Wang and Zhao used dendrochronology to look at the dates of one of the Silk Road routes used during the Qin-Han period called the Qinghai Route.
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.The ring widths were matched and cross-dated, and by the 1920s, chronologies were built back nearly 600 years. Haury, and dendrochronology conducted on Showlow eventuated the first single chronology for the southwest, extending over a period of over 1,200 years.The first ruin tied to a specific calendar date was Kawaikuh in the Jeddito area, built in the 15th century; charcoal from Kawaikuh was the first charcoal used in (the later) radiocarbon studies. The Laboratory of Tree-Ring Research was established by Douglass at the University of Arizona in 1937, and it is still conducting research today.A recent attempt to use tree ring analysis on olive trees (Cherubini and colleagues) revealed that too much variation of the cambium occurs in olives to make dendrochronology viable.
That study was one of ongoing attempts to determine a reliable chronology of the Mediterranean Bronze Age.The rings are the cambium layer, a ring of cells that lie between the wood and bark and from which new bark and wood cells originate; each year a new cambium is created leaving the previous one in place.How large the cambium's cells grow in each year--measured as the width of each ring--is dependent on seasonal changes such as temperature and moisture availability.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.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.