Storm helps turn Minneapolis into a lab for why trees fall

Damage from the June storms is providing University of Minnesota researchers with a crash course in treefall.

While cities across the state are still dotted with toppled trunks and heaved-up root balls, researchers are scrambling to document patterns that might reveal why some trees fell and others didn't. That might — or might not — prove whether trees rooted in tight spaces in urban boulevards are weakened by sidewalk, street, sewer and other public works projects, and ultimately change how those projects are managed and even how urban landscapes are designed.

Gary Johnson, U professor of urban and community forestry, said that with fresh evidence of 3,000 downed trees, Minneapolis is an ideal laboratory for the $30,000 study approved Wednesday night by the city's Park and Recreation Board.

Most of the tree loss appeared to have occurred on boulevards, the grassy corridors between sidewalks and streets, with far less loss in yards, Johnson noted. That's what most foresters would expect, he said, but his study aims to document how recently there had been any major excavation and pavement work around the fallen trees.

A need for data

"We've had some data pointing to 'Yes, it is a higher frequency,' " he said, describing the apparent relationship between relatively recent street work — say, within the past five years — and tree loss in storms. "But we haven't had enough data."

Johnson said the study could lead Minneapolis and other communities to remove and replace older trees as part of street and sidewalk projects to reduce the number of storm-vulnerable trees lining city streets.

Cities might even move sidewalks next to streets, eliminating boulevards but creating more space in the public right of way so trees would be at less risk from snowplowing and other work.

Johnson said he expects to have some conclusions by October.

Chipping away at debris

Meanwhile, more than 2,000 semitrailer truckloads of tree limbs and branches have been hauled from Minneapolis streets and parks to the Fort Snelling chipping center in the four weeks since the first-day-of-summer blowdown, Superintendent Jayne Miller told park commissioners Wednesday night.

But the cleanup won't be complete until the first week of September, Miller said. Wednesday was the first eight-hour workday for cleanup crews since the storms, Miller said.

Crews have worked nine- and 10-hour days, six days a week since the storms, with July 4 being the only day off for everyone.

Residents had until July 12 to place debris from public and private trees along boulevards, where Park Board crews are continuing to pick it up. Overtime has cost the district about $175,000.

But they're making only one pass, Park and Recreation Board forestry director Ralph Sievert said. "We're not going to go back," he said.

However, crews will continue pulling down "hangers" — broken limbs caught in trees' upper branches — and removing still-standing trees whose roots may have been sprung in the June storm.

Cleanup work in Hennepin and 17 other counties across central and southeast Minnesota will be eligible for federal reimbursement, due to a presidential disaster declaration announced Thursday. At least 75 percent of eligible could be covered after an application and review process.

Hennepin is the only metro county included in the declaration; Stearns and Benton, which include St. Cloud, are also eligible for assistance.

Miller said the declaration might actually slow down the cleanup, since it may be necessary to photograph and document the location of the stump of every destroyed tree.

Bill McAuliffe • 612-673-7646