Giant sequoias, long viewed as majestic, impervious guardians of the high Sierra, are beginning to struggle with the multi-year stretches of drought, according to research conducted in Sequoia and Kings Canyon national parks and elsewhere in the Sierra.
The iconic trees, which only grow in some 70 groves scattered over an area of about 55 square miles on the western slopes of California’s Sierra Nevada mountains, were spared the widespread tree mortality that recently occurred in California forests, claiming 102 million trees over a period coinciding with the state’s 2011-2015 drought. But recent field studies found that the sequoias are showing signs of stress, suggesting even these normally resilient trees are becoming increasingly vulnerable to multi-year droughts, which are projected to continue increasing in severity because of climate change.
The research was conducted by teams from the Sierra Nevada Research Institute (SNRI) at UC Merced, the National Park Service, the Chinese Academy of Sciences, and Sun Yat-sen University.
“Giant sequoias have this mystique, that once they reach maturity, they are practically immune to the forces that kill other trees,” said Koren Nydick, study coauthor and science coordinator and ecologist at Sequoia and Kings Canyon National Parks. “But during and just after the recent severe drought, we've seen a small number of sequoias die, at least in part due to the dry conditions. It's an important wake-up call.”
Using data from Landsat, an Earth-observing satellite fleet jointly managed by the U.S. Geological Survey and NASA, researchers evaluated greenness and wetness in sequoia groves and adjacent forests. The analysis did not tease out the effects on just the sequoia trees, but instead presents a picture of changing conditions for the suite of tree species in the groves.
The results indicate that groves experienced a 6 percent increase in greenness from 1985 to 2015. Enhanced greenness could indicate higher forest biomass, which likely led to a 10 percent increase in water usage during the same period.
In the past, increased biomass and water usage like this wouldn’t have raised any red flags. During multi-year droughts, when local precipitation falls short of the amount needed to sustain sequoia groves, the trees could tap into supplies of stored subsurface water. But with droughts projected to be more severe, and increasing forest biomass potentially placing ever higher demands on limited supplies of stored water, these water caches are being depleted without being replenished, limiting the length of time sequoia groves can survive during future dry spells.
But the study shows that not all sequoia groves are equally vulnerable. Lower-elevation groves that lie below the rain-snow transition zone experienced the greatest increase in greenness over the past three decades, potentially making them more vulnerable to droughts than higher-elevation groves, which have access to water stored in seasonal snowpack in addition to stored groundwater. The study also shows that grove areas that benefit from water drainage from the surrounding hillslopes are less vulnerable than groves upslope or on ridges.
Researchers also found that sequoia grove wetness — an indicator of forest health — dropped during the 2011-2015 drought to five times below the normal level of variability seen during the 1985-2010 pre-drought period, a 50 percent greater decrease in wetness than that observed in surrounding forests during the same drought.
“This work is telling us that during the drought, loss of moisture in sequoia groves was quite severe, but this change was not uniform across the groves,” Nydick explained. “That is to say, not all grove areas are the same. Some places are more vulnerable to droughts than others.”
Up to now, giant sequoia groves have proven themselves resilient refuges, areas where trees can survive in the face of prolonged drought and rising temperatures. But the study’s authors worry that this will change unless policy makers and forest managers take action.
“These changes suggest that while giant sequoia groves currently serve as ‘hydrologic’ refugia within the larger mixed-conifer forest, their refugial properties may be eroding,” said UC Merced Professor Roger Bales, study coauthor and SNRI director. “Reducing the density of competing smaller trees through appropriate forest management (e.g., forest treatment) may help to preserve their refugial properties.”
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Comments
I'm sure Zinke and drumpf will soon label these studies as "Baloney." Yet not a word from the Groper In Chief or his DOI secretary about the 210,000 gallon oil leak discovered yesterday.
Disgusting.
At the risk of crazy thinking, I wonder if "reducing the density of competing smaller trees..." would be construed as an open invitation to permit commercial logging within the national parks not only to "reduce the density" of those smaller trees, but of the stressed sequoias as well. You know - to give those other sequoia groves a chance. I wouldn't be the least bit shocked if this occurred ... saddened and angry, yes, but not shocked. Maybe I should delete this comment so as not to give Zinke any ideas??
There needs to be more controlled burns to reduce the burden of all the little white firs and others growing up in the shade of the giant Sequoias. They compete for water and compete with baby Sequoias. The natural history of the groves is light wildfires every 10 to 20 years which makes more liveable for the Sequoias by reducing this competition.
Come on people, you all don't really believe this crap? Those trees have seen drought and fire many times over hundreds and thousands of years. The climate has been and will change for thousands of years.This crap is all designed to steal Americas wealth and control the poppulation. Every prediction that has been made has been false. All research has been proven to be a fraud.
And every person who speaks to you only in broad generalities is full of bovine fertilizer and is always wrong. Sheesh. Real life is in the shades of grey, Jay.
No, there is no persecution of scientists that come to the "wrong" conclusion.
https://www.nature.com/articles/d41586-017-08236-y
EC--
Note that the persecution is being done by (Argentinian) politicians. It is _scientists_ who are defending Villalba for doing the right thing, respecting the limitations of the data & instrumentation he had.
Also, the 1km^2 minimum mapping unit for satellite data on glaciers that didn't pick up the smaller glaciers or icefields in Argentina also wouldn't pick up the Lyell glacier (demoted to icefield) in Yosemite by Donohue Pass, the last glacier there. Remnants that small require higher-resolution imagery & stakes in the ground.
Did you see the report this morning that the drumpf administration has handed scientists working at the Center for Disease Control a list of 7 words and phrases that are banned from use in any official communications from the CDC?
The forbidden words are “vulnerable,” “entitlement,” “diversity,” “transgender,” “fetus,” “evidence-based” and “science-based.”
Be careful, you nasty scientists, or we'll wash your mouth out with soap.
Lee--
I don't know if Kurt is going to do a news article on it, but Zinke ordered the superintendent of Joshua Tree National Park to fly to DC so Zinke could dress him down in person for allowing that park's twitter account to post a series of tweets about climate change. http://thehill.com/policy/energy-environment/364994-zinke-reprimanded-pa...
The park's twitter feed is https://twitter.com/JoshuaTreeNPS the tweets in question were on Nov 8, immediately preceeded by tweets on ancient soil levels and followed a couple of days later by multiple tweets on meteorites. The science behind the tweets is pretty uncontroversial: climate change projections have night tempertures warming substantially in Joshua Tree NP under all CO2 scenarios. When increased night time respiration exceeds daytime net photosynthesis, joshua trees can't grow and regenerate, and that is predicted to happen in most of the areas where they are in the park now. There also aren't cooler higher elevations for the joshua trees to recruit into. [I can provide links to the scientific peer reviewed papers behind those statements, here's one to start with: https://scholar.google.com/scholar?cluster=4621715100461437278&hl=en&as_... ] The series of tweets also mentions creosote and an iguana as species that will increase their ranges: not just doom & gloom. They also explicitly call out uncertainty in the estimates and models, and mention natural drivers contributingto climate change. And, the series is not an anomaly: look at the other series of tweets on astronomy, meteorites, migatory monarch butterflies, etc.
I don't know that superintendent, but he's a GS-14 or 15, not SES, so at least on paper he has substantial civil service protection. I'm trying to remember the exact words Zinke used last summer in his press event at Grand Canyon about his management style supporting front line field folks out in parks, and not tolerating bullying. Having to drop everything to fly to DC, and quite likely having to take that hit against the park's travel ceiling (back country rangers out overnight in a park are on travel), sure looks like bullying when they don't have sufficient grounds to have those tweets taken down. Note that the spokesperson for DOI said the report was all misinformation, but didn't deny that the superintendent was summoned to DC (the travel records & summons are very likely FOIA-able), and didn't specify what was wrong.
[There was a morbid discussion 6 or 7 years ago about joshua trees disppearing from Joshua Tree National Park, saguaros disappearing from Saguaro NP, organ pipe disappearing from Organ Pipe Cactus National Monument. Coastal redwoods should persist in Redwoods State & National Park (unless sea surface temperature warms enough to cut back on fog), many groves of sequoias should be fine in Sequoia National Park, and the fate of cypress are too hard to predict in Big Cypress National Preserve. Still, not great odds for namesake plant species.]
I saw the headline about that last night, tomp2, and shuddered at the echoes of 1984.
Thank you, Tomp. You just cleared up something that has had me wondering about a comment made by a ranger when I was in Joshua Tree just a week and a half ago. We were talking about climate change and the future of Joshua Trees (I had earlier read an article somewhere about concerns) and he mentioned that their superintendent had gotten into some trouble because of a park posting on the subject. I asked for details, but he was reluctant to go any further. He just advised me to "watch for news in the fake media." He added air quotes around the words fake media as he said it.
I bet this is what he was talking about.