The interaction of rainfall, tree diameter and sulphuric-acid treatments on resin yield of Palosapis (Anisoptera thurifera (Blanco) Blume ssp. thurifera)

Abstract

Thirty-two trees of palosapis (Anisoptera thurifera (Blanco) Blume ssp. thurifera), naturally growing in the logging concession of the Eastern Plywood Corporation in Llavac, Real, Quezon, Luzon Island, Philippines were tapped (boxed) for resin or oil yield. Four diameter at breast height (dbh) classes: 30–39, 40–49, 50–59 and 60 cm and over were selected. Eight trees were designated for each of four levels of aqueous sulphuric acid treatment at 0%, 40%, 50% and 60%. Resin yield per tree was determined and the influence of rainfall, diameter classes and sulphuric acid concentration was studied. Months with higher rainfall in most cases gave greater resin yield. The effect of different diameter classes on resin yield was not statistically significant except in the case of 60 cm and over which gave the highest yield. The four levels of acid concentration had no significant effect on the resin yield.