Biological Diversity

Through assessing a 5 by 5 meter plot of land in Cameron Park, an urban ecosystem, I obtained a better understanding of the natural stresses present in an environment and the resulting biological diversity that is affected by these stresses. My plot of land was located on a slope of medium steepness leading down to a small creek towards the Northwest and a path to the Northeast. The aspect of this plot was 330 degrees northwest. The soil was rich, noted by its dark and damp appearance and texture. The soil was deep as well, which allowed for plants with extensive roots to grow in that particular area. Dead leaves and moss-covered logs blanketed the soil, most likely contributing to its rich texture. Most of the greenery in this plot was low to the ground with several accompanying taller trees. There were 3 trees that reached about 45 feet tall, but the rest of the landscape was covered with younger, smaller trees, shrubs, and floor greenery.

After taking note of these characteristics I was able to propose my hypothesis: The biodiversity of my real estate is high because the soil appears to be rich and moist, the slope is not extremely steep which would promote erosion, and the presence of decaying plant parts suggests that the soil will continue to be fertile. Furthermore, the ground and plants seemed fairly undisturbed, which would allow for a greater survival rate from more plant varieties. These factors, as well as others, do have an influence on the diversity of this plot. The slope is not extremely steep, but it most likely does pose a problem for new, small shrubs whose roots do not hold them into the ground. When it rains, some of these smaller, younger plants have a chance of being washed into the creek below. Another factor to consider is that the tall trees provide shade for the smaller plants. This may hinder or improve the plants’ growth, depending on each plants preferred environment. I also noticed that most of the plant leaves were eaten away by insects. Almost all of the leaves contained several holes. There has obviously been a bug infestation within this area which probably affects the survival rate of young plants. This factor is important to take into account when assessing the ecosystem of this area. Since this park is an urban area, it probably is affected by man-made factors as well, such as pollution. I did find a glass bottle in the brush on my plot, so there was evidently human contact at some time in this area or surrounding areas.

The predominant plant inhabitants of this site consisted of shrubbery and low greenery but there were several young trees and vines along with 3 larger trees as mentioned before. I was able to identify 2 Carolina Snailseed (Cocculus carolinus) among the greenery, along with 1 Chinese Privet (Ligustrum lucidum), and 1 small tree, which I was unable to identify, characterized by smooth bark and light green pointed leaves. There were also 4 cedar elm (Ulmus crassifolia), 3 of which were the largest trees on the plot. I noted the presence of two Texas White Ash (Fraxinus texensis). I found that there were several plants in this area, but few appeared to be the same species. As for animals, I saw two brown moths, 3 black ants, a white spiral snail, a large black bumble bee, and three beetles each of a different color. Just as with the plants, there were several varieties of insects present, but few were from the same species.

Once I plotted the data I obtained regarding the different plants and animals in existence on this plot, I calculated the Simpson’s Diversity index. The total number of living species, both plants and animals, present in this plot was 20, 12 of which were different species. Using the following equation and the numbers as stated on my Plot Data sheet, I found the Simpson’s Diversity index to be 0.9368.

Ds = 1.0 – [total column D / (total column B x (total column B-1.0))]
Ds = 1.0 – [24 / (20 x (19))] = 1- (24/380) = .9368

The closer this Simpson’s Diversity index is to 1, the more diverse the area is. My index, 0.9368, is close to 1.0 and therefore suggests that there is a large biodiversity in that specific area. Due to this index value, I know that this area contains a variety of plants and animals and can be considered a fairly natural and organized environment. The ecology is fairly extensive in this particular area. Furthermore, this diversity index indicates that the external stresses affecting this ecosystem are limited. The medium-steep slope is obviously not so extreme as to result in serious erosion. Exposure to natural stresses, including exposure to sun, wind, and rain, are evidently at beneficial levels. If the slope was steeper, this 5 by 5 meter ecosystem may have been exposed to too much run-off water. However, the land in this area of Cameron Park slopes in several directions, preventing the run-off water from flushing away the organisms of a particular plot. My plot could have also been damaged by being overly exposed to the sun had its slope been facing directly East or West instead of Northwest. Obviously, there are many natural resources affecting the ecosystem, such as those mentioned above as well as the decaying material on the ground responsible for improving the quality of the soil. These natural resources are the reason for a high diversity index in this area. Without them, the ecosystem would fall apart and the biodiversity would fall. Only certain organisms would be able to survive in a different environment. Using counting techniques and the Simpson’s Diversity Index in Ecology allows for a standard to be used in comparisons. Describing an ecosystem using numbers makes the information more understandable to other people. Otherwise, the biodiversity of an ecosystem would appear to be an opinion rather than a standardized measurement.

This Simpson’s Diversity index value proves my hypothesis to be correct; there is a high biodiversity in my real estate. When making my initial hypothesis I was influenced by the general appearance of the ecosystem; it was fairly well covered in greenery and other forms of life, but few of the organisms looked the same. I was also influenced by the soil’s rich appearance. I thought that since the soil was deep and dark brown, it could provide nutrition and stability for a variety of plants.

Although the ecological system in this plot seems to be thriving, external stresses continue to exist and influence the environment. The diversity I calculated is close to 1.0, but it could be even more diverse. External stresses are the reason for this plot not reaching its potential diversity. First of all, natural disturbances act as a natural selection agent. Plants that need more sun than this plot is provided with, due to its aspect and location, will not survive here. Some plants may need less water than they would receive here and would therefore die. Plants and animals that cannot naturally survive in this environment are “weeded out” by natural stresses. Man-made stresses, however, result in a different type of destruction. Since this plot is part of an urban park, the ecosystem is susceptible to pollution, trash, and human contact. All of these factors may result in the killing off of organisms that would have naturally survived had there been no man-made disturbances. These too result in the lowering of the plot’s biodiversity.

Through ecology, I have attained a better understanding of the effects external stresses can have on an ecosystem. Both nature and man provide stresses on an environment, therefore determining its diversity. Overall, my particular plot was quite diverse. Hopefully future man-made disturbances do not change this, but as I have learned from this lab, man’s stresses have a great influence on environment and will continue to impose changes upon ecosystems.

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