摘要
Resin production in trees probably depends on trade-offs within the tree, its environment and on tapping activities. Frankincense, the highly esteemed resin from dry woodland frankincense trees of Boswellia papyrifera is exploited in traditional ways for millennia. New exploitation practices lead to weak trees and non-sustainable resin production. For 500 trees from four populations of B. papyrifera we evaluated how frankincense yield is affected by different tapping intensities (number of incision spots) and frequencies (number of resin collection rounds during the dry season), since both of them have been intensified recently. These effects are considered for trees of different size, since larger trees probably provide more resources for resin production. We predicted that frankincense production would initially increase with tapping intensity and tapping frequency, but later level-off because of resin depletion. Frankincense production varied highly: yield per tree per year of all 500 monitored trees averaged 261 g (¡À231, but largely varied and ranged from 41 to 1829 g. We indeed found that resin yield increased with tapping intensity, but not anymore beyond an intensity of 6-9 incision spots. Yield peaked around the seventh collection round, and declined thereafter. Yield increased with trunk diameter, but leveled-off beyond trees with a stem diameter of >20 cm. These patterns were similar across populations, and between contrasting areas. Our results suggest that high tapping intensity risks short-term resource depletion, warranting tuning down the intensity of the current collection practices. Less intense tapping rounds per season will reduce damage, increase the health of tree populations, and contribute to long term frankincense production. This study thus allows for developing less damaging and more sustainable management for frankincense trees.