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WonderTree-ring science fact

Tree rings can date wood to the year it grew. The science, called dendrochronology, matches ring patterns across living trees, old beams and buried wood to reconstruct past climates, droughts and fires, and to date old buildings.

University of Arizona Laboratory of Tree-Ring Research / National Park Service

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The story behind the card

Each year a tree adds a ring, wide in good years and narrow in dry or cold ones, so a run of rings forms a pattern like a barcode. Overlapping those patterns, from living trees back through old timbers, builds long calendars: in central Europe, a continuous oak and pine record reaches back 12,460 years. The method was founded by the American astronomer A. E. Douglass in the early 1900s. He hoped tree rings would show sunspot cycles affecting climate; that link never held up, but the dating did. In 1929 his tree-ring calendar gave exact dates to ancient Pueblo ruins in the American Southwest, and he later founded the University of Arizona's Laboratory of Tree-Ring Research.

Türkçe oku
Ağaç halkaları, bir ahşabın hangi yıl büyüdüğünü gösterebilir. Dendrokronoloji denen bu bilim, yaşayan ağaçlardaki, eski kirişlerdeki ve toprak altından çıkan ahşaptaki halka desenlerini eşleştirerek geçmişteki iklimi, kuraklıkları ve yangınları ortaya çıkarır, eski yapıların yaşını belirler.

Ağaç her yıl bir halka ekler: İyi yıllarda geniş, kurak ya da soğuk yıllarda dar. Böylece art arda gelen halkalar barkoda benzeyen bir desen oluşturur. Bu desenler yaşayan ağaçlardan eski kerestelere doğru üst üste bindirilerek uzun takvimler kurulur; Orta Avrupa'da meşe ve çamdan oluşan kesintisiz bir kayıt 12.460 yıl geriye uzanır. Yöntemin kurucusu, 1900'lerin başında çalışmaya başlayan Amerikalı gökbilimci A. E. Douglass'tır. Douglass, güneş lekesi döngülerinin iklimi etkilediğini ağaç halkalarında görmeyi umuyordu; bu bağlantı kanıtlanamadı, ama tarihleme yöntemi tuttu. 1929'da ağaç halkası takvimi, Amerika'nın güneybatısındaki eski Pueblo yerleşimlerine kesin tarihler verdi. Douglass daha sonra Arizona Üniversitesi'nde Ağaç Halkası Araştırma Laboratuvarı'nı kurdu.

Sources and further reading

Background reading: Dendrochronology
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Some Great Basin bristlecone pines in the western United States are more than 4,800 years old, older than Egypt's Great Pyramid of Giza.

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