Tropical Climate Reconstruction with Tree-Ring Chronologies from the Central Amazon and Eastern Highlands of Brazil

这一合作项目将涉及阿肯色州大学（大卫Stahle）、巴西国家亚马逊河研究所/马克斯普朗克研究所（Jochen Schongart）和巴西拉夫拉斯的联邦大学（Ana卡罗莱纳巴博萨）。 严格的树木年代学方法将被用来培训学生和教师在这两个机构，并制定几个确切的日期，以及复制的年轮宽度年表，涵盖了过去300年的季节性淹没低地森林的亚马逊河流域中部和季节性干燥的高地森林的巴西东部。 精确的树木年轮年表提供了一个重要的工业化前的全球变暖的角度来看，并产生了唯一的空间分布的估计，过去的特大干旱和多雨需要测试气候模型模拟的动力学负责十年的水分制度在北美。 世界范围内绝大多数的树木年轮年表都是从温带和北方森林发展而来的。 然而，世界上最具生物多样性的森林生态系统，巴西亚马逊盆地的森林，还没有产生一个免费提供的多世纪树木年轮年表，可用于精确的年代测定或气候重建。 由于没有寒冷的冬季休眠季节，大多数热带树种不会产生解剖学上独特的年轮，因此不能用于常规的树木年代学。 然而，在一些热带森林中确实存在强烈的环境节律，并能诱导少数本地物种的年轮形成。 这包括深刻的降水季节性和长期洪水脉冲的低地森林在亚马逊河中部。 初步研究证明，这些淹没森林中的Acacifolium Macrolobium中存在年轮，其水文气候应用的潜在价值已被证明。 在Cedrelafissilis和C. odorata从季节性干燥的高地森林的巴西和东部玻利维亚，年轮宽度和氧同位素年表都与大尺度的气候变率。 在亚马逊河流域发展长期气候敏感的树木年轮年表的一个主要障碍是缺乏严格应用树木年轮学的专业知识，树木年轮学是地质年代学中最准确和精确的测年方法。 将通过该项目开发的树木生长和气候历史的300年主年表预计将利用广泛的跨学科研究，包括气候动力学，同位素古气候学和森林生态学。 一旦这一研究概念得到证明，进一步的合作调查设想，涉及美国和巴西的科学家，以模拟气候和水流的反应，推导年表，制定校准重建的年度水文气候条件，并调查大规模的海洋大气强迫的水分制度在热带南美洲。

This collaborative project will involve the University of Arkansas (David Stahle), the Brazilian National Institute for Amazonian Research/Max Planck Institute (Jochen Schongart), and the Federal University at Lavras, Brazil (Ana Carolina Barbosa). Rigorous dendrochronological methods will be used to train students and faculty at both institutions and to develop several exactly dated, well replicated ring-width chronologies covering the last 300-years in the seasonally flooded bottomland forests of the central Amazon basin and in seasonally dry upland forests of eastern Brazil. Exactly dated tree-ring chronologies provide a vital preindustrial perspective on global warming and have produced the only spatially distributed estimates of past megadroughts and pluvials needed for testing climate model simulations of the dynamics responsible for decadal moisture regimes over North America. The vast majority of tree-ring chronologies available worldwide have been developed from temperate and boreal forests. However, the most biodiverse forest ecosystems in the world, the forests of the Amazon Basin in Brazil, have not produced a single freely available multi-century tree-ring chronology useful for exact dating or climate reconstruction. In the absence of a cold winter dormant season, most tropical tree species do not produce anatomically distinctive annual growth rings and therefore cannot be used for routine dendrochronology. However, strong environmental rhythms do exist in some tropical forests and can induce annual ring formation in a few native species. This includes the profound precipitation seasonality and the prolonged flood pulse of lowland forests in the central Amazon. Preliminary research has proven that annual rings exist in Macrolobium acacifolium in these inundation forests and their potential value for hydroclimatic applications has been demonstrated. Annual rings have also been proven in Cedrella fissilis and C. odorata from seasonally dry upland forests of Brazil and eastern Bolivia, and ring width and oxygen isotope chronologies from both are related to large-scale climate variability. A major impediment to the development of long climate sensitive tree ring chronologies in Amazonia has been the lack of expertise with the rigorous application of dendrochronology, the most accurate and precise dating method in geochronology. The 300-year long master chronologies of tree growth and climate history that will be developed through this project are expected to leverage a wide range of interdisciplinary research, including climate dynamics, isotope paleoclimatology, and forest ecology. Once this research concept is proven, further collaborative investigations are envisioned that involve US and Brazilian scientists, in order to model the climate and stream flow response of the derived chronologies, develop calibrated reconstructions of annual hydroclimatic conditions, and investigate the large scale ocean-atmospheric forcing of moisture regimes over tropical South America.