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C. Hart Merriam

Clinton Hart Merriam was born in upstate New York on 5 December 1855. His family was a wealthy, successful family with a large estate surrounded by forests brimming with a variety of plants and animals. This atmosphere allowed Merriam to spend many hours in the woods, exploring the local flora and fauna. This early exposure encouraged Merriam to have a deep appreciation for nature.

Merriam was educated at Yale University and studied human anatomy. This education culminated in completing medical school and becoming a physician. Many early naturalists were in the medical profession, and Merriam used this time to go on field studies and collect vast amounts of biological information. At the age of 18, he published his first summaries of his biological studies.

In 1886, Merriam began work for the United States Department of Agriculture in the Entomology Division. He used this platform to promote in-depth biological surveys of the United States. Merriam felt this would discover new organisms in America and eventually lead to biogeographical studies, investigating interactions between biota and abiotic elements such as temperature and elevation.

Merriam first visited the Colorado Plateau in 1889 while on the Arizona Territory San Francisco Mountain Region Survey for the USDA. He chose this region to investigate biogeographical interactions because "different climates and zones of animal and vegetable life succeed each other from base to summit" and "because of its southern position, isolation, great altitude, and proximity to an arid desert." Merriam trekked greatly around and on the San Francisco Peaks, including the cinder hills, Walnut Canyon, Grand Canyon, and the Painted Desert. His expeditions included extensive plant and animal collections and elevation documentation from an aneroid barometer. These studies eventually supported his Life Zones concept of biogeographical elevation gradients.

 

Life Zones Concept as Proposed by Merriam

Warm Desert < 1500 m High temperature, low precipitation desert with cacti and desert flora and fauna.
Desert Grassland /
Pinyon-Juniper Woodlands		 1500 - 2000 m Extremes of temperature and precipitation. Open landscape with Colorado Pinyon Pine and one-seed juniper trees. Pinyon jay and large rock squirrel common to the area.
Ponderosa Pine Forest 2000 - 2500 m Largest stand of ponderosa pine trees in North America. Seasons characterized into long winters, harsh droughts, and strong monsoons. Fire plays an extensive role in forest ecology. Abert Squirrel, Rocky Mountain Elk, Steller's Jay, and broad tailed hummingbirds found extensively in this region.
Mixed Conifer Forest 2500 - 3000 m Rich moist soil supports stands of Douglas and white fire with limber pine and quaking aspen. Black bears, mule deers, and elk can be found in this zone.
Spruce-fir Forest 3000 - 3500 m Heavy shade and high precipitation supports mainly Engelmann Spruce and corkbark fir with extensive high-altitude meadows. Red squirrels, gray-collared chipmunks, Clark's nutcrackers, and red-faced warblers are found in this zone.
Sub-alpine ~ 3500 m At the timberline, dwarf Engelmann spruce and bristlecone pine cling to the mountain in a harsh environment. The water pipit can be found at the timberline and bighorn sheep used to be found there as well.
Alpine Tundra 3500 - 3852 m Extreme cold and high winds make this a harsh, brutal environment with small flowering plants and few animals. The San Francisco Peaks groundsel is found only in this zone and is currently under threatened status.