how does an air layer work

[tismeisthatu]

Silly question I know, but I've never understood how an air layer actually works. My logic tells me the top of the tree above the air layer has basically had it's supply of water/nutrients cut of by the air layer. The reason I ask is that I recently drowned a maple of mine to the point that the wood from the roots up started to rot & go black. This crept all the way up the tree until it was all black & dead. This process took about a month from first seen till the tree was totally covered. It was during this time I wondered if I could've air layered the top of the tree to salvage something out of it! Could I have done? Excuse my stupidity if I'm missing something to obvious to see. Thanks in advance

 

[jk_lewis]

http://www.evergreengardenworks.com/airlayer.htm

 

[jkd2572]

I would probably not try to air layer a sick tree.

 

[coppice]

I bet Mike Dirr would know.

 

[tismeisthatu]

http://www.evergreengardenworks.com/airlayer.htm

Thank you jkl, that was exactly what I needed to read.