The air bracing, leaves just starting to turn

Question

I found this sentence -

It was autumn in New England, the air bracing, leaves just starting to turn.

What does "leaves started to turn" mean? Does it mean that "the leaves started to bend due to dryness"?

Answer 1

This sentence has undergone some surgery; in particular, Conjunction Reduction has deleted the repeated auxiliary form of be required for the predicate adjectives in the second and third clauses.
As well as the repeated article before leaves in the third clause, and all the conjunctions.

I.e, this is the basic sentence
(Note: same meaning; boldface items have been deleted by rule):

• It was autumn in New England,
  and the air was bracing,
  and the leaves were just starting to turn.

As has been pointed out, leaves turning is short for leaves turning color,
referring to deciduous "Fall color" in temperate regions.

Answer 2

Turn in this context denotes colour

It is an expression relating to autumn. When the leaves turn they change colour to whatever is the autumn colour for that tree. Red, yellow, orange...

Bracing means fresh and invigorating. "the bracing sea air"

Answer 3

Bracing (TFD) means fresh, invigorating. So the air was cold, not too cold, no fog, probably a bit of wind, but not a lot.

The leaves turning means changing colour - a famous sight in New England, so the writer is referring to the beginning of the process.