Life Zones and the Sandia Mountains

Life zones are geographic areas that are defined by the plant and animal life and living conditions within them.  They are used by scientists to recognize patterns in the natural world, and are determined by a number of factors including elevation, precipitation, and temperature.  What makes understanding the distribution of life zones so difficult is the complex relationship between natural variables across the globe. The Koeppen system is a classification system used to describe Earth’s main climate groups according to latitude, degree of continentality, and location relative to topographic features (Richs, R).

            There is a strong correlation between latitude and elevation regarding plant and animal life.  The correlation between these two factors is positive; for every 1,000 miles in latitude, similar plant life is found 1,000 feet higher in elevation.  This is why similar plant life can be found at higher elevations of the Sandia Mountains as low-elevation places in Canada 4,000 miles north. 

There is also a strong relationship between elevation and temperature.  For every 100 meters in elevation the temperature drops 1°C.  This temperature change is the rate of Adiabatic cooling (Aguado, Edward). When air rises along a mountain side, pressure decreases and the air expands. Because it is doing work the air loses energy and cools, making it generally colder at the top of a mountain than at the bottom. Adiabatic cooling affects the environment of an area and has an influence on life zones found along mountain elevations. 

Mechanism of Adiabatic Cooling

 

A significant correlation between elevation and precipitation also exists.  As the elevation increases, the average precipitation levels also increase.  This is because the most common way to cause condensation in the atmosphere is to cool a parcel of air to its dew point.  Because warm air can hold more water than cold air, as the air is pushed up the mountain range, it cools adiabatically and as it cools it gets closer to the dew point, the temperature at which the moisture in the air saturates.  This causes condensation, cloud formation, and eventually precipitation (Aguado, Edward).

On the other hand, the adiabatic cooling process causes the area on the leeward side of the mountain to have little rainfall because, by the time the wind reaches the other side of the mountain, there is not enough moisture left to precipitate out.  Consequently, mountain sides facing away from the wind receive less moisture.  This area directly down-wind of the mountain is in a rain shadow. 

Illustration of a Rain Shadow

 

A very interesting fact about the Sandia mountain range: it does not follow the rules of a rain shadow. Contrary to what one would expect, because these mountains are exposed to such strong sunlight in the west, even though the prevailing winds come from this direction, the mountain still has very little moisture on the theoretically “wetter” side.  The area that lies in the rain shadow of the Sandia Mountains actually gets anywhere between 0.94 and 3.02 inches of rain per month with a yearly average of 17.39 inches of moisture.

The Rain Shadow of the Sandia Mountains is Affected by Intense Sun Exposure

 

The Sandia Mountains range from 6,200 feet to more than 10,628 feet in elevation. Temperature and precipitation correlate with elevation so closely that most life zones are found along elevation lines and include four main life zones:  the Spruce Fir life zone, the Mixed Coniferous zone, the Ponderosa Pine zone, and the Piñon/Juniper zone.  All four of these are only one life zone in the Koeppen system: a Dfb zone.

The Koeppen system is a classification system that recognizes five major climactic types and minor subgroups in each. The five types are designated by a capital letter and the minor types by lower case letters:

Letter	Description of Classification
A	Tropical Moist Climates: all months have average temperatures above 18 degrees Celsius
B	Dry Climates: with deficient precipitation during most of the year
C	Moist Mid-latitude Climates with Mild Winters
D	Moist Mid-Latitude Climates with Cold Winters
E	Polar Climates: with extremely cold winters and summers

In the case of the East Mountains, the main climate classification is a D—a moist, mid-latitude climate with cold winters—along with an f – signifying it gets precipitation in all seasons—and a b – indicating a land mass that is further into a continent away from any large bodies of water.

 According to the University of Elmhurst, "Dfb and Dwb climates are immediately north of hot summer continental climates, generally in the high 40s and low 50s in latitude in North America and Asia." In this case, because of the elevation of the mountains even though the East Mountains are not in the latitude range they qualify as this type of climate (see above correlation between latitude and climate).

Overall, the Climate of the East Mountains can be classified as a Dfb climate in the Koeppen System even though it does not completely describe the unique mountain environment.

 

 

Sources:

Aguado, Edward, and James E. Burt. Understanding Weather and Climate. Upper Saddle River, NJ: Pearson Prentice Hall, 2007. Print.

Julyan, Robert, and Mary Stuever. Field Guide to the Sandia Mountains. Albuquerque: University of New Mexico, 2005. Print.

Richs, R. "Koeppen Climate Classification." Elmhurst.edu. Elmhurst College, 2005. Web. 13 Mar. 2014. <http://www.elmhurst.edu/~richs/EC/101/KoppenClimateClassification.pdf>.

Day, John A. "Clouds." NWS JetStream - Online School for Weather. National Weather Service, 2008. Web. 13 Mar. 2014. <http://oceanservice.noaa.gov/education/yos/resource/JetStream/synoptic/clouds.htm>.