Reposted from UC ANR news
Study finds resilient, frequent-fire forests have...
Posted on
Thursday, January 20, 2022 at
2:36 PM
Focus Area Tags: Environment
Community ecologist and UC Davis doctoral alumnus Ash Zemenick, the newly selected...
Ecologist Ash Zemenick, shown here with pal Cosmo, is the newly selected manager of the Sagehen Creek Field Station, headquartered in Truckee, Sierra Nevada mountain range. (Photo by Marshall McNunn)
Ecologist Ash Zemenick, shown here with pal Cosmo, is the newly selected manager of the Sagehen Creek Field Station, headquartered in Truckee, Sierra Nevada mountain range. (Photo by Marshall McNunn)
Ash Zemenick with a tenebrionid beetle found on Mt. Lemmon near Tucson, Ariz. (Photo by Alex Webster)
Ash Zemenick with a tenebrionid beetle found on Mt. Lemmon near Tucson, Ariz. (Photo by Alex Webster)
Posted on
Wednesday, July 14, 2021 at
11:32 AM
Focus Area Tags: Environment, Innovation, Natural Resources
Reposted from UC Davis News
Sierra Nevada forests are losing plant diversity due to high-severity fires, according to a study from the University of California, Davis. These fires are turning patches of forest into shrub fields — indefinitely, in some cases.
For the study, published in the journal Ecosphere, scientists analyzed plant diversity across a spectrum of fire severity — from low to moderate to high. They found the sweet spot for plant diversity exists where tree stands burned with low-to-moderate severity, as mixed conifer forests did in this region for millennia before the imposition of fire suppression policies in the early 20th century. Such policies have greatly increased forest density and the amount of woody fuels in many California forests and led to more severe, stand-replacing fires.
On the extreme ends of the spectrum, unburned areas and high-severity burn areas showed relatively low plant diversity. Five to 10 years or more after experiencing high-severity burns, many forest stands were replaced by shrub fields that supported few plant species.
UC Davis' Clark Richter investigates plant diversity within a transect line of a Sierra Nevada forest affected by drought and wildfire. (Clark Richter/UC Davis)
'A different kind of fire'
The results suggest these forests, which are used to living with and even benefiting from fire, have not yet adapted to this newer regime of intense, high-severity fires.
“This system is experiencing a different kind of fire,” said lead author Clark Richter, a doctoral candidate at UC Davis. “The species are outside of their limits. More high-severity fires greatly change a diverse and highly varied forest to one where all the trees are dead and what's left is often just a few species of shrub, not the herbs and wildflowers you may be used to seeing.”
The researchers examined post-fire plant response in eight areas of yellow pine and mixed conifer forests that burned in California's Sierra Nevada between 2001 and 2012. These areas have experienced among the biggest increases in wildfire size and severity over the past 30 years in the continental United States. The areas stretched from the site of the Moonlight Fire (2007) in Lassen County southward to the Power Fire (2004) in Amador County.
Climate, current trends call for multi-pronged approach
The study states that under climate change and current fire trends, “there is a real possibility that large portions of the Sierra Nevada landscape could be caught in a feedback-loop” that prevents recovery of former forest.
“We will need enhanced management tools and resources to help forests adapt if we want to preserve plant diversity for soil, animal and ecosystem health,” Richter said.
The paper suggests a multifaceted management approach that combines forest thinning with a major expansion of prescribed burning and allowing naturally ignited fires to burn under moderate weather conditions.
Additional co-authors include co-leading and senior author Marcel Rejmánek from the UC Davis Department of Evolution and Ecology, Jesse E.D. Miller from Stanford University, Kevin Welch from UC Davis Plant Sciences, JonahMaria Weeks from the UC Davis Department of Environmental Science and Policy, and Hugh Safford from UC Davis and the USDA Forest Service.
The study was funded by the USDA Forest Service Pacific Southwest Region and the Eldorado National Forest.
Media contact(s)
Kat Kerlin, UC Davis News and Media Relations, 530-752-7704, kekerlin@ucdavis.edu
Clark Richter, UC Davis Graduate Group in Ecology, cjrichter@ucdavis.edu
Media Resources
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Posted on
Wednesday, October 2, 2019 at
1:05 PM
Reposted from UC Davis News
Scientists at the University of California, Davis, are taking the temperature — and other measurements — of lakes of all sizes and shapes throughout the mountains of California to see how climate change is affecting them and what, perhaps, can be done about it.
A study published this month in the journal Limnology and Oceanography Letters shows that, despite rapidly warming air temperatures, spring snowpack is the biggest predictor of summer warming in small Sierra Nevada lakes.
The study examined more than 30 years of climate and lake temperature data at Emerald Lake, a long-term study site in Sequoia National Park. It was led by UC Davis with colleagues at UC Santa Barbara and UC Riverside.
Benthic chambers measure sediment metabolism at a small Sierra Nevada lake in August 2018. (E. Suenaga)
High rates of warming air
The researchers found that summer air temperatures at Emerald Lake are warming at a rate of 1.0 degree Celsius, or 1.5 degrees Fahrenheit, per decade.
“That's huge,” said lead author Steven Sadro, a UC Davis assistant professor in the Department of Environmental Science and Policy and a member of the Tahoe Environmental Research Center. “That's as high a rate of warming as nearly anywhere on the planet. It's also consistent with what you'd find in a lot of mountain regions, which are warming at rates as high as those seen in the Arctic, in many cases.”
Yet these small alpine lakes are somewhat buffered from the higher air temperatures because they respond primarily to variation in the snow. The amount of snow controls when the lake becomes free of ice and can absorb radiation from the sun, which heats the water.
“That's not to say that there is no climate warming signal,” said Sadro. “In drought years, when the role of snow is small, we find a warming trend consistent with the rate of warming found in other lakes throughout the world.”
Climate affects phytoplankton, too
A companion study conducted at Emerald Lake and published in June in the journal Water Resources Research found that changes in snowpack also increased the abundance of phytoplankton in Emerald Lake. If droughts continue to be more frequent, high-elevation lakes in the Sierra are expected to become more productive. Researchers are not yet certain how that might affect the lakes. More phytoplankton could mean more food for lake organisms, but it could also impact lake clarity, which is often an indicator of ecosystem health.
Together, the papers show that yes, climate change is impacting these lakes and that its effects are somewhat buffered by snowpack. But what that means for the greater ecology of the area is still unclear.
A current project may provide additional answers.
Adrianne Smits, a NSF postdoctoral fellow at UC Davis, deploys a mooring in a Yosemite lake. (E. Suenaga)
There are upwards of 14,000 small lakes in the Sierra Nevada. This past summer, UC Davis limnologists and colleagues began installing high-frequency instruments in nearly 20 of these lakes, which stretch from Castle Lake in Northern California to Emerald Lake in the southern Sierra.
The project is called the California Mountain Lake Observatory Network, and it's being conducted through Sadro's lab by Adrianne Smits, a National Science Foundation Postdoctoral Fellow at UC Davis.
As weather events occur, be they storm, drought, wildfire or clear skies, the instruments capture data about water temperature, dissolved oxygen, light levels and other factors. Data from these lakes will be used to develop models to help predict how all the other lakes in the Sierra are responding to changes in climate.
“Castle and Emerald lakes are both long-term study sites, and together they provide unique bookends to the entire Sierra Nevada mountain range,” Sadro said. “We're trying to fill in everything in between to better predict how lakes across the Sierra are expected to change.”
This ongoing research could help resource managers identify which lakes are most sensitive to climate impacts and target them for mediation.
The analysis for the two published studies was made possible because of long-term research support for Emerald Lake and the Tokopah watershed since the early 1980s from the National Science Foundation, National Oceanic and Atmospheric Association, National Aeronautics and Space Administration, and the California Air Resource Board.
Co-authors for both studies include John Melack of UC Santa Barbara and James Sickman and Kevin Skeen of UC Riverside.
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Posted on
Wednesday, December 19, 2018 at
2:08 PM
Reposted from UC Merced News
Yosemite Valley in the western Sierra Nevada Mountains.
What if nature were to become a polluter, discharging millions of tons of planet-warming carbon into the atmosphere in much the same way as diesel-fueled trucks or coal-fired power plants?
This nature-as-polluter scenario might seem far-fetched, but it's well on its way to becoming reality, according to a recent study co-authored by UC Merced Professor LeRoy Westerling.
In a paper published recently in Scientific Reports Opens a New Window.— “Potential decline in carbon carrying capacity under projected climate-wildfire interactions in the Sierra Nevada” — Westerling and collaborators from the University of New Mexico and Penn State University used three climate models and data from the Intergovernmental Panel on Climate Change to examine how rising global temperatures and increasingly severe wildfires will affect Sierra Nevada forests.
Their conclusion: Changing conditions will turn today's Sierra Nevada forests into tomorrow's greenhouse gas emitters.
“Forests play an important part in regulating the levels of atmospheric carbon,” Westerling explained. “Forests are carbon sinks, essentially giant stockpiles of carbon. Forests are also active carbon consumers. They remove carbon dioxide from the air and convert it into biomass. This traps the carbon, which is no longer free to act as a greenhouse gas in Earth's atmosphere.”
Professor LeRoy Westerling
But projections from Westerling and colleagues suggest that this may change. According to their models, Sierra Nevada forests will experience both a dramatic loss of stored carbon and a substantial decline in their ability to remove CO2 from the atmosphere.
Rising temperatures are creating a warmer, drier Sierra Nevada climate. Westerling previously showed that these changes are leading to dramatic increases in the frequency, size and duration of wildfires. The new study suggests that these same changes will make it harder for forests to regenerate, leading to a loss of forest density, with plants better suited to the new climate eventually replacing trees.
“As trees are displaced, the Sierra Nevada will lose its ability to sequester carbon,” Westerling explained. “The plants that spring up in their place will be significantly smaller, making them less effective carbon sinks than the trees they replaced.”
But the carbon stored in forest trees has to go somewhere.
As trees are burned in more frequent wildfires, and as dead trees undergo decomposition, Westerling and his colleagues predict that as much as 73 percent of the carbon in Sierra Nevada forests will be released, resulting in a dramatic spike in atmospheric carbon. This will transform the Sierra Nevada from a carbon sink into a carbon emitter, making the nature-as-polluter scenario a reality.
Westerling and his collaborators note that their predictions are actually conservative. The effects might be more extreme than their models suggest.
“Our study does not account for a number of factors that might influence the dynamics of forest carbon,” Westerling said. “However, the factors we ignored are likely to accelerate the loss of forest. Our predictions likely underestimate the severity of actual effects.”
Though the predictions are alarming, the authors remain optimistic, hopeful that their findings can contribute to a larger conversation about environmental policy and promote avenues of research that lead to sustainable forest management.
Posted on
Thursday, June 15, 2017 at
2:56 PM
- Author:
Jason Alvarez. University Communications