Summer Sky Is Changing

The position of the sun has begun shifting, casting new and deeper shadows.
Summer is moving out.
The huge cherry tree at our cabin has already dropped all of it's leaves, with out our enjoying any color changes in them.
Across the river from our deck, sourwood trees are the first dramatic colors of the Fall season. They turn a rich, vibrant red and orange, which stands out against the green and yellowing trees around them.

Info from Ask.com on "Why there is Fall Leaf color change"
" The major factor influencing autumn leaf color change is lack of water and nutrients which effect formation of chlorophyll. Not a lack of water and nutrients to the entire tree, but a purposeful weaning of water from each leaf. Every leaf is affected by colder, drier, and breezy conditions and begins a process which results in its own dropping from the tree.

The broadleaf tree goes through a process of sealing off the leaf from the stem (abscission). This halts the flow of all internal water to the leaf and causes a color change. It also seals the spot of leaf attachment and prevents precious moisture from escaping during winter dormancy.

This lack of water to each leaf causes a very important chemical reaction to stop. Photosynthesis, or the food-producing combination of sunlight, water, and carbon dioxide, is eliminated. Chlorophyll must be renewed (by photosynthesis) or be taken in by the tree along with photosynthetic sugar. So chlorophyll disappears from the leaves. Chlorophyll is the green you see in the leaf.

Once the overwhelming chlorophyll color is removed, leaf colors will dominate over the receding green pigment. True leaf pigments vary with the species of tree and thus the different characteristic leaf colors. And because true leaf colors are water soluble, that makes the color disappear very quickly after drying out.
Carotenes and xanthophylls (the pigment found in carrots and corn) cause beech, birch, ash, hickory and poplars to turn yellow. The brilliant reds and oranges in this fall landscape are produced by anthocyanins and color maple, sweetgum, dogwood, sumac, sourwood and tupelo . Tannins give some oak species a distinctively brown color and is the final persistent color most leaves turn before becoming part of the forest floor. "