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

kettle bogs, lakes, or large rivers. Similarly, development
of forested swamps from wet meadows is
likely to be slow where the meadows have prolonged
surface water hydroperiods or where surface
microrelief is poorly developed.
Retrogressive Changes
The conversion of red maple swamp to nonforested
wetland is generally precipitated either by a
rise in the local water level or by the cutting of
vegetation (Fig. 6.4). A permanent rise in the water
level that inundates the root crowns of the trees
kills virtually all plants in the swamp and converts
the wetland to an open water body or deep marsh.
Beaver ponds constructed in former red maple
swamps typically contain aquatic beds dominated
by plants such as white water lily (Nymphaea
dmta) and bladdenvorta (Utricularia spp.) in the
deepest areas; marsh plants such as bur-reeds
(Sparganium spp.) where the average water depth
is 0.5 m or less; and a variety of rushes (e.g., Juncus
emus), sedges (e.g., Carex stricta), and grasses
(e.g., Glycericl, spp.) in seasonally flooded areas
along the margins of the pond (Fig. 6.5). Once a
pond is abandoned and the dam breaks, the former
flowage is usually first colonized by graminoids
(Fig. 6.6)) then soon after by shrubs, such as alders
and willows, and fmally by trees, such as red maple.
When the increase in the swamp water level is
gradual, or more limited in extent, trees may die
over a period of years. If microrelief in the swamp
is well developed, shrubs and herbs, which are
more shallowly rooted than the trees, may survive
and eventually dominate the site (Fig. 6.4). Such
a retrogressive change has been observed where
road culverts draining swamps have become
clogged with sediment (Golet and Parkhurst
1981). If shallow surface water persists throughout
the growing season, floating mats of Sphagnum
moss may develop locally, providing a base
for colonization of the site by bog plants such as
leatherleaf (Chamaeduphne calyculata) and cranberries
(Vaccinium macrocarpon).
Clear-cutting of trees causes a red maple
swamp to revert to shrub swamp or, less commonly,
to emergent wetland (Fig. 6.4). Shallow
marshes or wet meadows dominated by ferns and
various graminoids are often produced when trees
are removed from maple swamps that contain a
poorly developed shrub layer or when all woody
vegetation is removed. Due to a reduction in transpiration
losses at the site after cutting, a local
rise in the summer water table may occur. Such
an increase in wetness is most likely to occur in
I
Red maple swamp
I
(Seasonally flooded or
seasonally saturated)
Water level rise
I
Shallow Semipermanent Trees and Trees cut; Trees cut;
permanent shrubs shrubs shrubs
flooding cut absent present
Shrubs
present
Open water
Deep marsh
Fig. 6.4. Retrogressive changes in northeastern red maple swamps due to water level rise or cutting.