The Marketplace Winter 2017

Research on Ice Storms and the Effects on Northern Forest Ecosystems

ISE ice strom experiment Plot 8 sign

By: Kristen Bergstrand Utilization & Marketing coordinator, Division of Forestry, Minnesota Department of Natural Resources (DNR)

In recent years Minnesota has experienced more frequent and severe weather events ranging from high winds to heavy ice storms. Usually considered relatively rare, ice storms are major causes of forest disturbance in north temperate and boreal forest ecosystems worldwide. While the impacts of such extreme storms on our forests are not yet well understood or documented due in part to Mother Nature's unpredictable timing, we know that such storms have complex and potentially long-term effects on forest ecosystems.

To learn how a northern hardwood forest ecosystem may respond to ice damage from increasingly severe and frequent ice storms, USDA Forest Service (FS) researchers set up an experiment in the Hubbard Brook Experimental Forest located in New Hampshire's White Mountain National Forest. The "Ice Storm Experiment," funded by a grant from the National Science Foundation, is the first-ever controlled study that uses human-created artificial storms to study how ice damage impacts trees, forests, and ecosystems.

Spraying water on trees

A suite of experimental ice storms were created on 10 plots, each roughly the size of basketball courts. In both years, the ice had to be created under very specific weather conditions to get the desired level of ice on the trees. The icing was done at night—during the coldest part of the day—and took two to four hours per plot. In the winter of 2016, two plots received ¼" of ice (a modest ice storm), four received ½" of ice (a significant ice storm), two received ¾" of ice (an epic ice storm), and two received no ice, serving as the "control". Scientists returned in January 2017, and applied another ½" ice to two of the plots that had already received ½" ice, investigating what happens if a forest is hit by back-to-back ice storms in two consecutive years.

Some early results listed indicate that there is a dramatic response to the different levels of icing, with the amounts of coarse (>~1 inch) and fine (<~1 inch) woody material that came down in the simulated ice storm look to be roughly proportional to the amount of ice that was applied. They also think that the fine (<~1 inch) woody debris that came down in the one icing event was equal to what would typically come down over the entire year. The amount of large debris (>~1 inch) that came down in the half inch one icing event trial was much greater then what would typically come down in year.

In addition to the icing experiment, this broad program of research also includes monitoring forest recovery from the natural ice storm of 1998, as well as climate and forest process modelling.

tree limbs ice covered
Tree limbs covered in ice. Photo by: Klementocich

Together the compiled research can inform scientists, land managers, and the public on:

  1. New biogeochemical model simulations to help evaluate future ice storm impacts on the health and sustainability of northern hardwood forests,
  2. Evaluation of short-term (e.g., 2-3 years) forest ecosystem response to four different intensities and two frequencies of simulated ice storm events,
  3. Evaluation of longer-term (e.g., 15-20 years) forest ecosystem response to the "1998" ice storm event.
  4. Climate projections on possible changes in the future frequency and intensity of ice storms in the northeastern United States.

This research will also provide background data for lessons on climate change and extreme weather events, which can be used with students in science, technology, engineering, and mathematics; college students; and local stakeholders.

Importantly, the research will also help us manage our Minnesota forests, especially how we clean up and salvage timber damaged from severe ice storm events. Finally, we can use this data to manage forests to be their most resilient as extreme storms increase in severity and frequency over time.

"Ice Storm Experiment," USDA Forest Service Northern Research Station