The Science of
Autumn
~ by Bob Gustin
Brown County’ s natural beauty has drawn artists to it for more than a century, and the combination of spectacular changing hardwood trees and a thriving arts colony brings thousands of visitors to the area each autumn.
While the poets and painters enrich our imagination with mysterious images of autumn colors, scientists know it is simple chemistry behind the changing of the leaves.
For thousands of years we’ ve enjoyed, but also puzzled over, the cause of autumn’ s majestic pronouncement of the coming of winter. At one point, it was chalked up to cooler temperatures and shorter days. Turns out, that’ s right, but those conditions serve mainly as a catalyst. And the length of days is the main catalyst, because
weather is not as reliable of an indicator as the clockwork of the heavens caused by the tilt of the earth on its axis, which controls the amount of sunshine each area of the earth receives.
Brown County artist Susan Ahbe said autumn is her favorite season because of the distinct light as well as the subtle secondary colors which accompany the bright tones of October.
“ There’ s a softness to the autumn light in the morning,” she said, caused by the slant of the sun’ s rays. Like Brown County painters before her, many of her pieces are local landscapes, rich with various shades of green in the summer and celebrations of reds, oranges, and yellows in the fall.
To understand these changes, imagine a tree as not only a living organism, but also a selfcontained factory of sorts. The main products of this factory are oxygen, carbohydrates and chlorophyll. A tree releases oxygen into the atmosphere, helping keep humans and animals alive. It uses chlorophyll to capture the sun’ s energy and power the factory. And it manufactures sugars and starches to feed itself.
Here’ s how it works: Each leaf on a tree acts as a little solar panel, collecting sunlight to power the factory. Each root of the tree collects water from the ground and pipes the mineral nutrients it contains through the inner bark to the leaves. There, 90 percent of the water is evaporated.
Leaf cells containing chlorophyll absorb the sunlight and change water and carbon dioxide into oxygen and energy the tree can use to grow— mainly sugars
16 Our Brown County Sept./ Oct. 2016