2020 And 2021 CA Megafires Essentially Wiped Out Reproduction In Hardest-Hit Giant Sequoia Groves

[hatrack]

Last edited Fri Jul 26, 2024, 08:51 AM - Edit history (2)

Giant sequoia groves in California’s Sequoia and Kings Canyon National Parks that were extensively burned in the megafires of 2020 and 2021 produced numbers of seedlings that were so “drastically low” in some areas that they may not naturally regenerate, according to two new studies by government scientists. One of the studies, by researchers with the U.S. Geological Survey’s Western Ecological Research Center and published in the journal Ecosphere in March, tried to assess the “likelihood of natural recovery” in four Sequoia groves and found that “seedling densities fell far below the average density measured after prescribed fires” that were intentionally set to maintain grove regeneration and health.

In the second study, published last month in Forest Ecology and Management, the researchers developed “seedling reference densities” based on post-fire data from eight groves that burned in 26 different fires in the national parks from 1969 to 2016 to identify areas that might require planting by forest managers. In one “case-study sequoia grove” burned in one of the recent high-severity wildfires, the study found seedling densities that were “significantly (and dramatically) lower” than historic norms, “suggesting inadequate post-fire reproduction.”

The studies found that extreme wildfires have killed up to 20 percent of the world’s mature giant sequoias since 2015, with a majority of the trees dying in three wildfires in 2020 and 2021. The sequoias are the largest trees in the world and among the oldest, and only grow on the western slopes of the Sierra Nevada in California, according to the National Park Service.

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Under the constant threat of wildfires, the giant sequoia tree evolved to be more resilient to wildfire by growing thick bark that protects their trunks from flames and branches that rise far above fires burning on the ground, as well as using fires to reproduce. Yet, their adaptations are not enough anymore. “Recent fires have killed thousands of mature trees and, in some cases, their seeds too,” said Nathan Stephenson, lead author of the June study and a Ph.D. scientist emeritus at the USGS western research center. “What we used to call high-severity fire does not compare to the unprecedented scale and severity of the wildfires we’ve experienced in recent years in the Sierra Nevada.”

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https://insideclimatenews.org/news/23072024/california-sequoia-groves-impacted-by-wildfires/

[hunter]

1. Maybe we ought to establish these trees in places where they will fare better as the planet warms.

Do we have an ethical obligation to protect species our human carelessness and avarice has threatened?

I think we do.

[hatrack]

2. Species with a severely limited range, I'm afaid . . .

Maybe upslope from current locations for starters, but the sequoia is something of a relict. Not that it isn't worth trying.

[PufPuf23]

3. There was an article posted in several DU forums about the Giant Sequoia planted in the UK.

Said there were more living Giant Sequoia in the UK than left in the natural range on the west slope of the California's Sierra Nevada.

Could be true.

[PufPuf23]

4. Giant Sequoia cones take 2 years to develop with fertilization taking place the 2nd year.

There are male and female (the cone) "flowers". The cones with seed can be retained for years in the crown with some seeds being released each in a declining amount from the initial year ripe. The older seeds also decline over time in germination viability. In general, Giant Sequoia have lower seed viability than most conifers. In general, conifers produce cone in one or two (Giant Sequoia) years to maturity. Heavy seed years for conifers differ in cycles and are subject to climate and other external environmental conditions. If viable seeds were dropped in significant numbers, the mineral soil exposed by fire is where they would successfully germinate and persist.

Giant Sequoias persist because of resistance to fire once mature (thick bark, clean boles). Historically, the prevention of more frequent and lower intensity fires, resulted in understories of white fir and other species that provided fuel ladders, more fuel, and drought stress for the Giant Sequoia. Effort occurred in past 40 years at re-introducing fire in some Giant Sequoia stands.

Climate change causes havoc in California's forests, more so in the Giant Sequoia as the Sequoia is a remnant species from a distant pass living in what is now a highly stressful environment. I am not surprised by the results of the research. The lack of seedlings could be exacerbated by the time of the fires with the heavy cone crop cycle and fire-drought-smoke complex.