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Sustainable Forestry

Keywords: sustainable forestry, forest sustainability, forest harvesting, forest regeneration, interfering plants, overstory structure, high grading, stand age structure, stand vertical structure; Grade Level: ninth through twelfth grade and adults; Total Time Required for Lesson: 90 to 120 minutes; Setting: forest stand with small to large sawtimber trees (12 to 18 inches and larger), some overstory species diversity is desirable, nearby a stand with recent harvesting

Goals for the Lesson

  • Students will understand how tree harvesting changes forest stand structure
  • Students will understand how light affects forest stand dynamics
  • Students will learn six stand characteristics affected by harvesting
  • Students will understand the need evaluate residual forest conditions
  • Students will understand the need to establish regeneration

Materials Needed

For each plot (four to six students per plot)

State Standards Addressed: E & E Standards: Renewable and Nonrenewable Resources (4.2); and Human and the Environment (4.8)

Teaching Model: Experiential Learning Model (Experience, Share, Process, Generalize, Apply)

Subjects Covered: biology, ecology, and mathematics

Topics: forest ecology, plant competition, forest stand dynamics

Preparation

Locate suitable stand of at least one acre or larger, with an over structure of sawtimber size trees of a diverse species mix. Ideally, the stand will also contain trees in the smaller diameter-size classes (e.g., trees from one inch to ten inches). A stand with an understory component containing woody and herbaceous plants is also desirable (e.g., ferns, grasses, forbs, mountain laurel, striped maple, rhododendron, spice bush) as well as tree regeneration (e.g., seedlings and saplings of desirable and undesirable species).

Experience and Share Phases (45 minutes)

Explain to the students that the intent of this exercise is to understand that cutting trees changes things in a forest. Ask them to discuss with you why we cut trees. Discuss some of the products we use from the forest that necessitate cutting trees. Some students will likely oppose cutting. Point out that this is valid, but note that we all use wood and forest products and that people will have to cut some trees to meet these needs.

Locate plots such that they will not overlap when a radius of 37.2 feet is described around the center. Break the students into equal groups and assign each group a plot. Students will use a rope, held above the center point to describe the circle. Each group will then break into three "small" groups and students will select trees for harvesting based on species (one small group) and stem diameter (two small groups) using a specific ribbon color for each treatment. The intent is to show how different cutting decisions change forest species composition, structure, and potential to provide products and values.

For example, have one color ribbon placed on all trees in the plot of one or two species (e.g., all the red and white oaks, or all the sugar maples) have a second color used on all trees in the plot above a given diameter (e.g., 12 inches and larger, a common size used in diameter limit cutting), and have the third color used on all trees in the plot below a given diameter (e.g., 10 inches and smaller, representing a firewood harvest). None of these particular treatments will necessarily result in a sustainable harvest.

Process Phase (15 Minutes)

After the students have "carried out" the treatments, have them discuss and describe what would happen if the forest were harvested by these methods. Possible questions are:

  • Is there a species removed or severely reduced by one of the treatments?
  • What species are left?
  • How did the various "cuts" affect wildlife?
  • Will trees capable of producing seeds remain?
  • What has happened to the average tree diameter remaining?
  • How will the "cuts" change light conditions on the forest floor?
  • What will happen to the plants growing on or near the forest floor?
  • Where will the next forest come from after the harvest?

Students should then revisit the plots and discuss their observations. By sharing their observations, they will begin to address the ideas of sustainability. Sustainability involves taking from the forest those things we need for today, but retaining the options for future generations to have the same or improved options. Likely none of the treatments used by the students will result in a sustainable outcome.

Obviously, removing one species is not desirable in most cases. Removing just the big trees will likely swing species composition, reduce the average diameter, and create irregular use of the upper canopy space. This is a form of high grading and seldom results in a desirable outcome. Removing the smaller understory trees will create a park like appearance that may improve the stand's appearance, but these trees are often beneficial to wildlife and songbirds. Their removal is also likely not desirable. What is the proper decision?

The intent of a forest thinning or improvement harvest is to remove some of the trees of various sizes in all species, to improve the overall quality of the forest (i.e., taking trees at risk of dying, with poor or misshapen crowns, having stem defects, or of undesirable species). Those trees with large healthy well-shaped crowns are often the ones best retained in the forest canopy. A forest harvest should result in more options rather than fewer.

Generalize Phase (10 minutes)

After discussing with them the impacts of their cutting decisions on one or more of the plots, ask them to list things that we could do to make sure that forest harvesting is sustainable. Generally, from a timber perspective, the answers will fall into six groups:

  1. Retain species composition
  2. Retain tree quality
  3. Protect residual trees
  4. Establish regeneration (preferably natural and not planted)
  5. Improve growing conditions for the best trees
  6. Protect the soil and site productivity

Optional Activity (30 minutes)

If time allows, have the students use a 3.72 foot radius circle somewhere in their plot to count and identify forest regeneration species. This plot is 1/1,000 of an acre. They try to exercise care not to damage the regeneration. How many trees are there to the acre? Their count multiplied by 1,000 provides this answer. A stand in Pennsylvania is likely to successfully regenerate if there are from 20,000 to 100,000 seedlings per acre. Have the students speculate about why there are lots or few seedlings on their plot. Is it too much shade, lack of seed source, deer browsing? What?

Assessment/Apply Phase (20 minutes)

If possible take students to a properly marked and harvested forest. You may be able to locate a good example by contacting a local service or state agency forester. Refer to Forest Stewardship Bulletin Number 3: Teaching Youth about Forest Stewardship (276K pdf) "Appendix: Selected Resources" or look in the blue pages of your telephone directory under State Government to locate the office nearest you. Contrast the good example with a poor one. Again, ask the forester for suggestions on finding a poorly harvest site. Reflect on the plots the students marked.

Conclusion

In concluding the exercise, emphasize that forestry is not merely cutting trees. It involves understanding tree growth requirements, forest history, stand dynamics, and the potential impacts of poor decisions. Share with the students Forest Stewardship Bulletin Number 7 (238K pdf) and Forest Stewardship Bulletin Number 12 (144K pdf).

References

Smith, Sanford S., James C. Finley, Shelby E. Chunko, Stephen B. Jones, and Ellen M. O'Donnell (1999). Forest Stewardship Bulletin Number 3: Teaching Youth about Forest Stewardship. University Park, Pa.: The Pennsylvania State University.

Bihun, Yuriy M., James Finley, Stephen B. Jones, and Ellen Roane (1995). Forest Stewardship Bulletin Number 7: Timber Harvesting: An Essential Management Tool. University Park, Pa.: The Pennsylvania State University.

Shelby E. Chunko, and Wilbur Wolfe (1997). Forest Stewardship Bulletin Number 12: Best Management Practices for Pennsylvania Forests. University Park, Pa.: The Pennsylvania State University.

Author

James Finley and Sanford Smith, Department of Ecosystem Science and Management, Penn State