This study reports the preliminary results from a statistical screening of tree-ring width records from the International Tree-Ring Data Bank (ITRDB), to evaluate the strength of the hydrological signal, in dendrochronological records from the Tennessee Valley. We used United States Geological Survey (USGS) streamflow data from 11 gages, within the Tennessee Valley, and regional tree-ring chronologies, to analyze the dendroclimatic potential of the region, and create seasonal flow reconstructions. Prescreening methods included correlation, date, and temporal stability analysis of predictors to ensure practical and reliable reconstructions. Seasonal correlation analysis revealed that large numbers of regional tree-ring chronologies were significantly correlated (p ≤ 0.05) with the May–June–July streamflow. Stepwise linear regression was used to create the May–June–July streamflow reconstructions. Ten of the 12 streamflow stations were considered statistically skillful (R2 ≥ 0.40). Skillful reconstructions ranged from 208 to 301 years in length, and were statistically validated using leave-one-out cross validation, the sign test, and a comparison of the distribution of low flow years. The long-term streamflow variability was analyzed for the Nolichucky, Nantahala, Emory, and South Fork (SF) Holston stations. The reconstructions revealed that while most of the Western United States (U.S.). was experiencing some of its highest flow years during the early 1900s, the Tennessee Valley region was experiencing a very low flow. Results revealed the potential benefit of using tree-ring chronologies to reconstruct hydrological variables in the Southeastern U.S., by demonstrating the ability of proxy-based reconstructions to provide useful data beyond the instrumental record.
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Wood Anatomy of Douglas-Fir in Eastern Arizona and Its Relationship With Pacific Basin Climate
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 25 th to January 23 rd ), while a precipitation signal (October 27 th to February 13 th ) 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.
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- Award ID(s):
- 1903561
- NSF-PAR ID:
- 10325211
- Date Published:
- Journal Name:
- Frontiers in Plant Science
- Volume:
- 12
- ISSN:
- 1664-462X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract The teleconnection of the El Niño/Southern Oscillation (ENSO) to instrumental precipitation and temperature during the cool season over North America is strongest and most temporally stable in the TexMex sector of northern Mexico and the borderlands of southwestern United States. The ENSO impact on North American hydroclimate expands and contracts out of this region on multidecadal timescales, possibly associated with the positive and negative phases of the Atlantic Multidecadal Oscillation. A subset of tree‐ring chronologies from the TexMex sector also has the strongest and most stable ENSO signal detected in the North American network, similar to the strong ENSO signal measured in instrumental climate data from the same region. This subset of chronologies is used to reconstruct the multivariate ENSO index (MEI) as a measure of ENSO impact on North American hydroclimate during the instrumental and preinstrumental eras. The reconstruction exhibits improved fidelity in the frequency domain and better registration of spatial changes in ENSO signal over North America when compared to an MEI reconstruction based on all ENSO‐correlated tree‐ring chronologies irrespective of temporal stability of correlation. When correlated with gridded instrumental and tree‐ring reconstructed Palmer drought indices across North America, the stable MEI estimate reproduces the changes in spatial impact of ENSO signal measured with instrumental data, and it reveals similar multidecadal changes in prehistory, potentially linked to the Atlantic Multidecadal Oscillation. The Great Plains drought of the 1850s and 1860s may have been an example of this Pacific‐Atlantic configuration.
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Abstract. Given the short span of instrumental precipitationrecords in the South American Altiplano, longer-term hydroclimatic recordsare needed to understand the nature of climate variability and to improvethe predictability of precipitation, a key natural resource for thesocioeconomic development in the Altiplano and adjacent arid lowlands. Inthis region grows Polylepis tarapacana, a long-lived tree species that is very sensitive tohydroclimatic changes and has been widely used for tree-ring studies in thecentral and southern Altiplano. However, in the northern sector of thePeruvian and Chilean Altiplano (16–19∘ S)still exists a gap of high-resolution hydroclimatic data based on tree-ringrecords. Our study provides an overview of the temporal evolution of thelate-spring–mid-summer precipitation for the period 1625–2013 CE at thenorthern South American Altiplano, allowing for the identification of wet ordry periods based on a regional reconstruction from three P. tarapacana chronologies. Anincrease in the occurrence of extreme dry events, together with a decreasingtrend in the reconstructed precipitation, has been recorded since the 1970sin the northern Altiplano within the context of the last ∼4 centuries. The average precipitation over the last 17 years stands outas the driest in our 389-year reconstruction. We reveal a temporal andspatial synchrony across the Altiplano region of dry conditions since themid-1970s. Independent tree-ring-based hydroclimate reconstructions andseveral paleoclimatic records based on other proxies available for thetropical Andes record this synchrony. The influence of El Niño–SouthernOscillation (ENSO) on the northern Altiplano precipitation was detected byour rainfall reconstruction that showed past drier conditions in our studyregion associated with ENSO warm events. The spectral properties of therainfall reconstruction showed strong imprints of ENSO variability atdecadal, sub-decadal, and inter-annual timescales, in particular from thePacific NIÑO 3 sector. Overall, the recent reduction in precipitation incomparison with previous centuries, the increase in extreme dry events andthe coupling between precipitation and ENSO variability reported by thiswork is essential information in the context of the growing demand for waterresources in the Altiplano. This study will contribute to a betterunderstanding of the vulnerability and resilience of the region to theprojected evapotranspiration increase for the 21st century associated withglobal warming.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3389/fpls.2021.702442
