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The organism I plan to study for the field research project is three types of large forest trees, the western red cedar, the ponderosa pine, and the Douglas-fir tree, within the Woodhaven Nature Conservancy Regional Park.
The trees change along an environmental gradient. The first location (Figure 1) has many western red cedar trees and is dense with trees (Figures 2 and 3). The location is shady with lots of dead fallen trees. The ground cover are plants with dark green leaves; this seems to occur where there is sun exposure. Much of the ground does not have plant growth due to the shade. The distribution seems somewhat even.
The second location (Figure 4) is up a steep incline where the main tree is ponderosa pine (Figures 5, 6, and 7). The soil appears sandy and the ground cover is more grass-like. These trees are sparse and less dense than locations 1 and 3. The distribution appears more uneven than locations 1 and 3.
The third location (Figure 8) is densely populated with Douglas-firs but is less dense than location 1 with the western red cedars (Figures 9 and 10). The ground cover is a mix between grasses and the shrubs with dark green leaves. The distribution appears even.
An underlying process which may cause the changing of the dominant tree type pattern could be changes in elevation which could influence soil moisture. My hypothesis is elevation influences the types of large trees that grow within a forested area. My prediction is the first location with the western red cedars has the lowest elevation, the second location with the ponderosa pines has the highest elevation, and the third location with the Douglas-firs has an elevation in between the first and second locations.
The response variable would be the tree type (western red cedar, ponderosa pine, or Douglas-fir) that is growing within an area of the environmental gradient and the explanatory variable is elevation. The tree type is categorical as the three trees I’m interested in are western red cedars, ponderosa pines, and Douglas-firs and if they are present or absent at different elevations. Elevation would be continuous as it is measured on a continuous numerical scale.
