Factors Impacting Regional Climate: Yellowstone’s climate is characterized by
summer temperatures of around 25 degrees Celsius and daytime winter
temperatures ranging from -20 to -5 degrees Celsius. Hayden Valley specifically
experiences winter temperatures reaching -10 degrees Celsius, and summer
temperatures around 20 degrees Celsius. Thus, few trees exist in Hayden Valley—mostly
shrubs and grasses survive here.
Only certain species like bison can survive such cold, harsh winter weather.
Only certain species like bison can survive such cold, harsh winter weather.
Abiotic factors
Nonliving factors that influence Hayden Valley’s distribution and variety of organisms include the cold winter temperatures, its moderate precipitation levels, sunshine, topsoil that is fairly poor in nutrients, little shade availability due to lack of trees, etc. Below: In the summer, Hayden Valley typically relies on rain for its precipitation, but even then its levels are low. |
Biotic factors
Living factors, or influences of living organisms that impact the distribution of life in Hayden Valley include its scarce number of trees, its wide variety of shrubs and grasses, its presence of beavers who build dams, and presence fungi on plant/grass roots (especially near geysers) that allow them to better absorb minerals. Below: Few trees exist in Hayden Valley besides lodgepole pines and aspens. |
Limiting factors are factors of an ecosystem that limit its net primary production. Limiting nutrients can fall under this category; they are those nutrients that must be added for net primary production to increase in a given ecosystem or area.
Density-dependent factors are limiting factors that limit the population at an increasing level/degree as populations become denser. For Hayden Valley, these factors include competition for food, particularly competition for small-animal prey between coyotes and grey wolves. Competition for the resources space and sunlight occur in more forested areas of Yellowstone, demonstrating how fires can benefit those plants that are otherwise shaded by thick canopies. This particular competition may directly decrease the amount of biomass that plants can produce through photosynthesis. Predation, mostly by large birds, coyotes, red foxes, and grey wolves also regulates small rodent population of Hayden Valley. Disease, especially in the case of bison, can and would increase with increasing numbers of bison. As bison numbers increase in and around Hayden Valley, Brucellosis (which is believed to have come from domesticated cattle, and causes miscarriages among bison) may increase in frequency. Moreover, deer mice and other mice of Hayden Valley might potentially experience intrinsic factors like hormonal changes that lead to delays in sexual maturity if population sizes seem too large—overall regulating population sizes by decreasing reproduction rates.
Right: Predation of species like bison increases with predator populations like gray wolves. |
Density-independent factors are those that don’t fluctuate in level/degree with varying density levels of populations. For Hayden Valley, these include things like fires, that immediately decrease population sizes both by direct destruction and by the effects of smoke. Drought also can and has historically regulated both aquatic and terrestrial populations. Temperature, whether it is extremely hot or cold, regulates populations regardless of their densities.
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Nitrogen: A Major Limiting Nutrient
Nitrogen Cycle
Nitrogen is one important limiting factor to the net primary production in Hayden Valley. A 1992 study showed that flow of nitrogen from large hooved mammals to soil (in the form of feces) ranged from 8.1 to 45.6 kg/hecatre/yr. Nitrogen levels in Yellowstone National Park were deemed higher than those for other northern coniferous forests and northern grassland areas. Grazing mammals are a major part of this nitrogen cycle though.
Nitrogen in the atmosphere becomes ammonia through nitrogen fixation by nitrogen fixing bacteria in the soil, which then undergoes nitrification by nitrifying bacteria to become nitrite and then nitrate, that is usable by the shrubs and grass of Hayden Valley. Lightning also changes N2 directly into nitrate. This form of nitrogen is then consumed by large hooved mammals like bison, and other animals also inhale atmospheric nitrogen. All of these animals then release nitrogen in their feces, some of which is recycled by bacteria in the soil again, and some of which runs off into the ponds/waters contained by Hayden Valley. Nitrate dissolved in water and in soil often undergoes denitrification to return to the atmosphere.
Human Impact
Humans have impacted the nitrogen cycle of Yellowstone partly by restricting the habitat area of bison, and keeping them from spilling out too much beyond Yellowstone. This has led to an increase in bison feces, and thus nitrogen levels in soils due to animals. Much of this animal waste can run off into water though, potentially leading to eutrophication as algae bloom, then die, and are decomposed so that rivers/ponds in Hayden Valley and other ecosystems become less healthy and rich. This hasn’t been a major problem, but burning of fossil fuels has ultimately increased levels of nitrous oxides and NOx, leading to acid rain that potentially causes soil erosion, directly hurts plants, or raises pH in bodies of water in the park. Again, this hasn’t been deemed a major problem here though. Use of fertilizers can increase nitrogen run-off into natural bodies of water, but in Yellowstone this isn’t a major issue.
Below: a general diagram of the nitrogen cycle
Nitrogen is one important limiting factor to the net primary production in Hayden Valley. A 1992 study showed that flow of nitrogen from large hooved mammals to soil (in the form of feces) ranged from 8.1 to 45.6 kg/hecatre/yr. Nitrogen levels in Yellowstone National Park were deemed higher than those for other northern coniferous forests and northern grassland areas. Grazing mammals are a major part of this nitrogen cycle though.
Nitrogen in the atmosphere becomes ammonia through nitrogen fixation by nitrogen fixing bacteria in the soil, which then undergoes nitrification by nitrifying bacteria to become nitrite and then nitrate, that is usable by the shrubs and grass of Hayden Valley. Lightning also changes N2 directly into nitrate. This form of nitrogen is then consumed by large hooved mammals like bison, and other animals also inhale atmospheric nitrogen. All of these animals then release nitrogen in their feces, some of which is recycled by bacteria in the soil again, and some of which runs off into the ponds/waters contained by Hayden Valley. Nitrate dissolved in water and in soil often undergoes denitrification to return to the atmosphere.
Human Impact
Humans have impacted the nitrogen cycle of Yellowstone partly by restricting the habitat area of bison, and keeping them from spilling out too much beyond Yellowstone. This has led to an increase in bison feces, and thus nitrogen levels in soils due to animals. Much of this animal waste can run off into water though, potentially leading to eutrophication as algae bloom, then die, and are decomposed so that rivers/ponds in Hayden Valley and other ecosystems become less healthy and rich. This hasn’t been a major problem, but burning of fossil fuels has ultimately increased levels of nitrous oxides and NOx, leading to acid rain that potentially causes soil erosion, directly hurts plants, or raises pH in bodies of water in the park. Again, this hasn’t been deemed a major problem here though. Use of fertilizers can increase nitrogen run-off into natural bodies of water, but in Yellowstone this isn’t a major issue.
Below: a general diagram of the nitrogen cycle