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

Table 5.4. Nutrient mncvnfmtions jp&gl in lie:tcya~td su$~rypcnt fmm n Connecticut red mapleswamp
(fmrn r17 an 1979 cutd Luuntirc 1986)).
Leaf litter 2,687 77 8.6 12 225 7 2
stems (0.542 0.1Ph) reported by Elrrenfeld (19%)
for southern New Jersey red maple swamps fi1ll
within the general range reported for other swamps
and floodplain forests. Additional data on tllr? nutrient
content of red maple stem, branch, amld leLkf
tissues from New Jersey swmps are provided in
Table 5.3.
Damman (1979) and Laundre (1980) found
higher concentrations of K, Mn, and Zn in red
maple leaf litter of a Connecticut swamp than in
the upper 40 cm of organic soil beneath, but fourld
higher levels of Fe, Pb, and Ni in the soil; Ievcls of
Na and Cu were similar in the two compartnlcnts
flable 5.4). These data suggest that K, Mxl, and
Zn are readily taken up by the vegetation and
rapidly cycled, enriching the surface of the swamp
annually
The initial leaching of ions from Iitkr often
reverses with time, as concentrations of many
minerals subsequently increase there (van der
Valk et al. 1979). 1mmobiIization of nutrients by
microbes associated with decomposing plant. mnterial
has been demonstrated or inferred in many
wetland studies (Mason and Bryant 1975; Brinaon
1977; Day 1982). In the Great Dismal Swamp,
litter concentrations of N and P remained unchanged
or increased over a 1-year period, while
K levela decreased initiaHy and then increased
(Day 1982). These data suggest there was active
immobilization of nutrienh from external sources
and net mineralization of Ca and Mg. Laborabry
studies also have shown that, without accrual of
nukients from external sources, N and P levels in
decomposing red maple leaf litter continue tx, decline
(Day 1983). in studying a North Carolina
water tupelo (Nyssa aquatics) swamp, Brimon
(1977) concluded that element accumulation
through immobilization appesed to be an important
mechanism for trapping nutrients that might
otherwise exist in dissolved form and be expo*d.
He found that immobilization generally lasted
beyond spring months, making the nutrients
available for plant uptake during the growing 8 ~ -
SQn.
Them has been so little research on nutrient
cycling in rial-theastern forested wetlands that it is
I~~sibltx to develop oxdy a very simplified scenario
of sorrrc of the seasonal processes that occur in these
swaIrrps (Fig. 5.4). As with most wetlands, the extent
to which red maple swmps retain and cycle
nutrients is stroilgly influenced by hydrology,
which h~s prono~lnced seasonal variability. Both
leachirtg r~nct in~rnobilizat~ion of nutrients from extcmd
sources rnay occur from fall into spring.
l.fydrologi:ic cvents clearly can influenc~ the magnitrtdc
and tirnirrg of these processes; flushing events,
which rarnove detritus, or backwater flooding,
which brings enriched waters into the wetlands,
are examples. Streams carrying suspended sediments
and dissolved nutrients overflow into
Inany swamps during flood periods. As water
velocities decrease in the wetlands, suspended
particles and adsorbed constituents (e.g., phosphorus
and heavy metals) settle to the soil surface,
turd dissolved nutrienb in the water may
diffu~e within the soil and detrital layers. Surface
water runoff from surrounding upland areas alsa
may contribute significant loadings tx, wetlands
(van der Valk et al. 1979). The following are conservative
estimates for annual nutrient and metal
removal via sediment deposition in 1 m2 of
northeastern wetland soils: N, 1.5 g; F: 375 mg;
Cu, Pb, and Zn, 25 mg; Cd, 0.2 mg; and Wg, 0.2-
2.5 mg (Nixon and h e 1986). Soil adsorption,
immobilization by microbial decomposers, algal
uptake, denitrification, and chemical complexing
(e.g., as ferric phosphate) may all influence mtrient
pathways during the dormant season
(Richardson et al. 1978; Brinson et al. 1981a,b).
With the onset of the growing season and
warmer conditions in a red maple swamp, increased
decomposition of organic matter speeds
the releaae of nutrients at the same time that
plant uptake increases. Heightened evapotranspiration
gradualIy lowers the water table, typically
to a point within, or just below, the root
zone. As a result, soil oxygen levels increase,
and soil chemical and biochemical procestres are
affeekd. Brinson et al. (19$lb), for example,