Embedded Files
Welcome to the Biology 101 Journey Through the Cascades
Welcome to the Biology 101 Journey Through the Cascades
Field trip intro from Biology Instructor, Jennifer Johns
About the Virtual Field Trip
About the Virtual Field Trip
This trip from the floor of the Willamette Valley, over the Santiam Pass to the headwaters of the Metolius River will allow us to explore how ecological communities change over space. As we ascend the Cascade Range we will document the influence of elevation and precipitation on plant diversity. At each location we will consider how the particular assemblage of species may change over time through succession and will try to assess, which locations, if any, represent mature communities.
We will analyze the soil conditions, the species present, and the three dimensional structure of each community we visit to conduct a community analysis. Together with the vegetation data we collect, we will learn how populations are situated in communities, how communities together with their abiotic components make up an ecosystem, and how ecosystems are situated in a larger biome. Additionally, we will learn about the geology, history, and climate of each location, focusing on the age of the mountains, some local lore, and the role of fire in shaping these communities. And finally, we will compare the communities within and between ecoregions to fully understand the interaction of geology, climate, and history that caused each community to become what it is today.
Performance Based Learner Outcomes
Performance Based Learner Outcomes
Upon successful completion of the course, you should be able to:
Define the term ecoregion and provide examples of local ecoregions
Identify ferns and woody plants endemic to local ecoregions
Relate climate and elevation to the diversity of vegetation found at different local ecoregions.
Explain circumstances when local diversity does not match the ecoregion on the map.
Evaluate the successional stage for each community
Describe the role of fire in the maintenance of Oregon forests.
About the Cascade Mountains
About the Cascade Mountains
Three Fingered Jack, from Ray Benson Sno-Park
The Cascade Range was formed in two distinct periods, one about 37 million years ago formed a series of low lying volcanoes and the more recent period, about 5-7 million years ago, caused a series of taller volcanoes that we recognize today as Mt. Baker, Mt. Rainier, Mt. Adams, Mt. St. Helens, Mt. Hood, Mt. Jefferson, Three Fingered Jack, Mt. Washington, the Three Sisters, and peaks further south. Each of these formations occurred because the tectonic plates (large sections of the earth’s crust or lithosphere) that support this region move independently of each other. In forming both the Old Cascade Range and the New Cascade Range, the San Juan de Fuca plate that underlies part of the Pacific Ocean off the coast of Oregon and Washington is moving under the North American plate, forcing the mountains upward.
During the early formation of the Cascade Arc, the subduction occurred at a gradual angle and so the older mountains are not as steep. Around 5-7 million years ago, the San Juan de Fuca plate began descending at a sharper angle, causing the continental edge to fold more steeply. As we travel over the Cascades we will see the difference between these two parts of the mountain range.
Additionally as we travel we will see a marked difference in vegetation that is caused, in part, by differences in precipitation. The steepness of the new Cascades and the proximity of the Cascades to the Pacific Ocean cause a rain shadow effect. As air moving from the Pacific Ocean rises to pass over the Cascades it cools, causing the moisture in it to fall as precipitation. As the air reaches the eastern side of the Cascades, it has little moisture left, causing arid conditions to occur. Additionally, as precipitation interacts with elevation we will see that in some locations the precipitation falls mainly as snow and consider how this influences the community composition.
Through this trip, we will explore the effects of elevation, local topography, history, and precipitation on the plant communities at six locations throughout the Cascade Range. As we visit these different ecoregions, you will investigate which species are most abundant and which are rare. Examine the understory. Consider the elevation and precipitation. Ultimately we are trying to understand how the various conditions combine to create unique communities throughout the Cascade Range.
Guiding Questions
Guiding Questions
As you journey with us through the Cascades, consider the information you are given in the text and videos for each location about geology, soil, precipitation, and elevation, for each site and ask yourself: Is the community in each location a mature community or is it still in an earlier successional (or seral) stage?
As we continue throughout the sites we will also be addressing these questions:
As we continue throughout the sites we will also be addressing these questions:
How do the sites compare to each other?
Are their communities within the same ecoregion that have different types of vegetation? If so, why does this occur?
Do we see trends in the changes in the communities that correspond to changes in precipitation, elevation, or some other factor?
Does the overall description of the communities we visit relate to the biome designated for this region?
How to Complete the Pre-Lab
How to Complete the Pre-Lab
Click on the button below for your Pre-Lab (the worksheet is a Google Form on the next page)
Follow the directions to compare our route map with an eco-region map of Oregon to get a preview of each of the sites we will visit on this field trip
Answer the question about each site
Your instructor will check your answers for completion, so there no need to upload this assignment into eLearn
Page updated
Report abuse