Silviculture guidelines to minimize fungal attack risk to the Tropical sandalwood industry. The recommendations will as follows:
Ø High risk periods of high spore count in the air and what weather events cause a greater presence of spores.
Ø High risk periods of high spore count in the water system and what irrigation events cause a greater presence of spores.
Ø Methods of branch pruning – branch size, optimum length of stump, sealing of pruning, chemical spraying after pruning the plantation.
Ø A pruning strategy of single verses multiple stems on heartwood production. On the one hand, multiple stems may produce less heartwood oil than a single stem; however, the reduced pruning may reduce fungal attack.
Ø The effect of root pruning on fungal presence in sandalwood trees.
Ø The risk of keeping infected trees within a plantation
Heartwood Formation and Oil Content
Heartwood formation in sandal trees generally starts around 10-13 years of age, but what triggers this process has not been very well understood. Certain factors, generally relating to stress, such as gravelly dry soil, insolation, and range of elevation (500-700 m), seem to provide the right environment for the formation of heartwood, irrespective of the size of the stem after 10 years of age. The occurrence of heartwood varies. The value of heartwood is due to its oil content, and the superiority of the oil is due to the percentage of santalol.
(i) In a tree the oil content is highest in the root, next highest in the stem at ground level, and gradually tapers off towards the tip of the stem.
(ii) Similarly, there is a gradient in oil content from the core to the periphery of the heartwood in a stem.
Depending upon their age, trees can be called young or mature, although this is an empirical classification and holds good only for a particular population. The oil content and its composition may differ at the same age:
(i) Young trees (height less than 10 m, girth less than 50 cm, and heartwood diameter 0.5-2 cm) have heartwood with 0.2-2 percent oil content, which has 85 percent santalol, 5 percent acetate, and 5 percent santalenes.
(ii) Mature trees (height 15-20 m, girth 0.5-1 m, and heartwood diameter 10-20 cm) have heartwood with oil content of 2- 6.2 percent, which has over 90 percent santalol, 3-5 percent acetate, and 3 percent santalenes.
Ø Jonathan Brand,John de Majnik,Jessica Yu, Tropical sandalwood silviculture management to minimise fungal attack, An environmentally sustainable Australia, Report of Forest Products Commission, 2014.
Ø Shobha N. Ral, Status and Cultivation of Sandalwood in India, Presented at the Symposium on Sandalwood in the Pacific, April 9-11, 1990, Honolulu, Hawai, USDA Forest Service Gen. Tech. Rep. PSW-122. 1990.