6 minute read

Resilience After the Flames

By: Josie Lesage, Ph.D., Applied Ecologist

In Southern California, where wildfires are a natural part of our ecosystem, many native plants have adaptations that allow them to recover after a burn without human intervention. But this may be changing as climate change, increased urban development, and the spread of invasive species lead to more frequent wildfires. As a result, humans may need to step in more often to help landscapes recover after fire. At Santa Barbara Botanic Garden, we’re working to better understand exactly where, how, and when to intervene in post-fire landscapes to make the greatest impact.

Fire is a major evolutionary force in our local habitats, and many of our local species are well adapted to the historical fire regime. A fire regime describes the seasonality, frequency, size, intensity, severity, and type of fire. These factors are important to consider when understanding fires, especially because different habitats have historically had different regimes. For example, in many shrubdominated chaparral habitats, infrequent but intense canopy fires are thought to be more common, while in oak woodland systems, low-intensity litter fires would be considered the norm. Following a typical high-intensity summer crown fire in chaparral, the landscape is left looking like a moonscape, but that same fire also stimulates the seed bank and promotes resprouting of native species.

In Southern California shrublands, wildflowers proliferate after fire while native shrubs recover by resprouting or germinating from the soil seed bank. As climate change, increased development, and the spread of invasive species lead to more frequent wildfires, we need to step in more often to help landscapes recover and maintain the benefits nature provides.

However, fire regimes are changing as more humans move into the wildland-urban interface, as invasive species spread into new areas, and as our climate changes. The fire return interval, or period between fires, has historically been between 30 to 100 years for chaparral ecosystems. However, with fires occurring more often, intervals shortening, and fire season extending on both ends — stretching into the earlier summer and later fall/winter — seed banks and resprouting are pushed to their limits. In systems where the fire regime has been radically changed, or where unadapted invasive species dominate, it may take a landscape much longer to recover, or it may never return to its original state.

Over 900 native plants of 18 species were planted to restore post-fire habitat above Lake Piru.

In restored versus unrestored plots, we’ll compare habitat quality, carbon sequestration, and soil nutrients over the next two years.

We’re recovering former shrubland above Lake Piru that has been converted to invasive annual grasses and mustards.

Each plot is hand watered and monitored for survival.

How the Garden (and You) Can Help Our Landscapes Recover

With limited resources and funding, prioritizing where and when to intervene after fire is critical. At the Garden, we’re working to help fill gaps in our understanding by researching where the landscape needs help recovering, developing appropriate and effective techniques to help plants and habitats recover, working to measure the value of restoration after fire, and removing invasive plants that have established and are outcompeting natives after fires. Garden Conservation Symposium, we honored trailblazing scientist Carla D’Antonio, Ph.D., whose research on the California fire cycle has been critical in helping us understand how our local habitats respond to this natural but increasing disturbance. As she explained in her talk “When and Why Would We Need Post-fire Restoration?,” rising fire frequency and increasing drought could be pushing our ecosystems away from native, shrub-dominated landscapes and, terrifyingly, toward easily ignited grasses that can spread fire rapidly, as happened in the Marshall Fire, which destroyed over 500 structures near Boulder, Colorado, in December 2021.

At our recent ninth annual Santa Barbara Botanic Garden Conservation Symposium, we honored trailblazing scientist Carla D’Antonio, Ph.D., whose research on the California fire cycle has been critical in helping us understand how our local habitats respond to this natural but increasing disturbance. As she explained in her talk “When and Why Would We Need Post-fire Restoration?,” rising fire frequency and increasing drought could be pushing our ecosystems away from native, shrub-dominated landscapes and, terrifyingly, toward easily ignited grasses that can spread fire rapidly, as happened in the Marshall Fire, which destroyed over 500 structures near Boulder, Colorado, in December 2021.

After a fire, the first step to understanding how the landscape is recovering is to survey it. Over the past five years, the Garden has led several post-fire surveys with the help of our local community. In the scars left by the Zaca, Jesusita, Thomas, and Whittier fires, we’ve surveyed for rare plants, invasive plants, and signs of erosion. These surveys occurred on horseback, by four-wheel-drive trucks, and by the power of our own legs as we hiked along our local trails. But we couldn’t cover all that mileage alone; we’ve had a lot of help from the Santa Barbara community. Over 110 people have helped us map these post-fire landscapes over the past five years.

After conducting post-fire surveys, we use the data to predict and prioritize where restoration efforts would be most helpful, only intervening to replant natives and remove harmful invasive species where our projects are most likely to succeed. For example, along East Camino Cielo in the Jesusita Fire scar, we used our post-fire survey information to prioritize the removal of an invasive species that has started to choke out native plants: Spanish broom (Spartium junceum). With our partners, we’re working to remove over 15 acres (6 hectares) of this noxious weed and to return the native chaparral community that is found in that area. We are collecting native seed to spread in the areas where Spanish broom was removed, regenerating the native plant habitat that local animals rely on for food and shelter.

With our partners, we’re restoring more than 15 acres (6 hectares) above East Camino Cielo Road that is invaded by Spanish broom. Spanish broom increases the intensity of fires, changes soil chemistry, and is unpalatable to wildlife.

Spanish broom increases the intensity of fires, changes soil chemistry, and is unpalatable to wildlife.

The Garden is also helping post-fire landscapes recover by replanting native plants. At Lake Piru in Ventura County, we are collaborating on a post-fire restoration effort with researchers at University of California, Davis, and the U.S. Forest Service. This winter, we planted over 900 plants, representing 18 native, site-appropriate shrub and perennial grass species, covering an area of over 3,000 square feet (278 square meters). Together with our partners, we’ll monitor these plots over the next two years to compare how habitat quality, carbon sequestration, and soil nutrients are affected by restoration actions.

Overall, we’re working hard at the Garden to help maintain native plants on our local landscapes after fire and improve the methods we can use to do that, so that our landscapes continue to be resilient to fire. If you’re interested in helping, keep an eye out for opportunities to collect and seed native seed or survey in fire scars, or join us for weed removal and native species planting days. O

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