Pan American interactions of Amazon precipitation, streamflow, and tree growth extremes

Rainfall and river levels in the Amazon are associated with significant precipitation anomalies of opposite sign in temperate North and South America, which is the dominant mode of precipitation variability in the Americas that often arises during extremes of the El Niño/Southern Oscillation (ENSO). This co-variability of precipitation extremes across the Americas is imprinted on tree growth and is detected when new tree-ring chronologies from the eastern equatorial Amazon are compared with hundreds of moisture-sensitive tree-ring chronologies in mid-latitude North and South America from 1759 to 2016. Pan-American co-variability exists even though the seasonality of precipitation and tree growth only partially overlaps between the Amazon and mid-latitudes because ENSO forcing of climate can persist for multiple seasons and can orchestrate a coherent response, even where the growing seasons are not fully synchronized. The tree-ring data indicate that the El Niño influence on inter-hemispheric precipitation and tree growth extremes has been strong and stable over the past 258-years, but the La Niña influence has been subject to large multi-decadal changes. These changes have implications for the dynamics and forecasting of hydroclimatic variability over the Americas and are supported by analyses of the available instrumental data and selected climate model simulations.Fil: Stahle, D.W.. University of Arkansas for Medical Sciences; Estados UnidosFil: Torbenson, Max Carl Arne. Ohio State University; Estados UnidosFil: Howard, I. M.. University of Arkansas for Medical Sciences; Estados UnidosFil: Granato Souza, D.. University of Arkansas for Medical Sciences; Estados UnidosFil: Barbosa, A. C.. Universidad Federal de Lavras; BrasilFil: Feng, S.. University of Arkansas for Medical Sciences; Estados UnidosFil: Schöngart, J.. National Institute For Amazon Research; BrasilFil: Lopez Callejas, Lidio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Villalba, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Villanueva, J.. Instituto Nacional de Investigaciones Forestales Agrícolas y Pecuarias; MéxicoFil: Fernandes, K.. Columbia University; Estados Unido

Tree-ring dating of an Arkansas antebellum plantation house

As part of the Lakeport Plantation Restoration Project conducted by Arkansas State University, we examined tree-ring samples of baldcypress (Taxodium distichum L. Rich.) timbers from the Lakeport Plantation house in Chicot County, Arkansas. Our objectives for the study were to: (1) determine cutting dates of timbers used in the construction of the plantation house and an ancillary log shed in order to support or refute available historical and archaeological evidence for the construction date of the structures, and (2) provide tree-ring data to improve the spatial and temporal tree-ring record for the region. We determined that virtually all the cutting dates for the plantation house were confined to the dormant season of 1858–1859 suggesting that cutting and construction occurred at approximately the same time. We positively dated a total of 25 samples against the exactly-dated master chronology based on living baldcypress trees at Black Swamp, Arkansas, and compiled a 346-year chronology extending from 1537 to 1883. These findings provide absolute quantitative evidence of the age and construction history of one of the most important antebellum buildings in Arkansas and additional background on the material culture of the “cotton aristocracy”.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]

Bridging the Gap with Subfossil Douglas-Fir at Mesa Verde, Colorado

Old Rocky Mountain Douglas-fir (Pseudotsuga menziesii) trees and remnant "subfossil" logs have been found on the outcrop of a mafic igneous intrusion above the Mancos River Valley near Mesa Verde National Park. These trees and logs have been used to develop earlywood (EW), latewood (LW), and total ring width (TRW) chronologies dating from AD 722-2011. The new chronologies include good series replication during the former chronological "gap" from AD 1250 to 1400, which was so problematic for the initial development of the "Central Pueblo" chronology by A. E. Douglass. Discrete reconstructions of the cool-season (September-May) and early warm-season (June-July) moisture balance for Mesa Verde have been derived from the EW and adjusted LW width chronologies from the Mancos Valley. Cool-season drought is estimated to have been more severe and sustained than early warm-season conditions during the "Great Drought" of the late-13th Century when southwestern Colorado was depopulated. The combined archaeological, subfossil, and living tree chronologies of EW, LW, and TRW for the Mancos River and Mesa Verde Douglas-fir now date from AD 480-2011. Copyright © 2015 by The Tree-Ring Society.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]

The Relationship between Earlywood and Latewood Ring-Growth Across North America

The relationship between earlywood width (EW) and latewood width (LW) is investigated using 197 tree-ring collections representing several tree species from across the North American continent. Chronologies of LW have limited paleoclimate value when they have low variance or very high correlation with EW from the same site. The correlation of LW and EW can be removed by taking the residuals from linear regression to provide a chronology of discrete latewood growth free from the carryover effects of prior EW (the so-called adjusted latewood chronology, LWa). The correlation between EW and LW, along with LWa variance, varies dramatically across North America. The lowest correlations between EW and LW chronologies can be found in Pseudotsuga menziesii in the summer monsoon region of northwestern Mexico. Low correlations between EW and LW chronologies are also noted for Pinus echinata and Quercus stellata in the south-central United States. Q. stellata also displays the highest LWa variance among any species in the dataset. For three conifer species, correlations between EW and LW appear to increase with the biological age of the tree. An age-related decline in LWa variance was also detected for Douglas-fir, bald cypress and ponderosa pine older than 200 years. These results imply that heavy sampling to produce "age-stratified" chronologies based on trees ≤ 200 years in age throughout the record may produce the best quality LW chronologies with the highest variance and most discrete growth signal independent from EW. © 2016 by The Tree-Ring Society.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]

Five Hundred Years of Hydrological Drought in the Upper Colorado River Basin

This article evaluates drought scenarios of the Upper Colorado River basin (UCRB) considering multiple drought variables for the past 500 years and positions the current drought in terms of the magnitude and frequency. Drought characteristics were developed considering water-year data of UCRB’s streamflow, and basin-wide averages of the Palmer Hydrological Drought Index (PHDI) and the Palmer Z Index. Streamflow and drought indices were reconstructed for the last 500 years using a principal component regression model based on tree-ring data. The reconstructed streamflow showed higher variability as compared with reconstructed PHDI and reconstructed Palmer Z Index. The magnitude and severity of all droughts were obtained for the last 500 years for historical and reconstructed drought variables and ranked accordingly. The frequency of the current drought was obtained by considering two different drought frequency statistical approaches and three different methods of determining the beginning and end of the drought period (annual, 5-year moving, and ten year moving average). It was concluded that the current drought is the worst in the observed record period (1923-2004), but 6th to 14th largest in terms of magnitude and 1st to 12th considering severity in the past 500 years. Similarly, the current drought has a return period ranging from 37 to 103 years based on how the drought period was determined. It was concluded that if the 10-year moving average is used for defining the drought period, the current drought appears less severe in terms of magnitude and severity in the last 500 years compared with the results using 1- and 5-year averages.National Science Foundation/[CMS-0239334]/NSF/Estados UnidosUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones Geofísicas (CIGEFI