I counted the rings of this Fir tree this morning. The cut was at about the old 15 foot height and there are 103 rings, so I figure 7 years would be about right for a Fir to grow 15 feet. Pretty amazing seeing the differences between each tree's rings. This Fir grew pretty slowly and regularly with pretty even and concentric rings. A pine across the drive way that is being cut up has massive growth rings over various parts of its life.
We have distinct events that have happened locally in records and this tree's rings are not a very good show of any. The rings are very subtly thicker/thinner or lighter/darker which makes judging burn events, freeze events, drought, or wet a lot harder. It seems that given the slower growth the Fir is not as well suited to historical look as the Pine is. I have the last cut to do on the pine and will count it just above the base. That should give me a good idea of the above criteria.
I will get a good count and post about it soon. 4 trees are down in the yard, 2 Fir and 2 Pine, so I should get a nice idea of general age/size of the different trees on the property.