Tree-Ring Based Reconstruction of Drought over the Past 500-1000 Years in the Eastern United States

该奖项将支持利用两种长寿针叶树的年轮分析来重建美国东部过去500-1000年的干旱历史的研究，这两种树种是东部红柏(Juniperus Virginiana)和北部白柏(Thuja Ocsidentalis)。这一数据将极大地改善对全美干旱变化范围的估计。这些树种生活在或保存在东北部陡峭的悬崖上的古老森林的广泛发现，将使利用活树和保存完好的化石木材编制覆盖过去1000年的树轮年表成为可能。东部红柏和北部白柏可能代表了唯一广泛分布的物种，可以用来在美国东部建立这样一个对干旱敏感的树轮年表网络。还将研究生长在美国东北部湿地和沼泽中的黑胶(Nyssa Sylvatica)的树枝气候潜力。这是世界上寿命最长的硬木之一，有记载的年龄为500-700年。初步分析表明，该物种产生可交叉更新的年轮，与夏季温度显著相关。将开发一个小型的黑胶年表网络，以确定使用该物种重建过去500年前夏季气温的可行性。

This award will support research to reconstruct the drought history of the eastern United States over the last 500-1,000 years using the analysis of tree-rings from two species of long-lived conifers; the eastern red cedar (Juniperus virginiana) and the northern white cedar (Thuja occidentalis). This data will greatly improve estimates of the full range of drought variability across the United States. The widespread discovery of ancient forests of these tree species living or preserved on steep cliff faces in the northeast will enable the development of tree-ring chronologies covering the past 1,000 years from living trees and well-preserved fossil wood. Eastern red and northern white cedar may represent the only widely distributed species that are available for developing a network of such long drought-sensitive tree-ring chronologies in the eastern United States. The dendroclimatic potential of black gum (Nyssa sylvatica) growing in wetlands and swamps in the northeastern United States will also be examined. This is one of the longest-lived hardwoods in the world with a documented age of 500-700 years. Preliminary analyses indicate that this species produces cross-datable tree rings that correlate significantly with summer temperatures. A small network of black gum chronologies will be developed to determine the feasibility of using this species to reconstruct past summer temperatures in excess of 500 years before the present.