Centre for Ecosystem Studies, Forest Ecology and Forest Management, Wageningen University, PO Box 47, 6700AA Wageningen, The Netherlands.
Tree Physiol. 2013 Jun;33(6):601-8. doi: 10.1093/treephys/tpt035. Epub 2013 May 31.
Carbohydrates fixed by photosynthesis are stored in plant organs in the form of starch or sugars. Starch and sugars sum to the total non-structural carbohydrate pool (TNC) and may serve as intermediate pools between assimilation and utilization. We examined the impact of tapping on TNC concentrations in stem-wood, bark and root tissues of the frankincense tree (Boswellia papyrifera (Del.) Hochst) in two natural woodlands of Ethiopia. Two tapping treatments, one without tapping (control) and the other with tapping at 12 incisions, are applied on experimental trees. Trees are tapped in the leafless dry period, diminishing their carbon storage pools. If storage pools are not refilled by assimilation during the wet season, when crowns are in full leaf, tapping may deplete the carbon pool and weaken Boswellia trees. The highest soluble sugar concentrations were in the bark and the highest starch concentrations in the stem-wood. The stem-wood contains 12 times higher starch than soluble sugar concentrations. Hence, the highest TNC concentrations occurred in the stem-wood. Moreover, wood volume was larger than root or bark volumes and, as a result, more TNC was stored in the stem-wood. As predicted, tapping reduced the TNC concentrations and pool sizes in frankincense trees during the dry season. During the wet season, these carbon pools were gradually filled in tapped trees, but never to the size of non-tapped trees. We conclude that TNC is dynamic on a seasonal time scale and offers resilience against stress, highlighting its importance for tree carbon balance. But current resin tapping practices are intensive and may weaken Boswellia populations, jeopardizing future frankincense production.
光合作用固定的碳水化合物以淀粉或糖的形式储存在植物器官中。淀粉和糖合计为总非结构性碳水化合物库（TNC），并可作为同化和利用之间的中间库。我们在埃塞俄比亚的两个天然林地中，检查了在乳香树（Boswellia papyrifera（Del.）Hochst）的茎木、树皮和根组织中，敲打的行为对 TNC 浓度的影响。在实验树上应用了两种敲打处理，一种是不敲打（对照），另一种是在 12 个切口处敲打。树木在无叶的干燥期被敲打，减少了它们的碳储存库。如果在树冠完全展开的湿季中，通过同化作用没有补充储存库，那么敲打可能会耗尽碳库并削弱乳香树。最高的可溶性糖浓度存在于树皮中，而最高的淀粉浓度存在于茎木中。茎木中的淀粉浓度比可溶性糖浓度高 12 倍。因此，TNC 浓度最高的地方是茎木。此外，木材体积大于根或树皮体积，因此，TNC 更多地储存在茎木中。正如预测的那样，在旱季，敲打的行为降低了乳香树中的 TNC 浓度和库大小。在湿季，这些碳库在被敲打的树木中逐渐被填满，但从未达到未被敲打的树木的大小。我们得出结论，TNC 在季节性时间尺度上是动态的，并为树木提供了对压力的恢复力，突出了其对树木碳平衡的重要性。但是，当前的树脂提取实践是密集的，可能会削弱乳香树种群，危及未来的乳香生产。
