page_title: Fire history
section_title: Tree-ring data
hierarchical_section_title: Fire history / Tree-ring data
caption_attribution_description: Tree rings of Picea Abies (Norwegian Spruce). The height of this image is 10 mm (800 dpi). The sanded cores shown, are taken by a 5 mm increment borer from living Spruces growing in Dalarna, Sweden. The image was originally a part of a bigger image scanned in order to collect dendrochronological data.
context_page_description: Fire history, the ecological science of the study of the history of wildfires, is a subdiscipline of fire ecology. Patterns of forest fires in historical and prehistorical time provide information relevant to the pattern of vegetation in modern landscapes. It provides an estimate of the historical range of variability of a natural disturbance regime, and can be used to identify the processes affecting the occurrence of fire. Fire history reconstructions are achieved by compiling atlases of past fires, using the tree ring record from fire scars and tree ages, and the charcoal record from soils and sediments.
context_section_description: The growth record of a tree in seasonal climates is preserved in the growth rings in the stem wood; the field of dendrochronology is the study of the record of climate and other events preserved in the growth record. Each growth ring represents one year of life. The thickness of each ring indicates the amount of wood produced during that growing season. At the beginning of the growing season large cells are able to quickly divide creating a light colored wood. When growth slows down, generally in colder months, a darker wood is created from smaller cells dividing more slowly. Thus, one year is represented by a light inner ring and a darker outer ring. 
  Rings can be counted from dead trees as well as stumps left behind from logging. A sample can be collected from a living tree using tools like the increment borer. The increment borer is a hollow steel tube used to extract a core sample from a tree’s trunk. The growth rings in a core sample are counted to determine the age of that tree. Ages of stand-replacing fires may be determined by determining the cohort-age of trees that established after a fire. For example, tree-ring dating of large stands will show the age of the forest, and may provide an estimate of when the last large disturbance event occurred.
  Sometimes growth rings exhibit scars. A fire scar forms when heat kills the vascular cambium beneath the bark, which then heals over subsequent years as growth rings curl over the scarred area, thus protecting the tree from infection. This method can be used to date the year a fire occurred. Observing the scars establishes the timeline of a forest fire and the time between fires at a site. Surveying many trees over a large sample area provides a view to individual fire events and the overall fire regime. Not all tree species scar and show evidence of fire. Most pine species in the subgenus Pinus readily produce scars that are protected by resin; such scarring on other trees may result in death, leaving no fire record behind.
caption: Tree core sample collected with an increment boarer
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