P2C2: Relationships Between Regional Climatic Patterns, Wood Anatomy, and Hydraulic Architecture of Conifer Species in the Western US

本项目旨在研究美国西部针叶树种木材解剖特征中记录的与太平洋年代际涛动(PDO)和厄尔尼诺-南方涛动(ENSO)两种主要气候模式有关的气候信号。在美国西部干旱和半干旱的环境中，水是森林生态系统、植物群落和人类社会经济系统的主要限制因素。更好地了解美国西部过去PDO和ENSO变化的年际和年代际动态，将有利于土地管理人员和政策制定者为不同气候情景下预测的可能持续干旱事件做准备。该项目的主要目标是：1)确定与年代际和年际气候振荡驱动的长期和短期生长变化有关的树木解剖反应，特别是在太平洋年代际涛动正/负阶段和厄尔尼诺/拉尼娜事件期间表现出的水力适应；以及2)评估年内树木年轮解剖作为替代指标纳入树枝气候重建的可能性。研究人员预计将为美国西部的五个目标区域生成长达一个世纪的解剖学特征(即细胞大小和细胞壁厚度)序列，从美国西南部和大盆地的潮湿环境到温度有限的太平洋西北部。本研究以对气候敏感的针叶树为研究对象，对12个采样点进行采样。到目前为止，木材解剖特征已被用于在有限的空间和时间尺度上重建树状气候，但还没有研究集中于美国西部长期年内水力调节与区域气候模式之间的关系。这项研究通过开发和利用比以往调查更大的数据集，还可以评估样本大小对利用木材解剖重建气候信号的变化的影响。该项目将支持研究生和本科生，将通过培训从申请者中挑选出来的高中科学教师成为暑期研究员，为K-12 STEM教育做出贡献，并涉及与赫尔姆霍兹中心波茨坦-GFZ德国研究中心DendroLab的国际合作。

This project generally aims to investigate climatic signals recorded in wood anatomical features of western U.S. conifer species in relation to two leading climatic modes, the Pacific Decadal Oscillation (PDO) and the El Niño-Southern Oscillation (ENSO). In the arid and semi-arid environment of the Western U.S., water is the main limiting factor for forest ecosystems, plant communities, and human socio-economic systems. Improved understanding of past inter-annual and decadal dynamics of PDO and ENSO variability in the Western U.S. would benefit land managers and policy makers as they prepare for possible sustained drought events projected under different climate scenarios. The main objectives of the project are: 1) to define the tree anatomical response associated with long- and short-term growth variations driven by decadal and inter-annual climatic oscillations, in particular the hydraulic acclimation exhibited during positive/negative phases of the Pacific Decadal Oscillation and during El Niño/La Niña events; and 2) to evaluate the potential of intra-annual tree-ring anatomy as a proxy to be integrated into dendroclimatic reconstructions. The researchers expect to generate century-long time-series of anatomical features (i.e., cell size and cell-wall thickness) for five target regions of the western U.S., from the moisture-limited environments of the American Southwest and Great Basin to the temperature-limited Pacific Northwest. A total of twelve sites will be sampled by targeting climate-sensitive conifers (mostly Pseudotsuga menziesii, Pseudotsuga macrocarpa, and Pinus ponderosa).To date, wood anatomical features have been used as proxies for dendroclimatic reconstructions at limited spatial and temporal scales yet no studies have focused on the relationships between long-term intra-annual hydraulic adjustments and regional climatic patterns in the western U.S. This research, by developing and utilizing a much larger dataset than previous investigations, could also make it possible to assess the effect of sample size on the variability of climatic signals reconstructed using wood anatomy.This project will support graduate and undergraduate students, will contribute to K-12 STEM education by training high school science teachers selected from a pool of applicants to become Summer Research Fellows, and involves an international collaboration with the Helmholtz-Centre Potsdam - GFZ German Research Centre Dendrolab.