Wildland Intermix (Vegetation Types)
Local history has shown that wildfires often start within urbanized areas and that it is important that hazard mitigation takes place on private property as well as public property. The developed areas of the Berkeley & Oakland Hills are inspected by local fire departments. Residents are required to meet state and local codes.
Proper disposal of materials by:
Proper storage of flammable and combustible materials. Garden structures that meet the requirements for materials and construction techniques under structures.
Structures -- removal of combustible roofing materials and replacement with Class A rated roof materials. Standards for new and modified existing roofs include:
In addition, residents must:
Management prescriptions are recommended based on dominant vegetation types with the goal of calming the potential fire behavior. The general recommendations will be adjusted for specific site conditions. These recommendations apply to both public and privately owned lands.
Grasslands cover approximately 20% of the wildlands in the Berkeley-Oakland Hills. Grassland flames can reach lengths ranging from 12 to 38 feet that could overwhelm suppression forces. The more critical concern for this vegetation type is the rate at which grassland fires can spread and the ease of ignition. This is one of the most dangerous types of fires for fire fighter safety due to its rapid frontal speed.
Fortunately, narrow areas (30' to 100' wide) kept to a height of 4" to 6" can help "lay down" a fire and make it easier to contain. This can be done by hand labor, grazing, prescribed fire, mechanical mowing or roadside chemical treatments depending upon the location, topography, and environmental considerations.
Brush and Scrub Dominated Communities
Four vegetation types are recognized in this category that occur in the hills and account for approximately 24% of the wildlands.
Treatment strategy for these communities is to reduce the volume of fuel without removal of the entire specimens. Recommendations encourage the limitation of brush encroachment into other vegetation types by more aggressive treatments, that still protect desirable specimens, to maintain open grassland or speed succession into the woodland communities.
Large plantations of Eucalyptus Forest occur in the hills and represent approximately 12% of the wildland vegetation. These dense stands have been managed over the year to result in distinct vegetation types.
Fire behavior in the Eucalyptus forests varies from relatively low flame lengths from 6 feet up to 21 feet depending upon depth of litter in and below trees, amount of dead materials within trees, stand density and understory mix. The ignition potential for all of these forests is extremely high and directly related to the depth of litter and amount of dead materials on the ground.
These forests are non-native and support a low diversity of species. Long term replacement by native hardwood forest or other less flammable vegetation is generally desirable, though the transition is recognized as disruptive. Treatment includes removal of ground fuels to reduce crown fires, thinning, and removal of high hazard specimens. Treatment methods, limitations and standards emphasizes removal of leaf litter, dead materials, fuel ladders stand density reduction, as well as follow-up treatment to ensure trees are monitored to eliminate stump sprouts. Hand labor, prescribed burns, mechanical cutting and chemical follow-up treatment of stumps are discussed as potential treatments. It is critical that any conversion process attempt to maintain needed nursery trees to encourage the succession of native oak woodlands in ravines and on north slopes where it already is in progress. Conversion to grassland with scattered oaks on southern or western facing slopes and ridge tops may also be possible where it is part of eco-system rehabilitation project.
Where high crowning potential exists, the entire forest will need to be treated to reduce the spread of fire to the top of trees by the removal fuels on the ground, young trees less than 12 inch diameter and fuels in the lower ten feet of the trees. It is important to maintain canopy closure to reduce invasion of weedy species after treatment. In some locations there may be a rich understory of native species that may serve as a basis for conversion to an alternative fuel type. A choice must be made to manage for either the emerging forest or the existing canopy of eucalyptus. Young eucalyptus (1-5 year) should be removed while it is still relatively small and easy to remove. It is anticipated that eucalyptus forest will need treatment ever 2 to 3 years (perhaps even annual treatment in the dense, productive stands) to maintain them as either fuel Model #8 Closed Timber Litter, Model #9 Hardwood Litter (High) or Model #10 Timber Litter Understory (Low).
Monterey Pines were introduced to the study area in the 1900s and occur as mature groves, in dense plantations and mixed with Eucalyptus. Open stands often have a well developed understory of Oaks, Bays, Poison Oak and Blackberry.
This vegetation type accounts for approximately 6% of the study area wildland vegetation. A relatively small amount of the mature Pine Forest and mixed mature Pine and Eucalyptus are targeted for priority mitigation (total of 18 acres). None of the pine forest plantations currently represent a hazard as far as flame lengths and crowning are concerned. However, all of this vegetation type has a high potential for ignition if the needles and surface fuels are not removed on a regular basis.
Much of the species' population is aged and showing signs of decline. Many of the individual trees are approaching the end of their natural life cycle and should be replaced with other species as they are removed. It is likely that a larger proportion of this vegetation type will need to be managed in the near future for both structural and fire hazards. Public agencies and private land owners who manage a large number of aged pines will need to decide if these trees should be removed while structurally sound with wood that has commercial value that can offset the cost of removal, or if they prefer to wait until the individual trees begin to decline when the owners will end up paying significant cost for removal. In many locations as the trees age, there are serious liability issues related to trees falling on adjacent houses, cars, people or powerlines.
The fire behavior modeled varies from flame lengths of 2 feet to 16 feet depending upon understory conditions, development stage and slope. These vegetation types have the highest ignition potential due to the presence of needles, hazardous understory and dead wood on the ground and lower portions of trees.
Monterey Pine Forests in the study area are not essential for any known species of special concern that would suggest special management requirements. Aesthetically however, these forests are dominant in the landscape, with strong community support. Recommended treatment methods include grazing or prescribed burn to remove understory materials. Hand labor or mechanical cutting can be used to remove dead materials, selectively thin or remove hazardous aged stands. Treatment performance standards include reducing the overall stand density, removing dead materials, creating 10 feet vertical clearance between live needles and understory fuels and where appropriate encouraging succession of native oak woodlands to replace the Monterey Pines. It is important to maintain canopy closure where possible to reduce invasive species after treatment. It is anticipated that treatment may occur on a 3 to 5 year basis to maintain stands as a fuel Model #2 Timber Grass (Low), Model #8 Closed Timber Litter, Model #9 Hardwood Litter (High),or Model #10 Timber Litter Understory (Low).
These woodlands and forests are the most common vegetation type in the study area covering 27% of the study area wildlands. This vegetation type includes a mix of tree species such as Coast Live Oak, California Bay, Buckeye, Black Oak and Madrone. Woodlands have from 30 to 70% shrub understory and include many of the species categorized as Successional Scrub. Forests include little understory and have a greater than 70% canopy closure. The modeled flame lengths vary from 1 foot to 34 feet depending upon the understory vegetation. The forests with closed canopies and relatively little surface fuels represent very low hazards. Ignition potential is moderate due to the effects of canopy cover. Fire behavior in this vegetation type is depending on the build-up of surface fuels and dead materials within the tree that can carry fire to the crown.
Approximately 116 acres of Mixed Hardwood Woodland (13%) have been identified for priority mitigation treatment. A number of species of special concern occur in Mixed Hardwood Woodlands and Forests often at the edges bordering brush and grasslands. The mitigation and monitoring recommendations outlined in those communities also apply to the treatments in the woodlands and forest. Hand labor, grazing and prescribed burns are recommended with special protection measures in order to reduce the build up of understory fuels. Mechanical equipment may be suitable to reduce adjacent brush encroachment but was not viewed as a common technique in this vegetation type. The performance standards highlight the need to maintain canopy cover and encourage species diversity of tree and understory while reducing the overall fuel load. The identified hazards should continue to reduce as the surface and ladder fuels are removed and the woodlands succeed into Mixed Hardwood Forests. It is anticipated that treatment will be required on a 5 to 7 year cycle and begin to taper off as the woodlands succeed into a closed canopy forest that meet the characteristics of Fuel Model #8 Closed Timber Litter. Until that time they should be maintained as Fuel Model #4 Chaparral (low), Model #2 Timber Grass (Low), Model #9 Hardwood Litter (High) or Model #10 Timber Litter Understory (Low).
The last two vegetation types in the study area represent relatively low fire hazards. Redwood Forests comprise approximately 9% of the wildlands in the Study Area, with Riparian Forests accounting for less than 0.4%. Both communities were modeled with fairly benign flame height varying from 2 feet up to 7 feet in the most extreme development stage on steep slopes and with a large build up of ground fuels.
Neither of these communities are recommended for treatment as both represent
low fire hazards and often occur in environmentally sensitive settings.
Hand labor was the only recommended technique should site specific areas
of fuel buildup require mitigation. Prescribed burns may be utilized in
redwood forests with a low intensity fire to remove litter build-up especially
in open stands.