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Faculty Giving

Faculty Giving

My wife Tanya Williams and I are happy to be able to provide a planned gift to the School of Biological Sciences at the University of Utah. We moved to Utah in 2010 to establish my Biodiversity and Conservation Ecology laboratory. I am thankful for the research, teaching and service opportunities provided to me by the University of Utah and Tanya is grateful to be able to serve her patients at the U’s School of Medicine.

Our work has benefited greatly from the generosity, resources and collegiality provided to us by the U, its faculty, alumni and other benefactors. This support has enabled me to study, conserve and teach about the world’s endangered, biodiversity and helped Tanya to provide healthcare to the underserved people of this beautiful state.

We hope to “pay it forward” by providing a modest legacy gift for SBS. Planned gifts of this kind will help SBS continue to attract and support the best PhD students in biodiversity research, conservation biology, environmental science, ornithology and wildlife ecology during this time of rapid and devastating global change that requires all hands on deck.

We hope you will join us in making a legacy gift to the School of Biological Sciences.

Çağan H. Şekercioğlu, PhD and Tanya M. Williams, MD


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Interactive Forest Maps

Wildfire, Drought & Insects

Dying forests in the western U.S.

Threats impacting forests are increasing nationwide.

Planting a tree seems like a generally good thing to do for the environment. Trees, after all, take in carbon dioxide, offsetting some of the emissions that contribute to climate change.

But all of that carbon in trees and forests worldwide could be thrown back into the atmosphere again if the trees burn up in a forest fire. Trees also stop scrubbing carbon dioxide from the air if they die due to drought or insect damage.

The likelihood of those threats impacting forests is increasing nationwide, according to new research in Ecology Letters, making relying on forests to soak up carbon emissions a much riskier prospect.

“U.S. forests could look dramatically different by the end of the century,” says William Anderegg, study lead author and associate professor in the University of Utah School of Biological Sciences. “More severe and frequent fires and disturbances have huge impacts on our landscapes. We are likely to lose forests from some areas in the Western U.S. due to these disturbances, but much of this depends on how quickly we tackle climate change.”


William Anderegg

"We’ve seen devastating fire seasons with increasing severity in the past several years. Generally, we expect the western U.S. to be hit hardest."


The researchers modeled the risk of tree death from fire, climate stress (heat and/or drought) and insect damage for forests throughout the United States, projecting how those risks might increase over the course of the 21st century.

See their findings in an interactive map at

By 2099, the models found, that United States forest fire risks may increase by between four and 14 times, depending on different carbon emissions scenarios. The risks of climate stress-related tree death and insect mortality may roughly double over the same time.

But in those same models, human actions to tackle climate change mattered enormously—reducing the severity of climate change dramatically reduced the fire, drought and insect-driven forest die-off.

“Climate change is going to supercharge these three big disturbances in the U.S.,” Anderegg says. “We’ve seen devastating fire seasons with increasing severity in the past several years. Generally, we expect the western U.S. to be hit hardest by all three of these. And they’re somewhat interconnected too. Really hot and dry years, driven by climate change, tend to drive lots of fires, climate-driven tree mortality and insect outbreaks. But we have an opportunity here too. Addressing climate change quickly can help keep our forests and landscapes healthy.”

The study is published in Ecology Letters and was supported by the National Science Foundation, U.S. Department of Agriculture, David and Lucille Packard Foundation and Microsoft’s AI for Earth.

Find the full study at Ecology Letters.


by Paul Gabrielsen, first published at @TheU.


Randy Rasmussen

Randy Rasmussen

Randy Rasmussen & Denise Dearing

BioFire Diagnostics began when three college friends came together on the University of Utah campus to collaborate and build a transformative company.

Many of today’s most successful companies were created by groups of friends: Bill Hewlett and Dave Packard started Hewlett-Packard in a garage in Palo Alto, California; Bill Gates and Paul Allen, childhood friends from Lakewood, Washington co-founded Microsoft; and Larry Page, Sergey Brin, part of the same PhD cohort at Stanford University founded Google.

The University of Utah has its own version of this story: BioFire Diagnostics began with a group of three college friends who came together on the University of Utah campus to collaborate and build a transformative company.

The precursor to BioFire Diagnostics, Idaho Technology, Inc., was founded in 1991 by three U alumni: Carl Wittwer (Residency, ’88, Pathology), Kirk Ririe, BS’05, Chemistry, and Randy Rasmussen, PhD’98, Biology. Their unique backgrounds and experience perfectly complemented one another—Ririe was a chemist and engineer, Randy with a molecular and cellular biology background, and Wittwer a medical professional.

BioFire started small, with the trio working on prototypes of PCR machines which included hair dryers taped to fluorescent tubes. But the they set their sights higher to lead the molecular diagnostic industry, and BioFire’s product development has since evolved to include sophisticated diagnostic tools including Film Array®, a proprietary molecular diagnostics system that uses PCR and melt-curve analysis and simultaneously tests for multiple infectious agents in a single panel in the short time of about an hour.

From its humble beginnings in the corner of Ririe’s parent’ business, to their current location in University of Utah Research Park, BioFire has always had a simple, yet tremendously impactful, mission: “To help make the world a healthier place.”

Randy Rasmussen

"I urge students to explore their passion. A degree in the STEM field will open doors to many opportunities."


Due to its great success, BioFire was purchased by BioMerieux in 2013. Under the leadership of Dr. Randy Rasmussen, who currently serves as CEO, the company grew from 250 employees, in 2012, to over 1,400 employees in 2017. Their new, built-to-spec, 30,000 square foot building in Research Park, “allows visitors to see the research, development and manufacturing underway while simultaneously integrating the beauty of the foothills, says Denise Dearing, Chair of the Biology Department while on a recent tour of the building. “It’s stunning.”

Later this year, BioFire will have sold its 10,000th instrument—an astounding figure when considering there are only 6,000 hospitals in the U.S.

Born in Lansing, Michigan as the son of a horticulture professor at Michigan State University, Rasmussen has always had a passion for science. With family ties in Utah, Rasmussen began his education in biology at Utah State University and later spent time working with the U medical heart transplant team. From there, his passion for science led him to pursue a PhD in molecular and cellular biology at the U. While there he worked in Sandy Parkinson‘s lab which transformed him during his first year of core classes.

Rasmussen relates how in one year he went from “knowing nothing to knowing a lot.” It was a dramatic life transformation which exposed him to many new ares in biology.

At BioFire, going from scientist to CEO was a unique transition. Rasmussen expressed, “It was initially difficult to start off from a focus of research and development, to being primarily focused on the day-to-day of building a business. The other unique transition was, “Giving up control over the small, but important details that I oversaw, to fully trusting those you work with to get the job done.” Rasmussen shares that most of the leadership team has been with BioFire for over 15 years. This longevity shows the tremendous trust and loyalty of the BioFire team.

Rasmussen is tremendously appreciative of his time at the University of Utah where he met nt only his future business partners, but also his wife Heather Ross, BS’88, communication. Kirk Ririe introduced Randy to Heather—now married, they reside near the U and have a son Aidan, who currently studies economics at Wesleyan University.

Today, Rasmussen has a passion for Utah and the mountains where he enjoys skiing, biking and hiking. Continuing his connection to the U, he notes that many of BioFire’s talented employees are U graduates.

Reflecting on his life and career, Randy Rasmussen has some advice for current student at the U. He urges them to explore their passion, and explains that a degree in the STEM field will open doors to many opportunities. He believes that students should take classes in business to complement their technical background and should participate in internships to gain additional experience and perspective.

This story originally appeared in 2017 in the debut issue of OUR DNA.

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Thure Cerling Awarded the Rosenblatt

Thure E. Cerling, Distinguished Professor of Biology, is the 2022 recipient of the Rosenblatt Prize for Excellence.

Cerling is also department chair of the Department of Geology & Geophysics, Francis H. Brown Presidential Chair, and Distinguished Professor of Geology and Geophysics.

The Rosenblatt Prize is the University of Utah’s highest faculty accolade and is presented annually to a faculty member who transcends ordinary teaching, research and administrative efforts. A group of distinguished faculty members on the Rosenblatt Prize Committee recommends esteemed colleagues for consideration and the university’s president makes the final selection.

“Dr. Cerling has made important and impactful contributions to science using isotope geochemistry to learn about natural processes,” said Taylor Randall, president of the University of Utah. “He’s multiplied that impact many times over by sharing his knowledge with graduate students and countless colleagues around the world. With demonstrated excellence in research, teaching and leadership as chair of the Department of Geology & Geophysics, Dr. Cerling epitomizes the ideals of the prestigious Rosenblatt Prize.”

About Thure Cerling

Through his pioneering scientific career and his decades of dedication to sharing his knowledge with colleagues around the world, Cerling, who began teaching at the U in 1979, has been instrumental in expanding the use of isotopes (What’s an isotope? Learn more here) as a tool in geoscience and biology.

“Thure Cerling never met an isotope he didn’t like!” one nominator wrote.

Using isotopes, he has devised innovative methods to understand the paleoecology of early human sites in East Africa, determined the timing of floods in the Grand Canyon, discovered a major global transition in vegetation types 7 million years ago, and has even analyzed his own beard hair to show how his diet changed over the course of a few days during a trip to Mongolia. By one metric of research publication impact, Cerling’s more than 300 scientific papers represent an exceptionally productive and remarkably influential career. His legacy includes graduate students who now are faculty at a number of leading research universities.

The impacts of isotope analysis go far beyond academic research, however. Cerling’s methods and expertise have also been used to identify ivory taken by poachers, determine if medicines are counterfeit, and help identify human remains. Cerling and distinguished professor of biology Jim Ehleringer co-founded a spinoff company, IsoForensics, in 2001 to bring the power of isotope science to criminal cases.

Cerling and Ehleringer also founded IsoCamp, an annual two-week short course that they started in 1996 to teach colleagues the theory and methods of stable isotope analysis. The course, which is now held at the University of New Mexico, has trained nearly 1,000 scientists from around the world in the use of stable isotopes for widespread applications in physical and life sciences; the cumulative impact on the scientific enterprise is incalculable. The American Geophysical Union recognized the unique contributions of IsoCamp with the 2017 Excellence in Earth and Space Science Education Award.

Cerling’s notable list of awards includes the 2020 Emile Argand Award from the International Union of Geological Sciences, awarded only every four years, the 2017 President’s Medal from the Geological Society of America, and the 2012 Utah Governor’s Medal for Science and Technology. He also shared in the 2017 Mineral of the Year award from the International Mineral Association with eight other coauthors for the discovery of the mineral Rowleyite and holds one patent for a “Device and system to reconstruct travel history of an individual.”

He’s also a member of the National Academy of Sciences and a Fellow of the American Geophysical Union, the Geological Society of America, the American Association for the Advancement of Science, the Geochemical Society and the International Association of Geochemistry and Cosmochemistry. He served by presidential appointment on the United States Nuclear Waste Technical Review Board from 2002-2011.

When the U’s Department of Geology & Geophysics needed a new chair in 2016, Cerling placed his name in consideration. When a College of Mines and Earth Sciences administrator asked Cerling why he wanted to be considered for chair, Cerling replied “because it’s my duty, and my turn.” Having benefited from others’ leadership for many years, he felt that he could provide a platform for younger faculty to develop their own successful careers at the U.

He is nearing completion of his second term as chair, having instituted faculty mentorship initiatives, improved faculty hiring and department internal communication, and extended a hand of outreach to the community with a department Open House Night intended for K-12 students and their families, as well as a fellowship that sends Geology and Geosciences grad students into Salt Lake City schools.

Thure Cerling, featured speaker at the Frontiers of Science Lecture Series, College of Science, 2014
Throughout the COVID-19 pandemic, Cerling “encouraged patience and creativity,” a nominator wrote, facilitating the development of digital resources like 3-D models of rocks and minerals and high-resolution photos of field sites that will continue to improve online teaching and accessibility of geological education into the future.

Cerling’s lifelong dedication to advancing scientific understanding and sharing that understanding with students and colleagues is encapsulated in the words of two nominators, who both described Cerling as “widely knowledgeable and endlessly curious.”

About the Rosenblatt Prize for Excellence

The Rosenblatt Prize for Excellence is an endowed award, given annually to a member of the faculty at the University of Utah “to honor excellence in teaching, research and administrative efforts, collectively or individually, on behalf of the university.”

The endowment was created to honor Nathan and Tillie Rosenblatt on the centenary of their immigration to Utah and in recognition of their legacy of civic leadership and generosity. Originally established in 1983, the award was later increased by Joseph and Evelyn Rosenblatt and their family. The endowment and its gifts ensure the annual award of $50,000.

Click here to learn more about the Rosenblatt Prize for Excellence. Click here to watch Dr. Cerling giving the 2014 Frontiers of Science lecture.

This story by Paul Gabrielsen originally appeared May 9, 2022 on @TheU.

Mina Done

Mina Done

Beckman Abstract

  • Comparative Quantification of Oxidative Damage in the Genome, Telomere, and mtDNA using qPCR

    Oxidative stress occurs when there is an unbalanced amount of reactive oxygen species (ROS) in the cell. These ROS can cause oxidative damage in the DNA which lead to mutations that can contribute to cancer, neurodegenerative diseases, and aging. One common form of oxidative damage is 8-oxoguanine (OG) and this can be used as a marker for oxidative stress. One type of oxidative stress is the production of superoxides. These superoxides are produced in the mitochondria and get converted into hydrogen peroxide which then can be activated by reacting with iron in the cell. Because hydrogen peroxide can diffuse into other cells before it reacts with iron, oxidative stress isn’t necessarily contained within the mitochondria where most of the ROS are produced. We want to quantify OG in mitochondrial DNA targets as well as nuclear DNA targets to gain a better understanding of where in the cell is DNA most susceptible to oxidative stress. To quantify oxidative damage in DNA, we will be using a qPCR method. Bacterial Fpg, a base excision repair enzyme, can be used to detect and cleave the DNA where OG occurs which will decrease DNA amplification in qPCR. After adding bacterial Fpg to our qPCR sample, the amount that we see decreased DNA amplification will correspond to the amount of oxidative damage present in that region of DNA. We can then use this information to compare the amounts across the different DNA target regions to gain a better understanding of where oxidative stress is most felt in the cell. This will then allow further research into the mechanisms of ROS as well as where to target for repair of oxidative damage.


Maxwell Austin

Maxwell Austin

Beckman Abstract

  • Antimicrobial Peptide Stabilization and Natural Product Scaffold Mimicry Using Triazolinedione-Based Cyclization Methods

    Antimicrobial peptides (AMPs) are a promising, yet underdeveloped class of therapeutics with structural characteristics that go beyond traditional drug discovery guidelines. Though structurally diverse, most AMPs have defined peptide secondary structures that promote their mechanisms of action. A common hypothesis is that the stabilization of these peptide secondary structures may enhance their biological properties. The main goals of this project involve the development and application of a selective cyclization reaction to stabilize and mimic the cyclic structures of these bioactive peptides. Triazolinediones (TADs) are reactive molecules with remarkably selective chemical reactivity that have enabled applications in organic synthesis, chemical biology, and medicine. Substituted TADs are used for tyrosine-selective bioconjugation reactions that satisfy ‘click reaction’ chemical requirements. TAD-containing peptides can react selectively with tyrosine (Tyr) to yield TAD-Tyr linked cyclic peptides. Toward antimicrobial peptide therapeutic discovery, I will use TAD-based cyclization methods to stabilize and mimic the structures of the bioactive peptides magainin and arylomycin. The magainins are naturally produced helical AMPs isolated from the African clawed frog that exhibit Gram-negative antimicrobial activity. Using an electrochemical oxidation method I will prepare a series of structure-stabilized magainin peptides and evaluate their biological properties. The naturally produced arylomycin AMPs are structurally defined by a smaller, biaryl-linked cycle. Here I will use on-resin TAD-based cyclization chemistry to prepare a close mimic of the biaryl-linked cycle. Long-term, the development of TAD-based cyclization methods for the stabilization and mimicry of peptide secondary structures could expand future access to stable peptide therapeutics.


Phi Beta Kappa

Phi Beta Kappa Society Scholar

Muskan Walia Named Phi Beta Kappa Society Scholar.

Muskan Walia, a second-year student at the University of Utah Honors College, studying math
and philosophy, has been named a Key into Public Service Scholar by the Phi Beta Kappa Society. The Society is the nation’s most prestigious academic honor society, and the Key into Public Service award highlights specific pathways for arts and sciences graduates to launch public sector careers.

Chosen from nearly 900 applicants attending Phi Beta Kappa chapter institutions across the nation, the Key into Public Service Scholars hail from 17 states. These are high-achieving college sophomores and juniors, who display notable breadth and depth in their academic interests.

“I am extremely grateful and honored to be receiving this award from Phi Beta Kappa,” said Walia. “My community here at the University of Utah has provided me with a prodigious liberal arts and sciences education and has nurtured my interest in exploring the dynamics between science, society, and the public sector. I am excited for the incredible opportunity to further explore this interest this summer.”

Walia is an ACCESS Scholar and undergraduate researcher, working with Dr. Fred Adler, Professor of Biology and of Mathematics. In her research, Walia adapted an epidemiological SIR model for spread of disease to model the number of cells infected with SARS-CoV-2 in order to predict when different types of tests will produce false positives or false negatives.

“My summer in the ACCESS Scholars program sparked an interest and motivation to pursue a career in public service,” she said. “Being taught by faculty across the University of Utah in diverse disciplines, I learned about the intersections of science, communication, and policy and how scientists can practice the art of advocacy.


Muskan Walia

"My community here at the University of Utah has provided me with a prodigious liberal arts and sciences education and has nurtured my interest in exploring the dynamics between science, society, and the public sector."


“Working under the mentorship of Dr. Fred Adler has been invaluable. I wanted to be engaged in mathematics research that centered on justice and informed public policy. There was truly no better pairing than with Dr. Adler. He has wholeheartedly supported and encouraged my curiosity and passion to utilize mathematics principles to tackle the most pressing social justice related questions of our time.”

In addition to her studies, Walia currently serves as the ASUU student government Senate Chair and works as a youth environmental organizer in the Salt Lake City area. She founded a campaign to commit her local school district to a 100% clean electricity transition by 2030, and has assisted with the expansion of local clean energy campaigns in Utah school districts. She is also a leader and mentor at Utah Youth Environmental Solutions Network (UYES), where she supports the development of a new youth-based climate justice curriculum. Her experiences have cultivated a passion and commitment to community building, climate education, and environmental justice.

Each Key into Public Service Scholar will receive a $5,000 undergraduate scholarship and take part in a conference in late June in Washington, D.C. to provide them with training, mentoring, and reflection on pathways into active citizenship.

Below are the names of the 2022 Key into Public Service Scholars and their chapter institutions:

Aylar AtadurdyyevaUniversity of Kansas
Miguel Coste, University of Notre Dame
Noelle Dana, University of Notre Dame
Grace Dowling, Clark University
Brandon Folson, Loyola University Chicago
Justin Fox, University of Maryland- College Park
Sora Heo, University of California - San Diego
Alec Hoffman, Clark University
Samiha Islam, State University of New York at Buffalo
Ruthie Kesri, Duke University
Katherine Marin, University of Florida
Sondos Moursy, University of Houston
Olivia Negro, Ursinus College
Emily Geigh Nichols, Stanford University
Paul Odu, University of Missouri
Vaidehi Persad, University of South Florida
Diba Seddighi, University of Tennessee
James Suleyman, Roanoke College
Jonah Tobin, Williams College
Muskan WaliaUniversity of Utah
For more information about the scholarship and links to individual biographies of the recipients, please visit


by Michele Swaner, first published at


Societal Impact Scholar

Societal Impact Scholar

Ken Golden Named U Presidential Societal Impact Scholar

President Taylor R. Randall has named Ken Golden, Distinguished Professor of Mathematics, as an inaugural recipient of the University of Utah Presidential Societal Impact Scholar Award.

Dr. Golden and four other scholars are a select group of faculty. Recognized as experts in their respective fields and disciplines, they share and translate their scholarship, research, creative activities and ideas with opinion leaders, policy makers, the public and other audiences outside the university and in ways that can transform society.


Ken Golden

"Dr. Golden is among the rare group of top-level mathematical scientists who is able to reach to the broader public about one of the central issues of our time."


Golden is a brilliant expositor and a passionate advocate for public awareness of our changing climate and the critical role of mathematics in climate modeling. He has given over 40 invited public lectures since 2008, and over 500 invited lectures since 1984. His public lectures emphasize the rapid and significant loss of Arctic sea ice, and how mathematics is helping us predict the future of the Earth’s polar marine environment. Dr. Golden is among the rare group of top-level mathematical scientists who is able to reach to the broader public about one of the central issues of our time.

From tackling the social determinants of health and wellness, to addressing the underlying causes of crime and poverty, to designing interventions to curb poor air and water quality, to helping better inform public debate on society’s most pressing issues, these scholars’ works have a positive impact on people and institutions and help make our world a better, more equitable and enjoyable place in which to live.

The 2022 cohort of impact scholars are:
Kenneth Golden, Distinguished Professor, Department of Mathematics
RonNell Andersen Jones, Professor, College of Law
Michelle Litchman, Assistant Professor, College of Nursing
Susie Porter, Professor, College of Humanities and the School for Cultural and Social Transformation
Paisley Rekdal, Distinguished Professor, Department of English

The Presidential Societal Impact Scholar Award was conceived by and is supported by a gift from University of Utah Professor Randy Dryer.


by Michele Swaner, first published at


How Trees Grow

How Trees Grow

William Anderegg

What we’re still learning about how trees grow.

What will happen to the world’s forests in a warming world? Will increased atmospheric carbon dioxide help trees grow? Or will extremes in temperature and precipitation hold growth back? That all depends on whether tree growth is more limited by the amount of photosynthesis or by the environmental conditions that affect tree cell growth—a fundamental question in tree biology, and one for which the answer wasn’t well understood, until now.

A study led by University of Utah researchers, with an international team of collaborators, finds that tree growth does not seem to be generally limited by photosynthesis but rather by cell growth. This suggests that we need to rethink the way we forecast forest growth in a changing climate and that forests in the future may not be able to absorb as much carbon from the atmosphere as we thought.

“A tree growing is like a horse and cart system moving forward down the road,” says William Anderegg, an associate professor in the U’s School of Biological Sciences and principal investigator of the study. “But we basically don’t know if photosynthesis is the horse most often or if it’s cell expansion and division. This has been a longstanding and difficult question in the field. And it matters immensely for understanding how trees will respond to climate change.”

The study is published in Science and is funded by the U.S. Department of Agriculture, the David and Lucille Packard Foundation, the National Science Foundation, the U.S. Department of Energy and the Arctic Challenge for Sustainability II.

Growth rings - oldest growth is at the top.

Source vs. sink

We learned the basics in elementary school—trees produce their own food through photosynthesis, taking sunlight, carbon dioxide and water and turning it into leaves and wood.

There’s more to the story, though. Converting carbon gained from photosynthesis into wood requires wood cells to expand and divide.

So trees get carbon from the atmosphere through photosynthesis. This is the trees’ carbon source. They then spend that carbon to build new wood cells—the tree’s carbon sink.

If the trees’ growth is source-limited, then it’s limited only by how much photosynthesis the tree can carry out and tree growth would be relatively easy to predict in a mathematical model. So rising carbon dioxide in the atmosphere should ease that limitation and let trees grow more, right?

But if instead the trees’ growth is sink-limited, then the tree can only grow as fast as its cells can divide. Lots of factors can directly affect both photosynthesis and cell growth rate, including temperature and the availability of water or nutrients. So if trees are sink-limited, simulating their growth has to include the sink response to these factors.

The researchers tested that question by comparing the trees’ source and sink rates at sites in North America, Europe, Japan and Australia. Measuring carbon sink rates was relatively easy—the researchers just collected samples from trees that contained records of growth. “Extracting wood cores from tree stems and measuring the width of each ring on these cores essentially lets us reconstruct past tree growth,” says Antoine Cabon, a postdoctoral scholar in the School of Biological Sciences and lead author of the study.

Measuring carbon sources is tougher, but doable. Source data was measured with 78 eddy covariance towers, 30 feet tall or more, that measure carbon dioxide concentrations and wind speeds in three dimensions at the top of forest canopies, Cabon says. “Based on these measurements and some other calculations,” he says, “we can estimate the total forest photosynthesis of a forest stand.”


The researchers analyzed the data they collected, looking for evidence that tree growth and photosynthesis were processes that are linked, or coupled. They didn’t find it. When photosynthesis increased or decreased, there was not a parallel increase or decrease in tree growth.

“Strong coupling between photosynthesis and tree growth would be expected in the case where tree growth is source limited,” Cabon says. “The fact that we mostly observe a decoupling is our principal argument to conclude that tree growth is not source-limited.”

Surprisingly, the decoupling was seen in environments across the globe. Cabon says they did expect to see some decoupling in some places, but “we did not expect to see such a widespread pattern.”

The strength of coupling or decoupling between two processes can lie on a spectrum, so the researchers were interested in what conditions led to stronger or weaker decoupling. Fruit-bearing and flowering trees, for example, exhibited different source-sink relationships than conifers. More diversity in a forest increased coupling. Dense, covered leaf canopies decreased it.

Finally, coupling between photosynthesis and growth increased in warm and wet conditions, with the opposite also true: that in cold and dry conditions, trees are more limited by cell growth.

Cabon says that this last finding suggests that the source vs. sink issue depends on the tree’s environment and climate. “This means that climate change may reshape the distribution of source and sink limitations of the world forests,” he says.

A new way to look forward

The key takeaway is that vegetation models, which use mathematical equations and plant characteristics to estimate future forest growth, may need to be updated. “Virtually all these models assume that tree growth is source limited,” Cabon says.

For example, he says, current vegetation models predict that forests will thrive with higher atmospheric carbon dioxide. “The fact that tree growth is often sink limited means that for many forests this may not actually happen.”

That has additional implications: forests currently absorb and store about a quarter of our current carbon dioxide emissions. If forest growth slows down, so do forests’ ability to take in carbon, and their ability to slow climate change.

Find the full study @

Other authors of the study include Steven A. Kannenberg, University of Utah; Altaf Arain and Shawn McKenzie, McMaster University; Flurin Babst, Soumaya Belmecheri and David J. Moore, University of Arizona; Dennis Baldocchi, University of California, Berkeley; Nicolas Delpierre, Université Paris-Saclay; Rossella Guerrieri, University of Bologna; Justin T. Maxwell, Indiana University Bloomington; Frederick C. Meinzer and David Woodruff, USDA Forest Service, Pacific Northwest Research Station; Christoforos Pappas, Université du Québec à Montréal; Adrian V. Rocha, University of Notre Dame; Paul Szejner, National Autonomous University of Mexico; Masahito Ueyama, Osaka Prefecture University; Danielle Ulrich, Montana State University; Caroline Vincke, Université Catholique de Louvain; Steven L. Voelker, Michigan Technological University and Jingshu Wei, Polish Academy of Sciences.


- by Paul Gabrielsen, first published in @theU


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