Over the past few tutorials, we have been introducing some basic concepts regarding
dendrochronology, so let’s use just one more to discuss the ways in which this field can inform
other scientific disciplines. Tree ring analysis is so incredibly useful that it is utilized in a
multitude of studies, so let’s examine some of the applications of dendrochronology.
First up is archaeology. Dendrochronology can be used to study wooden artifacts,
whether they are derived from old buildings, furniture, art, or musical instruments.
Tree-ring techniques are considered the most accurate and precise method of absolute dating
since the last ring that grew is the first year the tree could have been incorporated
into a wooden artifact. Archaeologists often collect samples from structural beams in houses
or wood that is in place for hundreds of years. Dates produced through dendrochronology can also
be used to refine radiocarbon dating results. Charcoal can also be dated using tree-ring
analysis to help study archaeological structures. Once wood is carbonized, meaning turned to
charcoal, it is relatively inert and can last for hundreds or even thousands of years without
any biological decay. Scientists compare the ring patterns in a charcoal sample to long tree-ring
series in order to date samples that go back thousands of years. Some of the most famous and
longest tree-ring series include the bristlecone pine chronology for the species Pinus longaeva, at
over 10,500 years old, the Eastern Mediterranean chronology that dates back 9,000 years,
and the Long Oak chronologies representing Ireland and Germany which extend back 11,000 years.
Next up is ecology. Dendrochronology can be used by ecologists to study the ecological
and environmental changes catalogued in tree rings such as wildfires, insect outbreaks,
and stand-age structure. Earlier in this series we talked about ring anomalies. These and other
phenomena are crucial in the study of specific ecological events that impact whole landscapes.
Scientists can also study Forest Productivity and Succession, which refers to tree health,
disturbance, and development over time. A powerful application of tree rings for ecology is the
reconstruction of fire history. These histories are especially useful in forest management
and are often used to determine the proper use of fire as a disturbance agent. When forest managers
recommend a controlled burn, a fire that is purposely ignited and controlled in a forest with
the purpose of maintaining its ecology, they need data on past fires to guide management decisions.
By studying tree ring widths and fire scars, scientists can learn about past fires to
better inform current policy decisions. Another major disturbance that ecologists
study are pathogen outbreaks, especially invasive insect damages. Forest managers
are interested in the historical effects of pests in order to better prepare for future
conditions and inform policy decisions on insecticide and fungicide applications.
Perhaps the most common application of dendrochronology is paleoclimatology,
or the reconstruction of past climates from tree rings. Since trees respond to their surroundings,
they are subject to climatic effects, such as temperature, moisture, and cloudiness.
Because tree rings are influenced by various aspects of climate and can be so accurately dated,
they are extremely useful proxies for the study of past climates.
Paleoclimatology requires many samples with which to construct chronologies that can more
accurately reflect climate history. Ring width measurements collected to reconstruct climate
are corrected for an age-related growth trend. The resultant index values are averaged together
to create a robust chronology with a large-scale signal that is analyzed for its climate response.
An important part of this standardization is the removal of non-climatic trends from the ring
widths. This is usually accomplished using splines or simple linear regressions. Dendroclimatology
provides researchers with an understanding of the natural range of past climate variability
to better prepare for the future. Some research even combines ecology
and paleoclimatology to better learn how trees respond to climates. Results from these studies
allow us to predict how forests might react to future climates, which is useful information.
Finally, let’s talk about how dendrochronology can be applied to chemistry. Scientists can use
the measurement and analysis of trace minerals in tree rings to study the spatial and historical
estimates of the atmospheric concentrations of different elements. This includes the field of
stable isotope dendrochronology, one of the fastest growing fields of dendrochronology,
whereby certain isotopic ratios, such as carbon-13 to carbon-12, that is locked within tree rings,
can tell us about past climates or how trees respond to current climate.
Various kinds of isotopes can provide new sets of information that complement ring
width and density data. Since trees annually sequester chemicals through photosynthesis,
and each tree ring is an individual year of growth, it is possible to cut out tiny pieces
of specific rings and analyze their chemical composition to learn more about past climates,
volcanic eruptions, and tree response, among many other aspects of environmental change.
This not only sheds light on past conditions, but can also help with future predictions.
And with that, we conclude a brief introduction to the field of dendrochronology.
I hope you’ve enjoyed this discussion about wood and its implications in the scientific world.
Tree rings are a window into the past that can be used to better predict the future. Given that
the future of Earth’s environment is uncertain at the present time, we will certainly be relying on
many aspects of dendrochronology in order to help make the best decisions we can as a civilization.
So beyond their beauty, let’s never forget the wisdom of trees.