Observation: when I do an air-layer, often the parent plant will start growing new branches below the girdle point, before the air-layer is removed.

Undesirable result: if I pruned the branch early in the season, then I would lose the fruit that forms (or would have formed) farther up the branch above the point of pruning. If I wait till the fruit is ripe, it is probably too late in the season to get the tree to push new growth after pruning.

Possible solution: what if I girdle the branch, to force new growth at the lower point, but leave the branch and fruit above the girdle till after it ripens? Best of both worlds? I don't know. If the fruit growth and ripening is a product of the photosynthesis taking place in the leaves above the fruit, then no harm -no foul. If the fruit needs something from the roots in order to develop and ripen and which is interrupted by the girdle, then it doesn't work.

The goal: if this works, then the new branches that formed below the girdle might be short enough to not need pruning. Tip buds always seem to break dormancy earlier than side buds (on a pruned branch), which I am assuming will lead to earlier fruit formation and, hence, earlier ripening, which would give better results in short season climates, or with later ripening varieties.

Gina, I agree, but what if some "stuff" needs to go from leaves to roots and back again for fruit production, i.e. what the leaves produce needs to be transformed in the roots before being used by the fruit.

Girdling should interrupt the bark and cambium, but no more.

Mike, I have done the air-layering, but have always pulled the fruit off when doing so. I guess now I will have to experiment with the fruit on.

The goal was not to increase fruit size (though that would be good) but to accelerate bud break, and thus, fruit set and fruit ripening.

I thought about this a little bit more after I posted that last night.  I think it's possible to hit some kind of optimization point, but there's an inherent conflict in most climates.  The issue is when to do the girdling.  And there are two things you want to optimize:  One is top growth of the new branches that form below the girdle, and the second is figs produced above the girdle (which implies the top growth above the girdle too).  So when to place the girdle to optimize both?  You may be able to make an optimal "tradeoff" between the two, but there's some degree of inherent conflict between the two, for most climates.  

Trying to push new growth on the new branches that form below the girdle argues for placing the girdle early, when the leaves are sugar sinks and the roots are sugar sources.  That's when you get the spring flush of new top growth (which encourages the top growth on the girdled branch too.  So anything you do to interrupt the feedback loop between up flow and down flow will reduce the energy going to the top of the girdled branch.  Put more simply, if you encourage top growth in the branches below the girdle, that comes at some expense to the energy that will flow to the top growth above the girdle.  And that growth is what will be needed later for any figs on that branch above the girdle to ripen.
  
Meanwhile, if you want to optimize fig production on the branch above the girdle (rather than on your new branches below), that argues for placing the girdle later.  If you want those figs to develop and ripen, then early on you need to be pushing top growth above the girdle point.  How early or late do you want to place the girdle?  Well, there's probably some "optimal" time in the sense of getting "some" of each of your two desirable things.  i.e., some kind of best balanced point where you hinder both outcomes just a little in order to get "pretty good" on both.  But to get "best possible" on either one implies that you'll pay a bigger price on the other.

OK, so I said "in most climates".  What I really meant was:  in a climate like mine.  (LOL... my thinking is obviously geocentric or provincial).  In my climate, there's typically only one spring flush of new top growth.  With these containers and greenhouses, it's possible to extend the first half of the season (when daylight hours are increasing day by day), to get two flushes of new growth.  But out there in your land of almost-paradise-for-figs, you can probably routinely get two growth flushes, maybe even three, in that first half year when daylight is increasing.  It would depend on the weather patterns within each year I suppose, but that first half of the season is the set of top growth flushes over which you'd want to optimize.  Can you time your moment of girdling to come right between two spring growth flushes?  If so, you can optimize top growth above the girdle (and hence fig production above) for one growth flush, and then optimize branching of the new branches below the girdle for the second growth flush.  Doing this would depend on your ability to know when the growth flushes will occur though.  Might be tricky given crazy old weather.  But I think that's your best hope of doing this.

OK, enough droning on from me.  I'd still bow to empirical results and the knowledge from experience.  But I'm convinced after thinking about this that your ability would be very dependent on climate.  Optimizing for both desired outcomes here in the land of short summers is completely different from the same optimization of both in a land of multiple "spring flushes".  Very interesting thread query... thanks for posting it!

Mike   central NY state, zone 5 (one of the lands of relatively short growing seasons, and with a nod of recognition to my friends in Canada... many of you may have more warmth in your climate than I have, but all of you have shorter duration of summer, unless you're extending with greenhouses).
  

Not to go in too much of a different direction but I have a couple of figs that I am also trying to air layer in my sun room. I set them up without girdling at all and all three have produced surprising growth above the air layer with average growth below the air layer. The parent cultivar is a 1 year old RdB in a 3 gallon pot and maybe it is just vigorous. 

Jon, looks like our last two posts overlapped.  (I was busy writing a book while you posted).  I get it now (second of my posts) about the two things you're trying to optimize.  I won't repeat my mini-dissertation, but the net is I think you'd have to pick an optimal time to girdle right between a couple of flushes of top growth  (and then do the obvious things about pinching to encourage fruit in one place and top in another).  I think ripening is mostly about grabbing sugar from the leaves above, but only after a certain point in fruit development.  Knowing that point in time, and knowing when the xylem switches over it's roles (xylem changes over the season are complex), that means in a climate like yours it might be possible to optimize this.  In a climate like mine (single growth flush), the optimizing would be very different from yours (multiple growth flushes).

Mike   central NY state, zone 5 

What I love here is that Jon, our mentor, has issues too!  And I love that he is not arrogant, but asks advice from others so we may all learn!  I have no advice or questions.  Just support and bookmarks for future reference!

Suzi

It is apparent, and I have observed this over many years, that tip buds break dormancy much earlier than other buds, and most often where there is a tip bud, the lower buds do not break at all. So, where I have wanted greater branch development, I have always removed the tip buds, or more accurately, pruned the branch, in the hope that 2-3 buds would break dormancy near the pruning point, thus producing more than one branch. I am observing the tip versus side bud break phenomenon, currently.

Assuming that the tip bud, which breaks earlier, would also lead to earlier ripe fruit, the question was how to obtain more tip buds while still maintaining a smaller tree size (pruning without removing the tip buds). Earlier ripening would be desirable in most climates, either where they are too short, or where you want to produce a more extended harvest season. However, leaving tips buds and pruning seemed to be mutually exclusive goals. Air-layers started in late August (in my climate) seemed to give the desired affect of producing the desired growth of new branches which did not have enough season to grow to be very long.

What was more unknown was the relationship between fruit development and ripening and the various parts of the tree. It seems, in general, that fruit ripens best when grown in warm weather and in full sun, which would seem to indicate that the predominant input is through photosynthesis in the leaves. What is not apparent is whether that transfer is direct from leaves to fruit, or requires further "processing" in the roots before being useable to fruit development.

Now, I just have to remember to experiment this season.

Good clarifications of your questions.  Regarding the part about the elements of ripening of the figs:  I believe the two primary inputs are
        a) sugars and products of photosynthesis from the leaves above the fig, and
        b) fluids from below (from the roots).
I don't believe that the products of photosynthesis return from leaves to roots and thence back up to the fruit.  If that were so, then it would not matter so much whether the leaves providing the inputs to the figs were on that same branch.  Yet I believe there must be leaves on that branch above the fig in order to see ripening, which (if accurate) suggests that the sugars and other products reach the fig as they descend.  Leaves above the fig seem a necessary condition (but probably not a sufficient condition... gotta get something from the roots too... the full complement of which is not clear... may require multiple specific things from the roots).  So don't pinch that terminal bud too early if you want figs on that branch to ripen.  It'll be interesting to see what your experiments/observations show actually happens.

Mike