Tree rings/dendrochronology

blue5000

Just thought that I'd put this up as it really spans my farming career to date. It's a 30 year old ash tree, cut down last winter. I was wondering why the rings vary so much from year to year, then I noticed the rings for the last 5 years are very small compared to the years between 1998-2002. Has anyone else noticed this in trees cut recently? Dieback wasn't visible locally until 2019.

looksee

It does relate to weather conditions in any particular year, but a tree grows more slowly as it ages so has narrower rings.

https://arbordayblog.org/misctrees/living-forest-tree-rings-tell-us-life-tree/#:~:text=So%2C%20growth%20rings%20may%20become,a%20cold%20and%20dry%20season.

Snickers Man

Some time ago I read a fascinating book by Jared Diamond called Collapse. it is a study of how certain civilisations throughout history disappeared or were greatly depleted because of a variety of factors, mainly pertaining to the way they damaged their environment, usually inadvertently due to their lack of knowledge, by their farming, building and forest-clearing activities.

For the non-specialist reader such as myself, it describes in fascinating detail the various techniques archaeologists can use to paint a picture of climactic conditions throughout history and the type of vegetation that existed in certain regions that often bears no resemblance to the flora and vegetation that exists today. These techniques included inspecting the middens of rats that had survived for hundreds of years in the Arizona desert for evidence of the types of trees and shrubs that existed in that region several hundred years ago, examining soil layers at the bottom of lakes for similar evidence of previous vegetation and so on.

Dendrochronology is a useful tool for dating old buildings. The number of rings in a tree gives you an indication of how old the tree was when it was cut down, but the thickness of the rings tells you much about the climate variations year to year. As I remember, the thickness of the ring gives you some indication of the amount of moisture in the atmosphere in any given year. Thick rings meant a wet year, thin rings a relatively dry one. What that means is that for trees that were cut down at the same time and from the same region, the pattern of thick and thin rings is replicated in each tree. It becomes like a sort of bar code, a particular sequence of rings revealing that a group of trees were growing in the same time period.

If one tree had a sequence of rings at the periphery of its trunk that were replicated in another tree closer to its centre, and if you had a reliable date for which one was cut down, then you could date the other one back in time long before the life of the first one. With several trees from the same area the patterns of thick and thin rings allow archaeologists to data not only how old a tree was when it was cut down but to estimate, to a high degree of accuracy, what year it was first planted. Also the varying patterns allow climate researchers to estimate the changing weather patterns from year to year going back centuries.

Hope this is of some use.

My father used to send bog oak and deal samples to QUB dendrochronology lab. Helped to get the local tree map backdated by another 1500 years.