Background

1. Background • Tree roots and other life in forest soils provide valuable ecosystem services such as: • Water and nutrient supply to trees, resulting in healthy and productive forests • Carbon storage to help slow the accumulation of atmospheric CO2 –a potent greenhouse gas • Beneficial and pathogenic soil organisms • Structure to support trees and prevent soil erosion • Restoration of compacted or degraded soil • Water purification and toxin removal for soil, surface water, and ground water • Beneficial and antagonistic tree root system interactions which impact forest productivity. Belowground Forest Management -our forest management to date has been largely based on what we see aboveground not what we see belowground-- The Houghton Rhizotron will enable us to better understand the environmental controls and management impacts on these services by providing a research facility that enables repeated non-destructive access to forest soil as it really is in nature.

2. Site Selection The Rhizotron facility is located at the Forest Service’s Northern Research Station, Forestry Sciences Laboratory in Houghton, Michigan. A site was chosen near the existing laboratory facilities on the Michigan Technological University campus to provide easy access for researchers. This facility is one of two in the world located in a northern forest ecosystem. The site is dominated by white ash and sugar maple trees. Test pits were dug in various locations to locate a suitable site. At the chosen location the upper 27 inches of native soil was classified as a loamy sand. The native soil from 27-67 inches below land surface was classified as a sand. Basalt rock was also encountered.

3. Groundbreaking June 2005 The Groundbreaking ceremony was held on 14 June 2005. Shown are (from left) David Reed, Dale Tahtinen, Peg Gale, Dan Greenlee, Glen Mroz, Kurt Pregitzer, Mike Henricksen, Alex Friend, Christian Gardina, Ruth Gleckler, Noah Karberg, Erik Lilleskov, and Martin Iskra.

4. Excavation July 2005 Excavation began in July, 2006. It was anticipated that bedrock would be encountered and that blasting would be necessary. However, all rock encountered was able to be broken up with the excavator. Tree roots even found their way through this soft rock! Excavation was completed to an average depth of about 9 ft. Sheet pilings were used on the east side of the excavation so that the Rhizotron could be built as close as possible to the undisturbed soil on this side.

5. Construction August 2005 The Rhizotron facility was constructed with a 2 foot gap between the undisturbed soil and the east side of the building. A drain was installed along the foundation to help prevent unnatural water buildup along the facility wall. 24, 60 x 40 inch windows were installed along the length of the facility. The entire facility was slanted to follow the natural slope of the land.

6. Construction August 2005 15 panels of steel reinforced glass were installed in each of the 24 windows. The panels were designed to so that they may be individually removed for manipulative studies. The glass is sealed against the elements using an organism-friendly aquarium sealant. The walls, floor and ceiling of the Rhizotron were constructed of steel reinforced concrete. A head house was constructed for storage of supplies, records, and experimental preparatory work.

7. Backfill November 2005 Backfill of the excavated areas adjacent to the Rhizotron was designed to emulate natural stratigraphy. The east side of the facility was backfilled using the same material that was excavated. This material had been stockpiled according to soil type as it was removed. Backfill was conducted to emulate local conditions. The west side of the facility was backfilled with a sandy soil from a red pine forest. It was donated by Plum Creek Timber Company from a site in Atlantic Mine, MI. Backfill was conducted to emulate the soil layers in the forest of origin. Backfill was watered as it was placed as a natural means of compaction. Fill material was brought just up to the top of each window.

8. Finish Work June 2006 The exterior of the facility was finished with metal siding and a brick retaining wall. White Pine, Aspen, Sugar Maple, Norway Maple, and Buckthorn tree seedlings were planted on the previously excavated areas. Each window was fitted with a stainless steel cover to prevent light pollution while working in the facility. Interior lighting includes fluorescent tubes and photographic dark room lights to permit observation and image capture of photosensitive organisms. A climate control system was also installed to keep the open space at ground temperature.