Goal: Gain an understanding of the trophic levels of a local riparian ecosystem and of some of the abiotic environmental factors that influence this ecosystem.
Objectives:
1) To estimate the density, frequency, dominance, and species diversity of trees, shrubs, herbaceous plants, macroinvertebrates, microinvertebrates, and microorganisms found in a riparian ecosystem.
2) To describe the trophic levels of the riparian ecosystem and the relative importance of particular species, using examples from the field data.
3) To describe the abiotic environmental conditions that influence the biotic components of the riparian ecosystem.
Methods: The methods are described in Lab Topic 25 of the laboratory manual by Morgan, J.G. and Carter, M.E.B. 2002 Investigating Biology, 4th edition, The Benjamin Cummings Publishing Co.
Results: The pertinent results are summarized in the tables within the Discussion portion of this report. Full tables of results are attached at the end of the report. {{Note from Hamnavii: The full result tables are not on this webpage, sorry.}}
Discussion:
In the Oak Creek Riparian zone, several different trophic levels were studied. These levels were broken into the areas of trees, shrubs/saplings/vines, seedlings/herbaceous vegetation, macroinvertebrates, microinvertebrates, and microorganisms. Species for each were counted, and their frequency, density, and other information was calculated. In Table 1, you can see information about the most abundant species for each area of study. For the Trees category, the most abundant species was the Fraxinus latifolia, with 28 individuals in a total of 5 plots. The density of F. latifolia was 0.056, and its relative frequency was 50. Moving on to Shrubs, Saplings and Vines, the most commonly occurring species here was Heracleum lanatum. H. lanatum had a total of 10 individuals in a total of 5 plots with a density of 0.1 and a relative frequency of 10. For the grouping of Seedlings and Herbaceous Vegetation, the most frequent species was the Orchard Grass, with an average percent cover of 52.7%, and a relative frequency of 17.24. Chilopoda occurred most often in the Macroinvertebrates category. It had a total of 40 individuals, with a density of 80 and relative frequency of 3.45. Acari was the only species found for Microinvertebrates. Table 2 shows the most frequent type of Microorganism. Bacteria in the leaf litter made up the majority for this group, with a total number of clusters at 64.
| Scientific Name | Total Number of Individuals | Density | Relative Frequency | Average Percent Ground Cover (%) | |
|---|---|---|---|---|---|
| Trees | Fraxinous latifolia | 28 | 0.056 | 50 | N/A |
| Shrubs/Saplings/Vines | Heracleum lanatum | 10 | 0.1 | 10 | N/A |
| Seedlings and Herbaceous Vegetation | Orchard grass | N/A | N/A | 17.24 | 52.7 |
| Macro-Invertebrates | Chilopoda | 40 | 80 | 3.45 | N/A |
| Micro-Invertebrates | Acari | 1 | 1 | 1 | N/A |
| Classification | Total Number of Clusters of This "Species" |
|---|---|
| Bacteria (Leaf litter) | 64 |
These different groups can be representative of the different trophic levels in this ecosystem. Trophic levels are the levels on which organisms fall in the food chain. At the bottom of this flow, are the primary producers. These are the autotrophic organisms. Included in this category are plants, and some protists. Trees, such as F. latifolia from Oak Creek, bacteria from the leaf litter, and other plants such as H. lanatum or Orchard grass, are among the primary producers in this riparian area. The next trophic level includes the primary consumers. These are mostly herbivores like deer, elk, etc., or as demonstrated at Oak Creek, also macroinvertebrates such as Chilopoda or Isopoda. The next highest trophic level is the secondary consumers. In this category are mostly carnivores, those consumers that eat other consumers. Large predators would fit in this grouping, but also some microinvertebrates, such as Acari. Energy flows from one trophic level to the next, providing the higher level with the sustenance it needs to survive.
The Oak Creek riparian zone has examples from each of these trophic levels, as previously stated. These species are most likely living within this area because it fits their environmental needs. The climate is fairly moderate, allowing a variety of organisms to live comfortably. Rainfall and average temperature are at good levels to support plant growth. Soil pH and temperature are also in a decent range for plant life to grow. With a larger number of plants inhabiting a given area, there can thus be a greater amount of primary and secondary consumers. Each organism living within the Oak Creek riparian area has adapted to its environment and found a niche in which it can live. Each trophic level depends on the levels below it to survive, thus creating a chain of life within this ecosystem. By having adjusted to the specific niche it is living in, each species is filling a role in this chain, and promoting continued habitation of Oak Creek by many different species.
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