A small satellite, called Venus, launched by Israel's and France's space agencies is capturing images of green spaces around the world to learn whether they show signs of global climate change. One of those splotches of green is UW-Milwaukee’s Downer Woods, an 11.1-acre natural area on the northwest corner of campus.
Scientists have been studying the wood's trees for years, tracking how they're affected by the climate. But ecologist Alison Donnelly's focus is closer to the ground: shrubs.
“The species that we’re looking at in the minute is an invasive species, a European privet," she says. "The leaves are quite dark compared to a native species called the chokecherry.”
These are two of eight shrub species – some native, others invasive – within the parcel.
Venus is capturing images from about 100 sites around the globe, passing over Downer Woods every other day.
“So, we will observe every two days the percentage of leaves that will start to turn yellow. And the reason that we’re doing that is because we are a part of a project that is looking at this new satellite data,” Donnelly says.
Graduate student Chloe Rehberg is collecting data on the ground that will be compared to images captured high above the woods.
“I’m gonna be looking at more of the visual changes — when shrubs are beginning to brown or blossom. Are times changing?” Rehberg says.
She also measures concentrations of chlorophyll in leaves with a handheld reader, then cuts a small circle of leaf and plops it into individual plastic bags.
“But we have so many parts to this project, I think that all of us combined are gonna create a really, really awesome project,” Rehberg says.
UWM biologist Erica Young (left) added another layer to the shrub project by gathering data with her fluorometer, "There a measuring probe at the end, you put it against the leaf. It shoots light at it and the light coming back measures how functional the leaf is," Young says.
Credit Susan Bence
Donnelly says the shrubs they're focusing on are a forgotten but important structure of the woodland, and she wants to squeeze as much data out of the project as possible.
“Because once the leaves on the shrubs start to photosynthesize, they’re taking carbon dioxide out of the atmosphere,” Donnelly says.
Of course, vastly less than the trees above them, “But in early spring we think shrubs are going to have a small but significant effect,” Donnelly says.
Donnelly says her shrub research came to life thanks to students. When Donnelly joined UWM’s geography department, a student needed an independent study project.
“She said she would like to do something to do with trees, but the trees weren’t leafing out early enough for the project to be finished. We said ‘good opportunity, we’ll have a look at the shrubs’, not really expecting to find anything significant,” Donnelly says.
She thought they'd find that invasive shrubs showed new life earlier than native species, “But we found the opposite — it was very interesting and warranting further research,” Donnelly says.
And it was a former Ph.D. student who tipped Donnelly off about the Venus satellite project.
Once in motion, Donnelly’s colleague UWM biologist Erica Young contributed her expertise in the woods and lent Donnelly her lab in Lapham Hall. Together they began analyzing 1,044 leaf samples, which Donnelly says requires lots of little test tubes.
“What we do is put in the solvent, then put in the leaf disk, then pop them in a water bath for two hours. Come back, take a small sample out of it and put it in the spectrometer. Then write down all of the numbers,” Donnelly says.
The next big step comes next spring, as monitoring picks up again in Downer Woods. And the former PhD student who told Donnelly about the satellite project will return to UWM. She’ll analyze images capture generated by the satellite and comparing the data amassed by Donnelly’s team.
She hopes the project quantifies how much shrubs contribute to swallowing up carbon dioxide.
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