North Central Research Station

The Aspen Free-Air Carbon and Ozone Enrichment (FACE) Project Facility Expansion Environmental Assessment Information Center.

This web site is the online center for public information and involvement in the environmental assessment of the planned expansion and resulting operation of the Aspen Free-Air Carbon and Ozone Enrichment (FACE) project facility located near Harshaw, Wisconsin.

The Aspen FACE (Free-Air Carbon Dioxide Enrichment) Experiment is a multidisciplinary study to assess the effects of increasing tropospheric ozone and carbon dioxide levels on the structure and function of northern forest ecosystems. The Aspen FACE experiment consists of twelve 30m rings in which the concentrations of carbon dioxide and tropospheric ozone can be controlled. The design provides the ability to assess the effects of these gasses alone, and in combination, on many ecosystem attributes, including growth, leaf development, root characteristics, and soil carbon.

Purpose and scope

The tallest trees in the Aspen FACE experiment are nearly overtopping our existing infrastructure, especially in the elevated CO₂ rings. Our ring infrastructure was originally designed to accommodate an 8-10 year study, but it is adaptable to longer term by extension of the existing infrastructure. Three main components of the rings must be adapted.

Composite image at left shows current canopy and equipment conditions. 
A. The wind speed/wind direction sensors near the top of the center pole will soon be overgrown by the canopy.
B. The vertical vent pipes will soon be taken over by the canopy.
C. The canopy access walkway and towers will need to be raised to continue upper canopy access.

First, extensions are needed for the center pole (on which wind-speed and wind-direction detectors and our canopy air monitoring lines used to monitor treatment exposure are attached) to keep specific sensors at the top of the canopy (Figure A).

Second, extensions are needed for the vertical vent pipes and their supporting poles to accommodate dispensing of the gases from the forest floor through the canopy. As with the center pole, the vertical vent pipes are being overtopped by the canopy (Figure B).

We had engineers from Brookhaven National Lab and Wisconsin Public Service Corporation (who installed our original pole system for vertical vent pipe support) examine options for extending the center poles and vertical vent pipes, and the tentative plan is to use galvanized steel poles for both extensions. The existing wood poles will be removed and replaced with new longer poles. The first extension will be five meters (approximately 15 feet) above the current pole heights. The poles will be designed so that a further 15 feet extension can be accommodated in about 5-6 years. The current height of vent pipes and center poles is 30 feet. Therefore, the height could double if both phased extensions take place over the next ten years. Extensions of both the central sensor pole and vertical vent pipes and supporting poles will commence in 2005.

Third, the canopy-access walkways will have to be raised to allow access to the live canopy (Figure C). We have contacted the original company who installed these walkways to get their assistance in raising the three support towers for the walkways and the walkways themselves. This will likely have to be done in 2006.

Richard D. Sindt
Acting Station Engineer
North Central Research Station
1992 Folwell Ave.
St. Paul, MN 55108

More information about ongoing research at the Aspen FACE site

The Aspen FACE Experiment website

Physiological mechanisms of growth and multiple stress responses in Northern forest trees.

Atmospheric-Ecosystem Interactions - Global change research

Pdf files require installation of free Adobe Reader software

USDA Forest Service - North Central Research Station
Last Modified: Thursday, 02 June 2005