Dendrochronology · Hoot Woods, Indiana · 1940–1949
The Year That
Repeats
Bark does not tell you which year produced each ring. A run of narrow and wide rings can do that when the same pattern appears in more than one core. Place the anonymous strip over the dated one and give a piece of trunk a date.
Line up the evidence
Find where the rings match
The top core has years, while the lower one is anonymous. Move the lower strip until the wide and narrow rings sit over the trace above, using the arrows or the slider.
Each bar represents a ring, and its height shows relative width within that core. The original values are in the table above. Correlation compares the shape of the two sequences. It does not say that the two trees grew at the same rate.
The same trace
The trace repeats.
The cause stays open
Both cores follow the same order: a very wide ring in 1940, a drop in 1941–1942, then a shared descent to the end of the window. The widths differ, but the sequence remains recognisable.
In 1943–1949, mean ring width is 485 in core A, compared with 1,211 in its first three years. In core B, the mean is 364, compared with 1,016. Compared with the first three years, mean width falls 60.0% in A and 64.2% in B. The signal is shared. By itself, it does not tell us whether weather or another cause produced the drop.
How a trunk gets a date
Alignment puts years on wood
The dated core supplies the scale for a piece with no years. When the same sequence appears in both cores, you can place the years on the anonymous wood.
A year can disappear from memory and still remain in wood.
What the match tells us
The date is fixed.
The cause is still open
The match in this window fixes a place in time. Core B carries the same sequence as A, and A carries the years 1940–1949. That is where `r = 0.903` comes from, a strong resemblance between the two series.
The window is ten years, and the widths are raw. Dendrochronologists check longer sequences, more cores and nearby matches. A narrow ring can have several causes, from drought to competition between trees. The wood keeps the trace, but it cannot say on its own why it appeared.
Keep in mind
Correlation shows a repeated shape. A single fluctuation can have several causes.
Where the wood comes from
NOAA/WDS Paleoclimatology, Maxwell, Hoot Woods, FRAM, ITRDB IN035; white ash (Fraxinus americana), Indiana, 1854–2013. View the NOAA record.
Cores HWF07A and HWF07B, raw ring widths published in the NOAA measurement archive. The unit is 0.001 mm, as defined in the ITRDB documentation.
The ten-year window appears in the original values. The correlation and percentage comparisons come from the two sequences. For context on the international archive, see the NOAA International Tree-Ring Data Bank.
Two cores from one site show how the alignment works. They are not enough for a complete reconstruction of past weather. Raw measurements alone do not separate tree age, weather and local conditions.