Fuels & Fuel Treatments
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Researchers measured 14 transects across two different fuel treatment types on three different units. For both fuel treatment types, only ladder fuels had been removed. They found that while severity was reduced at all sites, the spatial distribution of fire severity within the treatment areas varied by treatment type and unit as well as which fire severity metric they were analyzing. They found fuel treatments reduced fire severity anywhere from -7 m to 533 m into the treatment area. Kennedy and Johnson (2014) caution that local site conditions, topography and vegetation type will be other sources of variation in fire severity.
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This study estimates that fire has approximately twice the treatment life of cutting at time horizons approaching 100 yr, but, has high up-front conservation costs due to temporary loss of sagebrush. Cutting has less up-front conservation costs because sagebrush is unaffected, but it is more expensive over longer management time horizons because of decreased durability. Managing conifers within sage-grouse habitat is difficult because of the necessity to maintain the majority of the landscape in sagebrush habitat and because the threshold for negative conifer effects occurs fairly early in the successional process. The time needed for recovery of sagebrush creates limits to fire use in managing sage-grouse habitat. Utilizing a combination of fire and cutting treatments is most financially and ecologically sustainable over long time horizons involved in managing conifer-prone sage-grouse habitat.
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This study evaluated nutrient availability and herbaceous recovery following various cutting and prescribed fire treatments in late succession western juniper woodlands on two sites in southeast Oregon from 2007 to 2012. Treatments were untreated controls, partial cutting followed by fall broadcast burning (SEP), cut and leave (CUT), and cut and burn in winter (JAN) and spring (APR). Soil inorganic N (NO3−, NH4+), phosphorus (H2PO4−), potassium (K+), and cover of herbaceous species were measured in three zones; interspace, litter mats around the tree canopy (canopy), and beneath felled trees (debris). Peak nutrient availability tended to occur within the first two years after treatment. The increases in N, P, and K were greatest in severely burned debris and canopy zones of the SEP and APR treatments. Invasive annual grass cover was positively correlated to soil inorganic N concentrations. Herbaceous composition at the cool, wet big sagebrush-Idaho fescue site was generally resistant to annual grasses after juniper treatments and native plants dominating post-treatment even in highly impacted debris and canopy zones of the SEP treatment. The warm dry big sagebrush-bluebunch wheatgrass site was less resistance and resilient, thus, exotic annual grasses were a major component of the understory especially when tree and slash burning was of high fire severity.
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This study found while understory perennial herbaceous plant cover remained low 1 and 2 yr post treatment, it increased by > 700% in all fuel-reduction treatment plots six growing seasons post treatment. Furthermore, while we observed minor increases in invasive annual grass, Bromus tectorum L. (cheatgrass), colonization in 2010 and 2011, there were substantial increases in B. tectorum cover by 2015. B. tectorum cover varied among treatments with the greatest cover in the unseeded mastication plot at nearly 30%. Seeding applications did not increase overall seed mix species cover but enhanced seed mix species richness and, thus, may have increased resistance to B. tectorum invasion in seeded treatment plots.
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Fuel treatments decreased intrinsic water use efficiency relative to the control in Arizona although the differences were not sufficiently large to reach the threshold of statistical significance. Very dry conditions characterized post-treatment climate in Arizona and treatment decreased competition among trees for water. Decreased competition appears to have led to higher stomatal conductance in surviving trees and thus lower intrinsic water use efficiency, even with post-treatment growth increases as measured by basal area index. The treatment response supports our hypothesis of the expected treatment response.
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This study showed higher levels of resilience to fire than is typically discussed in the sagebrush steppe, in part because the studied ecosystems were in good condition before the fire, but also because the longer post-fire monitoring time (17 years) may be more appropriate to capture patterns of succession in these ecosystems.
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The LANDFIRE program provides a data safety net by producing biannually updated fuels products for all-lands in the United States. But even these data are two to three years old when they are delivered, and while they provide a good starting point, they are designed for national and regional level application. Local review and calibration is recommended to ensure that the data are suitable for smaller landscapes. An example from Idaho illustrates how adjusting LANDFIRE fuel data can ensure that current, accurate fuel information is ready to support fire and land management activities.
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This study examined bark beetle mortality for two-years after fuel reduction treatment in mid-elevation mixed conifer forests at the University of California Blodgett Research Forest. As part of the National Fire and Fire Surrogate Study, the experimental treatments included prescribed fire (fire), mastication, the combination of the two, and a control.
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This study found that:
- Few changes in most of the measured masticated fuel bed properties were detected over the 10 years represented in the sample. This indicates that in dry environments, it may take at least 10 years for ecological processes to change fuel characteristics enough for adverse fire effects to be mitigated.
- Burning masticated fuel beds in a laboratory revealed that there is a great deal of heat that is pulsed into the soil that could cause major mortality to belowground systems. This is especially true in high loading fuel beds with duff layers present.
- All masticated fuel beds dried to equilibrium in less than seven days, indication that these quickly drying fuels can be readily susceptible to smoldering combustion after 5-7 days of drying.
- Existing fuel models (including 11, SB1, SB2 and two existing custom fuel models) were good at representing fire behavior, indicating that there is no need to develop new, custom fuel models for masticated fuel beds.