Doctoral Dissertation Research: A Multi-Proxy Approach to Understanding Environmental Dynamics in Old-Growth Rocky Mountain Juniper Woodlands, New Mexico, U.S.A.

长寿树木提供了与树木年生长相关的主要环境因子的数千年记录，如降水和长期气候振荡。树木年表学家已经确定，一些西南针叶树，包括道格拉斯冷杉、黄松和落基山杜松，在某些森林环境中可以活到很老。先前对位于新墨西哥州格兰茨附近的El Malpais国家纪念碑（EMNM）和Cibola国家森林（CNF）的偏远熔岩流的研究为该项目奠定了基础。在这里，针叶树主要构成了一个发育不良的林地，其中有一些特殊的古树，有些树已经有2000多年的历史了。实际上，熔岩流是岛屿生态系统，它展示了与周围景观非常不同的植物群，而周围景观具有不同的基质。博士生Mark Spond在Henri gris中国- mayer教授的指导下，将使用EMNM和CNF熔岩地层中收集的跨年代落基山杜松样本来评估过去2000年月度和季节性气候因素与落基山杜松生长之间的多尺度关系。本研究还探讨了EMNM/CNF落基山杜松生长之间的关系，以及10年气候模式（如厄尔Niño-Southern涛动和太平洋涛动）和区域天气模式（如北美季风）之间的关系。通过建立永久性研究地块、编制年龄结构数据和比较重复照片，对EMNM老林地内较小尺度的植被动态进行了评估。这项研究的结果将回答理论和应用问题：哪些气候变量与落基山杜松的生长最相关？落基山杜松的平均年增长率是多少？落基山杜松的生长与气候模式之间存在什么关系？从20世纪40年代到现在，在EMNM的古老混合针叶树林地中可以观察到什么植被变化？最后，落基山杜松树年轮数据能否帮助为美国西南部的水资源可用性提供一个扩展的框架，这是一个容易出现极端水文特性的地区？这项研究将帮助当地和地区政府官员制定政策，有效解决新墨西哥州西部的水资源分配、侵入性植被处理、规定的燃烧时间表、野火管理和其他管理问题。目前，国际树木年轮数据库（ITRDB）不包括美国西南部落基山杜松的树木年轮数据。本博士论文研究产生的落基山杜松年表将提交给ITRDB。研究结果将通过论文、几份专业报告和同行评议的期刊文章与土地管理官员和更广泛的科学界分享。这项研究还将被纳入田纳西州和新墨西哥州的K-12学生和教师、环保组织以及政府官员的教育计划中，采用由美国国家科学基金会资助的田纳西大学GK-12地球项目的成功模式。这项研究的主要研究者致力于在项目的各个阶段让代表性不足的群体参与进来，并成功地招募了几名女本科生来协助这个项目。

Long-lived trees provide multi-millennial records of the principle environmental factors associated with annual tree growth, such as precipitation and long-term climate oscillations. Dendrochronologists have established that some Southwestern conifer trees, including Douglas-fir, ponderosa pine, and Rocky Mountain juniper, can live to old ages in certain forest settings. Previous research on the remote lava flows at El Malpais National Monument (EMNM) and Cibola National Forest (CNF) located near Grants, New Mexico set the stage for this project. Here, conifers largely comprise a stunted woodland that harbors pockets of exceptional old-growth trees, some trees being over 2,000 years in age. The lava flows are, in effect, island ecosystems that exhibit a very different flora than the surrounding landscape which has a different substrate. Doctoral student Mark Spond, under the supervision of Professor Henri Grissino-Mayer, will use cross-dated Rocky Mountain juniper samples collected from the lava formations at EMNM and CNF to assess multi-scale relationships between monthly and seasonal climatic factors and Rocky Mountain juniper growth of the past 2,000 years. This study also investigates relationships between Rocky Mountain juniper growth at EMNM/CNF and within and between 10-year climate patterns (e.g., El Niño-Southern Oscillation and the Pacific Oscillation) and regional weather patterns (e.g., North American Monsoon). Smaller-scale vegetation dynamics within the old-growth woodlands at EMNM are assessed by the creation of permanent study plots, compilations of age structure data, and comparisons of repeated photographs. The results of this research will answer both theoretical and applied questions: Which climate variables correlate best with Rocky Mountain juniper growth? What is the average rate of annual growth for Rocky Mountain juniper? What relationships exist between Rocky Mountain juniper growth and climate patterns? What changes in vegetation can be observed in the old-growth mixed-conifer woodlands of EMNM between the 1940s and the present? And finally, can Rocky Mountain juniper tree-ring data aid in providing an expanded framework for water resource availability in the American Southwest, an area prone to extremes in hydrologic properties?This research will assist local and regional government officials in developing policies that can effectively address such issues as water allocation, invasive vegetation treatment, prescribed burn schedules, wildfire management, and other management issues in western New Mexico. Currently, the International Tree-Ring Data Bank (ITRDB) does not include Rocky Mountain juniper tree-ring data from the American Southwest. Rocky Mountain juniper chronologies produced by this doctoral dissertation research will be submitted to the ITRDB. Findings will be shared with land management officials and the broader scientific community through the dissertation, several professional presentations, and peer-reviewed journal articles. This research will also be incorporated into educational programs for K-12 students and teachers, conservation organizations, and government officials in Tennessee and New Mexico, using the successful model of the University of Tennessee's GK-12 Earth Project, funded by the National Science Foundation. The Principal Investigators of this research are committed to involving underrepresented groups in all phases of their project, and have successfully recruited several female undergraduate students to assist on this project.