Friends of mine have a grove of 5 fairly closely spaced Pseudotsuga menziesii (Douglas fir) in their front yards which are about 15 years old. They are thinking about girdling the smallest to produce a wildlife snag but are worried about root rot affecting the other trees.
Is this a valid concern? My feeling is no, but it's strictly based on the assumption that health trees can fight off the rot.
Ben I am thinking you are right. Those roots rotting as part of the decomposition process should not harm healthy roots of plants nearby as long as there are no drainage issues that caused a healthy tree to get root rot. Stuff is decomposing in the soil all of the time. That is normal and part of a healthy soil. Make sure that the grove of trees aren't in some 'bowl' where the water collects and then anaerobic decomposition can get stinky as well as unhealthy for the other trees.
