Aspen stands: Fuel or Fuelbreak at a Landscape Scale?

Introduction Do aspen stands make good strategic (landscape scale) fuelbreaks for community protection and commercial forest protection?Do aspen stands make good strategic (landscape scale) fuelbreaks for community protection and commercial forest protection? Effectiveness varies with burning conditions and fuel loads.Effectiveness varies with burning conditions and fuel loads.

In spite of sophisticated fire management, fire still operates at a landscape scale

75 year Okanagan fire history map shows: ½ the area burned at least once½ the area burned at least once Significant areas re- burnedSignificant areas re- burned 90% of lightning fires suppressed at <0.1 ha90% of lightning fires suppressed at <0.1 ha Large fires in 1920s, 1930s, 1990s, 2003Large fires in 1920s, 1930s, 1990s, 2003 No large fires in Okanagan Mountain ParkNo large fires in Okanagan Mountain Park

Okanagan Mountain Park Fire, 2003 Severe drought and windSevere drought and wind Entire 10,000 ha park burned in 25,000 ha fireEntire 10,000 ha park burned in 25,000 ha fire East half of fire burned before (1920s, 1930s)East half of fire burned before (1920s, 1930s) No landscape-scale fuelbreaksNo landscape-scale fuelbreaks

Only 2000 ha of 1.66 M ha burned/year (0.12%)Only 2000 ha of 1.66 M ha burned/year (0.12%) Not enough fire to maintain fire-dependant ecosystems in crown fire-resistant stateNot enough fire to maintain fire-dependant ecosystems in crown fire-resistant state Solutions include community fuelbreaks, prescribed burning, home ignition zone fuel reductionSolutions include community fuelbreaks, prescribed burning, home ignition zone fuel reduction South Okanagan fire history

Limitations/constraints on fuel reduction Most burned area associated with synoptic- scale weather patternsMost burned area associated with synoptic- scale weather patterns Fuelbreaks may fail in extreme burning conditions of drought, low RH, high windsFuelbreaks may fail in extreme burning conditions of drought, low RH, high winds Prescribed burning is risky, requires skills and experience in short supply, and smoke is a problemPrescribed burning is risky, requires skills and experience in short supply, and smoke is a problem

Limitations/constraints on fuel reduction Prescribed fire effects unlikely to override extreme weather, especially areas subject to wind and droughtPrescribed fire effects unlikely to override extreme weather, especially areas subject to wind and drought

Expensive to reduce fuel loads at landscape scaleExpensive to reduce fuel loads at landscape scale Limitations/constraints on fuel reduction

Fuel reduction measures are not one- time events, their impacts are short-termFuel reduction measures are not one- time events, their impacts are short-term Limitations/constraints on fuel reduction

Chisholm Fire Study Weather Conditions & Fuel Moisture Weather Conditions Three year moisture deficit, Slave Lake area Dry spring followed light snow pack Heavy fuels and forest floor drier than normal Fine fuels dry, warm temp, low RH, windy Conifer foliar moisture near its annual minimum Greenup of grass and herbaceous vegetation delayed by drought

Previous area May record BUI=121 (1991), ISI=41, FWI=60 Chisholm Fire Study Fire Weather Observations and Peak Weather Indices For May 28 th 2001

Chisholm Fire, FBP Fuel Type Map

Weather Conditions & Fuel Moisture Fuel Types Boreal Spruce (C2) predominates (39%) Cured standing grass (O-1b) significant (35%) due to reburn in 1998 Mitsue and Chisholm burns Leafless aspen (D-1) significant (18%), generally has conifer understory Boreal mixedwood - leafless (M-1) (3%), generally has 25-50% conifer Mature pine (C-3) significant on benches along Athabasca River, minor overall (3.5%)

Special situations Grass fuels were 100% cured and standing, due to low snowpack and dry spring Deciduous stands (0-1) had begun leaf- out, but grass and herbaceous vegetation in stands had not Extensive 30 year old aspen stands from 1968 Vega Fire along west flank

Chisholm Fire Behavior and Effects in Aspen All overstory trees killed, all plots Vigorous aspen suckers, all plots Herb and shrub response vigorous, all plots Grass sparse on CFS plots, significant on Vega plots

Chisholm Fire Behavior and Effects in Aspen Fire intensity 10 times higher on CFS plots, due to fire history, fuel load and rate of spreadFire intensity 10 times higher on CFS plots, due to fire history, fuel load and rate of spread Highest intensity established for CFS plot = 228,000 kW/mHighest intensity established for CFS plot = 228,000 kW/m Highest intensity established for Vega plot = 27,000 kW/mHighest intensity established for Vega plot = 27,000 kW/m

Fuel loads and fuel consumption Much higher fuel loads established on CFS plots due to falldown of natural mortality and 1978 fire-killed treesMuch higher fuel loads established on CFS plots due to falldown of natural mortality and 1978 fire-killed trees Downed-woody fuel loads much lower on Vega Fire plots due to salvage logging after Vega FireDowned-woody fuel loads much lower on Vega Fire plots due to salvage logging after Vega Fire

Drought conditions in 1968 and 2001 contributed to high consumption of downed-woody fuel and forest floor

Higher than predicted aspen fuel consumption if spring burning conditions severe and/or fuel loads highHigher than predicted aspen fuel consumption if spring burning conditions severe and/or fuel loads high Under-estimation of potential aspen fire behavior may result in over-estimation of benefits of aspen stands as fuelbreaksUnder-estimation of potential aspen fire behavior may result in over-estimation of benefits of aspen stands as fuelbreaks Landscape fuel management interpretations

Large stands of aspen were effective at stopping fire spread under severe spring burning conditions when: downed-woody fuel loads were light, anddowned-woody fuel loads were light, and cured grass is not a factorcured grass is not a factor Landscape fuel management interpretations

Aspen Fuelbreaks should:Aspen Fuelbreaks should: Maximize canopy closure to exclude grass, andMaximize canopy closure to exclude grass, and Reduce downed-woody fuel loads to a single ground layerReduce downed-woody fuel loads to a single ground layer Landscape fuel management interpretations