Hydrogen isotopes in lignin: a new proxy for the Amazon hydrological cycle?

亚马逊河流域是世界上最大的集水区，并维持着地球上最大的连续雨林。全球变化正在以不确定的方式影响亚马逊气候，近几十年来，亚马逊雨季降雨量增加，干旱频率增加。为了更好地了解这些变化背后的驱动因素，需要长期准确地记录水文循环。在这个项目中，我们将测试一种新的气候代用指标，它来自树木年轮中的氢同位素，可以促进这种重建。与亚马逊河中现有的氧同位素替代物相比，木质素甲氧基中的氢同位素被认为保留了降水中氢同位素的信号。我们将测试到什么程度的氢同位素生长沿着海拔横断面从亚马逊到安第斯山脉确实保存在降水中的氢的变化，并应用这种新方法的热带树种雪松在干燥和潮湿的网站重建降水氧同位素在过去的50至150年的年度分辨率。如果成功的话，这个新的代理人可以用来产生的热带水文气候变化的反应的见解。当与来自树木年轮的氧和碳同位素结合使用时，源水中的氢同位素的重建可以进一步用于解释植物生理对CO2的长期变化。

The Amazon basin is the world's largest catchment and sustains the largest continuous rainforest on Earth. Global change is affecting the Amazon climate in uncertain ways, with recent decades seeing an increase in Amazon wet season rainfall, as well as, increasing drought frequency. To better understand the drivers behind these changes, long-term accurate records of the hydrological cycle are needed. In this project we will test a new climate proxy derived from hydrogen isotopes in tree rings that can contribute towards such reconstructions. In contrast to existing oxygen isotope proxies in the Amazon, hydrogen isotopes in lignin methoxyl groups are thought to preserve the signal of hydrogen isotopes in precipitation. We will test to what degree hydrogen isotopes growing along an elevational transect from the Amazon to the Andes indeed preserve variation in hydrogen in precipitation, and apply this new method for the tropical tree species Cedrela odorata at a dry and wet site to reconstruct precipitation oxygen isotopes for the past 50 to 150 years at annual resolution. If successful this new proxy can be used to generate insights in the response of the tropical hydrological to climate change. Reconstructions of hydrogen isotopes in the source water can further be useful to interpret long-term change in plant physiology to CO2 when used in combination with oxygen and carbon isotopes from tree rings.