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Researchers take on berry timing amid climate change

Jul 14, 2020

CREDIT ELIZABETH EARL

Alaska’s summer is short, but one of the ways it softens the farewell each fall is through a parting gift of delicious berries. In the late summer and early fall, Kenai Peninsula residents regularly flock to the wild lands for salmonberries, cranberries, blueberries, and crowberries and more.

Like everything, berry plants are being affected by the changes in the environment as climate change increases the temperature, lengthens the summer and, in many cases, dries it out. But according to University of Alaska Fairbanks researchers, the effect isn’t exactly clear-cut, nor directly in line with what you’d expect.

Researchers Christa Mulder and Katie Spellman of UAF have been researching berry phenology—essentially, timing. What they’ve found so far is that the results are mixed. While other things, like salmon runs and tree flowering, are happening in trends either earlier or later in the years, Mulder said some berries have been more variable rather than following a single trend.

Alaskans love their berries. In rural Alaska, many families depend on them as a source of fresh fruit where produce is prohibitively expensive, but even in the urban areas, they’re a link to tradition and delicious flavors. Spellman said a survey showed that the average Alaska family gathers at least five gallons of berries each year, while some families gathered up to 20 gallons.

"Berries are an important resource for us in Alaska," she said. "They supplement our diet, like when fresh fruit is really expensive, especially off of the road system, and they also are a superfood that many studies in Alaska have shown they reduce our chances of getting cancer, reduce our risk of getting diabetes, they are associated with lower rates of obesity dementia in Alaska."

Mulder says Alaska’s berries, like other temperate, subarctic and arctic plants, actually initiate a flower bud the year before they bloom. That means two years of temperature data are necessary to track the actual effect on when these plants produce fruit. And what they’ve found so far surprised them—when it’s warm the first year, the year before they flower, lowbush cranberries actually bloom later. That’s exactly the opposite of what they would have thought, she said.

"So that was just really odd," she said. "And I scratched my head a lot and asked a lot of different experts about what could be going on, because I couldn’t figure out why plants would be delayed if it was warm the year before. And then finally I figured out it had to have something to do with what was happening developmentally, the year before plants flower."

In general, she said lowbush cranberries seem to have changed very little in when they bloom and produce fruit. Blueberries, on the other hand, have become more variable over time. The main thing affecting when they bloom and produce fruit is when the snow melts rather than overall temperature, though temperature does affect snowmelt.

Cranberries seem to balance two years’ temperature variations, and that may be why the researchers didn’t see much change in cranberry timing, Mulder said. Blueberries, though, add the two years’ effects together.

"In contrast, for blueberries, we did have a little bit of evidence that two warm years would make the plants a little earlier," she said. "On the other hand, two cool year would make the plants bloom extra late. Instead of being opposite, these effects add together. This could explain our increased variability in the blueberries."

Berries are important to more than just humans. Migrating wildlife eat them year round, even in the winter, when the berries may have fallen off the plants, be rotting on the stem, or be beneath the snow. They’ll gorge on them in the summer, too. Spellman said tracking the timing of when berries bloom is important to keep an eye on trophic mismatches—essentially, when the timing of the eater and the food, or the pollinator and the plant, don’t match up any more.

"If the flower comes early but the pollinator doesn’t come early, then you could have a mismatch between the plant and the pollinators that they need in order to produce fruit," she said. "And finally, the last thing we’re thinking about is what’s happening between flowering and earlier fruit ripening between the summer and the fall. Could this affect when the berries are ready in relationship to migrating animals, for example, or could it lead to greater amounts of berries rotting on the plant?"

The two researchers focused on Interior berries for their studies, but they are also interested in looking into more southern varieties like salmonberries. Spellman said one major source of information for them was citizen science through the Local Environmental Observation, or LEO, network. Citizens have taken an interest in tracking the data of their berries blooming, which has been very helpful for research, she said.