Tree ring dating reliability
Environmental inputs into the cambium are primarily regional climatic variations, changes in temperature, aridity, and soil chemistry, which together are encoded as variations in the width of a particular ring, in the wood density or structure, and/or in the chemical composition of the cell walls.
At its most basic, during dry years the cambium's cells are smaller and thus the layer is thinner than during wet years.
Dendrochronology is the formal term for tree-ring dating, the science that uses the growth rings of trees as a detailed record of climatic change in a region, as well as a way to approximate the date of construction for wooden objects of many types.
As archaeological dating techniques go, dendrochronology is extremely precise: if the growth rings in a wooden object are preserved and can be tied into an existing chronology, researchers can determine the precise calendar year--and often season--the tree was cut down to make it.
Evergreen cambiums are commonly irregular and not formed annually.
Trees in arctic, sub-arctic and alpine regions respond differently depending on how old the tree is--older trees have reduced water efficiency which results in a reduced response to temperature changes.
The interlopers defaced the ships, damaged the grave goods and pulled out and dispersed the bones of the deceased.
Fortunately for us, the looters left behind the tools they used to break into the mounds, wooden spades and stretchers (small handled platforms used to carry objects out of the tombs), which were analyzed using dendrochronology.
It had long been known that three 9th century Viking period boat-grave mounds near Oslo, Norway (Gokstad, Oseberg and Tune) had been broken into at some point in antiquity.Tying tree ring fragments in the tools to established chronologies, Bill and Daly (2012) discovered that all three of the mounds were opened and the grave goods damaged during the 10th century, likely as part of Harald Bluetooth's campaign to convert Scandinavians to Christianity.Marmet and Kershaw were able to recognize a pattern of increased growth in trees in the high Canadian mountains, growth undoubtedly tied to recent global warming.Because of that precision, dendrochronology is used to calibrate radiocarbon dating, by giving science a measure of the atmospheric conditions which are known to cause radiocarbon dates to vary.Radiocarbon dates which have been corrected--or rather, calibrated--by comparison to dendrochronological records are designated by abbreviations such as cal BP, or calibrated years before the present.