Oak trees

[Richard Wagner]

As many of you may know, Atlanta has a fair number of trees here and there around 
the city. The hurricane "Opal" toppled many trees, and a large proportion of those 
were oaks. The root masses of these trees, many of which are up to 200 years old, 
show no sign of a tap root. I am wondering what happened to the tap roots. 

I have dug many smaller trees in the past, and found heavy tap roots extending many 
feet under the surface. Do these disappear with age? Or is this some kind of root 
pathology associated with urban life?

Dick Wagner, Atlanta