Oak Ridge FACE

Oak Ridge Experiment on CO₂ Enrichment of Sweetgum

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Goals

The response of natural ecosystems to an increasing concentration of carbon dioxide in the atmosphere is a key component of analyses of the current and potential impact of global change. Efforts to understand how eastern deciduous forests will be affected by carbon dioxide enrichment of the atmosphere have heretofore been addressed by studying components of the forest system (individual small trees, specific processes), but it is now time to take the critical leap to measuring the integrated response of an intact forest with a focus on stand-level mechanisms.

Goal
To understand how the eastern deciduous forest will be affected by CO₂ enrichment of the atmosphere, and what are the feedbacks from the forest to the atmosphere. This goal is being approached by measuring the integrated response of an intact forest ecosystem, with a focus on stand-level mechanisms.

Features
A free-air CO₂ enrichment (FACE) facility, comprising five 25-m plots was constructed in a deciduous forest on the Oak Ridge National Environmental Research Park. The study site is a sweetgum (Liquidambar styraciflua) monoculture planted in 1988. This closed-canopy, 18-m tall stand offers the opportunity for rigorous tests of hypotheses that address the essential features of a forest stand and how they could influence the responses to CO₂. These features include:

the closed canopy, which constrains growth responses
full occupancy of the soil by the root system, which constrains the nutrient cycle
the larger scale of the trees compared to saplings in open-top chambers, which changes the functional relationships of carbon cycling
and the longer time scale that can be addressed, permitting studies of soil carbon changes.

A User Facility
The Oak Ridge FACE facility is a user facility operated by the Environmental Sciences Division of the Oak Ridge National Laboratory (ORNL). It is open to researchers from universities and other research laboratories who are interested in pursuing other questions relevant to forest response to elevated CO₂. The facility was established with support from the ORNL Director’s R&D Fund and the Biological and Environmental Research program of the U. S. Department of Energy Office of Science. Additional support was provided by the Terrestrial Ecology and Global Change (TECO) program through the National Science Foundation.

A Network of CO₂ Enrichment Experiments
This project was part of the CO₂ research network fostered by the Global Change and Terrestrial Ecosystems core project of the International Geosphere-Biosphere Programme. Results from the experiment contributes to the Terrestrial Ecosystem Response to Atmospheric and Climatic Change (TERACC) project, a 5-year initiative integrating experimental data and global change modeling.

A description of FACE technology, site characteristics of FACE experiments worldwide, and links to other sites and resources are provided by the Carbon Dioxide Information and Analysis Center (CDIAC).