Trees tell us about history. Trees grow in height and diameter each year, producing rings that scientists observe to study weather and temperature patterns over time. The science of studying tree rings is not exact, but it does provide information useful to understanding an ecosystem's climate history.
Tree rings, sometimes called annual rings, are the yearly addition of a new layer of wood on a tree. Scientists, called dendrochronolgists, study tree rings to learn about the history of weather patterns, temperatures and disease in a particular area. Tree rings can also help scientists make an accurate estimation of a tree's age. One ring, in most cases, equals one year of growth. John Punches, in his report "Tree Growth, Forest Management and Their Implications for Wood Quality" cautions, "Trees may take several years to reach the height at which the rings are being observed, so the resulting ring could underestimate total age." Still, tree rings can provide a reasonable approximate tree age.
Role of Rain
Tree rings can provide scientists with a great deal of information. One of the primary reasons to study tree rings is to help determine the amount of rainfall that occurred during a given period of time. Healthy trees that receive an abundant amount of rainfall in a year will have wide rings indicating plenty of new growth. If a tree experiences a season of drought or disease tree rings will narrow. This is an indication that the tree's growth was impeded.
Sometimes a tree can develop what are referred to as false rings. These rings occur when a tree stops growing due to some stress during a season. When the stress, such as a severe drought, passes, then growth will resume. Therefore there can be two rings produced in one year. Dry summers followed by early fall rains can cause these false rings to happen.
Dendrochronologists study trees rings as a part of monitoring climate change. By looking back at the history of weather patterns in an area, particularly rainfall versus drought conditions, scientists can hypothesize how weather patterns are changing now, as well as how they may change in the future. This information is one tool scientists use to better understand climate change.
Tree rings are an accurate way to study past temperature and weather patterns, but scientists also have to consider how old a tree is and where it is located in an ecosystem. Older trees tend to put on less growth a year and thus will by nature have narrower rings. Also, not all trees in an area receive the same amount of sunlight, rainfall or nutrients. Scientists have to try to factor in all of these variables when conducting their research.