Tuesday, November 29, 2011

Factors that affect vegetation, by Ivan

Figure 1.  This is the area where we worked.  Note the uneven distribution of trees and shrubs.
Autotrophs, or vegetation, are the most important part of any biome, and forms the basic foundation upon which various biological organisms can survive on. The forest has several main types of autotrophs: trees, herbaceous plants, grasses, and shrubs, all of which have a number of different species. These species interact with each other and animals to form the unique forest biome of Nose Hill Park. Because of the fact that vegetation is so crucial to the development and continuation of a biome, we felt it is pertinent to explore the different types of vegetation and what affects it. We focused on many factors such as land shape, tree density, availability of sunlight, soil quality, diversity of species, invasive species, and human interference. While there are other factors, these are the major factors that will determine the general scope of the vegetation in Nose hill Park.            In order to gather sufficient data without being swamped by the diversity of vegetation, we decided to limit our observations to a 10m long by 1m wide transect that we set up prior to data collection. In our transect, we observed a quite diverse number of vegetation; trees, shrubs, herbs,
saplings and seedlings were all present, and we managed to identify quite a few of them. The most obvious one was  Populus tremuloides, commonly called trembling aspen. It was found in great quantities, at a density of 0.8/m­2 within the transect. Other common sights were Rosa woodsii (Wood’s rose), various species of Salvia, Rosa acicularis (Wild Rose) and also Symphoricarpos (Snowberry). These types of plants suggests that either the area is commonly disturbed or the soil quality is bordering on poor, as Wood’s Rose is most often found in disturbed and poor soil, along with the Wild Rose, and to a lesser extent, the Snowberry.
A rather interesting observation we made was that the vegetation tended to congest together in segments, rather than spreading themselves out. 9 Aspen trees, 33 shrubs, 11 herbs, 12 saplings, and 7 seedlings were counted in our 10 m by 1 m transect (thus a density of 7.2 plants/m2), but in a 1 m by 1 m quadrate we randomly selected within our transect, we counted 2 trees, 5 herbs, 16 shrubs, 1 sapling, and 4 seedlings. This generated a density of 28 plants/m2, which is significantly larger than the average density within our transect. As previously mentioned, vegetation within the forest biome in Nose hill Park tends to congest together; within our transect, there were areas were very little vegetation was present. Soil samples extracted from areas with dense vegetation and areas with sparse vegetation within our transect indicated that the soil was harder and more compacted in areas where vegetation was abundant, and looser in areas where vegetation was sparse. The data collected supports a positive feedback system; because the soil is more compact, nutrients and minerals are more likely to be retained and not washed away by rain, therefore aiding vegetation growth. Vegetation then start to develop in the nutrient-rich soil, and drop roots; these roots secure the soil and prevents the soil from eroding away.
Figure 1. A picture of a Rosa acicularis hip taken in the forest

As Calgary is situated in the Rocky Mountain region, the climate can be very unpredictable and tend to flux very frequently. This poses a large problem to the vegetation within Nose Hill Park; there were no coniferous trees observed in our transect, therefore all the vegetation would have perished in the winter. This is partly due to the fact that the forest biome is situated on the slope of a fairly steep hill; the plants that had the most chance of surviving grew beside another already mature plant and derived some structural support from the other plant. There’s also another reason for this clumping of vegetation: Because Calgary’s weather tends to fluctuate, that poses another problem to the vegetation; during early spring, the grasses and saplings may have begun to grow and develop, but are hit by a sudden wave of violent and harsh cold front. That is extremely devastating to the vegetation, as they are still young and cannot survive that impact. As such, this occurrence provides valuable insight into the location of vegetation; the vegetation are bunched up together in clusters because that would provide them with the most protection from the harsh winter, as well as offering a positive feedback in the nutrient cycle (more vegetation equates to more heterotrophs; more heterotrophs equate to higher levels of natural fertilizer available for the vegetation). Even though clustering together is a helpful adaptation to the harsh climate, there are drawbacks to the method, two of which being interspecific and intraspecific competition.
            As the vegetation is severely clustered together, they compete for light, water, nutrients, among other things. This can lead to starvation for certain types of vegetation; for example, the relatively larger Aspen blocks most of the incoming sunlight from the smaller shrubs, therefore slowing and rejecting their development. Also, since only Trembling Aspen were found in our transect, we can assume that they are better competitors than perhaps other species of trees, and have driven them away from the area by means of interspecific competition, or between-species. Similarly, we observed that even though the Aspen was populous, they were not very tall, nor were they well-built, and their foliage and branches were invading into the space of nearby Aspen. This competition for space, light and nutrients is intraspecific, or within-species; the low-lying shrubs also exhibited this kind of competition, which is further compounded by interspecific competition with the Aspen trees. Competition, such as the ones mentioned above, can be detrimental to the health of vegetation within Nose Hill Park, but it can also be a good thing; introduced species often cannot survive because they are not adapted to the competition that occur, and native species, being adapted to the competition, will come out ahead. In addition to lowering numbers of introduced and invasive species, competition keeps the vegetation population in check; too many plants can be negative for the ecosystem, as with too few plants. There are natural ‘checks’ to the growing number of vegetation; competition is one, and other organisms is another one.
            If allowed to flourish and grow at the current rate, the vegetation in Nose Hill Park would soon overrun much of the park, and other organisms would become rarer and rarer.  What keeps the number of vegetation in check? One effective method that Mother Nature utilizes is insects. Within our transect, an innumerable quantity of insects were found: different types of ants, flies, wasps, mites, and arachnids (mostly spiders); we also discovered a hawkmoth larvae, hyles gallii, lurking on the outskirts of the forest biome. Most of these insects consume foliage and vegetation as their primary source of food, especially the moth caterpillar (a small number of caterpillars can ravage vegetation if left unchecked). These insects keep the vegetation population in check, but not so much as to wipe them out entirely.
            As humans living away from the ecosystem of Nose Hill Park, there is no way that we can impact it, right? Wrong. Human interference, intentional or unintentional, can cause drastic changes in the Park, especially for the vegetation. Despite efforts by the City of Calgary and many private organisations to protect Nose Hill Park, human interference is still an ongoing issue. Things like humans disturbing the environment and it’s organisms by walking through it are direct examples, but there are indirect examples as well. Acid rain, a by-product of all the sulphuric/nitric compounds released into the atmosphere by combustion in factories and such is very harmful to the vegetation, since it can cause the soil to be too acidic to support vegetation growth. Our transect would probably not be as affected by acid rain, since it is on a slope, so most of the water will flow down instead of collecting in the soil. However, it is still a major issue that should be solved as soon as possible, in order to protect the vegetation, along with protecting all the other organisms in Nose Hill Park. 

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