Post 202 Mt Macedon autumn colours

 When I was in Melbourne recently for the Natives in Bonsai Symposium I took an extra day for a little touristing and visited Mt Macedon, a little to the north west of Melbourne. It is a bit of a hill on the plains but enough to have a little more chill and is famous for a few private gardens that are open to the public to visit. I thought it might be a good time to see some autumn colours which are not a dominant feature of Brisbane gardening.

So just a short post and a puzzle.

 

This is a picture of an Acer in one of the gardens, very beautiful autumnal tones from bright red to yellow. This one small tree showed a feature evident on just about every other deciduous tree I saw that day; and that is the leaves mature at the top of the tree first. Is it colder at the top of the tree and does that mean it is even colder at the top of a tree twice the height.
I like to think its further evidence of radiative transfer, along with frost at above zero temperatures; the cosmos at close to absolute zero radiatively sucking warmth from the less protected upper leaves. Aren't we lucky our nights are relatively short. Is that why nights are always coldest just before the dawn?