A review of dipterocarps - Center for International Forestry Research

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