Our neighborhood is filled with oaks, and I have at least 6 or 7 on my relatively small property (~0.3 acres). I've always wondered how old they are, and if they pre-date the house or not (this house is just under 20 years old).
My neighbor recently cut down one of her oak trees due to disease (I don't know the details). It was similar in size to mine - some of mine are smaller and some of mine are bigger, so I figure its age is a rough average for the age of my trees. I checked the recently cut cross-section near the base of the tree, and while I can clearly see some rings on the inside, they are only distinct for about the inner third of the tree. I've successfully "aged" other trees like this, so I'm not sure what is going on here (the lack of discernible rings doesn't seem like it is caused by the chainsaw). In case it helps I'm in North/Central Florida.
Upon further inspection: The original and very indistinct photo of the tree was from when it was freshly cut down a week ago. I just took another picture today and the outer rings stand out substantially more, although now I'm more confused. Some sections in the middle are still very indistinct, but the outer rings appear substantially larger than the inner rings. Is this normal? I could understand differences in age/climate making tree growth more favorable, but it appears to be a factor of 2 or 3 difference, which makes me wonder if these outer rings are something other than annual growth rings. Presuming that the large outer rings are normal annual growth rings, then I think I can find at least 30 distinct rings. There are areas where there are obviously rings but I can't see them, so I'm guessing it is about 40 years old.
Any guesses as to how old this tree is? Am I "interpreting" it properly? I've also embedded the pictures below, but doing so required shrinking them. The above links will take you to the original, higher resolution images.