Citizen science offers lessons in understanding green-up | Cooperative Extension

The first of what became the Nenana Ice Classic netted the winner $800. The 2024 edition had a jackpot of $210,155, which will go to the person or people who guessed the closest time – 5:18 a.m. on April 27 – when the ice broke out this spring.

The ice classic is a 107-year climate record for interior Alaska. But it’s not the only citizen science effort in Fairbanks.

In his fifth annual ecology webinar on April 30, Rick Thoman discussed the history of ecology forecasting in Fairbanks.

Green-up doesn’t refer to the blooming of a specific tree, said Thoman, a climate expert at the Alaska Center for Climate Assessment and Policy. It’s on a landscape scale, when a particular hillside on Chena Ridge turns green when viewed from the University of Alaska Fairbanks Troth Yeddha’s West Ridge campus.

In the 1970s, UAF scientists Jim Anderson and Bob Elsner began systematically recording the vegetation on that slope, with the exception of 1975.

“From conversations with Jim Anderson many years ago, they probably noticed this, but the piece of paper they were on probably got lost before they compiled it,” Thoman said.

It’s a 49-year record of observations, which Thoman said is a unique set of data.

These observations show great variability, with periods of early green-up and periods showing later dates. The average green-up date is May 8th. Chances are, by the time you read this, the green-up will have touched that slope for the 2024 season.

“We are two weeks ahead of last year and about a week behind the 2016 initial green-up record,” Thoman said on April 18. Graphs showing long-term trends for Tanana River failure and green-up look remarkably similar.

“The green-up was about a week earlier than it was historically,” Thoman said. “That goes along with separation.”

Green-up begins first on lower south-facing slopes and spreads more quickly on the way down. Thoman and Fathauer saw this as a reaction to high daily temperatures.

Spring precipitation is not a major factor in greening. In fact, Thoman said, spring in Fairbanks is typically dry. But with snow melting during a season, there is plenty of moisture for the trees to use.

In the 1990s, Thoman and meteorologist Ted Fathauer began working on a way to predict greening using readily available climate data, such as high temperatures and solar input. A few years later, Jan Dawe, who leads OneTree Alaska at UAF, suggested that a similar model could be used to predict the rise of birch sap, which occurs weeks before greening. OneTree’s Birch Sap Collaborative is another project with lots of public input.

“This has been an ongoing and evolving work for 25 years,” Thoman said.

Thoman’s green-up formula takes the sum of daily high temperatures above freezing, starting March 1, and adds two variables that give weight to really warm temperatures and increased solar input as spring progresses.

This formula gives him a window he calls the green zone, which he is able to predict weeks in advance. While it was designed to predict vegetation on the southeast slopes of Fairbanks, Thoman said it also works quite well in Delta Junction and in Anchorage for birch and aspen trees. He was asked to see if it was possible to calculate greening in central British Columbia, but it didn’t work.

When greening occurs, it brings with it some changes, in addition to the color of the leaves. It is important for the biology of birch and aspen. This change affects birch sap, which is no longer useful to human tappers. It also signals a seasonal shift in the diet of elk, who are able to switch from the sticks, twigs and brush available in winter to green, leafy foods.

The green-up also affects humidity and climate, Thoman said. Once the leaves begin to unfurl, they begin the process of transpiration, which is the movement of water through the plant and its evaporation through the leaves. This raises local humidity, which fuels afternoon rain and, later, thunderstorms.

And the emergence of birch leaves means pollen isn’t far behind. Peak pollen typically occurs two to six days after green-up, depending on temperature, Dawe said during the green-up webinar. In 2020, an exceptionally warm year, pollen exploded shortly after greening and set a world record nearly twice the previous record.

High temperatures reached 82 and 80 degrees the two days after green-up that year, which had an unexpected effect, Dawe said.

Ronda Schlumbohm, a Salcha elementary school teacher who works closely with Dawe on projects involving birch trees, planted harvested seeds in the OneTree Alaska long-term monitoring area later that fall so her students could grow trees. Not a single seed germinated that year. In 2023, seeds collected from the same trees germinated.

“Field T’s research terrain is a seed orchard,” Dawe said. “We can collect seeds year after year from the same group of trees and see how seed viability varies year after year. Each year we harvest and test seeds, the data becomes more valuable when analyzed with the climate in mind.”