Baker Jessica C A, Santos Guaciara M, Gloor Manuel, Brienen Roel J W
1School of Geography, University of Leeds, Leeds, UK.
2Earth System Science, University of California, Irvine, USA.
Trees (Berl West). 2017;31(6):1999-2009. doi: 10.1007/s00468-017-1604-9. Epub 2017 Aug 20.
['Radiocarbon dating shows that', {'i': 'Cedrela'}, 'trees from Bolivia, Ecuador and Venezuela form one ring per year but', {'i': 'Cedrela'}, 'trees from Suriname form two rings per year.']
Tropical tree rings have the potential to yield valuable ecological and climate information, on the condition that rings are annual and accurately dated. It is important to understand the factors controlling ring formation, since regional variation in these factors could cause trees in different regions to form tree rings at different times. Here, we use 'bomb-peak' radiocarbon (C) dating to test the periodicity of ring formation in trees from four sites across tropical South America. We show that trees from Bolivia, Ecuador and Venezuela have reliably annual tree rings, while trees from Suriname regularly form two rings per year. This proves that while tree rings of a particular species may be demonstrably annual at one site, this does not imply that rings are formed annually in other locations. We explore possible drivers of variation in ring periodicity and find that growth rhythms are most likely caused by precipitation seasonality, with a possible degree of genetic control. Therefore, tree-ring studies undertaken at new locations in the tropics require independent validation of the annual nature of tree rings, irrespective of how the studied species behaves in other locations.
['放射性碳年代测定表明，来自玻利维亚、厄瓜多尔和委内瑞拉的', {'i': '洋椿属'}, '树木每年形成一圈年轮，但来自苏里南的', {'i': '洋椿属'}, '树木每年形成两圈年轮。']
热带树木年轮有潜力提供有价值的生态和气候信息，前提是年轮是一年生且年代测定准确。了解控制年轮形成的因素很重要，因为这些因素的区域差异可能导致不同地区的树木在不同时间形成年轮。在这里，我们使用“炸弹峰值”放射性碳（C）年代测定法来测试南美洲热带地区四个地点的树木年轮形成的周期性。我们发现，来自玻利维亚、厄瓜多尔和委内瑞拉的树木有可靠的一年生树木年轮，而来自苏里南的树木每年定期形成两圈年轮。这证明，虽然某一特定物种的树木年轮在一个地点可能明显是一年生的，但这并不意味着在其他地点也是每年形成年轮。我们探讨了年轮周期性变化的可能驱动因素，发现生长节律最有可能是由降水季节性引起的，可能存在一定程度的遗传控制。因此，在热带地区新地点进行的树木年轮研究需要对树木年轮的年度性质进行独立验证，无论所研究的物种在其他地点的表现如何。
