Forest After Fire – Q&A with Hannah Ormshaw

Butano Ridge

Hannah Ormshaw is the Natural Resource Manager for the San Mateo County Parks Department. Hannah has an academic and professional background as a geographer & ecologist. Her work for the Parks Department includes overseeing all habitat enhancement, invasive species control, fuel reduction and forest health projects, mapping, and wildlife monitoring.

What did you see when you visited Pescadero Creek County Park?

So far, the extent of the burned area has mostly been visible from Old Haul Road. CalFire had not yet cleared the area for access due to unsafe conditions. What I saw was that there were differences in the burn intensity in some areas. Where the burn intensity was lower, there is still some understory vegetation and leaf debris visible with some ash and charring of trees and logs. Where the intensity of the burn was higher, most woody debris and leaf litter was fully burned, and there was a prevalent layer of grayish-white ash on the forest floor. There is charring along the tree trunks.

Areas further upslope, near the top of Butano Ridge and to the south burned at a higher intensity than the areas seen from Old Haul Road. Where this was the case, all understory vegetation was consumed, as well as the live canopy foliage. There are many heavily charred trunks and shrubs still standing. It is important to note that throughout the burned area, tree stumps and roots also burned in some areas, causing underground cavities invisible to the eye. There are also many trees that are now unstable and at risk of falling. This presents serious safety hazards for park staff and visitors.

As the smoke cleared, we were was able to get some distant vantage points and saw patches of tree canopy that had browned. Whether that is from a direct burn or from the fire below the canopy being so hot that patches dried off, it is hard to say right now. The trees may still be alive but will likely shed all of the dead browned foliage.

How are redwood trees adapted to fire?

Mature redwood trees have a very thick outer bark that can withstand heat and fire and protect the cambium phloem and xylem structure of the tree. This is the ‘live’ part of the tree where nutrients and water flow through the trunk. The bark of a younger coast redwood tree, younger than 20 years old, may not have developed the same thick bark and may be more susceptible to fire damage. Sometimes, you will see a redwood tree that is hollow and you can walk inside it – this is called a ‘goose pen’. If the inside trunk is burned, it may sustain more internal damage, and that tree could die. If it is just the outer layer that burns, the tree is more likely to withstand fire. Other factors that make  redwood trees more resilient to fire is their height, low number of branches on the lower portions of the trunk, and their ability to re-sprout rapidly. As long as the trunk and roots are alive, the branches and foliage can regrow.

slow moving fire

How do wildfires affect wildlife?

Larger and more mobile animals have a chance to escape and can run or fly away. Smaller animals like banana slugs, salamanders and reptiles will seek out areas of refuge like creek beds, in burrows, under logs or anyplace with some cool moisture. Wildlife have a long relationship with fire built over thousands of years and can escape or find refuge as needed.

Why can fire be good for forests and grasslands?

Fire is a natural process in ecology. It breaks down and recycles leaf litter and allows for soil regeneration. While fires can result in a loss of the soil organic layer and loss of soil microbes, the ash can increase the carbon and nitrogen in the soils, which are basic nutrients required by plants.

Certain plant species have adapted to and benefit from fire. Seeds for certain species will germinate more readily after fire stimulating the plant’s growth.

Fire can create openings in the tree canopy which allows for more light and precipitation to reach the forest floor. This creates the opportunity for larger, more mature trees to grow, expand and access more nutrients. With more space to grow in width and height, they can strive for old growth status.

What comes next?

After the fire is completely suppressed, efforts will shift to making sure the parks are ready for winter. Our initial concern is that once it rains, we’ll see erosion and soil loss. This could happen where the burn was more extensive and in areas where fire suppression activity resulted in some soil disturbance. Preventing erosion is our top priority now. Parks staff and CalFire will be working together to make sure that we are ready for rainfall, and that all drainages will be functioning, and erosion concerns can be addressed. In addition, Pescadero Creek County Park will remain closed for some time, while Parks staff work to ensure that safety hazards, such as falling trees, are addressed.

banana slug

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