Resin yield response to different tapping methods and stimulant pastes in Pinus pinaster Ait

Selecting the best resin tapping method and stimulant paste in the resin tapping process is crucial. In timber-oriented rainy Atlantic pine forests of north-west Spain, the interest in resin tapping is raising but information on the best tapping methods and pastes is still lacking. In this study, an appropriate experimental design used on five representative plots of Pinus pinaster, allowed us to explore the resin productive differences between two tapping methods (traditional Spanish method and circular groove) and three stimulant treatments (control, Ethephon and ASACIF). The use of a standardized measure of resin yield allowed to adequately compare methods differing in groove length. Results indicated that the standard resin yield was 1.43 times greater with the traditional method than with the circular groove method. The two stimulant pastes drastically increased resin yield (up to sixfold) in all sites and for all tapping methods. The effectiveness of the paste was also influenced by the tapping method, obtaining greater increases in resin yield after the application of stimulant paste in trees with the circular groove method. Resin yield was only slightly related to the dasometric variables and varied among test sites when no pastes were used, but differences among sites disappeared when stimulant pastes were used. Our results contribute to the understanding of the factors involved in resin performance and the technological development of the sector.