Tree Rings. Basics And Applications Of Dendroch...
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The practical applications of the study of tree rings are numerous. Dendrochronology is an interdisciplinary science, and its theory and techniques can be applied to many applications. See our subdisciplines for examples. These research interests have in common the following objectives:
Around the Upper and Lower Cliff Dwellings, small, numbered plugs dot pieces of wood. These plugs mark the spot where researchers have taken a core sample to try to determine the age of the wood by examining its tree rings. Scientists do this by comparing the tree-ring pattern of samples with unknown dates to known samples from the same geographical area. If they can find a match, then the unknown sample can be dated, providing archeological information. Tree-ring dating is also called dendrochronology.
Archeologists use tree-ring dating to understand past human chronological, behavioral, and environmental events and conditions. Tree-ring dating can be performed on woody plants that produce recognizable and unique tree rings during a single growth season (Ahlstrom and Smiley 1998). However, conifers often yield the most accurate readings because their growth is sensitive to climatic and environmental changes. Dendrochronology is performed by finding identical sequential tree-ring patterns among many different trees (Dean 2009). A yearly incremental interval scale is used to measure these rings. Each interval is marked by the start of one tree growth season to the beginning of the next (Ahlstrom and Smiley 1998).
Chronological analysis involves studying tree-ring core samples taken from structures such as pit-houses, pueblos, and cabins. This process places these sites into a time sequence defined by archeologists for a certain geographic area. Archeologists strive to recover tree-ring cross-sections that contain bark, or the final growth rings.
Climatic analysis involves studying environmental conditions that generate the variations observed among the tree rings. From these variations, archeologists can reconstruct past climate conditions.
Tree ring data is only collected outside of the tropics. Trees in temperate latitudes have annual spurts of growth in the spring and summer and periods of dormancy in the winter, which creates the distinctive pattern of light and dark bands. Tropical trees grow year-round, and so they do not have the alternating dark and light band pattern of tree rings.
Scientists do not typically cut down a tree to analyze its rings. Instead, core samples are extracted using a borer that's screwed into the tree and pulled out, bringing with it a straw-size sample of wood about 4 millimeters in diameter. The hole in the tree is then sealed to prevent disease.
Old trees tell us about conditions on Earth long before people started measuring and recording the weather. Some tree species, such as the bristlecone pine, that live for several thousand years, contain long records of tree rings. However, climate scientists typically work with trees that are not so long-lived and extend their tree ring records back more than 10,000 years by comparing ring patterns of living trees with the rings in dead but not-yet-decayed trees that have fallen. Scientists match patterns from the early stages of a living tree's rings with the sequence formed in the latter parts of the lives of older, dead trees to assemble an unbroken paleoclimate record extending back thousands of years.
Tree rings in these seven cores don't look round like rings because the boring tool only extracts a small segment of the rings. Each dark and light layer makes up a year of growth. Wide layers indicate years when the trees grew more. Narrow layers indicate years when the trees grew less. These cores are from white spruce trees in Alaska. Credit: SERC/Tree-Ring Expeditions
Three aspects of cross-dating warrant emphasis. First, tree-ring dating is about matching patterns, not counting rings. Second, sample sizes must be large in order to understand tree-growth variability in a given region. Third, one begins by studying living trees in a given area, cross-dating their ring series internally and working back in time to successively older specimens that are usually found as dead snags on the landscape or as construction beams in ancient dwellings.
There is sustained reason, though, to be positive about the future forecasts in dendrochronology and its developing applications. As the long tree-ring chronologies are unlimited and their associations to one another are more obviously understand, as geographical breaks are overflowing in to generate a web of absolutely-dated and interlinked chronologies worldwide, and as a new technique of their explanation is developed, projection on a hemispheric level should be possible. The result that tree-ring dating should have on archaeology in the subsequent generation and the modification in archaeological philosophy that will in this manner be obligatory is certainly going to be ground-breaking.
Trees and other woody plants grow by covering themselves with a new layer of tissue every year. When seen in a horizontal section, such wood layers appear as concentric tree rings, familiar to anyone who has looked at a tree stump. Because tree growth is influenced by the environment, tree rings are then natural archives of past environmental conditions. For instance, trees grow less when climate conditions are less favorable, producing narrower rings. The study of past changes recorded by wood growth is called dendrochronology.
Tree-ring dating is the assignment of calendar years to each wood growth ring. This requires more than simply counting visible rings, because not every growth layer is always present or clearly noticeable, especially in very old trees. When only one or two trunk radii are available per tree, the chance of dating errors is greater than when examining entire cross-sections. To ensure dating accuracy, ring patterns from many different trees of the same species and location are matched with one another. This allows the creation of a master chronology for this location. This cross-dating exercise, which is similar in principle to matching fingerprints or deoxyribonucleic acid (DNA) sequences, is first done visually under a binocular microscope using 10 to 30 power magnification. Once a tree-ring sample has been properly surfaced , that magnification is high enough to distinguish individual wood cells. After measuring the thickness of each ring, cross-dating can be verified using specialized numerical procedures. While numerical cross-dating is based on alternating patterns of narrow and wide rings, visual cross-dating can incorporate other anatomical elements as well, such as the proportion and color of earlywood and latewood within individual rings.
Cross-dating has found other important applications in dendro-chronology. Once a (master) tree-ring chronology is established, a wood sample from the same species and area can be accurately dated by matching its ring-width patterns against the master. This procedure is commonly used in archaeological and historical investigations to date wood material, artifacts , and structures. In addition, as wood samples from older living trees are cross-matched against those from historic and prehistoric times, the length of the master chronology can also be extended farther back in time, a process that has allowed the development of tree-ring chronologies for the last ten thousand years, over the entire Holocene epoch.
Children around the world know that to tell how old a tree is, you count its rings. Few people, however, know that research into tree rings has also made amazing contributions to our understanding of Earth's climate history and its influences on human civilization over the past 2,000 years. In her captivating new book, Tree Story, Valerie Trouet reveals how the seemingly simple and relatively familiar concept of counting tree rings has inspired far-reaching scientific breakthroughs that illuminate the complex interactions between nature and people.
Trouet, a leading tree-ring scientist, takes us out into the field, from remote African villages to radioactive Russian forests, offering readers an insider's look at tree-ring research, a discipline formally known as dendrochronology. Tracing her own professional journey while exploring dendrochronology's history and applications, Trouet describes the basics of how tell-tale tree cores are collected and dated with ring-by-ring precision, explaining the unexpected and momentous insights we've gained from the resulting samples.
The data set presented represents 15 years of collection. It contains tree-ring width measurements from 64 sites of living trees and ten historical chronologies based on archaeological and construction wood up to year 572 CE, altogether 2909 tree-ring series and more than 450000 measured and cross-dated tree rings. It covers the vast territory of European Russia, including its forested northern and central parts, and the Northern Caucasus mountains. The potential use of these data include climatic reconstructions of regional and hemispheric scale, dendrochronological dating of historical and cultural wood, ecological and remote sensing studies.
One of the most innovative and perhaps also one of the least known applications of trees relates to their use in environmental forensics for accurate age-dating, source identification, and reconstruction of subsurface transport of contaminants over time. Such applications provide reliable evidence in litigation, helping to identify responsible parties and to cover remediation costs. In addition, trees provide useful characterization tools at non-litigated sites, enabling efficient remediation design.
Trees produce rings each year that they grow. Trees grow more during wet years, producing wide rings, and less during dry years, leaving narrow rings. Since no two years have the same precipitation levels, this generates unique patterns of wide-to-narrow rings. However, because trees from the same region receive similar amounts of moisture, they develop ring patterns that are close enough to be synced up. 59ce067264