Formation, Chemistry, and Biology of Wetland Soils

1
Formation, Chemistry, and Biology of Wetland Soils

• Maverick, Dana,
• Devon

2
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

3
Soil Forming Factors

• Climate
• Parent material
• Time
• Topography
• Living organisms

4
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

5
Parent Material

• The primary material from which the soil is
  formed.
• Soil parent material could be
• bedrock
• organic material
• old soil surface
• deposits from water, wind, glaciers, volcanoes,
  or material moving down a slope

6
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.

7
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.
  

8
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.

9
Properties important to the development and
identification of wetland soils

• Horizonization
• Organic matter content
• Texture
• Permeability
• Drainage
• Color

10
Horizonization

• Soil Horizon- layer 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
11
Organic Matter Content
Mitsch and Gosselink, 2000.
12
Texture

• Relative proportion of sand, silt, clay
• Influenced by interaction of geologic and
  environmental factors
• Important property affecting permeability

Soil Survey Manual, USDA, 1993
13
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 soils permeability

Sand
Clay
14
Drainage

• Used to describe amount of water present and its
  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

15
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

16
Definitions of Wetlands

• 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
• at least periodically, the land supports
  hydrophytes
• the substrate is predominantly undrained hydric
  soil
• 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).

17
Hydric Soils!

• Formation influenced by interactions of
  soil-forming 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.

18
Hydric Soils

• Critical factors
• Saturation
• Reduction
• Redoximorphic features
• Two types
• Organic
• Peat or muck
• When waterlogged and decomposition is inhibited,
  histosols
• Mineral
• Inorganics

19
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 micro-organisms (bacteria and
  fungi).
• thus, limited breakdown of plant material.

20
Hydric Soil Indicators for Non-Sandy Soil

• 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

21
Hydric Soil Indicators for Sandy Soils

• High organic matter in surface horizon
• Streaking of subsurface horizons by organic
  matter
• Organic pans

22
Hydric
Non-Hydric
23
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

24
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.

25
Bogs

• 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, chocolate-colored mass of moss
  fragments
• water moves more slowly through this layer
• Bogs are ombrotrophic- water supply is from the
  mineral-poor rainwater

26
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
• Dont have organic soil
• Dont have year-round water

27
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

28
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

29
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

30
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

31
Chemistry of Wetland Soils
32
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

33
Classification of Wetland Soils

• Techniques for classifying soil types
• Organic versus Inorganic
• Bulk density and porosity
• Hydraulic conductivity
• Nutrient availability
• Cation exchange capacity
• Organic soils are further classified by
• Percent organic carbon and clay
• Hydroperiod

34
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

35
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)

36
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 lt5 organic carbon

37
Chemical Reactions

• Oxidation-Reduction Reactions (Redox)
• Carbon Transformations
• Phosphorous Transformations
• Sulfur Transformations
• Nitrogen Transformations

38
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

39
Redox Reactions

• Anerobic Conditions
• 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

40
Redox Reactions

• 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

• Oxygen depletion depends on
• Temperature
• Availability of organics
• When Oxygen is depleted, oxidized conditions
  occur
• Causes the soil to be red-brown
• Reduced soil is grey-blue

41
Measuring Redox Reactions

• Eh E0 2.3RT/nFlogox/red
• 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

42
Carbon Transformations

• Aerobic carbon transformations
• Photosynthesis H2O is oxidized
• Aerobic respiration Oxygen is reduced
• Decomposition of organic matter this way is
  efficient

43
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

44
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
• 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

45
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

46
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

47
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

48
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

49
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

50
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

51
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

52

• 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

53
Study Location
54
Marsh Vegitation
55
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

56
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

57
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

58
Spatial Results

• Oxygen soil consumption
• Greater in creek soils then in vegetated areas
• DIN
• Highest fluxes and dentrification rates in
  non-vegetated creek soil
• Lagoon retains nitrate and releases ammonium into
  the water column

59
Biology of Hydric Soils

• Dana Rohrbacher

60
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.

61
Functions of Biological Soil Components

• 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

62
Soil Communities

• Biological crust
• Fungi
• Bacteria
• Protozoa
• Nematodes
• Annelids
• Arthropods
• Seed bank
• Root System

63
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.

64
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.

65
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.

66
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. (ie-Nitrogen 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.

67
Nutrient Cycles

• Both fungi and bacteria play important roles in
  the making nutrients such as nitrogen and carbon
  available for living plants.

68
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.

69
Diatoms

• Benthic pennate diatoms found in the Cape Fear
  River
• Scanning electron microscope image of
  Pseudo-nitzchia australis.

70
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.

71
Annelids

• 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.

72
Annelids cont.

• Annelids include
• Polychaetes
• Oligochaetes
• Leaches
• Most species prefer soft soils often found under
  rocks.
• Serve as a food source for other animals.

73
Arthropods

• Jointed invertebrates generally referred to
  asBUGS!
• 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.

74
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.

75
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.

76
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.

77
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 0-2, 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.

78
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.

79
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.

80
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.

81
Biological Indicators

• 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.

82
Indicators cont.

• 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.

83
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.

84

• 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.

85
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/soi
  l/. 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.

86
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/alfa
  betica/L.html UIB, University of Illes Balears,
  Dept. of Biology 2002.

87
References

• http//www.frtr.gov/matrix2/section4/4-50.html
  Remediation Technologies Screening Matrix and
  Reference Guide