Documentation:Open Case Studies/SOIL/Soil Quality of Forest Landings

Case specific learning outcomes

With the help of a series of guiding questions and the interaction with instructors and your group members, you will be able to:

1. Characterize the soil quality of forest landings, with an emphasis on soil physical properties
2. Interpret the results of two past experiments.
3. Describe your learning in written format (as individual students) and orally (as a working team).

Background

Forest landings are areas of cutblocks where harvested trees are processed and loaded onto trucks. Their construction involves removal of topsoil and leveling. Soil degradation on landings may be so extensive as to completely prevent tree growth; in which case, the land is lost from the productive forest land base. Soil productivity on landings with degraded soils is limited by compaction and nutrient depletion that may also be accompanied by reduced water availability and aeration.

In British Columbia (BC) the area covered by access structures within any particular cutblock is generally limited by regulation to 7% of the harvested area. Individual landings and other access structures (e.g., haul roads, skid trails) associated with forest harvesting occupy a relatively small area (individual landings are typically 0.3 - 0.5 ha in size) but the overall area that they cover in a particular forest region can be substantial. Rehabilitation of access structures that are no longer needed makes them available for tree growth, and in the long-term increases timber production; however, rehabilitation methods need to be improved. Examples of current soil rehabilitation methods include tillage, topsoil conservation and replacement, sidecast material replacement on skid roads and topsoil conservation, application of fertilizer sewage sludge, wood chips and sawdust, and forage seeding. Even though some of these methods have led to successful rehabilitation their extensive acceptance has been prevented by the high cost.

During this case study you will focus on results of two past studies carried out on:

• Rehabilitated landings (Bulmer and Krzic. 2003. Soil properties and lodgepole pine growth on rehabilitated landings in northeastern British Columbia. Can. J. Soil Sci. 83:465-474) and
• Unrebabilitated landings (Blouin et al. 2005. Effects of mechanical disturbance on soil properties and lodgepole pine growth in BC’s Central Interior. Can. J. Soil Sci. 85:681-691) in BC.

Soil disturbance can be defined as any disturbance that changes the physical, chemical, or biological properties of the soil. Not all types of soil disturbance are necessarily bad. Forest management strategies need to strike a balance between “favourable” and “detrimental” disturbances by limiting the latter. In BC, potentially detrimental disturbance within a harvested area is defined by specific categories under the Forest Practices Code (FPC). The FPC recognizes that some level of disturbance is necessary to permit access to timber.

Since roads and landings create the deepest disturbance into the soil they need to be carefully planned and their area minimized to reduce potential for impact on other resources. Landslides and erosion events are often associated with roads, or drainage diversions from roads. In the interior of BC, almost all landslides attributed to forest harvesting are related to this. On the Coast, roughly half of landslides attributed to forest harvesting are related to permanent access or its drainage. If a road or landing is not to be used until the next rotation, it should be rehabilitated to restore site productivity and minimize risk to other resources. Rehabilitated soil disturbance should be replanted to encourage tree growth.

Week One

Learning objectives

Identify and discuss the soil formation factors focusing on the soil type present on the study sites in northeastern and central BC.

Student tasks

1. Review background information on soil formation and classification, focusing on the Brunisolic and Luvisolic soil orders.
2. Share individual learning with group members (ongoing for weeks 1-4).

NOTE: Before next week’s session, your team should research any gaps in knowledge regarding the guiding questions for today’s session.

Guiding questions

1. What are key properties of Brunisols (present on the unrehabilitated landings) and Luvisols (present at the rehabilitated landings)?
2. What study sites characteristics (other than soil properties) could be relevant to tree growth? Hint – think topography and climate (precipitation and temperature).
3. Briefly describe soil properties that are of an importance for management considerations on these soils.

Key references

1. Canadian System of Soil Classification by Agriculture Canada Expert Committee. 1998. (3^rd edition) available on line at http://sis.agr.gc.ca/cansis/publications/manuals/1998- 1646-ed3/intro.html [NOTE: focus just on the two soil types present in the two forest landings studies that you are working on]
2. Bulmer and Krzic. 2003. Soil properties and lodgepole pine growth on rehabilitated landings in northeastern British Columbia. Can. J. Soil Sci. 83:465-474.
3. Blouin, V.M., M.G. Schmidt, C.E. Bulmer, and M. Krzic. 2005. Effects of mechanical disturbance on soil properties and lodgepole pine growth in BC’s Central Interior. Can. J. Soil Sci. 85:681-691.
4. Bulmer, C.E. 1998. Soil rehabilitation in British Columbia: a problem analysis. Land Management Handbook 44. BC Ministry of Forests, Victoria, BC. Available at http://www.for.gov.bc.ca/hfd/pubs/docs/lmh/Lmh44.pdf
5. Dyanatkar, S., M. Krzic, J. Wilson, C. Crowley, N. Sidles, K. Watson, A. Bedard-Haughn, N. Basiliko, and P. Sanborn. 2013. Soilx. Virtual Soil Science Learning Resources. [www.soilx.ca]

NOTE: It might be useful that you view sections on Brunisols and Luvisols presented on the following web site http://soilweb.landfood.ubc.ca/classification/

Week Two

Learning objective

Evaluate the extent of mechanical disturbance during landing construction and use on soil physical properties.

Student tasks

1. Review the soil data collected during two studies on forest landings.
2. Review background information on management practices carried out on the study sites.
3. Gain basic understanding of soil quality concept.

NOTE: Before next week’s session, your team should research any gaps in knowledge regarding the guiding questions for today’s session.

Guiding questions

1. Based on the data presented in rehabilitated landings and unrehabilitated landings studies, what can you infer about the effects of mechanical disturbance on soil physical properties?
2. What are potential effects of the soil organic matter on the soil physical properties?

Key references

1. Ballard, T.M. 2000. Impacts of forest management on northern forest soils. Forest Ecology Management 133:37-42.
2. Schoenholtz et al. 2000. A review of chemical and physical properties as indicators of forest soil quality: challenges and opportunities. Forest Ecology Management 138:335-356.
3. Bulmer, C.E. 1998. Soil rehabilitation in British Columbia: a problem analysis. Land Management Handbook 44. BC Ministry of Forests, Victoria, BC. Available at http://www.for.gov.bc.ca/hfd/pubs/docs/lmh/Lmh44.pdf

Week Three

Learning objective

Identify soil quality indicators that could be used to monitor the sustainability of management practices on forest landings.

Student tasks

1. Given the information for the rehabilitated landings and unrehabilitated landings, develop the soil quality framework for forest landings (NOTE: the emphasis should be on the soil physical properties/attributes and indicators).
2. Preparation for group presentations

NOTE: Before next week’s session, your team should research any gaps in knowledge regarding the guiding questions for today’s session. Start preparing for the group presentation and please consult guidelines for oral presentations given in the course syllabus.

Guiding questions

1. List some soil quality indicators, with emphasis on physical properties, that could be used to monitor the sustainability of the management on forest landings.
2. Why does compaction take place on forest soil?
3. What are the ways of preventing compaction on forest soils?

Key references

1. Ballard, T.M. 2000. Impacts of forest management on northern forest soils. Forest Ecology Management 133:37-42.
2. Schoenholtz et al. 2000. A review of chemical and physical properties as indicators of forest soil quality: challenges and opportunities. Forest Ecology Management 138:335-356.
3. Krzic, M. and M.P. Curran. 2005. Forest soils and tree nutrition In S.B. Watts and L. Tolland (eds.), Forestry Handbook for British Columbia. 5^th edition. University of British Columbia Forestry Undergraduate Society, Vancouver, BC. pp. 357-393.

Week Four

Group presentations and synthesis

Each group will present results of their work on case 1 (please remember that your presentation should be max 20 minutes long) and along with the instructors compare and contrast the methods of diagnosis and interpretations of soil physical quality in the case studies:

1. Forest landings
2. Soil erosion in the middle mountains in Nepal
3. Rangelands in southern BC

The presentations will be evaluated on the basis of content, structure, and delivery, (pls see course outline for more details). One of the signs of successful presentation is how well the presentation engages other groups into discussion.