Research Updates, Santalum|

Sandalwood is an important international commodity, recognised for its aromatic oil which is a key ingredient in many fragrances and cosmetics. Western Australian (WA) sandalwood (Santalum spicatum) is known to be a cheaper alternative for the superior Indian sandalwood (Santalum album) as it has a lower oil content and lower quality oil. The natural stocks of S. album have declined due to illegal poaching, mismanagement, and disease. WA sandalwood’s natural stands have also reduced due to historical mismanagement. As a result, WA sandalwood (S. spicatum) has been established in plantations in the southern half of WA to attempt to meet the demands of the sandalwood industry. Plantation WA sandalwood is promoted to farmers as agroforestry, with the promise of economic and environmental benefits. While these benefits are attractive, sandalwood has an estimated 25 year rotation. This research aimed to determine the effect of physical and chemical treatments on oil production and heartwood formation in WA sandalwood, with the aim being to increase oil production, thus allowing the time between establishment and harvesting to be reduced. This study was conducted over three plantations in the Wheatbelt region of Western Australia; ‘Sandawindy’, ‘Kylie Reserve’, and ’Brookton’. At each site, four treatments were applied: a dowel soaked with the plant hormone Methyl Salicylate (MeSA) and inserted into the tree (Treated Dowel treatment), a dowel with no MeSA inserted into the tree (Blank Dowel treatment), a drill hole left empty (Empty Drill treatment), and a section of bark removed from the tree (Bark Removed treatment), as well as a group of trees left as a control for comparison. The Blank Dowel and Empty Drill treatments were established to determine if any significant increases of sandalwood oil in the Treated Dowel treatment were a result of the MeSA, the foreign dowel, or drilling into the tree. The Bark Removed treatment was used to mimic drysidedness; a condition that occurs naturally in the Rangelands of WA as a result of sun scald. The sandalwood trees were measured and treated in November of 2016. Plantations were divided into 30 evenly sized blocks per site, with 6 replicate blocks allocated to each treatment and control group. Two replicate blocks for every treatment and control group at each plantation were harvested in November of 2017, and all trees were remeasured. Of the approximate 300 trees harvested, 150 were cored using a 12 mm auger drill. These core samples were analysed for oil yield and composition at Wescorp’s laboratory. The total oil was measured an analysed, as well as the oil constituents α-santalol, β-santalol, farnesol, nuciferol, and β-bisabalol oil compositions (percentage) and yield (%w/w). All trees that were harvested ii were cut into 8 discs measuring 25 mm each, and the percentage of heartwood area at each height was measured and recorded. All data was statistically analysed using a univariate general linear model. There was no treatment that consistently increased total oil or oil component yields, qualities, or heartwood area percentages. The Empty Drill treatment resulted in more oil production than the control group on the most occasions, however it did not consistently increase oil production. This showed that the presence of MeSA did not have a significant effect on oil production, and the physical wounding of the tree had the overall greatest effect. The Kylie Reserve plantation showed low oil yield and low heartwood area percentages compared to the Sandawindy and Brookton plantations, although also showed the highest oil yields. This research, while not showing significant increases in oil production for the different treatments used, has giving a promising indication that a longer time between treatment and harvesting could influence the oil production. Further research extending this study should be conducted to give more information on the effect of the treatments on oil production.

Reference: Smith, P.-A. (2019). “Stimulation of Western Australian Sandalwood (Santalum spicatum) oil production using multiple treatments.”

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