Areas of Tundra Around the World

Primary and Secondary Ecological Succession

Primary Succession: When the earth warmed the glaciers retreated and left behind land that was lifeless and rocky. It took a very long time before pioneer plants like lichen started to grow on these rocks. In time, rocks broken down by the lichens mixed with decaying lichens and formed the first soil. Wind also blew dust, which congregated in small cracks in rocks where moss and small plants started to grow. Like lichens, moss obtains water by absorbing moisture in the air. Soon, more moss and more soil forms. Decaying moss mixes with rock chips and dust to form more soil. Because of this, grass begins to grow in the area. As soil becomes more plentiful, more and more plants begin to grow. These stages of soil and plant sophistication are called primary succession.

Secondary Succession: When an event, like a fire or a hurricane, reduces an already established ecosystem, but the soil remains and succession then follows. This is faster than primary succession because the soil is already present. In the tundra this could occur after a fire or a mudslide.

: At Denali National Park, once-frozen hillsides are unleashing cascades of mud as they thaw

Type of Soil in the Tundra

Arctic Tundra- When the snow above the active layer melts (the layer of soil where plants can grow), the water remains on the surface of the soil. This is because water cannot be absorbed by the permafrost (a permanent layer of frozen ground below the active layer), leaving the top layer of the soil wet and soggy. Evaporation of the water is also not possible. The arctic tundra's cool air does not promote much Evaporation from taking place. The arctic tundra landscape is formed by the freezing, thawing and refreezing of this soggy soil. This type of land formation is only unique to the arctic tundra.

Alpine Tundra- The alpine tundra's soil also has a layer of permafrost, but its active layer is not as soggy as the arctic tundra's. This is because rainfall in the alpine tundra runs off of the steep mountain sides instead of becoming saturated in the soil. Strong winds also sweep moisture from melting snow out of the soil leaving the top layer dry and dust like in the summer. The alpine tundra of course is made up of mountains either formed by volcanoes, the collision of continental plates, or by retreating glaciers. These mountains are always being changed by earthquakes, strong winds, mud slides, and avalanches.

Biogeographic Cycles

Phosphorus Cycle

 


Nitrogen Cycle




Limiting Factors

Density Dependent Factors: Density Dependent factors are characteristics that are influenced by the size of a population. Density-dependence generally regulates populations within ecosystems that have many species, if they are not stressed by physical conditions. This is not typically true of the tundra. Its extreme climate reduces the number of species that successfully survive there. Even though this is true, species are still affected by predation and competition in the Tundra. Musk Oxen and Caribou can compete for sedges and grasses. Also, when the population of arctic hares increases the population of artic foxes will go up due to increases predation.

Density Independent Factors: Density Independent Factors affect populations by the same percentage, regardless of density.Temperature is a major factor in the Tundra because most species aren't able to tolerate the cold temperature and harsh winds. Trees and other tall plants cannot survive in the Tundra. Another density independent factor is the amount of sunlight. Depending on the latitude, the Sun can remain below the horizon for up to 2 months, leaving the Arctic tundra in darkness. Although the sun remains in the sky 24 hours a day during the summer, it stays close to the horizon and provides only low intensity sunlight. This is another reason why trees cannot survive in the tundra; they require an ample amount of sunlight.

Introduced Species

Felis catus, the common house cat, was domesticated in the eastern Mediterranean c. 3000 years ago. It was brought to the tundra by people from all around the world who wanted pets. It has threatened native bird species, especially on islands where native species have evolved in relative isolation from predators.

  

Symbiotic Relationships

Mutualism- Lichen is a composite organism that is usually made up of a fungus and a green alga or cyanobacterium. The alga is photosynthetic in nature and so, reduces carbon dioxide into sugars that feeds the fungus as well. The fungal counterpart in the meantime, helps provide protection to the alga by retaining water and helping in obtaining minerals from substrate. Thus, both the fungus and the green alga benefit from this relation.

Commensalism- The caribou or reindeers tend to feed on lichens when the weather is at its worst and coldest, as more often than not, this is the only food available to them which can provide them with carbohydrates and can give them energy and heat. So, when the caribou is on the lookout for food, the arctic fox follows it. Then, when the caribou digs the ground snow in a quest to find food, it digs up the soil and slightly exposes, or at least brings closer to the surface some of the subnivean mammals, with whom the arctic fox shares a predator prey relationships in the tundra. So, once the caribou is done with its hunting, the arctic fox then follows and digs further deep and gets its food in the form of the mammals. Hence, this is one of the best examples of commensalism in the tundra region, wherein the caribou remains unaffected but the arctic fox manages to get its food with some help from the caribou.

Parasitism-  One of the lesser known tundra facts is that even parasitism is seen in the tundra region. This is usually seen in cases of liver tapeworm cysts. The liver tapeworm cysts tend to stay and grow in the body of various animals like moose, caribou and even wolves. These tapeworms then feed on the food that is eaten by these animals, which leads to malnutrition in the host body, that is, in the animal.

Competition- Caribou and Musk Ox can compete for food if the supply is low. Both eat plants and may compete for sedges and grasses. For the most part, animals in the Tundra do not have to compete for resources since the Tundra is only inhabited by a select number of species who can survive the harsh conditions.