Hayden Valley Food Web
Above: Hayden Valley shelters organisms at various trophic levels. Its actual list of producers, primary consumers, secondary consumers, and tertiary consumers is in reality much more extensive than the above diagram would suggest, and the flow of energy is similarly more complex in actuality, since many organisms function at various trophic levels,
Lower Left: A mother grizzly bear searches for fish Lower Right: A gray wolf eats a bison carcass
Keystone Species: Gray Wolves
A keystone species is one that is essential to maintaining the balance of an ecosystem. Its removal will have a larger impact on an environment than its biomass would indicate. The gray wolf is a keystone species of Yellowstone and specifically Hayden Valley. Their decreased populations have historically led to increased elk populations (since they are prey of the wolves), and thus decreased aspen tree populations (as elk eat/damage these plants). This has then led to fewer ponds in Hayden Valley specifically, as beavers have less wood for creating dams in rivers, thus depriving other species of pond-based niches. The gray wolf is also important as it leaves behind elk carcasses that are then consumed by scavengers like bald eagles, golden eagles, ravens, coyotes, etc. During the 1900s their population numbers in the Yellowstone area were depleted by habitat loss and overhunting by farmers who were worried about their cattle being eaten, which ultimately led to increased elk populations as explained above, causing stress to the vegetation and other wildlife of Hayden Valley. A decrease in gray wolf numbers though would probably allow for increases in numbers of coyotes, since these species compete for similar food sources.
Dominant Species: Coyotes
A dominant species is one with a higher abundance or biomass than most other species in its habitat. Coyotes are very common in Hayden Valley. The removal of the coyotes would lead to an increase in smaller predators like red foxes that experience interspecies competition for food, but an increase in small rodent populations that are controlled by coyotes throughout Hayden Valley, and possibly a consequential decrease in grasses/shrubs eaten by those rodents. This is because the coyote acts as a secondary consumers, directly consuming small animals like door mice whose populations are regulated by the coyotes. Looking at the ecosystem as a whole, certain species (mostly small rodent species) would experience increased competition for food, space, etc. if the coyote were removed. Other species like gray wolves, who compete with the coyote, would experience decreased competition.
+/- interaction: A variety of parasites have and continue to hurt bison in the Hayden Valley and Yellowstone area overall. Lungworms for example sometimes like in bronchi of bison lungs, and benefit from its sheltering. They often leave eggs there which are similarly sheltered until they hatch and exit bison bodies through their feces. Infected bison often suffer from respiratory problems, increased heart rate, etc. This examples a parasitic relationship, in which one species an interaction (lungworms) benefit, while the other (bison) suffers.
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+/+ interaction: Hayden Valley contains a few geysers. Dichanthelium lanuginosum, more commonly known as ‘panic grass’ survives in the hot soils near these geysers like Sulphur Caldron partially because of Curvularia protuberate, a fungus that is believed to provide the grass with minerals and something that helps it to tolerate the heat. The fungus in return receives sugars from the plant, exampling a symbiotic relationship where both species in an interaction are benefitted.
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Disturbances to Yellowstone: Forest Fires
Pros/Benefits to Species Diversity
Yellowstone National Park has a history of being disturbed by fires, which can sometimes be attributed to both human and natural causes. Fires remove both dead and living vegetation, allowing for new growth to occur and ultimately increasing species diversity. Many plant species actually need fire to help with seed germination. Lodgepole pines for example need fire for their seeds to be released from pinecones. Fire helps recycle nutrients back into the soil and controls plant diseases, by killing sick (vulnerable) individuals. It can decrease competition for space and sunlight, as those trees/plants left living have more available space, and can have more sunlight exposure with a less dense canopy above them. Thus, a fire can increase species diversity by preventing one species from becoming too dominant. Secondary succession, in which an ecosystem recovers from a disturbance while soil is present, occurs after forest fires. |
Cons/Negative Impacts on Species Diversity
Yet fires can also lead to immediate loss of species diversity. Issues like soil erosion arose immediately after the great 1988 fire, due to an immediate decrease in trees and thus healthy root structures. An immediate decrease in animal species richness also followed as many individuals died, chiefly because of all the smoke. Overall though, fires are an opportunity for an ecosystem to restore its balance. |
Below: Yellowstone's 1988 fire was probably its most famous and serious