Giant sequoia are the largest trees on the planet, and the only place they occur naturally is the Sierra Nevada. Decades of prescribed burning and careful management in Sequoia and Kings Canyon National Park have helped create sunny, open forest conditions that allow giant sequoia seedlings to establish in mineral-rich soils exposed by fire. These prescribed burns reduce fuel loads and help create conditions necessary to encourage giant sequoia reproduction. 

However, climate change poses many questions about how to encourage the persistence of this species. Though shade-intolerant giant sequoia depend on fire to clear out other plant competition, they also require a substantial amount of water -- a single mature giant sequoia may use several hundred gallons of water every day in the summer (USFS 2016). Thus, drought and snowpack decline in the Sierra Nevada are expected to create management challenges for giant sequoia in coming decades; drought makes these trees more vulnerable to beetle attacks, and may also influence when, where, and how often prescribed burns are conducted. 

Giant sequoia refugia modeling and mapping can predict where sequoia groves will be more or less sensitive to hot droughts in the future (potentially due to hydrological characteristics), which can inform prescribed burns and other management action. A refugia approach may also help assess whether current sequoia refugia areas will remain refugia under longer, hotter droughts, and may identify areas where sequoia could be encouraged to migrate. 

Focal Resources identified at November 8, 2019 workshop:

• Giant Sequoia (Sequoiadendron giganteum)

Potential Management Actions:

• In “less refugial” areas, do more extensive fuels reduction and minimize fire residence time

• Model and map to figure out where prescribed fires should be conducted and at what frequency (i.e., should prescribed fires happen more or less often in refugial vs. non-refugial areas?)

• Experimental planting of sequoia in areas identified as refugia

• Facilitate natural regeneration of sequoia in areas identified as refugia (i.e. use fire to get down to bare mineral soil)

• Increase tree species diversity in sites more vulnerable to drought/beetles (to confuse beetles)

Data Gaps/Future Work:

• Learn from sequoias that have been planted outside of their range over the past 100 years -- what are their climate characteristics? 

Current efforts, data, and partnerships that could support identification and mapping of refugia for Giant Sequoia: 

• Research and partnerships at Sequoia and Kings Canyon and Yosemite National Parks

  • Leaf to Landscape Project: investigating giant sequoia response to 2012-2016 drought

• Nate Stephenson data

References

USFS. 2016. Giant Sequoia Trees Face “Drying” Times. Accessed on 4/10/2020 at: https://www.fs.usda.gov/features/giant-sequoia-trees-face-drying-times