Joseph Poracsky, Geography Department, Portland State University (poracskyj@pdx.edu)                            
James Gillen, Green City Data Program, Saturday Academy
Douglas Saulter, Portsmouth Middle School
Kim Wilson, Audubon Society of Portland

 

(This paper was originally presented at the Cary Conference VIII, Institue of Ecosystem Studies, Millbrook, NY, April 1999. It may also be found, along with other conference papers, at http://www.ecostudies.org/caryconference8.html )

• Learning fundamental concepts of botany and ecology, as related to the urban forest.
• Performing a street tree inventory and developing a computer database of their findings.
• Analyzing their data preparing a written that outlines findings and recommendations.
• Reporting their data and promoting their recommendations to the local community.
  

The urban forest consists of a variety of vegetated sites that fall along an ecological continuum. At one end of the continuum is a diverse, multi-layered forest composed of a soil layer, ground covers, shrubs, small trees, and an upper canopy. At the other end of the continuum is a landscape of isolated trees over a nearly continuous surface of concrete and asphalt, frequently surrounded by a canyon wall of buildings.

Typical urban features along the continuum include:

• natural / native forest remnants
• naturalistic park environments
• yard plantings
• landscaping around commercial buildings
• parking lot plantings
• street trees

• micro-climate moderation
• storm water interception and retention
• wildlife habitat
• carbon sequestering
• oxygen production

The methodology has evolved from what was originally conceived as an adult volunteer program aimed at educating the public about the ecology of the urban forest, to a largely school age program that works with students in grades 7-12.

1993    Portland State University students in an Urban Forest class perform
           a pilot inventory.
1994    A graduate student implements a methodology that georeferences
           the data to a GIS-based digital map.
1995    A graduate student coordinates a full-scale implementation and
           analysis for a community of 13,600 people.
1998    Eighth graders from Portsmouth Middle School collect and analyze
           street tree data in the Cathedral Park neighborhood.
1999    The program is expanded to include a total of five middle and high schools. 

The education process begins with traditional lecture and demonstrations on topics such as:

• Water, Light and Soil / Nutrient Needs of Plants
• Tree Structure and Growth
• Soils / Compaction / Stress of Tree Roots
• Proper Pruning / Maintenance / Tree Health
• Plant-People Conflicts (e.g., overhead wires, street signs, root-lifted sidewalks)
• Diseases and Pests / Tree Health
• Species Site Selection / Right Tree in the Right Place

• Field Observation
• Discussion of the Range of Observed Situations
• Data Recording
• Data Entry
• Analysis, Discussion and Recommendations
• Formal Written Report and Oral Presentation
  

An important aspect of the data compilation process is the ability to enter the data to a Geographical Information System (GIS). The manipulative ability of a GIS means that a variety of map themes are possible, such as maps by species, or tree size, or health
condition.

This example presented here illustrates the potential value of the map as visualization tool for identifying patterns and assisting in analysis.

In addition to the educational value, the tangible nature of the physical map product can capture the interest of students and serve as a motivator.

City regulations, the growth needs of trees, and local site conditions dictate that each street can support only so many trees (potential carrying capacity).  Stocking level is the percentage of the total potential tree sites that actually have trees.  Stocking level thus serves as an easy-to-calculate and readily-understandable measure of how close a street is to carrying capacity.  This measure is all the more powerful because it is derived from the students' own field-collected data.

This pie chart allowed the students to identify potential planting sites, in two categories:  bare soil sites, where planting would require simply that a hole be dug; and paved sites, which would require that a concrete cutout be made before digging a hole. The students readily understand that a cutout is both more work and more expense. The chart thus serves to illustrate what it would take in terms of additional resources to achieve full carrying capacity in the urban environment. They understand that a recommendation to "Plant more trees" is not as simple as it might first appear.

An important issue in the urban forest is the diversity of the tree population. Urban forestry literature generally recommends that no more than 10% of the trees be from any one species. The concern underlying this recommendation is with the possibility of a species-specific pest or disease (e.g., Dutch elm disease) sweeping through the area and damaging or destroying a large segment of the trees.

Student-collected data for the Cathedral Park neighborhood found that 59% of the street trees were maples -- a dramatic example of over-planting of one species.

The student response in this case was to make a recommendation to increase diversity by:

• Planting new tree species that are not found in the neighborhood.
• Planting existing tree species that currently occur in small numbers.
  

Having determined the stocking level, the students asked the question, "What does a stocking level of 49% mean?" To answer this, they prepared the bar graph below, comparing the stocking level for their study area with that found in three other Portland
area inventories.

This illustration dramatically demonstrated that their neighborhood had a stocking level most similar to that of an industrial area (NINA), and noticeably lower than that of two residential areas (Forest Grove and Irvington).

This graph suggested to the students a goal -- seek to achieve a 75% stocking level so that Cathedral Park would be better-treed than Irvington.

• Student interest and enthusiasm for the project.
• Visible changes in student attitudes as noted by teachers and parents.
• Willingness of volunteer students to stick with the project to the finish.
• Quality of the student thinking and recommendations.
• Quality of the student written reports and oral presentations.
• Tangible action by the community on student recommendations.
  

• Recognition that there are quantifiable differences from one part of the city to another.
• Increased awareness of the spatial patterns and interrelations of the traditional city infrastructure of streets and the "green" infrastructure of trees.
• Heightened sensitivity to what was formerly unexplored habitat: "I used to walk down the street and not pay attention to the trees.  Now I can't walk around and not notice them."
• A sense of stewardship and connectedness to the health and future of their surroundings.
• Exposure to aerial photos of their neighborhood and the city makes them more aware of the spatial patterns and connections between the traditional city infrastructure of streets and the "green" elements of the infrastructure.
• Longevity of the experience.  As one of the teachers noted, "These kids will know about street trees for the rest of their lives  -- as opposed to reading about them in a book and forgetting about it."
• A feeling of increased self-worth and empowerment: "The adults were listening to what we had to say."
  

• Base of involvement needs to be increased.  Many students who are not involved would like to have the opportunity.
• Improve access to computing facilities.
• Evidence from pilot groups indicates that street tree inventory has excellent potential as a family-based neighborhood activity, involving parents and youth together; this could be explored further.
• Establish a mentoring program for experienced students to aid in instruction of younger students.
• Encourage schools to institutionalize inventory expansion and update so that it is performed on an annual basis.
• Use inventory data collected over a number of years of to perform local studies of long-term change.
  

• Youth are capable of acquiring reliable data and deriving logic and relevant conclusions from that data.
• Making the educational process relevant to everyday experiences increases the interest level of the participants.
• Students reporting their findings to the community leads to the acknowledgment and the support needed by youth.
• Seeing their data and their recommendations actually put to use is a powerful motivator for students.
• Partnerships between a variety of agencies and interest groups makes the program more powerful.
• Motivated teachers and/or adult volunteers are an essential element for success.
• Effective urban ecosystem education must consider people and incorporate the human decision-making dimension.
• Familiar features such as street trees are less intimidating as a starting point than some other aspects of the urban ecosystem.  More complex lessons can later be tied to the initial simple ones.
• An integrated approach combining ecology training with skill topics such as writing, computer usage, visualization and presentation skills provides a lesson to students about the connections between academic subjects.
• The holistic nature of the process makes this approach to ecosystem education attractive to administrators and curriculum specialists.

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