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MONITORING CONCERNS

The eight topics displayed here were identified by the soil scientists of Region 1 as the most important concerns or issues related to soil quality. Each topic has its own guidelines, methods for measurement, associated problems, methods for avoidance and amelioration, pertinent research and literature list.

COMPACTION

Measurement

No quantitative measure of soil compaction exists. Instead, approximations based on changes in soil characteristics are substituted for direct measurement.

Procedures:

  • Core sampling - Deb: Is there a paper describing this procedure (thumping)?
  • Cone Penetrometer - Locate a user's manual.
  • Spade - Locate a description (Clayton, et al. 1987).
  • Infiltrometer (percolation test) - ???

Guidelines

A 15% increase (20% in volcanic ash soils) in natural bulk density or a 50% reduction in the infiltration rate is considered detrimental.

Problems

Soil compaction is accompanied by decreases in soil permeability and porosity, air exchange, root penetration, and infiltration. Associated problems include

  • loss of moisture holding capacity
  • decreased rooting zone
  • loss of C, N, and P sources
  • changes in soil pH
  • changes in soil bulk density
  • increased erosion due to increased overland flow

Effects

Soil compaction presents a physical barrier to root growth, inhibiting seedling and mature tree growth. Compaction may also reduce tree growth by reducing oxygenation of the roots, preventing adequate water movement, and limiting mycorrhizal growth (Froehlich and McNabb 1984).

Solutions

To Avoid or Reduce Effects To Mitigate Effects
  • Operate over frozen ground or deep snow
  • Avoid operations on moist or wet soils
  • Operate over slash
  • Restrict equipment to dedicated roads and trails
  • Restrict size and type of equipment
  • Surface tillage
  • Subsoiling
Activity Sites 

Research Summary

Factors affecting soil compactability include:

  • Soil moisture
  • Soil texture
  • Soil bulk density

Literature

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Displacement

Measurement

Guidelines

Problems

Effects

Solutions

Research summary

Literature

Detrimental displacement is displacement that results in "the loss of as much as 1 inch or one-half of the humus-enriched surface layer (A-horizon), whichever is less." The loss of the organic layer alone could be detrimental on some marginal sites.

Lateral displacement of soil may decrease productivity by disruption of water distribution, damage to root systems or, in extreme cases, uprooting and toppling of trees. Studies have attempted to quantify the relationship between lateral soil displacement and productivity (Clayton 1987).

Natural erosion and slope failure are considered to be beyond the scope of this document, except where efforts to control them have altered the landscape forming processes (sedimentation dams, post-harvest mulching, contouring, etc.).

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Puddling

Measurement

Guidelines

Problems

Effects

Solutions

Research summary

Literature

The deformation of wet soil with sufficient clay results in puddling. Soil puddling that adversely affects hydrologic function and site productivity is detrimental.

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Burned Soil

Measurement

Guidelines

Problems

Effects

Solutions

Research summary

Literature

Soils are severely burned if all surface organic matter is consumed and the blackened layer is more than 1 inch deep. Oxidized soil (reddish color) is also indicative of severely burned soil.

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Ground Cover

Measurement

Guidelines

Problems

Effects

Solutions

Research summary

Literature

The minimum cover, following the cessation of disturbance in an activity area, should be sufficient to prevent accelerated runoff and prevent erosion from exceeding the rates of natural soil formation.

Erosion rates are dependent on soil erodibility (k-factor), erosivity (rainfall factor), and slope gradient and length. Local adjustment of these factors by geographic area or potential natural plant community types may be required.

On rangelands, at least 80% of the A or surface horizon should be occupied by abundant fine and very fine roots.

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Surface Organics

Measurement

Guidelines

Problems

Effects

Solutions

Research summary

Literature

Currently, there are no specific requirements for litter retention. Ground cover requirements generally assure sufficient litter retention.

The minimum amounts of large woody debris required to maintain nutrient supplies adequate to sustain site productivity are ascertained by research studies (Harvey, 1987).

In general, a figure of 15 tons per acre is used for harvested or burned sites. This figure varies by habitat type, from 10 to 40 tons per acre.

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Nutrient Cycling

Measurement

Guidelines

Problems

Effects

Solutions

Research summary

Literature

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Regeneration

Studies from the Pacific Northwest indicate that disturbance can reduce ectomycorrhizal formation and forest regeneration. However, the degrees of reduction and impact on forest regeneration vary widely and depend on many factors. Among these are the type and severity of disturbance, ectomycorrhizal diversity, climatic conditions, biotic conditions, and the effects of nonhosts over time. Mycorrhizal formation and regeneration are most greatly impacted on severely disturbed and environmentally limited sites. The rapid occupation of such sites by ectomycorrhizal host plants following disturbance is critical to stabilizing native mycorrhizal populations that may aid forest regeneration.

Measurement

Guidelines

Problems

Effects

Solutions

Research summary

Literature

Amaranthus, Michael P., 1991, Factors Affecting Ectomycorrhizae and Forest Regeneration Following Disturbance in the Pacific Northwest.

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