Friday, October 24, 2008

"I started looking and the bubble burst"*

One of the highlights of living in New England is the fall foliage. Last year I felt like I missed the best part of autumn because I was in Tahiti for two weeks in October (oh, the sacrifice!), so this year I made an effort to really enjoy and observe the fall colors. I had grown accustomed to the yellow and gold tones that had dominated the past few years. This year, however, the bolder red and orange hues graced the trees. These colors were particularly ascetic, but I couldn't help but wonder why they were so bright.

I am familiar with the basic science of why trees turn color (see "Chlorophyll? More like borophyll!" for more—a gold star goes to whoever can name that movie!), but I wasn't quite satisfied with what I found. Mostly I came across explanations of the processes that take place within the tree and how an extra chemical has to be present for the red hues to appear. There was some mention of how dryer, cooler (but not freezing), and sunnier autumns are more likely to cause these red leaves. Great! I still wasn't satisfied.

As I see it, things don't just arbitrarily happen in nature. We may not be able to scientifically explain why certain things happen, but that doesn't mean there isn't a reason; maybe we just haven't found it yet. Why would a tree expend extra energy to produce red leaves if it didn't benefit the tree in some way?

Then I came across another article that suggested that the red leaves may actually mean the tree is in distress and that leaf color may be indicative of tree health. To further this point, Emily Habinck came across an interesting correlation between soil and foliage color while working on an undergraduate research project.

Her research shows that the extra chemical found in red leaves, which acts like a sunscreen, helps the trees absorb more food in preparation for winter, and that a tree in soil with fewer nutrients is more likely to produce this chemical. (Now we're getting somewhere.) It makes sense that a tree that gets fewer nutrients from the soil needs more nutrients from photosynthesis. So that means the trees in my area may not be as healthy as they were in previous years.

And here I was thinking that this fall was more spectacular because of the brighter colors, but it really wasn't spectacular at all! The red leaves were a natural warning sign. Warning colors (called aposematic coloration) are actually quite common in nature. The poison dart frog and black widow spider use bright colors to warn predators that they are dangerous (i.e. don't eat me!). While red-hued trees aren't poisonous, their demise would have a devastating impact on the earth.

Nothing like having a little curiosity and knowledge complicate something that appeared so simplistically beautiful. Why couldn't I have just admired the pretty colors?