Oleoresin yield of Pinus merkusii trees from East Banyumas

Pinus merkusii is the main pine found in Indonesia to produce oleoresin. The present study assessed the oleoresin yield treated by various stimulants (ETRAT, SR4, sulphuric acid, sulphuric acid-Ethepon mixtures), and relate it with several tree characteristics. Trees were selected from different two different class ages i.e. IV (16-20 years) and VII (31-35 years) and were tapped for 8 days by bark chipping method in 5 replications. The pine stand was located in East Banyumas of Perhutani. Results showed that the mixture of sulfuric acid and Ethephon gave comparatively high oleoresin yield levels. In general, tree from age class of VII exhibited higher amount of resin production than those of age class of IV. The levels of oleoresin yield were significantly correlated with tree height in 31-35-year-old trees. After combining data from the two age classes, only a positive relationship between tree diameter and oleoresin yield was measured in untreated trees. For stimulated trees, the oleoresin yield exhibited positive significant correlation coefficient with tree diameter, tree height, and crown closure for certain stimulants. The negative significant correlation was observed between oleoresin yield and site elevation. As no consistent pattern of correlations with regard to stimulating agents, it suggests that the role of other factors should be explored in future works.