{"id":105803,"date":"2024-08-19T16:58:10","date_gmt":"2024-08-19T23:58:10","guid":{"rendered":"https:\/\/www.savetheredwoods.org\/?p=105803"},"modified":"2024-12-23T10:56:08","modified_gmt":"2024-12-23T18:56:08","slug":"can-the-giant-sequoias-recover-on-their-own","status":"publish","type":"post","link":"https:\/\/www.savetheredwoods.org\/redwoods-magazine\/autumn-winter-2024\/can-the-giant-sequoias-recover-on-their-own\/","title":{"rendered":"Can the giant sequoias recover on their own?"},"content":{"rendered":"
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A USDA Forest Service field team, in partnership with the National Park Service, assesses areas of Redwood Mountain Grove in which most trees died from direct fire effects. Recent wildfires have killed an estimated 20 percent of mature giant sequoias. Photo by Cole Diemer, USGS.<\/figcaption><\/figure>\n

In August of 2020, the Castle Fire swept through the Board Camp Grove, a small, remote stand of giant sequoias at the southern end of Kings Canyon National Park. The fire burned through the crowns of many trees and left a charred landscape in its wake. Nearly every sequoia died. Four years later, few seedlings have sprouted to renew the grove.<\/p>\n

Two new comprehensive research studies published by the USGS Western Ecological Research Center discuss the drastically low number of seedlings found in sequoia groves in the wake of recent mega-fires. Their findings: inadequate natural seedling recovery and high tree mortality rates create a substantial risk of losing portions of sequoia groves.<\/p>\n

This research is helping members of the Giant Sequoia Lands Coalition<\/a>, including Save the Redwoods League, to better understand how giant sequoias regenerate in the wake of extreme fires\u2014and what type of management actions to take in response.<\/p>\n

Sequoias unprepared for modern mega-fires<\/strong><\/h3>\n
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After more than a century of fire suppression, flammable materials have built up in sequoia groves, fueling mega-fires that can incinerate seed cones. Photo by Ben Blom.<\/figcaption><\/figure>\n

Historically, giant sequoia groves experienced frequent wildfires that burned mostly at low to moderate intensity. The species adapted to not only survive these fires, but to use fire to their advantage.<\/p>\n

\u201cGiant sequoias are a pioneer species; they colonize after a disturbance using lots and lots of tiny seeds,\u201d says Nate Stephenson, scientist emeritus at USGS Western Ecological Research Center.<\/p>\n

Heat from the fire coaxes open giant sequoia cones, which rain thousands of seeds onto the forest floor. These seedlings sprout in \u201chot spots\u201d\u2014patches of bare, fluffy soil where all the vegetation and litter on the forest floor has burned away. While only a small fraction of the sequoia seedling ultimately survive, it\u2019s enough to ensure the continuance of the grove.<\/p>\n

But thanks to a century-long policy of fire suppression, \u201cthe majority of giant sequoia groves haven\u2019t seen fire in a long time,\u201d says David Soderberg, ecologist at USGS Western Ecological Research Center. \u201cThere\u2019s so much fuel built up on the ground that when fires hit, they have these drastic effects.\u201d<\/p>\n

“The parent trees are gone”<\/strong><\/h3>\n
\"A
Nate Stephenson, USGS scientist emeritus, stands below a cluster of dead ‘monarch’ giant sequoia in Redwood Mountain Grove, Kings Canyon National Park. The sequoias, each likely over 1,000 years old, were killed by the 2021 KNP Complex fire. Photo by David Soderberg, USGS.<\/figcaption><\/figure>\n

In one of the studies, researchers analyzed data from sampling plots in giant sequoia groves that had been treated with prescribed fires. These mimic the moderate intensity fires that the groves experienced for millennia.<\/p>\n

Average seedling densities were calculated one, two, and five years following the prescribed burns. The results followed a pattern typical to groves that burn naturally: A burst of germination immediately after the fire, followed by much lower rates of sprouting in subsequent years.<\/p>\n

However, Board Camp Grove and three other groves that burned at high intensity in 2020 and 2021 told a vastly different story.<\/p>\n

\u201cIn areas where most or all giant sequoia were killed, the parent trees are gone,\u201d Stephenson explains. \u201cYou have these large areas where you\u2019ve lost the seed source and lost parent trees that could offer seed in the future.\u201d<\/p>\n

When giant sequoia crowns scorch rather than burn, they can still contribute seeds. But when the entire crown burns, the cones are incinerated, either on the tree or on the ground after they drop. Researchers found that groves that burned at the highest intensity suffered the greatest mortality. Far fewer seedlings sprouted and survived in the wake of these fires compared to the prescribed burn plots.<\/p>\n

Drought and warming temperatures could be making the situation worse, says Soderberg.<\/p>\n

\u201cWe\u2019re having some of the hottest and driest summers that we\u2019ve seen in recent history,\u201d says Soderberg. \u201cAre enough seeds falling, but the conditions are too hot and too dry for regeneration to be what\u2019s been seen in the past?\u201d<\/p>\n

Prescribed burns key to sequoia survival<\/strong><\/h3>\n
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A crew member puts fire on the ground during prescribed fire operations at Calaveras Big Trees State Park. Such low- to moderate-intensity fires help remove excess vegetation and clear the ground for sequoia seedlings. Photo by Linnea Hardlund.<\/figcaption><\/figure>\n

Researchers also found that devastation from extreme wildfires was not spread equally. In general, areas fared better in the high-intensity fires if they had recently experienced lower intensity fires, whether prescribed or natural.<\/p>\n

For example, when the KNP Complex Fire entered an untreated portion of the Redwood Mountain Grove from the south, it burned hot through the canopy, killing many mature giant sequoias. By comparison, when the fire encountered forest that had been treated with prescribed fire, it dropped to the ground and crawled underneath the trees. Most giant sequoias in this part of the grove survived.<\/p>\n

\u201cIt was a good example of the value of reintroducing fire to giant sequoia groves to prepare them for these kinds of wildfires,\u201d says Stephenson. \u201cIf they\u2019ve had prescribed fire within last 15 years or so, they\u2019re going to do really well during a high-severity wildfire.\u201d<\/p>\n

Research helps stewards make science-informed decisions<\/strong><\/h3>\n
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Planting seedling in severely burned portions of Alder Grove. New research will help sequoia stewards prioritize which severely burned groves to replant and which unburned groves to restore for greater fire resilience. Photo by Smith Robinson Multimedia.<\/figcaption><\/figure>\n

In the last two years, the Giant Sequoia Lands Coalition has treated more than 14,000 acres with thinning and prescribed fire and planted more than 542,000 native trees in burned areas, including the Board Camp Grove.<\/p>\n

Unfortunately, many giant sequoia groves remain at risk, including some in remote wilderness areas.<\/p>\n

Findings from the USGS will help coalition partners to prioritize unburned groves for restoration work and burned groves for planting nursery-grown seedlings.<\/p>\n

\u201cA lot of the data we\u2019re collecting now will be used to assess risk for groves that we haven\u2019t surveyed yet and that haven\u2019t seen wildfire in a long time,\u201d says Soderberg. \u201cWhat we\u2019re trying to do is give managers what they need to make science-informed and risk-informed decisions.\u201d<\/p>\n

By looking at how sequoia mortality and regeneration are impacted by fire severity, as well as by vegetation density, elevation, and other factors, researchers can forecast which other groves might be most vulnerable. They will \u201cground truth\u201d their forecasts by physically visiting these groves.<\/p>\n

This new research will help sequoia advocates and grove managers to give these magnificent trees the best chance to thrive in a changing climate.<\/p>\n

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This feature appears in the beautiful printed edition of Redwoods<\/em> magazine, a showcase of redwoods conservation stories by leading scientists and writers, as well as breathtaking photos, and ways you can help the forest. Only a selection of these stories are available online.<\/p>\n

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