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

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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.