Livestock Grazing Influences on Community Structure, Fire Intensity, and Fire Frequency within the Douglas-Fir/Ninebark Habitat Type

Zimmerman, G. Thomas; Neuenschwander, Leon F.

doi:10.2307/3898893

Cited by 82 publications

(66 citation statements)

References 11 publications

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“…These two species were preferred by cattle and declined with overgrazing (Hall 1975). In Idaho, pinegrass production in grazed stands was only 28 percent of that in ungrazed stands (Zimmerman and Neuenschwander 1984). Conifer regeneration has been encouraged by the decline in competition from rhizomatous species and disruption of the ground by hooves.…”

Section: Grasslands Shrublands and Woodland Ecosystems-the Perenniamentioning

confidence: 99%

Fire and weather disturbances in terrestrial ecosystems of the eastern Cascades.

Agee¹

1994

108

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Fire has been an important ecological process in eastside Cascade ecosystems for millennia. Fire regimes ranged from low severity to high severity, and historic fire return intervals ranged from less than a decade to greater than 300 years. Fire history and effects are described for grassland and shrubland ecosystems, and the range of forested communities by plant series: Ponderosa Pine, Douglas-fir/White fir/Grand fir, Lodgepole pine, Western hemlock/Western redcedar, and subalpine fir/Mountain hemlock. The riparian zones within these communities may be more or less impacted by fire. The effects of extreme weather events, including unusual temperature, wind, or moisture have generally had less significant impact than fire. Management practices, including fire suppression, timber harvesting, and livestock grazing, have altered historical fire regimes, in some cases irreversibly. The management issues for the 1990s include both management and research issues, at a grand scale with which we have little experience. Ecosystem and adaptive management principles will have to be applied.

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Section: Grasslands Shrublands and Woodland Ecosystems-the Perenniamentioning

confidence: 99%

Fire and weather disturbances in terrestrial ecosystems of the eastern Cascades.

Agee¹

1994

108

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“…Treating large blocks of damaged forests to allow for greater expression of understory vegetation might improve the quality of hiding cover in future stands, if such treatment blocks are at least the size recommended by Lyon and Canfield (1991). The harvested units could be managed for a few years by light or moderate grazing by livestock to reduce the effects of herbaceous vegetation on regenerating conifers Winward 1976, Zimmerman andNeuenschwander 1984).…”

Section: Discussionmentioning

confidence: 99%

“…Herbivory by cattle also alters the frequency and intensity of wildfires (Madany andWest 1983, Zimmerman andNeuenschwander 1984) by removing fine fuels. Herbivory by wild ungulates may have similar influences.…”

Section: Predicted Effects Of Large Herbivores On Plants and Soils Inmentioning

confidence: 99%

“…Studies with herbivore exclosures in and near the Blue Mountains Ecoregion provide insight on the effects of livestock and big game herbivory on understory vegetative composition (Edgerton 1987;Winward 1974, 1976;Tiedemann and Berndt 1972;Zimmerman and Neuenschwander 1984), soil fertility (Tiedemann and Berndt 1972), and establishment and growth of tree seedlings (Kingery and Graham 1990;Weigand and others, in press). …”

Section: Observed Effects Of Large Herbivores On Plants and Soils In mentioning

confidence: 99%

“…Persistent grazing by herbivores throughout development of forest stands in the Blue Mountains may improve production of wood fiber by reducing competition from understory vegetation (Krueger and Vavra 1984;Weigand and others, in press;Wheeler and others 1980;Zimmerman and Neuenschwander 1984). If long-term herbivory reduces soil fertility (Pastor and others 1988), however, then removal of competing understory vegetation via herbivory may result in a net loss in the rate of wood-fiber production.…”

Section: Observed Effects Of Large Herbivores On Plants and Soils In mentioning

confidence: 99%

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Effects of long-term use by big game and livestock in the Blue Mountains forest ecosystems.

Irwin¹,

Cook²,

Riggs³

et al. 1994

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There is empirical evidence that persistent herbivory by large mammals caused moderate to severe reduction of shrubs and forage productivity in a variety of logged and unlogged forest communities, with subsequent effects on frequency of wildfire and conifer seedling establishment in some plant communities. Long-term herbivory was shown to have alternative effects by either improving or reducing wood-fiber production by reducing competition from understory plants or reducing soil fertility. The changes in plant communities caused by the herbivores may have had negative feedback effects to productivity of both elk and cattle. Cattle do not achieve desired weight gains on summer allotments. Empirical studies on forage quality and livestock nutritional status support a view that large domestic and wild mammals subsist on suboptimal forage conditions most of the year in the Blue Mountains. Survival of elk calves appears low, partly as a result of density-induced shortages of high-quality forage. The reduced calf production appears to be exacerbated by low adult bull:cow elk ratios, which reduces calf survival via delayed and lengthy birthing periods. The low bull:cow ratios are a result of reduced cover due to logging and increased access to hunters due to logging roads. Reduced big game productivity has led to restrictions on hunting opportunities, with concomitant losses in revenue to local economies. In addition, the dense elk herds, in concert with forest management activities on federal lands, have resulted in increased use by elk on private lands, where they damage crops. The paper identifies adaptive management experiments that could identify options for-clarifying the complex relationships between herbivores, vegetation, and ecosystem processes and identify management options for restoring forest health.

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Vegetation dynamics following compound disturbance in a dry pine forest: fuel treatment then bark beetle outbreak

Crotteau

Keyes

Hood

et al. 2019

Ecological Applications

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In the western United States, restoration of forests with historically frequent, low‐severity fire regimes often includes fuel reduction that reestablish open, early‐seral conditions while reducing fuel continuity and loading. Between 2001 and 2016, fuel reduction (e.g., thinning, prescribed burning, etc.) was implemented on over 26 million hectares of federal lands alone in the United States, reflecting the urgency to mitigate risk from high‐severity wildfire. However, between 2001 and 2012, nearly 20 million hectares in the United States were impacted by mountain pine beetle (MPB; Dendroctonus ponderosae), compounding restoration effects in wildfire‐hazard‐treated stands. Knowledge of the effects of treatments followed by natural disturbance on long‐term forest structure and communities is needed, especially considering that fuel treatments are increasingly being implemented and warming climate is predicted to exacerbate disturbance frequency and severity. We tested the interacting effects of treatments designed to reduce high‐severity wildfire hazard in stands subsequently challenged by MPB outbreak on vegetation dynamics using a factorial experimental design (control, thin only, burn only, thin + burn) in a ponderosa pine (Pinus ponderosa)‐dominated forest. Stands were treated by 2002, then impacted by MPB outbreak from 2005 to 2012. We assessed change in overstory and understory forest community structure, composition, and diversity over time. There were distinct thinning, burning, and year effects. Thinning immediately reduced overstory density; pine density then declined 4.5 times more in unthinned than thinned treatments due to MPB. Burning immediately reduced graminoid, shrub, and total understory cover by as much as 52%, resulting in greater species evenness than unburned treatments, but differences disappeared by 2016 due to growth and MPB outbreak. Similarly, multivariate analyses indicated forest communities were starkly different after treatment but became more similar over time, though key understory and overstory attributes still distinguish control and thin + burn. This study shows the value of long‐term silvicultural experiments to evaluate treatment longevity and the compounded effects of treatment and natural disturbance. We demonstrate the homogenizing effects of treatment‐induced growth coupled with MPB‐caused tree mortality on management strategies that just treat the overstory (thinning) or understory (burning), showing that only combined treatments can provide the unique structural and compositional outcomes expected of restoration.

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Livestock Grazing Influences on Community Structure, Fire Intensity, and Fire Frequency within the Douglas-Fir/Ninebark Habitat Type

Cited by 82 publications

References 11 publications

Fire and weather disturbances in terrestrial ecosystems of the eastern Cascades.

Fire and weather disturbances in terrestrial ecosystems of the eastern Cascades.

Effects of long-term use by big game and livestock in the Blue Mountains forest ecosystems.

Vegetation dynamics following compound disturbance in a dry pine forest: fuel treatment then bark beetle outbreak

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