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Abstract
Dendroclimatic reconstructions, which are a well-known tool for extending records of climatic variability, have recently been expanded by using wood anatomical parameters. However, the relationships between wood cellular structures and large-scale climatic patterns, such as El Niño-Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO), are still not completely understood, hindering the potential for wood anatomy as a paleoclimatic proxy. To better understand the teleconnection between regional and local climate processes in the western United States, our main objective was to assess the value of these emerging tree-ring parameters for reconstructing climate dynamics. Using Confocal Laser Scanning Microscopy, we measured cell lumen diameter and cell wall thickness (CWT) for the period 1966 to 2015 in five Douglas-firs [Pseudotsuga menziesii (Mirb.) Franco] from two sites in eastern Arizona (United States). Dendroclimatic analysis was performed using chronologies developed for 10 equally distributed sectors of the ring and daily climatic records to identify the strongest climatic signal for each sector. We found that lumen diameter in the first ring sector was sensitive to previous fall–winter temperature (September 25th to January 23rd), while a precipitation signal (October 27th to February 13th) persisted for the entire first half of the ring. The lack of synchronous patterns between trees for CWT prevented conducting meaningful climate-response analysis for that anatomical parameter. Time series of lumen diameter showed an anti-phase relationship with the Southern Oscillation Index (a proxy for ENSO) at 10 to 14year periodicity and particularly in 1980–2005, suggesting that chronologies of wood anatomical parameters respond to multidecadal variability of regional climatic modes. Our findings demonstrate the potential of cell structural characteristics of southwestern United States conifers for reconstructing past climatic variability, while also improving our understanding of how large-scale ocean–atmosphere interactions impact local hydroclimatic patterns.
Highlights
The climate of the North American West is closely connected with ocean–atmosphere variability in the Pacific Basin, which is often defined through indices, such as the El Niño-Southern Oscillation (ENSO) index (Barnett et al, 1991) and the Pacific Decadal Oscillation (PDO) index (Mantua and Hare, 2002)
Despite falling within the core region of the North American Monsoon (NAM), where precipitation is mostly concentrated in the summer months (Griffin et al, 2013), mountain areas in this part of the southwestern United States are sensitive to cool-season conditions linked to ENSO, and the Dendrobox tool allowed us to search the International Tree-Ring Data Bank (Grissino-Mayer and Fritts, 1997) for existing sites with ring-width chronologies
From the Quantitative wood anatomy (QWA) data produced by ROXAS, our analysis focused on the intra- and inter-annual variability in radial diameter of cell lumen (LD) and tangential cell wall thickness (CWT)
Summary
The climate of the North American West is closely connected with ocean–atmosphere variability in the Pacific Basin, which is often defined through indices, such as the El Niño-Southern Oscillation (ENSO) index (Barnett et al, 1991) and the Pacific Decadal Oscillation (PDO) index (Mantua and Hare, 2002) Both climatic modes play a fundamental role in determining interannual variability of ecohydrological conditions, affecting water resources, in the moisture-limited environments of the western United States (Corringham and Cayan, 2019; White et al, 2019), and long-term vegetation dynamics (Viglizzo et al, 2015). Model predictions based on large-scale atmospheric circulation patterns have been shown to unsatisfactorily reproduce observed precipitation dynamics (Jong et al, 2018) This is because linking ENSO- and PDO-driven regional climatic conditions with local hydroclimatic variability requires properly accounting for additional site-specific factors. Wind direction and local topography can cause abnormally high rainfalls to occur, contrary to expectation, during La Niña events in the southwest United States (Feldl and Roe, 2010)
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