|
FACE:
Free-Air CO2, Enrichment of a Closed-Canopy
Sweetgum Plantation |
|
A
potential outcome of climate change is an enrichment of atmospheric CO2
levels. Past research has addressed responses of individual tree seedlings
or saplings but not how mature forests might respond. |
|
| The
FACE facility is designed to examine how a stand of 12 m tall sweetgum trees with
a closed canopy influences a forest's response to CO2. The FACE
rings (2 ambient, 2 enriched, 2 controls) are composed of 15 m towers with suspended
vertical vent pipes that are computer controlled for CO2 release based
on wind speed and direction, and feedback control from the ring center.
Rings encircle up to 173 trees. |
|
|
Project tasks examine tree growth, foliar physiology and biochemistry, whole plant
transpiration and canopy conductance, stem respiration,
root dynamics, nutrient cycling, and the integration of ecosystem feedback response
of elevated CO2 levels using simulation models. |
Ecosystem
Management
|
Ecosystem Management is the integration of ecological, economic, and social principles
to manage biological and physical systems in a manner that safeguards the ecological
sustainability, natural diversity, and productivity of the landscape. In
order to accomplish this goal multidisciplinary research on a variety of ecosystems
under different levels of human influence is required. The location of the
Oak Ridge Reservation (ORR) in a suburban/industrial setting makes it a particularly
valuable site for addressing issues dealing with ecosystem management as the growth
of urban areas increases stresses on the forests and aquatic ecosystems.
These
issues include
• Global Climate Change
• Biodiversity
• Tropospheric Air Quality
• Sustainable Development
• Endocrine Disruptions
• Multiple Stress Interactions
• Landscape Dynamics/Land Use/Urban Ecosystems |
|
| |
| | |
Walker Branch
Throughfall
Displacement Experiment |
|
|
| Goal: | Use
stand-level manipulations to understand forest adjustments to potential changes
in regional rainfall. | | | |
| Findings: | Seedlings
and saplings may be at risk in a drier environment, but mature trees appeared
buffered against change. | | | |
| | Changing
annual rainfall inputs by one third can produce changes in net carbon sequestration. |
| | | | | Changes
in the seasonality of rainfall are likely to be more important than simple changes
in total annual rainfall. | | | |
Key
Products: | Comprehensive
synthesis of impacts of variable rainfall input on ecosystem and individual species'
productivity. | |
|
|
Walker Branch Stream Nitrogen-15 Addition Experiment:
|
|
 Streams
serve as key hydraulic and biochemical links between uplands and downstream aquatic
systems. Field tracer experiments using 15N were conducted during 1997
in a first order stream to identify uptake rates of NH4 by a stream
ecosystem and the transfer of nitrogen through the food web.
Hydraulic,
chemical, and biological characteristics were measured to identify mechanisms
for differences in 15N dynamics observed between streams of an intersite
comparison study (Lotic Intersite Nitrogen Experiment: LINX).
|
