Transcript Document 7220087

Formation, Chemistry, and
Biology of Wetland Soils
Maverick, Dana,
Devon
General Information on Soils
• Unconsolidated, natural material
• Supports or capable of
supporting vegetation
• Can be described as an
independent body (soil type)
having specific properties and
morphological characteristics
that can be used to differentiate
it from adjacent soil types
Soil Forming Factors
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Climate
Parent material
Time
Topography
Living organisms
Climate
• Weathering forces such as
heat, rain, ice, snow, wind,
sunshine, and other
environmental forces, break
down parent material and
affect how fast or slow soil
formation processes go
Parent Material
• The primary material from which
the soil is formed.
• Soil parent material could be
–
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bedrock
organic material
old soil surface
deposits from water, wind, glaciers,
volcanoes, or material moving
down a slope
Topography
• The location of a soil on a landscape can affect
how the climatic processes impact it.
– Soils at the bottom of a hill will get more water than
soils on the slopes
– soils on the slopes that directly face the sun will be
drier than soils on slopes that do not.
• Also, mineral accumulations, plant nutrients, type
of vegetation, vegetation growth, erosion, and
water drainage are dependent on topographic
relief.
Living Organisms
• All plants and animals living in or on the soil
• The amount of water and nutrients plants need
affects the way soil forms.
• The way humans use soils affects soil formation.
• Animals living in the soil affect decomposition of
waste materials and how soil materials will be
moved around in the soil profile.
• On the soil surface remains of dead plants and
animals are worked by microorganisms and
eventually become organic matter that is
incorporated into the soil and enriches the soil.
Time
• All of the
aforementioned factors
assert themselves over
time, often hundreds or
thousands of years.
• Soil profiles
continually change
from weakly developed
to well developed over
time.
Properties important to the development and
identification of wetland soils
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Horizonization
Organic matter content
Texture
Permeability
Drainage
Color
Horizonization
• Soil Horizonlayer of soil
parallel to the land
surface which can
be differentiated
from adjacent
layers, or
horizons, by
identifiable
physical,
chemical, and
biological
characteristics
MDEQ 2001
Organic Matter Content
Mitsch and Gosselink, 2000.
Texture
• Relative proportion
of sand, silt, clay
• Influenced by
interaction of
geologic and
environmental
factors
• Important property
affecting
permeability
Soil Survey Manual, USDA, 1993
Permeability
• Measure of the ability of gases and liquids to
move through a layer of soil
• Sand has high permeability
• Clay has low permeability
• Arrangement or aggregation in soil structure also
affects a soil’s permeability
Sand
Clay
Drainage
• Used to describe amount of water present and it’s influence
on potential use of that soil
• Indicate frequency and duration of wet periods that may
occur
• Seven drainage classes
– Very poorly drained
– Poorly drained
– Somewhat poorly drained
– Moderately well drained
– Well drained
– Somewhat excessively drained
– Excessively drained
• Poorly drained and very poorly drained usually indicators
of wetlands
Color
• Color and location
within profile can
indicate conditions of
soil development
• Affected primarily by
– Presence of iron
and manganese
– Organic matter
content
• Dominant color
referred to as soil
matrix
• Contrasting colors or
areas with spots are
mottles
Definitions of Wetlands
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U.S. Fish and Wildlife
– Wetlands are lands transitional between terrestrial and aquatic
systems where the water table is usually at or near the surface
or the land is covered by shallow water. For purposes of this
classification, wetlands must have one or more of the
following three attributes:
1. at least periodically, the land supports hydrophytes;
2. the substrate is predominantly undrained hydric soil;
3. the substrate is nonsoil and is saturated with water or
covered by shallow water at some time during the growing
season of each year
U.S.A.C.E.
– Those areas that are saturated or inundated by surface or
groundwater at a frequency and duration sufficient to support,
and under normal circumstances do support, a prevalence of
vegetation typically adapted for life in saturated soil
conditions. Wetlands generally include swamps, marshes,
bogs, and similar areas (USACE, 1987).
Hydric Soils!
• Formation influenced by
interactions of soilforming factors, but
overriding factor is water
• Hydric soils
– soil that formed under
conditions of
saturation, flooding or
ponding long enough
during the growing
season to develop
anaerobic conditions in
the upper part.
Hydric Soils
• Critical factors
– Saturation
– Reduction
– Redoximorphic features
• Two types
– Organic
• Peat or muck
• When waterlogged and
decomposition is
inhibited, histosols
– Mineral
• Inorganics
What is Peat?
• Partially decomposed remains of dead
plants which have accumulated on top of
each other in waterlogged places for
thousands of years.
– Areas where peat accumulates are
called peatlands.
– Brownish-black in color.
– Consists of Sphagnum moss along
with the roots, leaves, flowers and
seeds of heathers, grasses and sedges.
– Occasionally trunks and roots of trees
such as Scots pine, oak, birch and yew
– Composed of 90% water and 10%
solid material
– Waterlogged soils cause anaerobic
conditions, hinder growth of microorganisms (bacteria and fungi).
– thus, limited breakdown of plant
material.
Hydric Soil Indicators for NonSandy Soil
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Organic soils (histosols)
Histic Epipedons
Sulfidic material
Aquic moisture regime
Reducing soil conditions
Soils colors
– Gleyed soils (gray colors)
– Soils with bright mottles and/or
low matrix chroma (dullness or
neutral color)
• Iron and Manganese
concretions
Hydric Soil Indicators for Sandy
Soils
• High organic matter in surface
horizon
• Streaking of subsurface
horizons by organic matter
• Organic pans
Hydric
Non-Hydric
Different Wetlands = Different soils?
All hydric, but still vary
• Tidal Marshes
• Fens
• Bogs
• Pocosins
• Non-tidal marshes
• Wet meadows
– Prairie potholes
– Vernal pools
– Playa lakes
• Swamps
– Forested swamps
– Bottomland hardwoods
– Shrubs
– mangroves
Tidal Marsh
• Salt marsh develops its
own soil
– Accumulated mud
– Roots and organic
material from the
decay and breakup of
salt-marsh plants.
• Soils in coastal fresh
marshes are generally
alluvial
– Fine material rich in
organic materials and
nutrients.
Bogs
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Poor draining, waterlogged
Peat depth varies from 2 to 12m (slow decomposition rate).
Cool climates
May be up to 98% water
– Water is held within the dead moss (e.g. sphagnum) fragments
• Consists of two layers
– The upper, very thin layer, known as the acrotelm
• only some 30cm deep
• consists of upright stems of the present mosses (water moves
rapidly through this layer)
– Below is a much thicker bulk of peat, known as the catotelm
• where individual plant stems have collapsed under the weight
of mosses above them to produce an amorphous, chocolatecolored mass of moss fragments
• water moves more slowly through this layer
• Bogs are ombrotrophic- water supply is from the mineral-poor
rainwater
Fen
• Glacial origins
• Hydrology
– waterlogged
– mostly groundwater, some surface water.
– Mineratrophic water- usually high in calcium,
other ions from mineral-rich groundwater
• Some drainage
– slightly alkaline or neutral (pH of 7 to 8)
• Soil is made of peat
– large amount of decomposing plant material.
– The technical term for this type of soil is muck
• Average peat depth up to 2m
• Wet meadows are similar
– Don’t have organic soil
– Don’t have year-round water
Pocosin
• Like bogs, they have lots
of sphagnum moss and
nutrient-poor acidic soil
and water
• Like bogs, they get most
of their moisture from
precipitation
• usually organic soil, and
partly or completely
enclosed by a sandy rim
• Slow decay of dead
vegetation contribute
to the deep peat and
acidic soils of these
areas.
• Naturally low nutrient
levels in the soil
Vernal Pool
• Ancient soils with an
impermeable layer such as
a hardpan, claypan, or
volcanic basalt
• Hardpans and claypans are
mostly impervious to the
downward percolation of
rainwater
• The restrictive soil layers
are duripansor claypans,
and the bedrock types are
volcanic mud or lavaflows
• Dependant on Rainfall
• Makeup similar to
surrounding soils, just
hydric
Forested Swamp
• Occur in a wide variety of situations
ranging from broad, flat floodplains
to isolated basins
– Meandering river channels
– Natural levees adjacent to rivers
– Meander scrolls created as
meanders become separated from
the main channel
• Texture ranges from mucks and
clays to silts and sands
• Organic levels may reach up to 36%
Compared to content of upland soils
(0.4-1.5%) (wharton et al. 1982).
• Peat depostition is characteristic
– Slow decomposition rates
– Thickness decreases toward shallow
end of swamp
Bottomland Hardwood
• Alluvial soils as a result
of flood pulses
• High organic matter
– Acidic
• Typically high clay
contents
– Poorly drained
– Low permeability
– Some sandier blackwater
environments an
exception
Chemistry of Wetland Soils
Introduction
• Classification of Wetland Soils
• General chemical characteristics of organic
and inorganic wetland soils
• Primary chemical reactions in wetland soils
and ways of measuring them
• Case study: Lagoon of Venice, Italy
Classification of Wetland Soils
• Techniques for classifying soil types:
– Organic versus Inorganic:
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Bulk density and porosity
Hydraulic conductivity
Nutrient availability
Cation exchange capacity
– Organic soils are further classified by:
• Percent organic carbon and clay
• Hydroperiod
Organic vs. Inorganic
• Bulk Density: dry weight of a soil sample
– Organic soils weigh less than more inorganic soils
• Hydraulic conductivity: capacity of soil to conduct
water flow
– Depends on the levels of decomposition in the soil
– Organic soils hold more water than inorganic soils
• Nutrient availability: availability of nutrients and
minerals to plants
– Organic soils can actually have low nutrient availability
because it is all tied up in decomposition and peat
formation
Organic vs. Inorganic
• Cation exchange
capacity: total amount of
positive ions (cations)
that a soil can hold
– Organic soils have a
higher capacity for H+
– Inorganic soils have a
higher capacity for
positive metal ions (Ca2+,
Mg2+, K+, and Na+)
Organic Soils
• Can be further classified
by the percent of carbon in
soil:
– Organic soil material: 10%
organic carbon
– Mucky mineral soil
material: 5-10% organic
carbon
– Mineral soil material: <5%
organic carbon
Chemical Reactions
• Oxidation-Reduction Reactions
(Redox)
• Carbon Transformations
• Phosphorous Transformations
• Sulfur Transformations
• Nitrogen Transformations
Redox Reactions
• Reduction: process of gaining an electron or
hydrogen atom during a chemical reaction
• Oxidation: process by which a compound loses an
electron or hydrogen atom during a chemical
reaction
• In wetland soils, redox occurs during the transport
of O2
• The anerobic conditions in wetland soils leads to
high rates of reduction in the soil
Redox Reactions
• Anerobic Conditions:
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O2 diffusion rates through the soil is determined by how saturated the soil is
O2diffuse slower through more aqueous mediums
Causes reduced soil conditions
Takes longer for oxygen depletion to occur
Redox Reactions
• Oxygen depletion depends
on:
– Temperature
– Availability of organics
• When Oxygen is depleted,
oxidized conditions occur
• Causes the soil to be redbrown
• Reduced soil is grey-blue
• Oxidized soil layer can
sometimes form but depends
on several factors:
– Transportation rate of O2
between the surface water and
the atmosphere
– Production of oxygen by algae
– Number of oxygen consuming
organisms in residence
– The amount of surface mixing
that occurs
Measuring Redox Reactions
• Eh = E0 + 2.3[RT/nF]log[{ox}/{red}]
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E0 = potential of reference (in millivolts)
R = gas constant (81.987 cal deg^-1 mol ^-1)
T = temperature (in Kelvin)
n = number of moles of electrons transferred
F = Faraday constant (23,061 cal/mole-volt)
• A normal redox potential is between
+400mV and +700mV
Carbon Transformations
• Aerobic carbon
transformations:
– Photosynthesis: H2O is
oxidized
– Aerobic respiration:
Oxygen is reduced
• Decomposition of
organic matter this way
is efficient
Carbon Transformations
• Anerobic carbon transformations:
– Fermentation: organic matter is reduced by the
anerobic respiration of microorganisms
– Methanogenesis: CO2 is reduced by bacteria
• Result can be methane gas
• Can only occur in extremely reduced wetland soils, with
a reduction potential of less than -200mV
• Gas production affected by temperature and hydroperiod
• Methane levels higher in freshwater wetlands than in
marine wetlands
Carbon Transformations
• Gas Transport:
– Released from sediment into water column
– Diffuses through sediment and mixes with the atmosphere at the
surface
• Carbon-Sulfur:
– In some wetland soils, sulfur cycle necessary for the oxidation of
organic carbon
– Methane concentrations low in soil with high concentrations of
sulfur
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Competition for substrate between bacteria
Sulfate inhibits methane bacteria
Methane bacteria dependent on products of sulfur reducing bacteria
Redox potential not low enough to reduce CO2 due to sulfate
Sulfur Transformations
• General information:
– Never found in low enough concentrations to be
called a limiting factor in wetlands
– Most likely to occur at a redox potential of -100mV
to -200mV
– Sulfur is used as a electron receptor by bacteria in
anerobic respiration
– Sulfides are usually oxidized by microorganisms
• Some wetland plants get energy from the oxidation of
H2S into sulfur
Sulfur Transformations
• Toxic Sulfides:
– H2S can be toxic to rooted hydrophytes if the
concentration of sulfates in the soil is high
– Effect on plants is caused by:
• Free sulfide is highly toxic to plant roots
• Sulfur will precipitate with metals, limiting
availability
• Stops precipitation of some metals in the soil
Phosphorous Transformations
• One of the most limiting elements in wetland soil
– Northern bog, freshwater marshes, southern deepwater
swamps
• Inorganic form
– Dependent on pH
• Organic form
– Bound in peat/organics
• Does not have a gaseous cycle
• Not affected by redox potential
Phosphorous Transformations
• Can be made inaccessible to plants as a
nutrient by the follow processes:
– Precipitation of insoluble phosphorous with
metals in aerobic conditions
– Phosphate absorbed into peat, clay metal
hydroxides and oxides
– Phosphate bound in organic matter if consumed
by bacteria, algae, or macrophytes
Nitrogen Transformations
• One of the major limiting factors in
saturated wetland soils
• Considered one of the best electron
acceptors for redox reactions in the soil
(after oxygen)
• Nitrogen levels in wetlands have increased
due to runoff from fertilizers
Chemical Transport
• Precipitation: sulfates and nitrates
– Influenced by the burning of fossil fuels
• Groundwater:
– High in dissolved ions from the chemical weathering of soils or
rocks, also dissolution, and redox reactions
• Stream flow:
– varies seasonally with the wet and dry seasons
• Estuaries:
– Where ocean water meets brackish river water many chemical
reactions can occur
– Dissolution, flocculation, biological assimilation and
mineralization
Temporal changes and spatial
variation of soil oxygen consumption,
nitrification, and dentrification rates
in a tidal salt marsh of the Lagoon of
Venice, Italy.
P.G. Eriksson, J.M. Svensson, and G.M.
Carrer
Estuarine, Coastal, and Shelf Science
2003 pgs.1-11
• Purpose of study:
– To determine seasonal and spatial patterns of O2 in
marsh soil, along with patterns of nitrification,
dentrification, and flux of dissolved inorganic
nitrogen (DIN)
• Location:
– Lagoon of Venice, Italy
• 540 square kilometers
• Lagoon surrounded by tidal salt marsh
• Study conducted in salt marsh on west side of lagoon
• Study length:
– Tests conducted April-October of 1999
Study Location
Marsh Vegitation
Methods
• Data was collected monthly at high tide in the study area
• Took fully enclosed core samples
– 6 samples in areas vegetated by Limonium serotinum
– 12 samples taken in April
– 6 samples taken in May from areas vegetated by Juncus maritimus
and Halimione portulacoides
– Also took water samples in sealed containers from same area
– Some samples taken from near by creek bed
• Put core samples in a box, unsealed, and covered with
water samples from same location
– Kept water aerated and maintained temperature of original marsh
location
Methods
• Incubated for 2-6 hours
• Water was then collected and filtered for nitrate and
ammonium, then frozen for later testing
• Then the same cores were incubated for another 5-6 hours
in the dark (sealed)
– Measured O2 flux, nitrates, and ammonium
• Used isotope-pairing techniques to measure rates of
dentrification in the core samples
• Sieved remaining marsh sediment from core samples and
collected microfauna
– Dried and weighed sediments
Temporal Results
• Ammonium:
– Released into the water in all
core samples
– Highest release rate in April,
June, July
• Nitrate:
– Twice as high in April as in
September or October
– Net removal in areas with a
higher vegetation densities
• Oxygen soil consumption:
– Increased with temperature
over time
• Dentrification:
– Higher rates in spring and fall
– Coincides with nitrate levels
Spatial Results
• Oxygen soil consumption:
– Greater in creek soils then in vegetated areas
• DIN:
– Highest fluxes and dentrification rates in nonvegetated creek soil
• Lagoon retains nitrate and releases
ammonium into the water column
Biology of Hydric Soils
Dana Rohrbacher
Hydric Soils
• Hydric soils contain complete complex
communities, each with very distinct
features.
• They have many important ecological
functions, and help sustain the system as a
whole.
Functions of Biological Soil
Components
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Fertilize soil
Break down dead organisms
Release nutrients for use by living plants
Maintain viable soils
Contribute to long term sustainability
Clean air and water
Act as biological indicators
Soil Communities
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Biological crust
Fungi
Bacteria
Protozoa
Nematodes
Annelids
Arthropods
Seed bank
Root System
Biological Crusts
• Consist of algae, cyanobacteria,
bacteria, lichens, mosses, liverworts,
and fungi that grow on or just
beneath the soil layer.
• Variable in appearance.
• Formation of crusts is a result of soil
chemical and physical
characteristics, and weathering
patterns.
• They have many functions including
serving as habitat for fauna, aiding in
making soil more fertile, and helping
to retain moisture.
Fungi
• Mycorrhizal fungi colonize roots of plants
in a symbiotic relationship that aids the
plant in the acquisition of nutrients and
water necessary for growth. In return the
plant provides energy to the fungus.
• Not all fungus is mycorrhizal however,
some fungus play a role in decomposition,
but to a lesser extent than bacteria.
Fungal Decomposition
• Fungal decomposition starts while dead
plants are still standing, before they fall into
the water.
• The decomposition process begins, and is
greatest during early Spring.
• In estuarine systems there is generally
greater colonization in non-impacted tidal
wetlands than in tidally impacted wetlands.
Bacteria
• Ubiquitous, single celled organisms.
• Some are primary producers and some are
decomposers.
• The decomposers consume organic matter
releasing the nutrients for use by other
living organisms.
• These decomposers are particularly
important in several nutrient cycles. (ieNitrogen and Carbon cycles)
• They are important in water-holding
capacity, soil stability, and aeration.
• They can also help filter and degrade
anthropogenic pollutants in the soil and
ground water.
Nutrient Cycles
• Both fungi and
bacteria play
important roles in the
making nutrients such
as nitrogen and carbon
available for living
plants.
Protozoa
• Single celled organisms that eat bacteria.
• Classified into 3 categories, all of which
need water to move but can rely on a very
thin film surrounding the particles.
• They play a very important role in the soil
food web.
Diatoms
• Benthic pennate
diatoms found in the
Cape Fear River
• Scanning electron
microscope image of
Pseudo-nitzchia
australis.
Nematodes
• Tiny ubiquitous roundworms
classified according to their
eating habits.
• They eat bacteria, fungi, roots,
and even some tiny animals.
• They also need a thin film of
moisture to survive, but they
have an ability to become
dormant until more favorable
conditions arise.
• Beneficial in boosting the
nutrient supply, assisting in
decomposition, and can even be
useful for pest control of
insects.
• Serve as a food source for other
animals.
Annelids
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Segmented worms
2/3 live in the sea, while the rest are terrestrial.
Some are parasitic, while others are filter feeders.
Their major
role is
in reworking
the soil.
Annelids ~cont.~
• Annelids include:
Polychaetes
Oligochaetes
Leaches
• Most species prefer soft
soils; often found under
rocks.
• Serve as a food source for
other animals.
Arthropods
• Jointed invertebrates generally referred to as…BUGS!
• Range in size from microscopic to large enough to see with
the naked eye.
• They eat everything from plants, animals, and even fungi.
• They aerate the soil, shred organic matter, assist in the
decomposition process, distribute beneficial microbes, and
serve as a food source for larger animals.
• They also help in the regulation of populations of other
organisms (ie-protozoa) to maintain a more healthy soil
food web.
Arthropods ~cont.~
• Can include many different types including:
insects
crustaceans
arachnids
myriapods
scorpians
• Fiddler crabs play an important role in aeration.
• Serve as a food source for other animals.
Seed Bank
• Consist of viable, ungerminated seeds in or on the
soil.
• Significantly different from upland soil banks
because of hydrology and soil properties.
• It is important for the emergence, maintenance,
and diversity of plants in a system.
• Also, the seed bank is a mechanism for plant
species to colonize newly disturbed areas. This is
particularly important in those wetland systems
that are frequently disturbed.
Seed Bank ~cont.~
• Seed banks provide a way in which several species
can co-exist over time. This temporal variation is
observed when a successful species experiences
conditions less favorable for its dominance, and a
new, less competitive species, existent in the seed
bank, is allowed to take advantage.
• In river and tidal systems, seeds can be dispersed
by water. The ease of transport of these seeds is in
part a contributing factor to the biodiversity of
these systems.
Seed Bank ~cont.~
• Leck and Robert (1987) Estimated seed bank (seeds per
m2) in the top 10cm of soil in three wetland sites based on
1982 and 1983 soil samples collected in March and June.
Values were obtained by extrapolation of depth data for 02, 4-6, and 8-10 cm.
• Indicates that the shrub forest generally has higher seed
density within the soil. While all three locations have an
overall higher seed density in March.
Root System
• Aid in the stabilization of
wetland environments.
This stabilization is
especially important in
some systems due to their
unstable nature.
• Some types of roots are
better at stabilizing than
others. A tap root sends a
single main root down,
while more adventitious
root systems have several
branching roots. The later
type tends to be a better
stabilizing root system.
Roots ~cont.~
• They also add biomass to soil, and can be
colonized by several different species.
• Some root systems,
such as those seen in
mangrove swamps,
play important above
ground roles.
Air and Water Quality
• Several soil species are important in
managing soil organic matter which is a key
factor in controlling air and water quality.
• Nutrient loads decline in both the soil and
water when biological species thrive.
• Vegetation health increases which in turn
provides habitat which contributes to the
overall wetland quality.
Biological Indicators
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Because of the characteristic differences among
different species, organisms can serve as indicators,
offering a signal of the biological condition of a
wetland.
They can indicate soil types, wetland types, and the
presence of pollution or other negative
anthropogenic influences.
Some organisms prefer specific conditions or tend
to be sensitive to pollution. Thus, when conditions
are altered or a pollutant is introduced, this can be
measured by the absence of those organisms that
cannot tolerate the new conditions.
Indicators ~cont.~
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Some organisms, such as
macroinvertebrates, such as
leaches, actually tend to thrive in
moderately polluted areas.
Several worm species are often
indicators of “dirty water”.
Other species such as the water
penny beetle and the dobsonfly
larvae are sensitive benthos. There
absence in areas that they generally
inhabit can be an indication of
pollutants.
Several species are also important
in managing soil organic matter
which is a key factor in controlling
air and water quality.
Case Study
Microcrustacean communities in streams from two
physiographically contrasting regions of Britain.
• This is a study by Simon D. Rundle and Paul M.
Ramsay that looked at benthic microcrustaceans
from forty-three streams at two different locations
in Britain; lowland southern England, and upland
Whales.
• The test sights consisted of two areas of varying
geology, vegetation, chemical, and compositional
components.
• Organisms were sampled, preserved, identified,
and counted.
• Results showed that lowland areas have
significantly higher species richness than upland
areas.
• There were also large differences observed in
community structure between the two sights.
• It is important to understand the species ecology
when assessing important issues such as pollution
impacts.
References
• Brij Verma, Richard D. Robarts, John V. Headley. Seasonal Changes
in Fungal Production and Biomass on Standing Dead Scirpus Lacustris
Litter in a Northern Prarrie Wetland. Applied and Environmental
Microbiology, Feb. 2003, p.1043-1050, vol. 69 no. 2.
• Biological soil communities. www.blm.gov/nstc/soil/. 12/4/98.
• Matthew Ramsey, Yongjiang Zhang, Sarah Baker, and Scott Olmsted.
Collecting and germinating seeds from soil seed banks. June 10, 2003
• Indicator Species. www.epa.gov/bioindicators/html/indicator.html.
10/29/03.
• Rundle, Simon D. and Ramsay, Paul M. Microcrustacean
communities in streams from two physiographically contrasting
regions of Britain. Journal of Biogeography. Vol. 24, No 1, p.101-111.
References
• Mitsch, William J., and James G. Gosselink; Wetlands:
Third Edition. John Wiley & Sons, Inc., New York: 2000,
p.155-187.
• P.G. Eriksson, J.M. Svensson, and G.M. Carrer; Temporal
changes and spatial variation of soil oxygen consumption,
nitrification, and dentrification rates in a tidal salt marsh of
the Lagoon of Venice, Italy; Estuarine, Coastal, and Shelf
Science. July 2003; p.1-11.
• http://www.uib.es/depart/dba/botanica/herbari/alfabetica/L.
html; UIB, University of Illes Balears, Dept. of Biology;
2002.
References
• http://www.frtr.gov/matrix2/section4/450.html; Remediation Technologies
Screening Matrix and Reference Guide