br />
Rai (1979, 1981a) has reported growth rates <strong>of</strong> Hopea<br />
parviflora and H. wightiana.<br />
Site quality has a direct influence on growth rates.<br />
However, little has been researched in this respect. The<br />
effect <strong>of</strong> elevation on height and diameter growth <strong>of</strong><br />
Dipterocarpus turbinatus was investigated by Temu et<br />
al. (1988). The decline in height and diameter growth<br />
was relatively small compared to the increase in<br />
elevation. The cause <strong>for</strong> the decline is probably due to<br />
the rapid drop in the water table and leaching <strong>of</strong> nutrients<br />
at the higher parts <strong>of</strong> hilly terrain.<br />
The economics <strong>of</strong> plantations <strong>of</strong> dipterocarp species<br />
have hardly been investigated. Lack <strong>of</strong> a sufficiently broad<br />
data base may have been the reason <strong>for</strong> the delay.<br />
Recently, some economic assessments were made on<br />
plantations <strong>of</strong> Shorea leprosula, S. parvifolia and S.<br />
platyclados in Peninsular Malaysia (Kollert et al. 1993,<br />
Zuhaidi et al. 1994, Kollert et al. 1994), and the<br />
following conclusions were drawn. The establishment<br />
and management <strong>of</strong> <strong>for</strong>est plantations are uneconomical<br />
if valued on financial terms alone. Forest plantations <strong>of</strong><br />
relatively long rotations do not produce sufficient returns<br />
early enough to attract investment, especially from the<br />
private sector. Investors avoid the long gestation periods,<br />
the relatively low rate <strong>of</strong> return and the relatively high<br />
risk <strong>of</strong> investment. The venture <strong>of</strong> <strong>for</strong>est plantations will<br />
become economically attractive only by end <strong>of</strong> the first<br />
rotation, when the age class sequence is complete and<br />
future stand establishment is not by clear cut and planting<br />
but through natural regeneration.<br />
<strong>Research</strong> Priorities<br />
It is recommended that all research is carried out with<br />
the same set <strong>of</strong> <strong>dipterocarps</strong> (the most promising species<br />
<strong>for</strong> plantations). For species/provenance tests (species<br />
elimination, site adaptation), which usually remain<br />
untreated, it is recommended to include a standard<br />
silvicultural treatment.<br />
• Silvics and species choice: Build up <strong>of</strong> in<strong>for</strong>mation<br />
on silvical and silvicultural characters including site<br />
requirements, establishment <strong>of</strong> a site adaptation trial,<br />
establishment <strong>of</strong> systematic species/provenance elimination<br />
trials, evaluation <strong>of</strong> the existing dipterocarp<br />
plantations throughout the region as a basis <strong>for</strong> the<br />
above-mentioned trials.<br />
• Seed: Seed production from trees/stands, seed orchard<br />
technology, dysgenic shifts as a basis <strong>for</strong> strategies<br />
in tree selection work.<br />
• Planting stock production: Comparative planting stock<br />
production test, comparative cutting propagation trial,<br />
mycorrhization techniques in nurseries.