Rooting a cutting VS air layering. What really is the difference?

[The Oak]

Hi people. I am very confused about one thing.
When we air layer a branch on a tree, we remove the bark and the tissue underneath the bark, and in this way we shut down the two water and nutrient transport systems of the plant - the xylem and the phloem. The air layered branch no longer receives water and nutrients from the roots of the tree and its survival relies on the wet moss that we wrap around the wound. This is why the air layered branch shoots out roots - it tries to get as much water from the wet moss as possible.
So why not chop off the branch entirely and try to root the cutting in wet moss (or in plain water)?
With either methods, the the xylem and the phloem will be cut off and interrupted and the branch will die without us supplying it with water. Then why bother air layering, when in theory the effect form this procedure does the same to the branch as does chopping it off completely?
Wouldn't it be much faster/easier/cheaper/less labor intensive to just chop cuttings and then root them?
Would like to hear people's opinions and learn about their experiences with both methods. Thanks!

 

[rorror]

From my understanding, you leave the upwards water flow, but only restrics the downflow, so roots can grow into the airlayer.
If you remove to much of the tissue underneath the bark, the upwards flow of water is stopped, resulting in the top part dying.
Did you do the airlayer on the proper way?

 

[The Oak]

Thanks for your fast reply. Makes sense.

 

[atlarsenal]

Cuttings are usually taken at pencil size and smaller branches. Air layering can be done on much bigger branches.

 

[BobbyLane]

Your chances of creating an 'instant bonsai' from a cutting are slim to zero

 

[Shibui]

From my understanding, you leave the upwards water flow, but only restrics the downflow, so roots can grow into the airlayer.
If you remove to much of the tissue underneath the bark, the upwards flow of water is stopped, resulting in the top part dying.
Did you do the airlayer on the proper way?

All correct.
Layers are only cut to remove outer bark and cambium layer. Inner upward flow should remain intact to maintain life until roots an form. The extra time given by continued supply of water and nutrients allows for older and thicker branches to produce roots.
Cuttings are generally limited to thinner and smaller pieces except for really precocious species that root exceptionally easy.

 

[MrWunderful]

Cutting= zero roots
Layer (ground, or air) = existing roots feed tree or branch, but tree doesnt feed existing roots. It forces new ones and feeds those.