Bio 104
Ecological Succession
May 6, 2010
Looking at a photograph of the spruce trees behind my parents house taken in 1995 and comparing it to a photograph of the same trees taken only a week ago, it is easy to see the succession that has taken place over only a fifteen year span. Gazing at the current picture it is obvious that the trees have defoliated, but why? What could have caused this significant change?
I believe the trees are in this condition due to parasites, such as gypsy moth caterpillars, using the trees as their host (from here on I will refer to them simply as caterpillars). In my estimation it was roughly 1995, or possibly a few years prior, when the area encountered an atrocious infestation of these caterpillars. Although their population has dwindled significantly since then, they are still a predator to our trees. The spruces have most likely survived as long as they have due to one important abiotic factor: temperature changes. Northeast Pennsylvania experiences cold winters whose frigid temperatures aid in the destruction of the caterpillar eggs. Additionally, it is not always warm in May, I can recall many years when it was snowing. During these sporadic cold spurts, the larvae that have already hatched are killed due to the unusually cold temperatures. Although the trees are weakened from the caterpillars, the winters allow them to have a small recuperation period.