Geography and Natural History of the Greater Yellowstone Ecosystem

 Geography

There are a variety of habitats in Yellowstone National Park and the surrounding areas.  From tundra to wetland, alpine to lowland and everything in between the geography of the park is unique and variable. 

The Yellowstone River and the Lamar Valley are at the north end of the park.  Harsh winters and deep snow are made even worse by the mountainous nature of the north end.  These mountains continue south for about 1/3 the length of the park and have an enormous effect on the vegetation and wildlife.  Tougher species are present and seasonal migrations are much more frequent. 

Yellowstone Lake, the largest mountain lake in North America, is in the middle of park and houses all the micro-ecosystems that a lake should.  Waterfowl, both migratory and resident, fish, and mammals exists in and around the lake in abundance.  Human activity is also very high in the region of the park thus effecting much of the wildlife.

More lakes and mountains exist on the southern border of the park but at less intensity.  Conditions are more mild here and hence species, especially ungulates, are in greater concentrations.

Click here for a map of the Yellowstone National Park.

Geology

Yellowstone National Park and the surrounding area has the most extensive collection of geothermal activity on earth.  This geothermal activity is caused by water meeting the molten rock of the earth’s crust.  The volcanic soil of the area is immensely permeable and much of the rain and snowfall of the area falls through the porous volcanic rock and soils to the molten rock only three miles deep.

Resulting in the temperature of the water far exceeding 500^oF, water’s contact with the molten also produces tremendous pressure.  The water is unable to boil or turn to steam at the this pressure and is forced upwards and in it travels toward the surface contacts cools rock and soon the pressure and temperature go down enough that the water is able to boil.  It is this boiling water that comes to the surface.  How and when it surfaces is a product of the composition of the rock through which it has traveled and the steam energy remaining after the cooling-off process has occurred.

Click here for a sight of Yellowstone geothermal activity.

Click here for definitions of geothermal phenomena.

Earthquakes

The Yellowstone, partly due to the geothermal activity, is a site of much seismic activity as well.  Click here for maps of the seismic activity over time.

Fire

The major seral event in Yellowstone National Park and the surrounding area is fire.  For this reason, many of the vegetative species in the ecosystem are those with abilities to thrive under this kind of pressure.

Douglas-fir (Pseudotsuga mensezii) is a self-pruning species with thick bark, and fast growth.  The thick bark helps protect the trees cambium from the intense heat of the fire thus allowing the tree to survive and grow.  Self-pruning affords Douglas-fir safety from ground fires by preventing fire ladders.  Fast growth allows the tree to grow to the states were it is able to use the prior traits.

Lodge-pole pine (Pinus contorta) is a thin-barked species with very well developed fire ladders making it very susceptible to fire damage and death.  However, the seed biology of the tree helps to ensure that it remain after an intense fire.  Lodge-pole pine has serrotinous cones.  These cones are held closed until temperature exceeds 140^oF at which time the seeds open and flood the area.  Lodge-pole pine also has normal seeds for times when fire is rare.

Quaking Aspen (Populus tremuloides), while possessing neither thick bark, nor serrotinous cones, uses its ability to sprout from unburned roots to continue itself.  Fires very rarely burn or damage the underground root system of large plants and hence the Aspen is able to vigorously resprout after a fire.

Forbes and grasses are usually the first to populate a disturbed area and do so via wind blown seeds that come from area of the park and surrounding ecosystem that were undamaged by fire.  Many of these species help to prepare the soil for larger, later seral species as well as feed the variety of wildlife of the park in the summer.

Human Disturbance

Yellowstone National Park proper has remained fairly untouched since it’s designation as such in 1872.  Aside from the paving of roads and construction of visitor centers, much of the park is still wild despite the some 5 million visitors it receives every year. 

The same can not be said for the surrounding areas.  Much of the land around Yellowstone National Park is ranching land and is used very heavily by the industry.  Vegetation once native to the area has been removed and many of the seasonal migrations have had to change or cease due to these environmental changes. 

Fire suppression and management has had an effect through loss of structural diversity.  Now that the “let it burn” policy has bee effect, this situation is on the mend.