The Laboratory of Tree-Ring Research at The University of Arizona was founded in 1937 by A. E. Douglass, founder of the modern science of dendrochronology. The LTRR is a research unit in the College of Science at the University of Arizona.

The faculty, students, and scientific staff of the Laboratory of Tree-Ring Research (LTRR) are engaged in a diverse array of research programs which include fire history and fire ecology, multiproxy paleoclimatology, archaeology, biogeography, isotope geochemistry, paleoecology, biogeochemistry, geomorphology, numerical and statistical modeling, and even public health. These collections represent a small portion of the research performed at the laboratory.


For more information about collections from the Laboratory of Tree-Ring Research, visit http://ltrr.arizona.edu.

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Recent Submissions

  • Riparian dendrochronology: a method for determining flood histories of ungaged watersheds

    Laing, David; Stockton, Charles Wayne; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1976-08)
    Examination of 106 crossdated tree-ring cores from the riparian zone of Pine Creek near Escalante, Utah, 10 cores from Bright Angel Creek, Grand Canyon, Arizona, 8 cores from South Taylor Creek, Zion National Park, Utah, and 5 cores from the Animas River near Silverton, Colorado, has yielded the following information: 1. Various riparian gymnosperm and angiosperm species crossdate with semi-arid site gymnosperms. 2. Tree growth is best correlated with snowpack water equivalent. 3. Flood damage to trees is manifested in growth suppression on root exposure or burial, in reaction wood on tilting, and in scarring. 4. Flood damage is very infrequent at Pine Creek from 1700 to 1880, more so from 1880 to 1909, and very frequent from 1909 to the present. (The town of Escalante was settled in 1875, and stocking of the range around Pine Creek reached a maximum shortly after 1900.) 5. Flood damage shows fairly constant frequency in the Bright Angel Creek watershed, which has seen little land use. 6. Flood damage on South Taylor Creek shows a marked increase in frequency between about 1900 and 1937 when the region was included in Zion National Monument, after which flood damage declined markedly in frequency.
  • Patterns of Climatic Change Revealed Through Dendroclimatology

    Fritts, Harold C.; Lofgren, G. Robert; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1978-10)
    The objectives of this report are, first, to summarize the findings to date of the dendroclimatic work performed by our research team at the University of Arizona with respect to the broad patterns of climatic variations over North America since 1600 AD. A secondary objective, as stated in the contract, is to select set(s) of those past climatic patterns which most closely resemble or provide a perspective for conditions of climatic variability expressed as possessing a substantial degree of mobility of occurrence by the National Defense University (1978) study of climatic changes.
  • Tree-Ring Chronologies of Western North America: California, Eastern Oregon and Northern Great Basin with Procedures Used in the Chronology Development Work Including Users Manuals for Computer Programs COFECHA and ARSTAN

    Holmes, Richard L.; Adams, Rex K.; Fritts, Harold C.; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1986)
    Well replicated tree-ring samples were collected, dated and measured for California west of the Sierra Nevada, eastern Oregon and the northern Great Basin. A computer program was developed and used to check crossdating quality. Another computer program to generate and analyze tree-ring chronologies was evaluated, further developed cooperatively and used to produce chronologies for the dated site collections. This report contains these site chronologies in three versions along with site descriptions and chronology statistics. Users manuals are included for the two computer programs. The effect on a chronology of poor crossdating is discussed, and a study of standardization of tree-ring measurement series is reported. Some new techniques are described for processing tree-ring samples.
  • To the Friends of Camille Flammarion

    Henri Tessier (Orléans), 1926-05-20
  • Using Dendrochronology To Measure Radial Growth of Defoliated Trees

    Swetnam, Thomas W.; Thompson, Marna Ares; Sutherland, Elaine Kennedy; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (U.S. Department of Agriculture, Forest Service, Cooperative State Research Service, 1985-06)
  • Northern Hemisphere Temperature Estimation Using Blue Group Northern Hemisphere 70-Chronology Set: High Latitude and High Altitude Sites

    LaMarche, Valmore C., Jr.; Cain, Cyra J.; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1986)
  • Climatic Regimes of the Pacific Sector and Adjacent Continents Since 1600: A Synoptic Description and Comparison of Independent Climate Proxy Records

    Fritts, Harold C.; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1987-06)
  • Tree Ring Evidence of a 22-Year Rhythm of Drought Area in Western United States and Its Relationship to the Hale Solar Cycle

    Stockton, Charles W.; Meko, David M.; Mitchell, J. Murray, Jr.; Laboratory of Tree-Ring Research, University of Arizona; National Oceanic and Atmospheric Administration, Environmental Data and Information Service, Silver Spring, MD (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1978-09)
  • Tree-Ring Evidence for Climatic Changes in Western North America

    Fritts, Harold C.; Laboratory of Tree-Ring Research, University of Arizona (American Meteorological Society (Boston, MA), 1965-07)
    The relationships between climatic factors and fluctuations in dated tree-ring widths are statistically evaluated. A wide ring indicates that the year's climate was moist and cool, and a narrow ring dry and warm. In general, ring width relates to a 14-month period from June through July but most tree-ring chronologies exhibit a closer relationship with autumn, winter, and spring moisture than with summer moisture. The climatic relationships for evergreen trees are attributed largely to the influence of environmental factors on photosynthesis and the accumulation of food reserves. Under abnormally dry and warm conditions, especially during the autumn, winter, and spring, little food is accumulated, new cells are formed more slowly during the growing period, and the resulting ring is narrow. Relative 10 -yr. departures are calculated for the entire length of 26 tree -ring chronologies from western North America. Those portions after 1500 are used to map areas of high and low moisture. Periods of widespread drought are noted in 1576-1590, 1626-1635, 1776-1785,1841-1850, 1871-1880, 1931-1940. Periods of widespread and above average moisture occurred during 1611-1625,1641-1650, 1741-1755, 1826-1840, 1906-1920. The moist periods of 1611-1625, and 1906-1920 were most widespread and markedly above average.
  • Geohydrological Implications of Climate Change on Water Resource Development

    Stockton, Charles W.; Boggess, William R.; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1979-05)
    One of the basic assumptions in hydrology is that hydrologic time series are stationary in the sense that the probability distribution of a series can be determined from a finite sample and that it will not change with time. This assumption implies that climate which is an integral part of all hydrologic series is stationary with time. The fact is that climate is nonstationary and this non-stationarity varies from region to region. The objective of this study is to evaluate the known physical state of hydrologic processes in each of the 18 Water Resource Regions for the conterminous United States as outlined by the Water Resources Council and to speculate on the response of the system to superimposed climate variability. Four climate scenarios are evaluated encompassing all combinations of a 2 °C change in mean annual temperature with an accompanying 10 percent change in total annual precipitation. The technique used involves estimated change in mean annual runoff with respect to that of the present using empirically developed curves that relate weighted mean annual temperatures to mean annual precipitation and runoff. An evaluation of presently available models and techniques for incorporating climate variability into synthetic hydrologic traces is also discussed. Tree-ring data series are mentioned as a possible way of investigating regional climatic variability on hydrologic responses. The region-by-region evaluation of climatic change impacts indicates that a change toward a warmer and drier climate (scenario 1) would have the greatest effect on a nation-wide basis. These effects are largely adverse and the most severe impact would be in the water deficient regions west of the Mississippi River. In contrast, mostly beneficial effects would accrue from a change to cooler and wetter conditions (scenario 2). The greatest positive effects would be in the dry western regions; some negative effects would result from increased flooding on most major river systems and their tributaries, especially eastward from the Missouri and Mississippi Rivers. The effect of warmer and wetter (scenario 3) and cooler and drier (scenario 4) climatic variations on annual runoff are conjectured to be trivial in most regions. Only in the Upper Colorado River Region did scenario 3 prove to be non-trivial on a region wide basis. Our impact analysis indicates all regions would be adversely affected by a warmer and drier climatic change. In one region, the South Atlantic -Gulf, the impact is considered negligible. The adverse impacts were considered minor in the New England, Ohio, Souris-Red-Rainy, Great Basin, Pacific Northwest, and Lower Mississippi Regions. Moderate impacts are postulated for the Mid-Atlantic, Great Lakes, Tennessee, and Upper Mississippi. Major changes in the response of the water resources system are postulated for the Arkansas-White-Red, Texas Gulf, Rio Grande, Upper Colorado, Lower Colorado, California and Missouri Regions. Even under warmer and drier conditions, total runoff from the Pacific Northwest Region is greater than the present combined total annual runoff from the California, Great Basin, Lower Colorado and Upper Colorado Regions. In fact, the Pacific Northwest Region is the only region in the western United States that presently appears to have a water supply surplus. For a cooler and wetter climatic variation (scenario 2) adverse effects are predicted for some regions, although the national impact would be mostly beneficial. Adversely affected regions are the South Atlantic-Gulf, the Lower Mississippi and the Great Basin. The remaining fifteen regions would be beneficially affected, although the New England, Mid-Atlantic, Great Lakes, Souris-Red-Rainy and the Pacific Northwest Regions fall into the negligible category. An apparently beneficial impact would be felt by the Ohio, Tennessee, Upper Mississippi, Missouri, Upper Colorado, Arkansas-White-Red, Texas Gulf, Rio Grande, Lower Colorado and California Regions, although there would be increased flooding in five of these. Several regions where water is currently abundant with respect to demand, would experience only negligible or minor impacts regardless of whether warmer and drier (scenario 1) or cooler and wetter (scenario 2) climatic variations would occur. These include New England, South Atlantic-Gulf, Ohio, Souris-Red-Rainy, Great Basin and Pacific Northwest. The effects of the postulated climatic changes on the total water reserve is shown by comparing the ratios of regional total reservoir capacity to mean annual runoff for the present and for warmer and drier (scenario 1) and cooler and wetter (scenario 2) climatic variations. The results show all regions east of and including the Upper and Lower Mississippi Regions would tend to fill the existing reservoir storage in 1.2 years or less regardless of whether scenario 1 or 2 climatic variations occurred. In the west, the region most affected by either change would be the Lower Colorado River Region. Under the present climatic regime and total available storage, there is enough capacity to accommodate 12+ years of mean annual regional flow, including present level of inflow. If a warmer and drier (scenario 1) variation occurred it would require nearly 19 years reservoir capacity. In the Missouri River, the present total reservoir capacity would be quite beneficial as only a little less than two years of mean flow would be required to fill to total capacity should a cooler and wetter (scenario 2) change occur; presently a little less than three years is required. If a warmer and drier (scenario 1) change occurred, a little over eight years would be required. What are the present trends in climate? At this time, there appear to be different lines of evidence suggesting a present cooling trend over much of the Northern Hemisphere with at least one study suggesting it will continue. Some climatologists indicate that with increasing carbon-dioxide in the atmosphere, this will reverse and warming will be the dominant future trend. Analysis of individual regional runoff series do not show any indication of trends in runoff data suggesting a uniform increase in mean annual runoff. In fact, the opposite is true. In a rather restricted segment of the western southern Rocky Mountain Region, the trend is toward reduced runoff. When the overall total streamflow of the nation is considered however, there is no apparent trend in the data.
  • Tree-Ring Evidence for Climatic Changes in Western North America From 1500 A.D. to 1940 A.D.

    Fritts, Harold C.; Smith, David G.; Holmes, Richard L.; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1964-12-31)
    Introduction: The details of the climatic history of the United States during recent centuries are not known. In this period, as in more ancient times, there is much indirect evidence of significant changes of climate. Dendroclimatic analysis represents an especially promising source of information on the chronology and character of such climatic changes, especially those in the semiarid regions of western North America. It is the purpose of this report to present: (1) some recent analyses of the climatic factors influencing ring growth; (2) a brief discussion of the current theory concerning the model of tree growth and climate and (3) a first approximation of synoptic dendroclimatological patterns from 1500 A.D. to 1940 A.D. using 26 selected tree-ring chronologies from western North America. This material is being circulated to professionals in related fields in hopes that they may compare these results with their own findings and make appropriate criticisms. The authors welcome any suggestions, especially those pertaining to correlation or lack of correlation of the maps with other lines of evidence. The paper is to be presented at the VII International Congress of the International Association for Quaternary Research which meets at Boulder, Colorado, during August of 1965. The analyses of the tree growth relationships were sponsored in part by the National Geographic Society and the U. S. Department of Interior, National Park Service, through the Wetherill Mesa Archeological Project. The authors are indebted to past and present staff at the Laboratory of Tree-Ring Research for the development of the regional tree-ring chronologies, and to the Numerical Analysis Laboratory, The University of Arizona, for free computing time and services. They are also indebted to James A. Erdman, Maurice E. Cooley, Nicholas Matelas, and Julie McMahan, who assisted in various phases of the project.
  • The Climate of Arizona: Prospects for the Future

    Brazel, Anthony J.; Fritts, Harold C.; Idso, Sherwood B.; Department of Geography, Arizona State University; Laboratory of Tree-Ring Research, University of Arizona; U.S. Water Conservation Laboratory, Phoenix, Arizona (The State Climatologist for Arizona (Tempe, AZ), 1978)
    Introduction: The climate of any region sets the tempo of indigenous life styles and largely dictates the scale and type of economic activity that can be sustained. In Arizona, we are subject to perhaps more climatic restraints than are many other areas, due to the high air temperatures in summer and the rather low yearly rainfall. But, weather is variable; and its sum total -- climate -- is not unchanging either. Thus, in planning the future direction economic activity should take, prospects for changes in climate should be considered. In this paper we attempt to marshal the best evidence available to outline the possibilities for Arizona's future climate. We hope that the information will prove useful to those who must make the difficult decisions that will shape the character of our state in the years to come.
  • Golden Trout '72

    Bard, Thomas R.; Carr, Clayton; Wright, William; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1972-06-06)
  • Ethylene Production By Different Age Class Ponderosa and Jeffery Pine Needles as Related to Ozone Exposure and Visible Injury

    Telewski, Frank W.; Laboratory of Tree-Ring Research, University of Arizona (Springer-Verlag, 1992)
    Ethylene production by different needle age classes was characterized using a mercuric perchlorate traps in natural populations of two ponderosa pine varieties (Pinus ponderosa var. arizonica [Engelm] Shaw and var. ponderosa Dougl. ex Laws.) and Jeffery pine (Pinus leffrevi Grev. and Balf.). All ozone -exposed populations contained individuals which were symptomatic and asymptomatic with respect to visible ozone injury. Ethylene production of different needle age classes was also characterized in Pinus ponderosa var. ponderosa seedlings grown in open top ozone fumigation chambers. Older age class needles produce more ethylene than younger age class needles. Needles of both P. ponderosa var. ponderosa and P. jeffreyi exhibiting ozone injury in the field produced significantly (p >0.05) higher levels of ethylene than asymptomatic conspecifics. Seedlings exposed to highest treatment level of ozone in the fumigation study produced the highest levels of ethylene followed by fumigation with medium and low ozone concentrations and carbon filtered air. These data indicate that measurement of ethylene in conifer needles as a measure of stress needs to be calibrated for needle age class. It also suggests that the sensitivity of a tree to ozone injury may be regulated by the inherent ability of the individual to produce ethylene.
  • Augmenting Annual Runoff Records Using Tree-Ring Data

    Stockton, Charles W.; Fritts, Harold C.; Laboratory of Tree-Ring Research, University of Arizona; Laboratory of Tree-Ring Research, University of Arizona (Arizona-Nevada Academy of Science, 1971-04)
    INTRODUCTION: Any statistical work involving hydrologic records is handicapped when the records are of relatively short duration, as are most such records in the Southwestern United States. This is because the short records are not necessarily a random sample of the infinite population of events, and consequently any statistical descriptions are likely to be in error to some extent. Work recently completed at the Laboratory of Tree-Ring Research [Stockton, 1971] has shown that tree ring data can be used to extend available runoff records backward in time, thereby providing a longer record from which to more accurately estimate the three most common statistics used in hydrology, the mean, the variance, and the first order autocorrelation.
  • Two Lectures on Water Law

    Clark, Robert Emmet (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1965-02-25)
  • Precipitation and Saguaro Growth

    Hastings, James Rodney; Institute of Atmospheric Physics, University of Arizona (Office of Arid Land Studies, University of Arizona (Tucson, AZ), 1961)
  • Projected Effects of Climatic Variation Upon Water Availability in Western United States (Progress Report)

    Stockton, Charles W.; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1983-07)
  • A Guide to Measuring Tree-Ring Widths

    Burns, James Michael; Laboratory of Tree-Ring Research, University of Arizona (Laboratory of Tree-Ring Research, University of Arizona (Tucson, AZ), 1979-01)
    Dendrochronologists in their scientific inquiries use quantitative data, of which tree-ring widths form a major part. In order to gather the necessary quantitative tree-ring data, someone must be trained to measure the widths of the tree rings. The purpose of this paper is to explain to the person who will actually measure the tree-ring widths how the measuring process should be performed at the Laboratory of Tree-Ring Research. The following three sections describe the three phases of the measuring process. The first section deals with the preparations that must be performed before the ring widths can be measured. The second section describes the procedures for measuring the ring widths. The final section describes the checking procedure used to test the reliability of the measurements.

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