Editor’s note: This week, scientists from the University of Alaska Fairbanks are presenting their work alongside thousands of colleagues from around the world at the 2022 American Geophysical Union fall meeting. Some of their discoveries are featured here. You can also find out more about UAF at AGU by searching for #UAFxAGU on Twitter, Instagram and Facebook.
Alaskan blueberry pickers are likely familiar with sphagnum moss — the luscious moisture-holding mat that leaves you with a soggy bottom seconds after sitting at a berry bush. As it turns out, sphagnum plays an important role in the boreal forest. It traps moisture at the surface, protecting the permafrost below from thaw.
Yongwon Kim, a permafrost scientist at the University of Alaska Fairbanks International Arctic Research Center, is studying sphagnum-killing organisms called crustose lichens. These lichens form a crust that slowly causes intact sphagnum to wither and die.
From a climate change perspective, these infestations of tiny lichen could be a big problem. The lichen eliminates the protective barrier that sphagnum provides for permafrost — an outcome that makes permafrost more susceptible to changing air temperatures. Also, the decomposing sphagnum releases more carbon dioxide.
“I found the CO2 emission in crustose lichen was higher than intact sphagnum moss,” said Kim. He measured a 34%-40% increase in carbon dioxide release at sites with crustose lichen compared to healthy sphagnum communities.
Arctic permafrost holds an estimated 1,700 billion metric tons of carbon. When that carbon is released during wildfires or from lesser-known sources like dying sphagnum moss and the subsequent permafrost thaw, the atmosphere warms, accelerating climate change.
Kim anticipates that crustose lichen outbreaks may become more widespread as the Arctic and sub-Arctic warm due to climate change. This demonstrates a positive feedback. More lichen releases more carbon dioxide and allows more permafrost to thaw. Both cause more warming, which, in turn, leads to more lichen.
UAF helping expand satellite radar’s reach
Satellite-based remote sensing by radar can reveal the world around us.
It’s called synthetic aperture radar, commonly referred to as SAR, and it has been around for a while as a means of monitoring Earth’s surface in all weather and lighting conditions.
The technology behind it has developed rapidly, though, and NASA wants to spread its use.
That NASA effort is something in which Franz Meyer, chief scientist of the Alaska Satellite Facility, is deeply involved. He is speaking about the NASA-funded SAR Capacity Building Center during the American Geophysical Union fall meeting.
The center is focused on Central and South America and has partnered with organizations in Ecuador, Colombia and El Salvador.
“If you look at their geographic location, they are heavily cloud covered, but they’re also affected by a lot of natural change, such as deforestation, flooding and volcanic eruptions,” said Meyer, who is also a professor of remote sensing. “So they are very interested in using SAR but were interested in understanding the workflows and understanding the data set better.”
The SAR Capacity Building Center held in-person workshops in Ecuador and Colombia before the Covid-19 pandemic. In 2020, because of the virus outbreak, it held a virtual multitrack workshop for El Salvador communities. In November of this year, it held training sessions for other communities in coordination with the Central American Integration System.
The Alaska Satellite Facility is a unit of the UAF Geophysical Institute and is also NASA’s center for archiving SAR data.
Boreal tree adaptation to seasonal drought conditions
Climate change is bringing shifting rainfall patterns and warmer temperatures to the boreal forest. At the University of Alaska Fairbanks, Jessie Young-Robertson is studying how boreal trees store and regulate water use.
“I want to talk about the drought response of boreal forest trees over a long period of time,” Young-Robertson said. “By drought response, I mean how the trees use water, how stressed they get and how they respond to environmental changes in air temperature and rainfall.”
Young-Robertson is presenting a paper on the topic at the 2022 American Geophysical Union meeting this week.
The study is focusing on two tree types: coniferous black spruce and deciduous aspen and birch in the Caribou-Poker Creeks Research Watershed near Fairbanks. In summer 2022, sensors measured environmental variables, sap (water) flux and trunk water content every 30 minutes. Canopy water stress measurements were taken weekly.
“The story so far is that we really need a snowpack,” Young-Robertson said. “We’re seeing the impact of earlier springs. We’re seeing the impact of super-hot summers, and we’re seeing the impact in the changing of the packaging of the precipitation.”
The “packaging” of precipitation refers to when and how much rain falls during the summer. Rain that just comes in August has a different effect than rain that falls all summer.
Trees grow in June and July. If it doesn’t rain while the trees are growing, that adds stress, she said.
Ongoing work is revealing that the trees are approaching their climatic limit with increased drought pressure.
Heather McFarland, Rod Boyce and Julie Stricker are public information officers at the University of Alaska Fairbanks.
