• 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.
    • 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.
    • 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.
    • 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.
    • 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.
    • 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.