Geoscience Reference
In-Depth Information
Figure 4-1.
The general water cycle showing wetland storage points for inland and coastal settings. Adapted from
an illustration by Evans (2011).
latitudes and mangroves that include trees with
special adaptations in tropical regions (van den
Bergh, Barendregt and Gilbert 2004). Coastal
areas that observe the mixing of fresh and salt
water along estuarine zones, tidal creeks and
inlets provide an environment ideal for the
development of brackish marshes. In both salt
and brackish marshes, salinity levels fall away
from the open ocean and in proximity to fresh-
water source inputs.
On the other hand, inland wetlands tend to
exhibit seasonal hydroperiod patterns based
on precipitation, spring thaw, and storm events
(Fig. 4-5). In headwater settings, wetlands typi-
cally have limited storage capacity and respond
rapidly to local storms or snow melt, especially
in areas with silty or clayey soils and steep
slopes that generate fast runoff. Sandy soils and
more gentle slopes allow more ini ltration, so
runoff is slower. Hydroperiods for headwater
wetlands may be quite variable, depending on
local weather events.
Large riparian wetlands in downstream loca-
tions tend to respond more slowly to individual
storm events. Such wetland hydroperiods display
average conditions over the larger watershed
Figure 4-2.
The Fegge peninsula extends into the
Limfjord estuary, northern Jylland, Denmark. Tidal
effect is minimal; water level and chemistry rarely vary
for the wet meadow, marsh, shore, and shallow-water
environments. Cattle in lower left corner for scale; kite
airphoto by S.W. Aber and J.S. Aber.
predictable patterns (Mitsch and Gosselink
2000).
Coastal wetland regions with ocean frontage
and the unrelenting onslaught of tidal action
followed by salt-water submergence provide
conditions conducive to the establishment of
salt marshes dominated by grasses in the upper
