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Review of the influence of Acacia species on establishment of Sandalwood (Santalum spicatum) in Western Australia
Jonathan E. Brand
Science Division, Department of Conservation and Land Management, Locked Bag 104, Bentley Delivery Centre, Western Australia 6983. Email: jonb@calm.wa.gov.au
Sandalwood (Santalum spicatum) is a root hemi-parasitic tree that produces valuable fragrant oils. Harvesting of S. spicatum timber occurs mainly from natural stands in the semi-arid pastoral regions of the Goldfields and Midwest, Western Australia. These natural stands consist mainly of mature trees, with very little successful recruitment. Recruitment failure is most likely due to grazing and poor seed dispersal. Trials show that the most dramatic way to improve recruitment in natural stands is by removing grazing and planting S. spicatum seeds near suitable host plants, especially Acacia species.
Sandalwood tree farm systems are also being established in the 400–600 mm mean annual rainfall areas of the Wheatbelt and Midwest. A successful establishment technique involves planting S. spicatum seeds near 1–2 year old Acacia acuminata seedlings. S. spicatum growth rates have been relatively fast, with mean stem diameters (at 150 mm) increasing up to 7–9 mm yr-1. Current research is determining methods to further improve S. spicatum performance by studying the influence of host species, parasite-to-host ratio and provenance.
In a host trial near Katanning, S. spicatum stem diameter was higher near A. acuminata (47 mm) than near Allocasuarina huegeliana (21 mm), at age five years. All S. spicatum seedlings died near Eucalyptus loxophleba subsp. loxophleba within two years. Foliar concentrations of N and K, and the K:Ca ratio were significantly greater in S. spicatum growing near A. acuminata than near A. huegeliana. Mean stem water potentials (Ψstem) of S. spicatum were significantly lower near A. acuminata than A. huegeliana in February–March 1999.
The performance of S. spicatum near four separate Acacia species is being examined at two sites, near Narrogin and Dandaragan. At age two years, S. spicatum mean stem diameter near A. saligna (28–33 mm) was 2–4 times greater than near A. microbotrya and A. hemiteles.
Recently, the A. acuminata group was divided into seven taxa. Seedlings from these different taxa have been planted together at two locations as hosts for S. spicatum. These trials will examine the influence of A. acuminata provenance on S. spicatum performance.
