We have Bristlecone pine trees in California dating back to the time of Christ. Very few are left because they were logged for building materials by miners in the area. The oldest one's location is kept secret. Lots of trees are larger than 6 foot diameter. On my Grandpa's property there are monster black oaks larger than that. One that had died I cut down for firewood as most of the core was rotten and useless for lumber. The stump was like eight feet wide. When the weather got real dry I burned out the stump which left a huge crater. The crater was smoking for about a week but the actual burning only lasted a couple days. Generally black oak top out in age at about 200 years and start declining. Not because they just die naturally as what happens is that maybe they get some damage in a top limb, like some wind damage or something and then rot slowly creeps down inside the trunk. Bit by bit over the years it can't keep up with damage and then it will go into a swift decline. If you cut down one that's about 100 or less you can get a nice clean trunk that makes great furniture wood if seasoned properly. A good one I cut down was about three foot diameter. Very straight attractive wood.