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by Joni Astrup
A survey of trees in Elk River has yielded a few surprises.
One is that the most prevalent type of tree in the city is spruce. A second is that there are fewer ash trees than anticipated.
The tree survey was done this summer in Elk River and other cities across Sherburne County in preparation for the anticipated invasion of the emerald ash borer, which can kill all species of ash trees.
Gina Hugo, resource conservationist with the Sherburne Soil and Water Conservation District, said the survey measured and counted trees that were maintained. It did not include trees in unmowed wooded areas of backyards or in parks. She said it’s a method used since the 1970s that allows cities to get an accurate composition of its urban tree canopy.
The survey recorded nearly 5,000 ash trees in Elk River. That’s about half the number expected, but still a large number, Hugo said. Ash trees make up about 10 percent of the city’s trees.
Spruce, meanwhile, make up 17.5 percent of Elk River’s trees. Hugo expected oaks to come out on top.
Rodney Schreifels, Elk River park maintenance supervisor, thinks that may be due to all the construction over the years. There used to be a lot of oak trees in Elk River but red oaks, in particular, don’t tolerate disturbance of their root systems well. If the soil around a red oak tree is compacted or the roots are cut, it often dies, Schreifels said. Then property owners typically plant a spruce tree or a maple as a replacement.
Elk River is the only city in Sherburne County where spruce turned up as the dominant tree species. In all the other cities, oaks topped the list, Hugo said.
Trained volunteers put in 1,240 hours doing the tree surveys in Sherbune County. In Elk River, 17 volunteers tallied 332 hours, she said.
The survey was spearheaded by Hugo. The project received financial support from the Minnesota Department of Natural Resources. The University of Minnesota Urban Forestry Department and St. Cloud State University Spatial Analysis and Research Center also worked closely on the project providing technical support.
In addition to the tree survey in Elk River, an emerald ash borer preparedness plan is also in place to address the threat.
Schreifels said it is all helping the city prepare in advance of an attack of the emerald ash borer.
The insect has been found as close as Shoreview in Ramsey County. Hugo said when it gets within 15 miles of Elk River, some steps could be taken. One thing the city could consider at that time is treating its highest value ash trees with insecticide, she said. Property owners could also choose to treat some of their trees.
The Sherburne Soil and Water Conservation District is also already making some different varieties of trees available to cities in Sherburne County at a low cost. The conservation district nurtures trees in a hydrated gravel bed at the University of Minnesota research farm in Becker, which improves the tree’s root system prior to planting. Some of them were scheduled to be planted this week at Riverplace Park and Trott Brook Park in Elk River.
An adult emerald ash borer spends warmer months on the tree surfaces, but its larvae will burrow beneath the bark and destroy the tree. One precaution that anyone can take to prevent the spread of this insect is to not transport firewood.
Species distribution of trees in Elk River
Spruce 17.5 %
Maple 14.5 %
Ash 9.2 %
White oak 4.9 %
Red pine 4.4 %
red oak 3.7 %
Elm 3.7 %
Boxelder 3.5 %
Birch 2.8 %
Other species 26.2 %
Source: Sherburne Soil and Water Conservation District