Monday, November 29, 2010

Human Interference and the Forest by victoria, David and Fejiro

How does human interference in abiotic factors affect the biotic factors of the forest ecosystem at Nose Hill?
By Victoria, David, and Fejiro

An ecosystem is comprised of many different aspects. Within abiotic factors are temperature, water, soil, and many others, while biotic factors include biomass, biodiversity, and food webs. Each part of an ecosystem is linked to every other part, which makes an ecosystem a unit that functions as one. If one factor changes even slightly, it can alter everything else in the system. Biotic and abiotic factors are constantly changing, but a big cause of change in natural areas can be human impact. When looking at Nose Hill Park, situated in Calgary, Alberta, it is obvious that the same is true for its ecosystems. Nose Hill Park is predominantly grassland, but also has extensive forest areas. These forest areas have their own particular characteristics that define them as ecosystems, and because the park is located in the middle of a large city, it can be assumed that humans have impacted the forests of the park in more than one way. By analyzing various factors and comparing them with other related research, we can discover exactly how humans have affected Nose Hill Park of Calgary, Alberta, Canada.
            Temperature plays a large role in the type of ecosystems that can exist in a region and what those ecosystems are like. In Alberta, which is primarily situated in boreal forest and grassland biomes, temperatures can range from 30°C in the height of summer to -30°C in the depths of winter. Because of these rather severe seasons, organisms must be adapted to survive in both the warm and cold months. In the forest of Nose Hill Park, there are many deciduous poplar trees, shrubs and wildflowers which inhabit boreal forest regions. There is also an abundance of grass found on the hills of the forest, even though it is not in the grassland part of the park. During the winter, trees are of course less active. During the other seasons, trees work to store water and nutrients to survive the winter. As for other leafy plants, many of them die in the winter and return in the spring, since the individual plants cannot survive the harsh temperatures but instead can reproduce each season. Animals are also affected by temperature; hares and coyotes, for example, develop thicker winter coats to insulate body heat while ground squirrels hibernate in the tunnels they have built underground. Although humans do not impact temperature directly or acutely, a well-known human impact on the environment is global warming through greenhouse gases. Greenhouse gases have a larger potential to affect Nose Hill Park because it is situated in the middle of a city where carbon dioxide is constantly being emitted due to industrial and domestic pollution in large quantities; these pollutants will affect local areas first. Greenhouse gases get trapped in the atmosphere and absorb heat, increasing the atmospheric temperature. This results in a slow increase in temperatures worldwide. Even slight temperature changes can drastically impact an ecosystem because organisms are accustomed to a particular climate and often do not have enough time to adapt to changes in that environment. As atmospheric temperatures increase, the types and populations of organisms in the Nose Hill forest could easily change. Organisms who survive in cooler climates may see decreases in populations which would decrease the biomass of the forest. Biodiversity would also decrease because many organisms would either be eliminated from the forest or migrate further north to a climate more similar to what they are adapted to. 
            In forests, having an abundance of available water in the ecosystem is crucial. Because trees require large amounts of water (they transpire more than other plants due to their size and must maintain a large water supply for functioning), regular rainfall and adequate ground water is very important. A main characteristic of forest ecosystems is the amount of water (grasslands have noticeably lower amounts of water) because it is required to sustain the types of vegetation and animals that are a part of that ecosystem. In the Nose Hill forest, a soil sample was found to contain 40.7% water. The canopy cover at the Nose Hill forest was rather sparse since the trees tended to grow upward as opposed to outward, so the amount of evaporation from soil and transpiration from plants will be higher. Because of this, it is a good thing that the forest has an adequate percentage of water in its soil.
            Ever-present in a forest is evapotranspiration. Evapotranspiration is the loss of water through evaporation from soil and transpiration from plants (, 2005). The chemistry of the forest depends on evapotranspiration; this is especially true at Nose Hill where the facing of a slope is crucial to the evapotranspiration, and therefore to the entire forest. Most of the forested areas at Nose Hill are along north-facing slopes. In the Northern Hemisphere, the rate of evapotranspiration tends to be higher on south-facing slopes. This is because, following the path of the sun, north-facing slopes have morning sun while south-facing slopes have afternoon sun, and in the afternoon, the heat from the sun tends to be hotter than in the morning. The hotter an area is, the more evapotranspiration is going to occur (water will evaporate into vapour from the soil, while plants will lose more water in the heat to transpiration). Therefore, it makes sense that most of the forests at Nose Hill Park tend to be on north-facing slopes; the sun they receive in the morning is less intense heat-wise than the sun they would receive in the afternoon on a south slope. On a north-facing slope, they will lose less water through transpiration, and there will be less water loss from the soil. Water is a limiting factor for the growth and survival of trees, so trees will survive better in areas where the water content is higher and there is less transpiration (Bachman, 2004). However, just because this is a natural occurrence doesn’t mean that human impact isn’t involved. Global warming is once again affecting environments everywhere, and Nose Hill is certainly no exception. If climate change continues at its current rapid rate, higher temperatures worldwide will result in higher rates of evapotranspiration. Since the forests at Nose Hill Park are already accustomed to the specific temperature conditions in Calgary, rapid rates of climate change will only negatively impact the situation. If the amount of evapotranspiration on even north-facing slopes becomes too much for the trees in the forest to handle, it may very likely result in the trees failing to survive, which will lower the biodiversity in the forest and impact the rest of the food chain in the forest ecosystem.
Soil content is a main factor in the health of a forest. It can dictate what the health of the plant life is, and therefore what the health of the animal life is. However, just as soil majorly affects an ecosystem, an ecosystem can majorly affect soil. Soil provides water, nutrients, and stability to plants, which all transfers to the organisms in the next level of the food chain. For example, the pH level of the Nose Hill forest soil is 5, which is good because healthy pH levels in boreal forests are found to be slightly acidic (USDA Forest Service, 2008). Trees adapted to a low pH can often have difficulty surviving in soil that is too alkaline (basic) because it can result in deficiencies of key nutrients such as iron (Buchdahl, 2004). With acid rain, we see the negative effects of high amounts of water in the soil. Acid rain (precipitation containing harmful amounts of nitric/sulphuric acid formed by sulphur oxides and nitrogen dioxides released into the atmosphere during fossil fuel combustion) acidifies the soils and waters where it falls. The more water there is in the soil of an area, the more likely acid rain is to dissolve in that water and enter the food chain through the root uptake of plants (Buchdahl, 2004). Because Nose Hill is situated in the middle of a city, the possibility of it being directly impacted by fossil fuel combustion is high. Industrial sources in the city, such as factories and power plants, emit large amounts of CO2 (which contributes largely to global warming) and can release other harmful substances into the atmosphere, such as those that contribute to acid rain.  However, returning to the idea of slopes, the slope of the hill on which we set up our forest transect was quite steep (see Figure 4). During precipitation, some of the water that falls on the forest is partly absorbed into the ground water supply, while some of the water travels down the hill as run-off. Because of the rather steep slope of the hill on which the forest is situated, it is likely that much precipitation will not enter the soil and ground water of the forest and instead travel down the hill. In this way, the slope of the hill helps to protect the forest from absorbing too much acid rain too quickly. This in turn benefits the biotic community of the forest because it means healthier soil, healthier plants, healthier animals, and an overall healthier ecosystem.
Nose Hill Park is a stubbornly natural area amidst suburbs, cars, and skyscrapers, and despite Calgary’s efforts to keep Nose Hill unaffected by human impact, that is an impossible goal. There will always be factors indirectly affecting the ecosystems of Nose Hill, and the forest ecosystem in particular. Nose Hill is a fragile place and must be guarded by the City of Calgary, but there is only so much we can do. In truth, the way to change what is happening to the park and dozens of other natural areas all over the world lies not just in local actions, but global actions. Each person’s decisions influence the global environment. If people begin to take responsibility for their decisions and work towards a healthier natural global community, it would not only benefit the plants and animals of Nose Hill Park; it would benefit every park and every person in every location anywhere in the world.

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