Opportunities for the smallholder sandalwood industry in ... - ACIAR

120
100
Heartwood yield (kg)
80
60
40
20
y = 2.56x – 18.0
R 2 = 0.71
0
–20
0 5 10 15 20 25 30 35 40
Age (years)
Figure 12. Relative weight of heartwood among sandalwood of different ages, sampled in Tanna and Erromango
each of soil type, rainfall and the level of sun exposure
on the canopy of the sandalwood. Among the
experienced respondents, there was consensus that
sandalwood growing in a shallow soil or one with
a high level of stone inclusions, together with a
distinct annual dry period, and exposure to full sun
developed heartwood rapidly. The expected period
for harvest under these conditions was 15–20 years,
but may be as much as 30–40 years for trees growing
in contrasting areas of deep, fertile soil, high
and evenly distributed rainfall throughout the year,
and a shaded canopy. Rai (1990) proposed that environmental
factors imparting stress on a sandalwood
tree were important in the promotion of heartwood
development in S. album. It is possible that the differences
in heartwood development between different
environments may account for the discrepancies in
the estimated rotations for many sandalwood species
(Doran et al. 2005).
The development of heartwood is most pronounced
in the roots and base of the tree, and gradually
reduces towards the trunk and branches. Low
branching limits the development of the heartwood
into the canopy of the tree and therefore reduces
the potential value of the tree at harvest. However,
pruning at an early age (years 1–3) can substantially
reduce the incidence of low branching and promote
the development of a single bole. This improvement
of tree form can potentially increase the individual
tree value and thus the profitability of planted sandalwood.
A tree with a single bole and clear grain
heartwood also has the potential to produce highvalue
carving logs. Therefore, the widespread use of
pruning to bring about such a commercial form can
potentially increase the overall value of the planted
industry in Vanuatu with minimal investment in the
form of labour.
Planting spacing and host plants
All species of Santalum are hemiparasites, forming
haustorial root connections with the roots of
a wide range of species, including annual and
perennial crops (Tennakoon et al. 1997; Tennakoon
and Cameron 2006). While much has been written
about the benefits of hosts (Tennakoon et al.
1997; Radomiljac and McComb 1998; Loveys
et al. 2002; Barbour 2008), good productivity of
S. austrocaledonicum over many years occurs in
plantings with few large woody hosts, provided that
sandalwood spacing is not lower than 3 m × 3 m. It
is likely that sandalwood gains much benefit from
forming associations with many herbaceous crops
and weeds, particularly the prevalent leguminous
34