Ecology of Red Maple Swamps in the Glaciated Northeast: A ...

y capturing sediment, reducing nutrient loads,
and fdtering other pollutanb before they reach the
wetland (Brown and Schaefer 1987).
A considerable body of experience has developed
on pollution attenuation in artificial buffer strips
(Clark 1977). Research on natural systems is more
limited, but recent findings are encouraging. For
example, forested buffer zones in Maryland and
North Carolina have been shown to remove as
much as W / o of the excess nitrogen and phosphorus
from agricultural runoff (Hall et al. 1986). In a
2-year study conducted in southern Rhode Island,
Gold and Simmons (1990) injected a "spike" of
nitrate, copper, and a tracer into the ground upgradient
from forested upland and red maple
swamp monitoring stations at three sites. They
found complete attenuation of copper in the groundwater
at all stations. Nitrate removal ranged from
14 to 87% in the forested upland, where soils were
moderately well drained or somewhat poorly
drained; in the swamp, it was almost complete in
both poorly drained and very poorly drained soils.
The highest attenuation occurred where groundwater
levels were closest to the surface. The authors
concluded that forested buffer zones can protect
wetland and surface-water systems from water
quality degradation throughout the year; however,
long-term performance may vary because plant
uptake and microbial immobilization of nitrate are
temporary nutrient sinks.
One of the unique aspects of many buffer zones
is the high species richness of both plants and
animals porter 1981). As a transitional area between
wetland and upland, the buffer zone commonly
contains species that are representative of
both communities (Anderson et al. 1980; Davis
1988). Moisture is characteristically abundant in
this zone, but not limiting to plant growth; as a
result, forest productivity is often higher there
than in more droughty upland soils (Braiewa et al.
1985). Upland habitats along the wetland edge
have also been cited as the main source for seeds
contributing to the spatial heterogeneity of wetlands
(Brown and Schaefer 1987).
The Issue of Buffer Width
One of the most vigorously contested issues in
public hearing rooms throughout the Northeast in
recent years has been the minimum width of buffer
zone required to safeguard wetland ecosystems
from the adverse impacts of development. Proposals
have ranged widely, from as much at3 150 m to
as little as 15 m. There has been so little research
on the basic characteristics and functions of wetland
buffer zones that the development of scientifically
valid criteria for determining buffer zone
width has been difficult (Jordan and Shisler 1988).
As a result, buffer zone widths established by
regulatory agencies often have been arbitrary.
The Rhode Island Freshwater Wetlands Act
(G.L., Chap. 2-1, Sect. 18 et seq.), passed in 1971,
was the first inland wetlands law to include a
buffer; all land within 15 m of the edge of ponds,
marshes, swamps, and bogs is considered part of
those wetlands and is regulated accordingly New
Jersey's Freshwater Wetlands Protection Act (NJ
S.A. 13:9B-1 et seq.), which was passed in 1987,
contains the most sophisticated treatment of buffer
zones (termed transition areas m the law) to date.
The act requires that all freshwater wetlands be
classified as exceptional, intermediate, or ordinary.
Exceptional wetlands, which provide habitat for
threatened or endangered species or which border
trout production waters, have a 46-m transition
area. Transition areas are not required for ordinary
wetlands, which include ditches, swales, detention
basins, and isolated wetlands less than 465 m2 in
area with development along at least 50% of their
borders. All other wetlands, which are considered
to be of intermediate value, have 15-m transition
areas.
A major contribution toward the development of
buffer zone criteria was made by researchers in the
New Jersey pinelands (Roman and Good 1985). In
their buffer delineation model, buffer width is determined
by numerically rating both the natural
quality, values, and functions of a wetland and the
potential for site-specific, cumulative, and watershed-wide
impacts of development. Indices for relative
wetland quality and relative environmental
effects are averaged, and the resulting buffer index
is translated into a buffer width by using a conversion
table. This is the only quantitative procedure
that rates both wetland values and impacts.
Working in the Wekiva River Bmin of central
Florida, Brown and Sehaefer (1987) also developed
quantitative criteria for buffer delineation. Key
functions addressed were water quality maintenance,
water quantity maintenance, and wildlife
habitat. Buffer width was determined from existing
scientii'ic data on soil erodibility, depth to the water
table, and the habitat requirements of representative
wildlife species known to inhabit the
area. Buffer zone widths were calculated for each
function, and the largest width was considered to
be controlling in any given area. Buffer widths