Now showing items 1-20 of 90265

    • Trimming and Planing Rough-Cut Wood for Efficient Dendrochronological Sample Preparation and Storage

      Minor, J.J.; Arizpe, A.H. (Tree Ring Society, 2015-07)
      Wood samples larger than increment cores collected for tree-ring studies are often obtained using chainsaws and, less frequently, 2-person crosscut saws. Saw marks on cross-sectional wood samples can be quite deep and uneven, and sanding rough-cut wood cross-sections is inefficient in terms of processing time and wear on sanding belts. Trimming rough-cut wood samples with a band saw or treating with a surface planer creates a smoother initial surface for sample sanding and polishing. Sample trimming with a band saw or surface planer is also useful for post-analysis archiving and wood storage, when excess wood can be removed and smaller samples entered into storage. Band saw and surface planer safety techniques are also discussed. Copyright © 2015 by The Tree-Ring Society.
    • A Method for Tree-Ring Analysis Using Diva-Gis Freeware on Scanned Core Images

      Arenas-Castro, S.; Fernández-Haeger, J.; Jordano-Barbudo, D. (Tree Ring Society, 2015-07)
      Tree-ring analysis is a basic technique of paramount importance in forest management, yet it may prove difficult and time-consuming for many slow-growth hardwood tree species. Moreover, it requires the use of specialized tools and proprietary software, which may hinder researchers working with limited budgets. We describe an innovative and inexpensive method using DIVA-GIS freeware software to analyze true color high-resolution scanned images of cores previously enhanced with ImageJ freeware (GIS-SDI), and test its accuracy against the widely-used LINTAB-TSAPWin™ and WinDENDRO™ methods. For this purpose, Abies pinsapo and Pyrus bourgaeana increment cores were processed independently using each of the three methods and the results were statistically compared. Dating results were consistent across all three methods, although identifying rings was easier and quicker to perform on the digital images. Using a modern but affordable flatbed scanner to digitize tree cores and the free DIVA-GIS software to analyze the scanned digital images proved to be an inexpensive but highly accurate and efficient approach to tree-ring analysis. Furthermore, this method greatly facilitates tree-ring analysis in species with inconspicuous rings, and enables a complete digital record of every core analyzed to be stored. Copyright © 2015 by The Tree-Ring Society.
    • Competitive Strength Effect in the Climate Response of Scots Pine Radial Growth in South-Central Siberia Forest-Steppe

      Babushkina, E.A.; Vaganov, E.A.; Belokopytova, L.V.; Shishov, V.V.; Grachev, A.M. (Tree Ring Society, 2015-07)
      This paper presents a method for classification of trees in groups depending on parameters of the age trend in tree-ring width. The method is tested on a sample containing 194 trees of Scots pine (Pinus sylvestris L.) growing in the forest-steppe zone of the South of Central Siberia. The climatic response of tree-ring width in such climatic conditions is complex. The influence of temperature in May-September is negative (moisture reducing). Warm-season precipitation serving as a source of moisture is a positive factor. Another positive factor is cold-season precipitation as frost protection. We determined the dependence of this response on the local conditions (soil, landscape and anthropogenic factors). The competitive strength of the trees influences both the sensitivity of individual trees to extreme climatic factors and the timing of growth processes. The latter implies the duration of the period of significant response to climate. It appears promising to take this influence into account in dendroclimatic reconstructions by using separate clusters of trees based on the competitive strength and having the maximum response to the reconstructed factor. Copyright © 2015 by The Tree-Ring Society.
    • Reconstructing Evaporation from Pine Tree Rings in Northern Mexico

      Pompa-García, M.; Camarero, J.J. (Tree Ring Society, 2015-07)
      Here we reconstructed evaporation using tree-ring width variability. Drought variability and its effects on forest growth have been mainly characterized by changes in precipitation and temperatures, whereas atmospheric drought and evaporation rates have been little investigated. The area of study corresponds to northern Mexico, a region where water resources are increasingly limited. We used correlation analyses to identify the months in which evaporation is most strongly related to tree-ring width series. Then, we built a linear regression model to predict seasonal winter-to-spring evaporation as a function of ring-width indices. Correlation analyses showed that the radial growth of P. cooperi decreased in response to reduced water availability and increased evaporation during the winter prior to the growing season, and also during spring and the early summer of the year of tree-ring formation. Pine growth mainly benefitted from wet and cool conditions from winter to early spring. Linear regression models used in reconstruction were statistically robust and allowed reconstructing January-to-April evaporation for the period 1900-2010. Our study contributes to a better understanding of historical changes in evaporation in northern Mexico and, most importantly, it also emphasizes how atmospheric moisture demand is linked to tree growth. Copyright © 2015 by The Tree-Ring Society.
    • Tree-Ring Investigation of Holocene Flood-Deposited Wood from the Oneida Lake Watershed, New York State

      Panyushkina, I.P.; Leavitt, S.W.; Domack, E.W.; Wiedenhoeft, A.C. (Tree Ring Society, 2015-07)
      Glacial deposition and fluvial/lacustrine sedimentation interact over terrains in central New York State to preserve a history of geological and hydrological events as well as hydroclimatic transitions. The lower reach of Fish Creek draining the eastern watershed of Oneida Lake, NY, is an area with prominent wood remains. This study explores a collection of 52 logs encased in organic-rich deposits exposed by bank erosion at three locations along Fish Creek near Sylvan Beach, NY, with respect to radiocarbon ages, species, and the crossdating potential of tree rings. Radiocarbon ages and successful tree-ring crossdating document what we interpret as seven major hydrologic episodes ca. 10 ka (i.e. ca. 10,000 cal yr BP), 7.4 ka, 6.8 ka, 6.4 ka, 5.5 ka, 3.1 ka and 2.2 ka cal BP, during which channel aggradation and tree burial may have been associated with abruptly increased flood frequency and/or high water tables. This pilot study establishes four floating tree-ring records: [1] early Holocene hemlock (Tsuga), mid-Holocene [2] walnut (Juglans sp.) and [3] sycamore (Platanus), and [4] late Holocene elm (Ulmus sp.), with sample sizes of 8-14 series of 55-135 years length. Despite the complexity of distribution of radiocarbon ages at each site, the wealth of well-preserved wood demonstrates great promise for understanding the paleoflood history of the Oneida watershed by documenting the magnitude, location, and timing of floods. Further additional systematic sampling can add and strengthen tree-ring dating and tree-ring based flood records, confirm results, and contribute to the Holocene hydrological history of the region. Copyright © 2015 by The Tree-Ring Society.
    • Do Rules of Thumb Measure Up? Characteristics of Fire-Scarred Trees and Samples

      Yocom Kent, L.L.; Fulé, P.Z. (Tree Ring Society, 2015-07)
      Dendrochronologists studying fire history must be strategic in their search for fire-scarred tree samples. Because it is desirable to extend the period of analysis in a site by looking for old scars, recent scars, and trees with large numbers of scars, researchers have developed rules of thumb regarding which trees are most likely to meet these goals as well as where fire scars are most likely to be found. To test our assumptions and quantify patterns about tree and sample characteristics, we analyzed a dataset of 2800 samples and 16,036 scars. On average, logs had the oldest scars and live trees had the most recent scars, although both very old and very recent scars were found on snags and stumps. Scars tended to be located on the uphill sides of trees, particularly on steeper slopes. The number of years between pith date and first fire scar ranged from 2 to 473 years, with a median of 52 and a mean of 67. The data confirm that searching for a variety of sample types and looking on the uphill sides of trees are useful methods for efficient sampling and extending a fire history record. Copyright © 2015 by The Tree-Ring Society.
    • Dendroecological Methods for Reconstructing High-Severity Fire in Pine-Oak Forests

      Guiterman, C.H.; Margolis, E.Q.; Swetnam, T.W. (Tree Ring Society, 2015-07)
      Recent high-severity fires in pine-oak forests of the southwestern United States are creating shrubfields that may persist for decades to centuries. Shrubfields embedded in conifer forests that pre-date documentary records are potential evidence of older high-severity fire patches, and may therefore provide insights into the occurrence and extent of past high-severity fires and vegetation type conversion dynamics. In this paper we test whether dendroecological evidence can be used to reconstruct a high-severity, type-changing fire of known date in a ponderosa pine-dominated (Pinus ponderosa var scopulorum Engelm.) forest. Dendroecological evidence included (1) Gambel oak (Quercus gambelii, Nutt.) regeneration dates, (2) fire scars, (3) death dates, and (4) tree-ring growth changes. We reconstructed the historical fire regime and fire-climate relationship to evaluate whether the recent high-severity fire was driven by climate or fuel build-up related to a fire regime disruption. The dendroecological evidence correctly dated the year (1993) and season (spring) of the documented fire, and synchronous oak re-sprouts provided a means to estimate the minimum high-severity patch size. The historical fire regime at the site (1625-1871) consisted of frequent, low-severity fires occurring in dry years preceded by wet years. Fires stopped in 1871, coincident with increased regional livestock grazing. The 1993 fire occurred under relatively cool and wet conditions, but followed a 122-year fire-free interval (four times the maximum historical interval). Multiple lines of evidence suggest that increased fuel loads from fire exclusion, combined with high winds, were primary drivers of the high-severity fire. The dendroecological approach we outline can be applied to reconstruct high-severity fire across a range of conifer-shrubland ecosystems. Copyright © 2015 by The Tree-Ring Society.
    • Bridging the Gap with Subfossil Douglas-Fir at Mesa Verde, Colorado

      Stahle, D.W.; Edmondson, J.R.; Burns, J.N.; Stahle, D.K.; Burnette, D.J.; Kvamme, E.; Lequesne, C.; Therrell, M.D. (Tree Ring Society, 2015-07)
      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.
    • August to July Precipitation from Tree Rings in the Forest-Steppe Zone of Central Siberia (Russia)

      Shah, S.K.; Touchan, R.; Babushkina, E.; Shishov, V.V.; Meko, D.M.; Abramenko, O.V.; Belokopytova, L.V.; Hordo, M.; Jevšenak, J.; Kędziora, W.; et al. (Tree Ring Society, 2015-01)
      The goal of this research report is to describe annual precipitation reconstruction from Pinus sylvestris trees on three sites in the Abakan region, located in the Minusinsk Depression, at the confluence of the Yenisei and Abakan Rivers, Russia. The study was performed during the 4th annual international summer course "Tree Rings, Climate, Natural Resources and Human Interaction" held in Abakan, 5-19 August 2013. The reconstruction, for the 12-month total precipitation ending in July of the growth year, is based on a reliable and replicable statistical relationship between precipitation and tree-ring growth, and shows climate variability on both interannual and interdecadal time scales. The regional tree-ring chronology accounts for 56% of the variance of observed annual precipitation in a linear regression model, with the strongest monthly precipitation signal concentrated in May and June of the current growing season. Composite 500 mb height-anomaly maps suggest that the tree-ring data from this site, supplemented by other regional tree-ring data, could yield information on long-term atmospheric circulation variability over the study area and surrounding region. © 2015 The Tree-Ring Society.
    • How to improve dendrogeomorphic sampling: Variogram analyses of wood density using X-Ray computed tomography

      Guardiola-Albert, C.; Ballesteros-Cánovas, J.A.; Stoffel, M.; Díez-Herrero, A. (Tree Ring Society, 2015-01)
      Knowledge of the spatial heterogeneity of wood is useful for industrial applications and improving dendrogeomorphic sampling, because it allows a better understanding of 3-D wood density structure in tree stems damaged by geomorphic processes. X-ray computed tomography (XRCT) scanning as a means of non-destructive measurement has become an important technique in tree research as it allows the detection of internal variations in wood density. In this paper a new methodology for modelling spatial variations of relative wood density using variograms on XRCT images is developed. For each tree, XRCT images perpendicular to the stem axis were obtained with 1-mm spacing. In a first step, ImageJ software was used to process each image. Then, more than 30 one-dimensional variograms were studied for a selected number of cross-sections. The results show that there is a pattern in the diffusion of relative wood density linked to the attenuation of the geomorphic damage along the stem from the wounded area. Although the number of samples could be increased, these preliminary results demonstrate that variograms of XRCT are a useful tool to optimize dendrogeomorphic sampling, saving time and costs. © 2015 The Tree-Ring Society.
    • The Dendroclimatological Potential of Willamette Valley Quercus garryana

      Gildehaus, S.; Arabas, K.; Larson, E.; Copes-Gerbitz, K. (Tree Ring Society, 2015-01)
      We develop a 341-year Oregon white oak (Quercus garryana Dougl.) tree-ring chronology in Oregon's Willamette Valley to evaluate climate-growth relationships and determine the species' dendroclimatological potential at our site and in the surrounding region. The standardized and residual chronologies exhibit significant positive correlations with previous-year April and May temperatures, inverse correlations with previous-year spring precipitation and summer PDSI, a positive correlation with current-year July precipitation and summer PDSI, and inverse correlations with current-year June temperatures. The strength of these relationships varies over time. Significant shifts in the chronologies' mean and variance align with phase changes in the Pacific Decadal Oscillation (PDO), with lower and more variable growth during the warmer, drier positive phase of the PDO over the instrumental record. The absence of similar shifts prior to the 1900s, suggests a lack of temporal consistency in the expression of PDO variability at our site. The strong crossdating at our site reflects a cohesive climate signal, and the climate analysis illustrates the potential to develop proxy data over multiple centuries. Together, these results indicate a potential to expand the network of currently available climate proxy data by utilizing Q. garryana in dendroclimatological research. © 2015 The Tree-Ring Society.
    • Morphological and Physiological Phenology of Pinus longaeva in the White Mountains of California

      Hallman, C.; Arnott, H. (Tree Ring Society, 2015-01)
      Natural variations and responses to climate change can be identified within climatically sensitive ecosystems by monitoring growing season events. In 1962-1964, Fritts conducted a phenologic study on Pinus longaeva in the White Mountains of California. He monitored growing season events, environmental data, and dendrometer readings. In this study morphological and physiological phenophases, dendrometer traces, and environmental data were collected throughout the summers of 2007 and 2008 in the White Mountains of California to better understand variability in Pinus longaeva phenology and identify any shifts in the growing season since the 1962-1964 study (Fritts 1969). As a result of a late-season snow storm, observable phenophases in 2008 were 12 days later than in 2007. Pollination onset was slightly earlier than in the 1962-1964, which may indicate that accumulated heat or a combination of environmental factors influence these phenophases. Duration and timing of cambial activity in the present study was similar to that recorded in the Fritts (1969) investigation despite a median summer temperature increase of at least 2°C. © 2015 The Tree-Ring Society.
    • Perceived Barriers and Facilitating Factors in Implementing Delayed School Start Times to Improve Adolescent Sleep Patterns

      Fitzpatrick, Julia M.; Silva, Graciela E.; Vana, Kimberly D.; The University of Arizona, College of Nursing (Wiley, 2020-12-02)
      BACKGROUND: Most adolescents in the United States do not obtain sufficient sleep. Early school start times play a significant role in adolescent sleep deprivation. Most primary and secondary schools begin classes earlier than the 8:30 am. Perceived barriers to implementing a delayed school start time have been suggested in the literature but have not been quantified. This study explored perceived barriers and facilitating factors for implementing delayed high-school start times. METHODS: A cross-sectional study. School administrators who had delayed their school start times were invited to complete an online questionnaire ranking the perceived barriers and facilitating factors for implementing the delayed start times. RESULTS: Most commonly cited perceived barriers were lack of a tiered bus system, school athletes missing more afternoon classes, and less time after school for athletics. Most commonly cited facilitating factors were school-administrator involvement in the decision-making process and sleep education for family members and school administrators. CONCLUSIONS: Participants found that providing sleep education to fellow administrators, teachers, school staff members, families, and students and including them in the decision-making process positively facilitated the implementation of delayed school start times. Perceived barriers to implementation may be overcome with support from stakeholders and planning committees. © 2020, American School Health Association
    • Assessment of High-Temperature Effects on Hypersonic Aerothermoelastic Analysis using Multi-Fidelity Multi-Variate Surrogates

      Sadagopan, Aravinth; Huang, Daning; Duzel, Umran; Martin, Liza E.; Hanquist, Kyle M.; University of Arizona (American Institute of Aeronautics and Astronautics, 2021-01-04)
      This study investigates the impact of the high-temperature effect, esp. the real gas effect and the chemical reactions, on hypersonic aerothermodynamic solutions of double cone and double wedge configurations, as well as the aerothermoelastic behavior of a double wedge configuration in hypersonic flow. First, a high-temperature computational fluid dynamics code was benchmarked and correlated with experimental results, emphasizing the impact of high-temperature effects as well as turbulence modeling on heat flux prediction. Subsequently, an aerothermal surrogate based on the multi-fidelity Gaussian process regression method was developed. The model achieves a balance between model accuracy and computational cost of sample generation, using the combination of a few high-fidelity sample and many low-fidelity samples. Finally, the new aerothermal surrogate was applied to study the impact of the hightemperature effect on the aerothermoelastic response of a hypersonic skin panel, emphasizing the necessity of the accurate characterization of the localized heat flux for reasonable assessment of the response of a compliant structure in high-speed high-temperature flowfield.
    • An Innovative United States–Mexico Community Outreach Initiative for Hispanic and Latino People in the United States: A Collaborative Public Health Network

      Flynn, Michael A.; Rodriguez Lainz, Alfonso; Lara, Juanita; Rosales, Cecilia; Feldstein, Federico; Dominguez, Ken; Wolkin, Amy; Sierra Medal, Ivan Roberto; Tonda, Josana; Romero-Steiner, Sandra; et al. (SAGE Publications, 2021-01-21)
      Collaborative partnerships are a useful approach to improve health conditions of disadvantaged populations. The Ventanillas de Salud (VDS) (“Health Windows”) and Mobile Health Units (MHUs) are a collaborative initiative of the Mexican government and US public health organizations that use mechanisms such as health fairs and mobile clinics to provide health information, screenings, preventive measures (eg, vaccines), and health services to Mexican people, other Hispanic people, and underserved populations (eg, American Indian/Alaska Native people, geographically isolated people, uninsured people) across the United States. From 2013 through 2019, the VDS served 10.5 million people (an average of 1.5 million people per year) at Mexican consulates in the United States, and MHUs served 115 461 people from 2016 through 2019. We describe 3 community outreach projects and their impact on improving the health of Hispanic people in the United States. The first project is an ongoing collaboration between VDS and the Centers for Disease Control and Prevention (CDC) to address occupational health inequities among Hispanic people. The second project was a collaboration between VDS and CDC to provide Hispanic people with information about Zika virus infection and health education. The third project is a collaboration between MHUs and the University of Arizona to provide basic health services to Hispanic communities in Pima and Maricopa counties, Arizona. The VDS/MHU model uses a collaborative approach that should be further assessed to better understand its impact on both the US-born and non–US-born Hispanic population and the public at large in locations where it is implemented. © 2021, Association of Schools and Programs of Public Health.
    • Comparison of Mixed Models and Paired T-Test for Analyzing Crossover Clinical Trials in the Presence of Missing Data

      Bell, Melanie; Vicenti, Anthony; Watkins, Joe; Zhou, Jin (The University of Arizona., 2020)
      AB/BA crossover clinical trials are popular designs that can achieve high power with a lower number of subjects than other randomized control trial designs. They are often analyzed using paired t-test or mixed models, and like many clinical trials, are often impacted by missing data. Mixed models have been shown to produced more powerful and unbiased results in the presence of missing data than t-tests for other designs, but these two approaches have not been compared in crossover trials. We conducted a simulation study to compare the bias and power of paired t-tests and mixed models when analyzing an AB/BA crossover clinical trial in the presence of missing data. Several different missing structures were simulated under two within-subject correlations, ρ =0.3 and ρ =0.7. Both methods performed similarly when analyzing complete data, but the mixed model produced both equal or less bias estimates and higher power than the paired t-test under all simulation scenarios. In the worst-case scenario we considered, the t-tests resulted in percent bias up to -105% and power as low as 5% compared the mixed model’s percent bias of 1% and 57% power. In less severe cases, both methods had 0% bias, but mixed models still achieved an absolute power gain of 2%-6%. In the presence of missing data, the mixed model achieved higher power than the paired t-test under all simulated scenarios. The mixed model also achieved equal or less bias under all simulated scenarios. Therefore, mixed models should be used over paired t-test when analyzing AB/BA crossover clinical trial in the face of missing data.
    • Reclaiming Mining Lands in Southern Arizona: A Scientific and Policy Inquiry towards Resiliency

      Maier, Raina M.; Neilson, Julia W.; Jennings, Lydia Luisa; Gornish, Elise; Rasmussen, Craig; Colombi, Benedict J. (The University of Arizona., 2020)
      Copper is critical to the sustainability of the modern lifestyle; however, mining creates massive land disturbance and generates large quantities of unstable waste materials that need to be managed for the long-term environmental and public health of neighboring communities (Lima et al., 2016). One waste challenge associated with modern mining is managing mine tailings. Mine tailing reclamation is site specific but often has a long-term goal towards ecological restoration and is impacted by stakeholder and rights holder associations (i.e. private, government or tribal) (Keller et al, 2011). Mine waste reclamation aims to stabilize waste to support self-sustaining plant communities. A critical limitation to vegetation success in mining waste is that these “soils” are deficient of the microbial communities and nutrients necessary to support plant establishment. The costs associated with these restoration activities can also be substantial, and vary with mine size, regulatory regimes, technology, presence of legacy reclamation costs, or cultural resources within the area (Mudd, 2009). Long-term ecological management of mine waste is an essential and problematic component of efficient mine site reclamation throughout the Southwest. Soil health properties essential to successful phytostabilization of reclaimed mine sites are poorly understood. This study found that total nitrogen and DNA biomass show promise as potential indicators of soil fertility that correlate with revegetation improvement. Our studies suggest that capping material source significantly influences the rate of plant establishment. Quantitative metrics must be further investigated to improve methods for screening potential capping material sources for mine tailings reclamation. Longer term studies are needed, particularly for mine recovery in the Southwest, where plants grow slower. Future work should consider how below ground fertility metrics reflect ecosystem stability and plant structure, and how the quality and application method of soil capping may impact future plant community structure.