Your Virtual Vacation


Now it’s time to hitch your wagon to a star…or a satellite. First, close your eyes and use your imagination.


Then go to the website Google Earth. (If you’ve never used it, you may need to download the basic controls to your desktop. The simple version is free. ) Pick a place in the United States you’d like to go. (Just double click and keep zooming in. You’ll find it easy and addicting.)


In the lower left corner, click “Terrain.” Then zoom in again. Keep going. Find your dream spot. What is the terrain like? Since there are no time limits on your virtual vacation, make a few more maps. Explore the resources on this amazing site. See what you can infer just by exploring.


Next, it’s time to look at the climate in the area of your “mind trip.” Go to That’s the National Climate Data Center. You can “Search by Map.” (Click on the Left Side.) When you’ve zoomed to a single orange dot (data collecting site.) Select a product (Local climatological data.) Make sure that your popup blocker is turned off. Make a map, or explore on your own. Often you can also grab a climatogram by going to Google Images and clicking “climate” or “climatogram.”


Then join our Discussion Board. Describe your virtual trip, including the climax community that you found in the undisturbed areas of your travels. Your virtual trip to an undisturbed area revealed a climax community. Think of the reasons why it looked like it did, and the difficulties involved in maintaining it undisturbed.

 How long does it take to make a forest? Here's a local story: In lower Michigan, there's only one small area where the native white pines were not logged over 100 years ago. They survived by accident, the unexpected beneficiaries of an inheritance mix-up. In the century since, no new white pine forests have evolved. Read more about Hartwick Pines at





Content Background: Scrambling for Light


When you took your virtual field trip using Google Earth, you zoomed down on a biome using the power of a satellite. But the resolution of your zoom tool was probably not great enough to tell you if you had landed at the edge of an area or right in the middle. From an ecological standpoint, that’s crucial.


The dynamics that influence the selection of plants and animals are complex, but almost always involve competition for light. If you have ever walked through a very old forest, you’ll remember the very special conditions of light that exist there. Many studies have compared the amount of light that reaches the top of a forest (the canopy) and the forest floor; depending upon the type of leaf coverage, only about 20% of the light that reaches the top of a middle latitude deciduous forest reaches the forest floor in midsummer.


In the darkest parts of a deciduous forest (one where most trees lose their leaves in the winter)

 you’ll find the leaves of plants that do most of their metabolism in a very few weeks between the time that the frost leaves the soil and the time that the leaves fill out the canopy above and darken the forest floor. The Lily of the Valley at the right is one of these special spring flowers that survives on such low light by hustling when conditions are right. Here’s a sense of scale. By midsummer, the light that reaches the top of a deciduous forest in Illinois might be as high as 1000 µmoles/sec.* Yet on the forest floor, the area called the litter area, the light can be as low as 5 µmoles/sec.* In a mature forest, everything must adjust to low light conditions. The seeds of potentially competitive trees or meadow plants won’t grow. Molds, fungi, and other decomposers dominate what is sometimes called the “brown food web” at the floor of such a forest. They may not need direct light but need the organic molecules that producers provide.


The status quo of the mature forest can be easily disrupted. A road-cut or clearing for a power line creates a gap for light to enter. A strong storm can defoliate the trees and create paths for light to enter. Then the rules change, and the ecosystem accommodates a different group of organisms for a time. It’s not possible to have a tiny forest in the true biological sense. Of course, some biomes have such severe limitations in other abiotic factors (such as water in a desert) that light isn’t the most crucial indicator of survival.


*1 mole of light = 6.02 × 1023 photons, Avogadro's number