Table 6 Effects of treatments to reduce woody fuels in sagebrush ecosystems experiencing pinyon-juniper expansion on vegetation and fuel structure, fire behavior, fire management implications, and ecological response
| Â | Vegetation/ Fuel Structure | Fire Behavior | Fire Management Implications | Ecological Effects |
|---|---|---|---|---|
Prescribed fire | • Reduces canopy fuels and woody debris for > 10 years with the greatest reductions occurring with higher pretreatment canopy cover • Decreases fire-intolerant shrubs for > 10 years, but increases sprouting shrubs and herbaceous species (fine fuels) 2–3 years posttreatment | • Reduces crowning and eliminates crown transmission for > 10 years • Reduces modeled reaction intensity with low canopy fuels (phase I), and for a shorter time with moderate (phase II) canopy fuels • Increases in shrub and herbaceous fuels over time may result in increases in rate of spread and flame length • High productivity years may increase fire behavior | • Treatment in phase I or II before declines in perennial grasses and forbs allow prescribed burns to carry and increase recovery potential • Patchy prescribed fire in moderate to high resilience and resistance areas may benefit habitat • Decreases in trees and shrubs may facilitate suppression activities, but greater rate of spread due to increased herbs may create challenges | • Loss of fire-intolerant shrubs, which may be slow to recover on warmer and dryer sites • Increases in perennial grasses and forbs typical after 2–3 years • High risk of invasive annual grasses in warm and dry lower resilience and resistance sites and where perennial grasses and forbs are depleted |
Cut and leave | • Reduces canopy fuels but leaves significant woody fuel loads on site that increase with increases in pretreatment tree canopy cover • Increases sagebrush, other shrubs, and herbaceous species with the largest increases in sites with higher pretreatment canopy cover • High amounts of downed wood can smother understory species | • Reduces risk of crowing and crown transmission • Modeled flame length, rate of spread, and reaction intensity increase due to large amounts of surface woody fuels • Fire behavior increases over time as cover of surface shrub and herbaceous fuels increase | • Treatments in phase I have the most beneficial effects for fire suppression and site recovery • High flame length, rate of spread, and reaction intensity due to increased surface fuels in phases II and III may increase fire suppression challenges • Failure to remove seedlings and saplings requires follow-up treatment | • Retaining shrubs, native perennial grasses, and forbs can improve habitat for sagebrush species • Increases in invasive annual grasses may occur depending on resilience and resistance, degree of disturbance, and initial cover of perennial grasses and forbs |
Cut and broadcast burn | • Removes tree canopy fuels by cutting down trees and broadcast burning of slash • Decreases fire-intolerant shrubs in the short term, but sprouting shrubs increase after 1–2 years • Typically increases herbaceous species (fine fuels) | • Reduces risk of crowing and crown transmission • Effects on flame length, rate of spread, and fire intensity are likely similar to prescribed fire depending on timing of burns • High productivity years may promote growth of herbaceous species and increase fire behavior | • Removes high amounts of slash in later tree expansion phases • Fire severity may be high in spring or fall, but can be decreased by burning slash in winter • Treatment longevity is relatively high as small trees are killed | • Fire-intolerant shrubs are killed and may be slow to recover on warmer and drier sites • Increases in perennial grasses and forbs typical after 2–3 years, but risk of invasive annual grasses is high in warm and dry lower resilience and resistance sites and where perennial grasses and forbs are limited |
Cut and pile burn | • Removes tree canopy fuels, typically by pile burning of slash • Results in increases in native herbaceous and/or annual fuels depending on site conditions • Leaving unburned piles may promote tree recruitment, but pile burn disks may be invasion sources | • Reduces risk of crowing and crown transmission • Modeled flame length, rate of spread, and reaction intensity may increase over time due to increases in fine fuels • High productivity years may promote invasion in pile burns and increase fire behavior | • Treatment longevity is related to the abundance of residual seedlings and saplings • Seedling burn disks, preferably with native species, may be desirable to minimize burn scars and invasive plant species | • Cover of shrubs as well as native perennial grasses and forbs typically increase • Increases in invasive annual grasses may occur depending on resilience and resistance, degree of disturbance and initial cover of perennial grasses and forbs |
Mastication | • Redistributes tree canopy fuels to the ground surface with a high abundance of compacted 1-h and 10-h woody fuel size classes • Typically results in an increase in sagebrush, other shrubs, and herbaceous species over time • Large amounts of masticated fuels can smother understory species | • Reduces crowing and crown transmission and appears to reduce fire intensity and rate of spread • Small and compacted fuels may result in a longer duration of combustion and therefore increased smoldering and smoke production | • Wildfires that burn at lower intensities and at a slower rate may enhance fire suppression efforts • Increased smoke production and high winds that blow burning masticated particles across fire lines may increase suppression challenges | • Cover of shrubs and native perennial grasses and forbs typically increase • Increases in invasive grasses may occur depending on resilience and resistance, degree of disturbance and initial cover of perennial grasses and forbs • Prolonged smoldering during wildfires may increase duff consumption, soil heating, and root injury |