Estimated heartwood weights and oil concentrations within 16-year-old Indian sandalwood (Santalum album) trees planted near Kununurra, Western Australia

Summary

Thirty-two Indian sandalwood (Santalum album) trees aged 16 y, growing near Kununurra (Western Australia), were harvested, de-barked and weighed to determine their commercial wood (heartwood and sapwood) weights. Within each tree, heartwood area, percentage and weight were measured in stem cross-sections at five different heights (0, 0.50, 1.00, 2.00 and 3.00 m above the ground) in the main stem, and used to estimate total heartwood volume and weight. Heartwood oil concentration and a—and β-santalol concentrations were also measured at the same heights in each tree.

At age 16 y, the 32 S. album trees had mean estimated air-dry weights (at ~12% moisture content) of 5.8 kg heartwood tree⁻¹ and 43.7 kg sapwood tree⁻¹. The mean air-dry wood densities were 940 kg m⁻³ for the heartwood and 840 kg m~³ for the sapwood. Estimated heartwood weight was variable between trees, with the three largest trees each containing 24–30 kg heartwood, while nine other trees each had 0–1 kg heartwood. The S. album plantation in this study contained about 260 trees ha ⁻¹, and its predicted yields (air-dry weight) at age 16 y were 1.5 t heartwood ha⁻¹ and 11.41 sapwood ha ⁻¹.

Within each tree, the mean oil concentration (w/w air dry) ranged from 6.2% (at 0 m) to 2.9% (at 3.00 m). Overall, the mean oil concentration within the heartwood was 5.0%, giving estimated yields of 0.28 kg oil tree⁻¹ and 73 kg oil ha⁻¹ (based on 260 trees ha⁻¹). The mean α-santalol concentration (44–50%) and β-santalol concentration (18–20%) at the five different tree heights met the current ISO standard for S. album oil.

In the 16-y-old S. album trees, over-bark stem diameter at 300 mm above the ground correlated well to both total air-dry weight of wood (heartwood and sapwood) per tree (r² = 0.88) and heartwood air-dry weight per tree (r² = 0.87). This indicated that large-diameter trees had markedly higher heartwood weights.

Keywords:

• heartwood
• sapwood
• oils
• yields
• concentration
• α-santalol
• β-santalol
• S. album