EHUF 475 Wetland Ecology
1.
Exam #1 – KEY
November 2001
Why is peat formation common in boreal North America, northern Europe, and Siberia but not the
tropics?
Precipitation exceeds evapotranspiration in the cold humid climates of the northern latitudes, and
decomposition rates are low in the cold, saturated, anoxic soils that result. Although productivity is
modest, it still exceeds decomposition, leading to an accumulation of partly decomposed organic
matter, or peat. In the tropics, productivity is high but is offset by high decomposition rates.
Organic matter is recycled rapidly and does not accumulate except in unusual conditions.
2.
The Cowardin system of the US Fish & Wildlife Service classifies wetlands and deepwater habitats
into five main systems and numerous classes and subclasses. Name and describe two such systems
and two vegetation classes.
SYSTEMS
Marine – Open ocean overlying continental shelf and associated high-energy coastline.
Estuarine – Tidal wetlands & deepwater habitats in which ocean water is at least occasionally diluted
by freshwater runoff from land.
Riverine – Wetlands & deepwater habitats contained within a channel, unless water has >0.5 ppt
ocean-derived salts or wetland is dominated by trees, shrubs, persistent emergents, emergent mosses,
or lichens.
Lacustrine – In a topographic depression or dammed river channel; tree, shrub, persistent emergent,
emergent moss, and lichen cover <30%; AND > 8 ha in area, or smaller if >2 m deep.
Palustrine – All nontidal wetlands (or if tidal, <0.5 ppt ocean-derived salinity) dominated by trees,
shrubs, persistent emergents, emergent mosses, or lichens.
VEGETATION CLASSES
Moss-Lichen – Mosses or lichens cover substrate other than rock; other vegetation cover <30%.
Emergent – Dominated by erect, rooted, herbaceous aquatic plants
Scrub-Shrub – Dominated by woody vegetation <6m tall.
Forested – Dominated by woody vegetation 6m tall.
[See Mitsch & Gosselink, 3rd Edition, pp. 737-739]
3.
What is a compatible solute (osmoticant), and how does it function in a salt-marsh plant?
A compatible osmoticant is a solute that balances the osmotic potential inside the cytoplasm of the
cell with the osmotic potential outside, without interfering with enzyme function or other metabolic
processes. Compatible osmoticants may include inorganic ions such as K + or soluble organic
molecules such as glycerol. A salt-marsh plant uses them to absorb and retain water and nutrients
while growing in saline water or soil. In plants that sequester salt in vacuoles, compatible solutes
balance solute concentration in the cytoplasm with the concentration in the vacuole.
4.
Describe three combinations of climate and topography that lead to wetland formation.
THREE EXAMPLES:
a) In boreal or subarctic regions, cold, wet climate and flat topography leads to ponding and, during
spring, flooding from runoff of melting snow and ice  Bogs, fens, muskegs.
b) Glacial kettles form shallow lakes and ponds in the Dakotas and central Canada; relatively modest
rainfall is augmented by snowmelt and other surface runoff to form seasonally flooded prairie
potholes. These often dry out in the summer because of high evapotranspiration.
c) Mangrove swamps form in frost-free latitudes in tidal seacoast shallows and lagoons that are
protected from high-energy waves.
5. What are aerenchyma? Where and how are they formed?
Aerenchyma are spongy, porous plant tissues whose air passages allow O 2 to diffuse from aerial
leaves and stems to roots in water or saturated soil. The plant hormone ethylene dissipates slowly in
water and thus builds up in inundated plant parts, triggering cell death and cell-wall disintegration.
The spongy tissue and large holes of aerenchyma are formed by cells pulling apart and
disintegrating. One can see such tissue in the submerged roots and stems of purple loosestrife and
bulrush species, for example.
6.
Using the diagrams below, provide the approximate proportions of inflows and outflows for any two of
the following, and name the system you are describing:
A) ombrotrophic bog B) alluvial swamp associated with a flooding river C) mangrove swamp
150
100
0
15
25
0
0
10
A) ombrotrophic bog
150
50
100
100
6000 .
flooding river
300
300
0
0
50
50
B) alluvial swamp with flooding river
100
0
100
100
-75
0
25
in = 1200
out = 1150
C) mangrove swamp
7.
Describe the procedures and studies that must precede the design of a wetland mitigation plan.
a) Development Site - Delineate and assess the functions of wetlands on the site to be developed.
Until you know the area, classification, and functions of wetlands that will be destroyed, you
won’t know how to compensate for impacts.
b) Reference Site - Select a reference site in the same watershed, if possible, that most closely
approximates the type of system that the mitigation wetland should emulate. Record the
characteristics and functions of the reference wetland that make it a worthy model.
c) Mitigation Site - Locate a site where mitigation can achieve the required compensation for losses
in wetland and area and function. Assess the soils, hydrology, and vegetation of the mitigation
site to verify its appropriateness. Determine if development of property adjacent to the site
could affect mitigation. Delineate and assess the functions of any wetlands on the mitigation site
and determine baseline values for plant cover, water quality, and other data that may be
important in measuring the success of the mitigation.
8.
Explain the differences between bog and fen, and between marsh and swamp. Can a bog or fen also be
a swamp or marsh?
A bog is a peat-accumulating wetland that receives no significant water from surface or groundwater
flows and supports acidophilic mosses, especially Sphagnum. A fen is a peatland that receives some
drainage from surrounding mineral soil.
A marsh is a frequently or constantly inundated wetland dominated by emergent (herbaceous )
vegetation. A swamp is a wetland dominated by trees or shrubs. (In European terminology, a marsh
has mineral soils and does not accumulate peat; wetlands dominated by reedgrass also are called
swamps.)
By U.S. definitions, a bog or fen dominated by herbaceous vegetation could be called a marsh; a bog
or fen dominated by woody vegetation is also a swamp.
9.
Define wetland hydroperiod.
Hydroperiod is the seasonal pattern of the water level of a wetland, its hydrologic signature. It
describes the rise and fall over time of a wetland’s surface and subsurface water, as influenced by
topography, soils, climate, and adjacent bodies of water.
10. Describe five wetland functions.
a) Flood mitigation – Wetlands act as reservoirs that slow runoff from a watershed and attenuate
peak flows. In urbanized watersheds with fewer wetlands and more impervious cover, floods are
more frequent and severe, and develop faster.
b) Streamflow maintenance – Gradual discharge of water stored during high rainfall maintains
flow during dry periods.
c) Shoreline stabilization & storm abatement – Wetland vegetation binds soil particles, reduces
erosion, and dissipates the energy of wind and water
d) Groundwater recharge – Although impermeable soils underlying most wetlands limit their
ability to recharge groundwater, recharge is important in smaller wetlands and at the wetland
edge.
e) Water quality improvement – Wetlands trap sediment and remove pollutants such as nutrients,
heavy metals, hydrocarbons, and pathogens.
f) Wildlife habitat (breeding, feeding, nesting, refuge) – Habitat for invertebrates, waterfowl,
songbirds, raptors, fish, amphibians, reptiles. and mammals.
g) Primary productivity & food web support – High primary productivity contributes to detritalbased, complex food webs. Invertebrates consume decomposed organic matter; insects, birds,
and small mammals consume detritivores, herbivores, and plants.
h) Biodiversity – As ecotones, transitional between upland and aquatic ecosystems, wetlands
accommodate a relatively high diversity of species and sustain a disproportionate number of
threatened and endangered species.
i) Peat accumulation – Sequestering carbon in peat can help offset the discharge of greenhouse
gases from burning fossil fuels.
j) Social values: aesthetics, education, recreation, etc.