Effect of four tapping methods on anatomical traits and resin yield in Maritime pine (Pinus pinaster Ait.)

Abstract

External induction of resin secretion, based on the defence system of Pinus trees, has been performed by humans since Classical times through various methods. The socio-economic implication of this practice in Spain and the expansion of the Chinese market justify a new approach to tapping methodology and the effects of this activity on the tree. The resin yield of 561 Pinus pinaster trees in a stand in central Spain, tapped in 2012 using four different methods (mechanised or traditional tool, upwards or downwards), was analysed. An anatomical study was made of 13 trees (8 tapped and 5 controls) in another stand 13km away with similar climate and soil conditions, tapped in 2011 using the same four methods. From each tapped tree, eight cores were taken at different locations and varying distances from the tapping wound. In each core, an analysis was made of growth ring, earlywood and latewood width, and axial canal frequency, area, mean size and location from one year before tapping to two years after (2010–2013). The highest mean annual resin yield was found for traditional tool upward tapping, which also induced the highest increase in axial canal frequency and area. The lowest yield was found for mechanised tapping, which showed no differences between the upward and downward directions. The strongest induction of systemic induced responses in terms of resin canal frequency and area was detected one year after tapping for upward tapping. This suggests the involvement of signalling processes that spread mainly upwards, and the importance of adaptive processes as a defence to periodic insect attacks for this forest tree.