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Dr. R. Scott Anderson

Associate Professor, Environmental Sciences

Research Location Site: Potato Lake, central Mogollon Rim

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Introduction

Though the earth's climate, landscape, and vegetation can seem very stable, especially on a human time scale, they are actually quite dynamic. Evidence for ongoing change is abundant in the science of paleoecology, the study of the earth's past ecological communities. Dr. R. Scott Anderson of Northern Arizona University undertook a paleoecological study of Potato Lake, Arizona to help understand changes in climate and vegetation that have occurred in this region along the Mogollon Rim over the last 35,000 years.

Methods

A major scientific method used by paleoecologists to interpret changes in vegetation is palynology, the study of pollen. Pollen preserved in lake sediments, which accumulate over time, can give a picture of what the environment around a lake may have looked like at different points in the past. For instance, if a lake was surrounded by ponderosa pine 10,000 years ago, one would expect to find mostly pine pollen in preserved lake sediments that are of the same age. Scientists using palynology often take cores form a lake by floating out on a boat and placing a special coring device down into the lake bed. This intact core is later dated and analyzed in a lab for pollen types and pollen composition.

Results and Discussion

Today Potato Lake, at 7300 feet atop the Mogollon Rim, is surrounded by a vast ponderosa pine forest. Has this always been the case? What was the lake's environment during the last ice age? Pollen analysis completed by Dr. Anderson suggests a varied vegetational history for the site extending back many thousands of years. From 35,000 to 21,000 years ago it appears most of the rim in this area was covered by a mixed-conifer forest, suggesting the climate was cooler and possibly wetter than today. From 21,000 to 10,400 years ago pollen studies suggest a subalpine forest dominated by Englemann Spruce surrounded the lake, indicating even colder conditions. Today this spruce is only found above about 9000 feet in the higher mountains of the state. It appears the lake almost dried up completely about 5000 years ago, as there were few lake sediments deposited during this period. Approximately 3000 years ago the lake and the surrounding forest began to appear much like it does today. Dr. Anderson's study and many like it give current scientists a better idea of how today's landscape evolved. By studying the past, scientists may better understand today's environment and possibly even predict some general changes that may happen in the future.

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