clearcutting effects on soil ecology most slides contributed by ellen mussman and amanda ogden l.
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Clearcutting effects on Soil Ecology Most slides Contributed by: Ellen Mussman and Amanda Ogden. Overview. Facts of Clearcutting Soil Environment Microbes and Invertebrates Mycorrhizas Decomposition Nitrogen Cycle Alternatives to Clearcutting Summary. Facts.

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Presentation Transcript
  • Facts of Clearcutting
  • Soil Environment
  • Microbes and Invertebrates
  • Mycorrhizas
  • Decomposition
  • Nitrogen Cycle
  • Alternatives to Clearcutting
  • Summary
  • Clearcutting aka “Even-Aged” Management
    • Involves removal of entire stand of trees
    • Site preparation for a new stand of trees to be planted
    • Promotes “edge” effects
      • Ecological conditions contrast with conditions of interior forest including:
        • Vegetation structure
        • Productivity
        • Understory species
        • Microclimate

(Davies-Colley et. al. 2000)

clearcutting issues
Clearcutting Issues
  • Cons:
    • Concerns that traditional U.S. forest management practices in the Pacific Northwest are unsustainable
    • Loss of biodiversity
    • Compromises the long-term productivity of the site
  • Pros:
    • Intensive site preparation for new seedlings more effective
    • Establishment of Even-Aged stands vs“selection management or high grading” (ie, taking the best and leaving the rest resulting in poorer genetic stock remaining)
  • Studies have shown an increase in forest floor temperature following clearcutting that persists for several years (Barg and Edmonds, 1999)

temperature and moisture and
Temperature and Moisture and…

Following clearcutting:

  • Soil temperature and moisture usually increase
  • Nutrient cycles are greatly modified
  • Changes lead to changes in the biogeochemistryof a catchment (R.L. Parfitt et al., 2002)
clearcut vs old growth temperature r l parfitt et al 2002 cont d
Clearcut vs. Old-GrowthTemperature(R.L. Parfitt et al., 2002-cont’d)
  • Mean forest floor temperature at the Cedar/Western Hemlock (CWH) site increased by more than 2C between sampling dates
  • Temperature was consistently 2-3°C greater in the clearcut than in the old-growth plot and much more dynamic

Fig. 1. Diurnal cycle of forest floor temperatures (10 cm depth) at the CWH site in clearcut and old-growth plots in mid-June, mid-July and mid-August 1999; symbols represent the 3-day average temperature value at 30 min intervals.

soil macro arthropods
Soil macro-arthropods
  • Soil macro-arthropods are an appropriate study object regarding the ecological effects of forest harvesting since they play an important role in decomposition processes (among other things), and
    • are represented by diverse animal groups in the upper soil horizons (many habitats), and
    • may be used as a sensitive indicator of changes (perturbation).

Siira-Pietikäinen (2002)

effects on macro arthropods study by siira pietik inen et al 2002
Effects on Macro-arthropodsStudy by Siira-Pietikäinen (2002)
  • Clearcutting followed by harrowing (site preparation) has a negative effect on predators and herbivores.
    • Spiders decreased the most.
  • Clearcutting also had a negative effect on thenumbersof detritivores.
    • However, no significant effects on the total numbers of macro-arthropods.

Siira-Pietikäinen (2002)

ectomycorrhizal study hagerman et al 1999
Ectomycorrhizal Study Hagerman, et al. (1999)
  • Investigated the effect of 3 different clear-cut sizes: 0.1, 1.0, and 10 ha, on the diversity of ectomycorrhizas.
  • One growing season after tree removal, no differences between the treatments in the numbers of active fine roots at any location nor were there any effects on the diversity of ectomycorrhizas.
  • However, after 2 and 3 growing seasons the numbers of active fine roots as well as the diversity of ectomycorrhizas in clearcuts was significantly reduced with distance from the forest edge.
  • Although no difference in ectomycorrhizal diversity were detected amongst the three silvicultural systems, the forest edge implies that smaller cut blocks will retain a higher diversity of mycorrhizas as they have a greater perimeter to area ratio than larger cut blocks.
ectomycorrhizal study jones et al 2003
Ectomycorrhizal Study Jones et. al. (2003)
  • Review of many studies
  • Clearcut logging and subsequent site preparation changes the environment of ECM fungi.
  • They expected to see differences in colonization or fungal species composition between seedlings growing on clearcuts and those growing in forests.

 A schematic diagram illustrating the two major groups of factors likely to influence the species composition of the ectomycorrhizal fungi communities in regenerating stands after clearcut logging. Interactions amongst factors are not shown

There are several major changes associated with clearcut logging that are likely to affect ECM fungi
  • Input of carbon to the fungi will decrease.
  • The age and species of plants present on site will change.
  • If site preparation is performed, the forest floor is removed or displaced.
  • The loss of the large overstory trees causes changes in the physical environment of the soil.
  • As a result of the physical and chemical changes described above, populations of soil microflora and fauna will change, as may processes in which these organisms participate, such as decomposition, nitrogen cycling, and production of hydroxymatesiderophores (helps with iron chelation and plant uptake of iron).

Jones et. Al. (2003)

conclusions from jones et al 2003
Conclusions from Jones et. al. (2003)
  • No clear evidence that inoculum of ECM fungi is disrupted to the extent that total colonization of roots is affected.
  • There are clear changes in the species composition of the ECM fungal community.
  • Biological, chemical, and physical changes in the soil environment are probably as important asalterations in inoculum in causing changes in the ECM fungal community.
clearcutting and decomposition rates
Clearcutting and Decomposition Rates
  • Commonly thought that decomposition rates are faster in clearcuts than in forests and many models of forest C budgets either assume or allow for faster decomposition.
  • Faster decomposition in clearcuts was first proposed to explain the accelerated leaching of nitrate and the reductions in forest floors after clear-cutting and was attributed to higher temperature and moisture in clearcuts.

Prescott et. al. (2000)

regional climate effects on clearcutting
Regional climate effects on clearcutting
  • In cold climates (high latitudes) the warmer temperatures after clearcutting may stimulate decomposition
  • In warm climates (low latitudes) clearcutting may impair decomposition because of the drying out of surface organic matter

Prescott et. al. (2000)

study by prescott et al 2000
Study by Prescott et. al. (2000)
  • Prescott et. al. (2000) studied the rate of mass loss of three standard substrates (pineneedle litter, aspen leaf litter, and forest floor material) in forests and adjacent clearcuts at 21 sites throughout British Columbia.
  • Hypotheses:
    • Rate of mass loss is greater in clearcuts than in forests
    • Clearcutting would stimulate decomposition most in colder zones.
study by prescott et al 200021
Study by Prescott et. al. (2000)
  • They found no evidence that litter decomposed faster in clearcuts than in adjacent forests in British Columbia
  • The effects of clearcutting on decomposition rates varied among sites and showed no clear relationship
  • Clearcut size did not explain much of the variation in response to clearcutting.
effects on decomposition rates
Effects on Decomposition Rates
  • However, studies have shown that decomposition rates may actually be faster, slower, or the same in clearcuts compared with forest, depending on the regional climate.
  • In a study by Prescott (1997) several silvicultural treatments had similar decomposition rates.
  • This might suggest that surface climatic conditions are more similar among the silvicultural systems relative to the old growth.

Prescott (1997)

clearcuts vs old growth
Clearcuts vs. Old Growth
  • Higher rates of decomposition can occur in old growth compared to clearcuts
  • Even if the decomposition potential of the site increases, decomposition of the forest floor is primarily limited by the nature of the material, and will continue to decompose slowly.

Prescott (1997)

study by siira pietik inen et al 2001
Study by Siira-Pietikäinenet. al. (2001)
  • Studied the short-term responses of decomposers to different forest harvesting methods in a boreal spruce forest.
  • The total biomass of decomposer invertebrates has often been observed to temporarily increase after clear felling of the Northern forests because of the drastic increase in the numbers of enchytraeids.
results of study by siira pietik inen et al 2001
Results of Study by Siira-Pietikäinenet. al. (2001)
  • Microbial community structure changed in the first year.
  • Microbial biomass and basal respiration decreased in the second year.
  • Density of the enchytraeid worm Cognettia sphagnetorum (Vejd.) increased in the third year after the clear felling.
  • Although there were changes in the microbial community, the invertebrates at higher trophic levels did not similarly respond to these changes.
nitrogen cycle
Nitrogen Cycle

differing views on n mineralization rates
Differing Views on N Mineralization Rates
  • Clearcutting in conifer forests may increase nitrification ( Frazer et al., 1990)
  • May increase ammonification only
  • May have little effect on either ammonification or nitrification in the forest floor
  • Clearcutting may bring on a flush of mineral N in organic forest floor horizons
effect of clearcutting on nitrate leaching
Effect of Clearcutting on Nitrate Leaching
  • Hubbard Brook initially showed nitrate leaching into the streams. However they had used herbicides which decreased plant assimilation (uptake) of nitrogen.
  • However in the Cedar River watershed studies in Washington, Cole et al found very little nitrate leaching after clearing. This seemed to be supported by many other studies in the western forests.
  • However, if significant leaching of nitrate occurs this may be coupled with significant losses of base cations (esp, Ca and Mg), as well as affecting potential eutrophication in the streams and lakes, as well as increasing the human health risks (blue baby syndrome).
facts and myths of clearcutting belt k and campbell r

Clearcutting is ugly

Clearcutting is not a cure-all, nor is it appropriate everywhere

Clearcutting is a viable forest management tool which has everything to do with good land stewardship and forest sustainability

A clearcut can be engineered to suit a combination of needs


Clearcutting is the same as deforestation

Clearcuts are the end and death of a forest

Clearcuts cause immensely more erosion than partial cuts

Clearcuts are biological deserts with no potential for wildlife habitat

Facts and Myths of Clearcutting(Belt K. and Campbell R.)
alternatives to clearcutting34
Alternatives to Clearcutting
  • Variable Retention Harvesting or Green-tree retention
  • Forest management policies on federal lands in the Pacific Northwest have changed in last 10 years
  • Increasing concern over:
    • Loss & Fragmentation of Old-growth forests
    • Habitat Loss
    • Reduction in biological diversity

green tree retention
Green-Tree Retention

“Green-tree” retention has replaced clearcut logging on federal forestlands subject to timber harvest regulations


  • Microclimate of a site
  • Influences decomposition rates and N availability
  • Provides refuge for belowground organisms such as mycorrhizal fungi
  • But more blow-downs?

  • Decomposition is generally considered to be faster in clearcuts than in forests, owing to higher temperature and moisture conditions.
  • The major impact of clearcut logging is to change the species composition of the ectomycorrhizal fungal community rather than to reduce the percentage of roots colonized. (Jones et. al. 2003).
  • Changes in fungal species composition occur in clearcuts(Jones et. al. 2003).
  • The shift in fungal species composition and diversity will have implications for seedling establishment and competition.
  • Increasedavailability of N is commonly reported after clearcutting.
  • Alternative silvicultural systems have been proposed as means of reducing the negative consequences of clearcutting (Prescott 1997).
  • Generalizations about the effects of clear-cutting on decomposition rates cannot be made.Prescott et. al. (2000)
review of soil ecology processes
Review of Soil Ecology Processes
  • Clearcutting like effects of hurricanes in tropical environments?
    • Warm climate, heavy ppt, poor soils,
    • lose nutrients with loss of vegetation assimilation?
  • If not, why????
  • Urban development effects on nitrogen loss from streams??