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Desert Diary


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Under the principle of uniformitarianism, the present is the key to the past. That is, by looking at the processes going on in the present, we can interpret the happenings of past times. This works out amazingly well, for the most part, but sometimes our ignorance of current conditions presents us with surprises when we look into prehistoric times.

For example, we tend to place plants into such habitat categories as desert, grassland, or desert plus grassland. But, when looking at plants preserved in ancient packrat middens, occasionally we find what appears to us to be an anomaly. For example, Four-winged Saltbush usually is a desert, grassland, and pinyon-juniper woodland plant. However, nearly 15,000 years ago in Rhodes Canyon in the San Andres Mountains, it occurred in a mixed coniferous forest association along with Douglas Fir, Ponderosa Pine, and Blue Spruce. Does this mean the present really isn't a key to the past? Nope. It merely means we don't know enough about the present—in this case, the factors that limit the distribution of Four-winged Saltbush.
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Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.