| Three
of the five major streams that drain the Savannah River Site were severely impacted
by thermal effluents. Although reactor operations ceased and natural succession
is occurring, these ecosystems remain different from unimpacted reference systems.
The SRS Strategic Plan states that DOE places a "high priority on the protection
of public health and restoration of the environment." Thus, the goals of
this research are:
| • | determine
whether these recovering and restored wetland ecosystems have a balanced indigenous
community, | | • | determine
the effect of various large-scale restoration practices on the recovery trajectory
of these ecosystems, | | • | determine
the "best" restoration strategies for specific biotic components of
the wetland ecosystem. |
Swamp
Forest Recovery Following Disturbance
| Baseline
information on natural successional recovery processes is valuable in assessing
the need for restoration efforts. In Fourmile Branch, analyses are being conducted
of color infrared aerial photographs from 1985, 1990, and 1993 to examine the
rate and pattern of plant succession following shutdown of C-Reactor in 1985. |
| | Fig.
1. Successional recovery of woody vegetation in Fourmile Delta, as determined
from analysis of aerial imagery. | |
Between 1985 and 1993, tree and shrub coverage in the 60-ha study area increased
from 3 ha to 33.5 ha, and trees and shrubs now cover well over half of the extensively
disturbed area. Woody species establishment was most rapid within 50 m of the
surviving forest around the edge of the delta.
|  |
| Fig.
2. Recovery of woody vegetation is most rapid near surrounding areas of surviving
forest. | |
Although vegetation recovery is proceeding steadily, the primary tree species
are loblolly pine (Pinus taeda) and willow (Salix spp.), both early-successional
trees that are wind-dispersed. There has been very limited recovery of the original
hardwood and swamp forest canopy species.
|  |  |
Fig.
3. Aerial views of Fourmile Branch delta at the time of reactor shutdown, showing
large area of swamp forest destroyed by thermal effluents.
|  |  |
Fig.
4. Ground view of Fourmile Branch
delta at the time of reactor shutdown,
showing swamp forest destroyed by
thermal effluents. | Fig.
5. Woody vegetation of Fourmile
Delta in 1995. |
|
