An Assessment of Riparian Vegetation in a Human-Influenced Landscape

Lisa Carlson, Centralia College

Summary

Given that humans historically have heavily used rivers and the lands along them for agriculture, transportation and other activities, how does human impact currently affect riparian ecosystems in a rural region? Students will address this question through several activities. From sites spanning a range of historical human influence, students will collect and analyze field data, including structure, composition and distribution of vegetation, soil pH and moisture, and light availability. Human use, both modern and historical, will also be assessed for each site. Using this collection of data, students will interpret and contrast ecosystem function across sites, and then place in the context of human land use. Students then investigate whether existing riparian laws provide adequate protection for ecosystem function.

Learning Goals

The "big ideas" for this activity are:

  • Structure and function of ecosystems are linked. Specifically, large trees as structures in riparian ecosystems support river ecosystem function by shading rivers to cool water temperatures, and providing a source of large woody debris to create complex riverine habitat.
  • Human activities can impair ecosystem function. In this project, human impacts on riparian vegetation are analyzed both quantitatively and qualitatively. Impaired riparian ecosystems are linked with impaired riverine ecosystems through group discussion in the field and student research following the field trip.
With respect to detailed learning outcomes upon completion of this activity, students will be able to:
  • Discern riparian from upland ecosystems.
  • Locate local rivers and riparian ecosystems.
  • Measure ecosystem attributes using ecological field equipment.
  • Identify native tree and shrub species, as well as common invasive plant species.
  • Collect and analyze ecological data.
  • Assess human impacts on riparian ecosystem structure and function.
  • Research state laws regulating activities in riparian ecosystems and assess their effectiveness.

Context for Use

During summer quarter, this activity is designed as a one-credit course embedded in a five-credit interdisciplinary field-based course on watershed health. Other units focus on hydrology and geology, stream insects, marine ecosystems, and water quality. To the degree possible, we work in a single watershed, return to common field sites through the course, and work inter-disciplinarily to integrate the units. Each of the five one-credit modules may also be taken independently, so this activity could be taught as a stand-alone unit. Students enrolling are a mix of science and non-science majors.

Timeframe: This activity spans two (2 hour) lecture sessions followed by an eight hour field trip. It can be taught as the first module or a later one within a series, or could be a stand-alone unit. The only time restrictions are planning for appropriate conditions for field work.

Description and Teaching Materials

This activity is designed as a one-credit course embedded in a five-credit interdisciplinary course on watershed health during summer quarter. This module consists of the following components:
  • Lectures include background on riparian ecology, human use of riparian areas, and laws regulating those activities. During one of those sessions and on the field trip, students will learn to identify common tree and shrub species of riparian areas.
  • Field trip consists of qualitative and quantitative stops, both including pristine and degraded riparian ecosystems within the Chehalis River Basin.
  • Data will be collected at two or more sites, including: trees by species, diameter, density and maximum height; shrub density; canopy cover; understory light levels; percentage of cover of natives versus. Invasive species, temperature and relative humidity.
  • Qualitative assessments are made at all sites of vegetation and land use by humans.
  • Data collected in the field are ideally shared in the field so that students can take home the summary data to write their reports. Alternatively, data may be posted on a web site for later access.
  • Students independently research state laws regulating activities in riparian ecosystems and assess their effectiveness at protecting riparian structure and function.


Riparian Assignments (Microsoft Word 39kB Oct26 11)
Riparian Forest Data Instructions (Microsoft Word 31kB Oct26 11)
Riparian Vegetation Data Sheet (Microsoft Word 57kB Oct26 11)

Teaching Notes and Tips

The activity can fit within a variety of biology, forestry or environmental science courses.
The data collected for this project can be varied according to equipment, time and expertise available. Additional data that can tie in directly with riparian ecosystem function include soil moisture, pH, bulk density, texture and fertility; water quality such as pH, dissolved oxygen, and nitrates; herbivory estimates; and litterfall.

Assessment

Formal assessments Upon completion of this activity, students will show evidence of their learning by producing:
  • data sheets collected in the field,
  • graphs and tables of data,
  • a written report of their riparian assessment, and
  • a written analysis of a state law regulating activities in riparian ecosystems.

Informal assessments

During the activity, student learning can be informally assessed during the field trip in several ways. The instructor should observe data collection to validate that methods are followed appropriately, and that species are identified properly. At each site, the instructor should lead a group discussion to solicit ideas from each student on riparian health and site history.

References and Resources

Partnerships with local environmental organizations, such as local stream teams, can work well. The Chehalis River Council is our local partner. They are directly supporting several modules of the five-credit class by providing canoes and water sampling equipment, giving background to land use issues, and may become a repository for water quality data collected by the class.


Washington State laws can be found on the web. Search for river or riparian for those most relevant:

http://www.leg.wa.gov/LawsAndAgencyRules/.

Book chapter: Riparian Management in the 21st Century. Gregory, Stanley V. 1997. In Creating a Forestry for the 21st Century: The Science of Ecosystem Management. Ed. Kathryn A. Kohm, Jerry F. Franklin. Island Press.
http://books.google.com/books?hl=en&lr=&id=XNiq_KJ-zpgC&oi=fnd&pg=PA69&dq=riparian+zone+s-gregory&ots=M0nB1FA3NV&sig=4Bdz-lMSXEx1xb9tNeaeWbP-S-M#PPA69,M1

Oregon Trout has some background resources for educators:
http://www.thefreshwatertrust.org/
http://www.ortrout.org/pdf/StreamBank%20One%20Sheet.pdf
http://www.ortrout.org/pdf/Executive%20Summary%20-%20StreamBank.pdf

Evergreen State College