Arboretum Scientist Describes Tree Mystery at Latest “Pizza”

Along the Niobrara River in Northern Nebraska lives a grove of aspens that until recently posed a mystery to plant biologists including Jake Grossman, a Putnam Fellow at the Arnold Arboretum in Jamaica Plain, Mass.

Grossman described that mystery and how he helped solve it at the NESW’s latest “Pizza with a Scientist” event on January 15.

Quaking or Bigtooth?

The conundrum? The Niobrara trees don’t look like quaking aspens, the only species that lives anywhere close by. Locals — including Buffalo Bruce MacIntosh, an environmentalist and aspen aficionado — believed they were hybrids, or a cross between quaking aspens and bigtooth aspens. But the closest bigtooths thrive in the east, several hundred kilometers away.

Grossman’s work with Drs. Nick Deacon and Jeannine Cavender-Bares from the University of Minnesota on the genetics of the trees conclusively showed that they are indeed hybrids. His hypothesis is that they are relics from some 4,000 years ago when the climate supported both species. As a result, his work also explores the effects of climate change on temperate trees.

Grossman is now working with the maples at the arboretum — the most important collection of that species in the world, according to Arnold Arboretum director Ned Friedman, who briefly joined our group. Grossman aims to study how drought tolerance has developed in maples over thousands of years. The results, he said, could help evaluate their current vulnerability and create tools to make decisions about what to plant and where.

Research at “the Arb”

Friedman noted that the arboretum’s Weld Hill facility — where we met for Grossman’s talk — is home to many different research projects related to plants, from genomics to climate change. In 2017 some 90 projects were underway. He invited NESW members to subscribe to his blog, which features photos that are available for non-profit use, and to feel free to contact the Arb for any additional information.

Elizabeth Thomson

Image: NESW member Eric Smalley (left) with Arnold Arboretum Jake Grossman. The two sit behind a table made from a black walnut that was a specimen tree at the Arb for many years before it had to be cut down.