Geology Cafe

Fire In the California Coast Ranges

Wildfires are an important environmental concern in Central California's Coast Ranges. For many people, wildland fires are viewed as dangerous and destructive, and should be put out at all cost. This is especially true in areas where human habitation and economic factors come into play. The fact is, fire is a force in nature that has existed as long as vegetation has adapted to the landscape. Native plants in California evolved through the interaction of natural fires over millions of years. Prehistoric peoples used fire to hunt and manage the landscape. However, in the past hundred years, the growth of human occupation and activities have significantly changed the landscape, and the role that fire now plays. The introduction of non-native species of grasses and other plants have change the way native fires occur. In addition, human foley has become a primary cause of fires, both in urban and non-urban areas. In general, the role of fire is poorly understood, and management of fires has become a complex and often expensive proposition. The natural role of fire, including the removal of sick or infested growth, and the provision of nutrients, and reseeding of native plants, is often overlooked, ignored, or denied.

The Central Coast of California has a Mediterranean climate, having cool, wet winters, and warm, dry summers - typically with little or no rain for months at a time. Central California also has periods of drought and periods of rapid vegetation growth following seasonably wet winters. Thunderstorms, although somewhat rare in the region, typically occur in the late summer, and can start wildfires naturally. When natural fuel conditions are right, fire can spread rapidly and over long distances. The natural landscapes we observe in the central California region have many vegetation types that form a natural distribution pattern, and fire history plays an important role in the appearance of vegetation on the landscape. Fire is an essential part of most wildland ecosystems. Many California plant species have adapted to a point that they could not exist without the presence of fire. Wildland fires spawn a period of rebirth and vigorous growth in post-fire environments. Fire removings dead materials and by releases nutrients back to the environment that are locked up in mature plants, organic litter, and topsoil.

The role of fire is not just with the occurrence of the event of burning, but the typically barren post-fire landscape behaves differently than a maturely vegetated landscape. Burned areas are subject to major erosion and debris flood events during following wet periods. Great amounts of sediment can be generated by erosion in burned areas. Fire/flood cycles are a natural component of the natural landscape. Post-fire debris floods can impact areas far away from burn areas. Land management officials and landowners need to have a clear and general knowledge of fire and flood prone impact areas.

fire/flood cycle has existed for millions of years, and where impacts of living in the wildland/urban interface have been so clearly illustrated following the Green Meadow and Old Topanga Firestorms of 1993. However, it should be noted that the fire/flood cycle is not unique to the Santa Monica Mountains, and that much of California and the West is under the influence of this cycle as well, although some differences will occur due to habitat type, and the environmental conditions and other factors present.

Types of Wildland Fires

There are three general classes of wildfires: suface, crown, and ground fires. The occurrence of fires is dependent upon factors of fuel conditions, location, and intensity. These factors are controlled in part by climatic conditions at the time of a fire: heat, wind, and humidity. Surface fires are typically, low, fast-moving fires that seldomly reach high temperatures. Many plants are adapted to surviving surface fires by having root systems, tubors, fire-retardent bark, fire driven reseeding habits, and/or the ability to rapidly regrow after a fire. Crown fires involved the burning of forest canopy and are typically a result of surface fires. Ground fires are typically the most intense fires where everything burns down to the barren ground, leaving little vegetation to survive in its wake. Large fire events can include all three classes of wildfires.

Patterns of Fire on the Landscape

The pattern of vegetation on the Coastal Ranges is influence by factors such as geology (and associated soils), slope and exposure, and fire history. The occurrence of primary vegetative habitats including grassland, chaparral, oak forests, mixed woodlands, and riparian habitats, are dependent of climate factors and soil substrates. In the region, grassland and chaparral dominate dry, sunny, south and west-facing slopes, where north-facing slopes where cooler and wetter local climate conditions persist and can support forest growth. How these vegetative communities appear on the landscape today is reflected in landuse history and occurrence of fires. Post fire regrowth may allow one vegetative community to replace another. Unfortunately, non-native species, especially grasses, can overtake fire-burned landscapes, preventing forest reseeding. Conversely, wildfires can destroy non-native species infestations, allowing native plants to regain a hold on the landscape. Fire managers working with wild plant specialists can conduct controlled burns for effect weed management.

October is National Fire Prevention Month
Wildfire
See these Selected Resources


California Department of Forestry and Fire Protection

CalFire: San Benito County

Firescope: California Wild Fire Information
 

http://geologycafe.com/fire/index.html
9/5/2011