Module 2
Wetland soils are often
Acidic due to the reduction of SO4 2- to H2S (hydrogen sulfide) by anaerobic bacteria, producing the characteristic rotten egg odor of certain wetlands (part of the sulfur cycle)
Denitrification
Anaerobic bacteria convert ammonia (NH3) to N2O and N2 N2 (inorganic) back to atmosphere, Nis lost to Wetland
Percipitation
Any form of water, such as rain, snow, sleet, hail or mist, that falls from the atmosphere and reaches the ground
Examples of Reduced soils (4)
Gray coloration soil appears wet iron reduction mottles in soil sample
Oxidation
Occurs during oxygen uptake by soils, or when they are rich in oxygen
Saturation
Occurs when the soil pores are holding the max amount of water and plants cannot uptake any more water either (Note: these conditions occur along a gradient of increasing soil moisture.)
Wetland water budget
Provide a basis for understanding these hydrologic process of a wetland
Wetland soils show signs of
Reduction
Si
Second, surface water flows into the wetland -Surface water in flow might come from an adjacent river for example
Go
Sixth, similarly water may leave a wetland by moving into ground water supplies
Cation Exchange Capacity
Some nutrients and heavy metals (pollutants)exist as cations (+), and absorb to negatively charged places (-) on clay particles
Saturated (non tidal Wetlands)
Substrate saturated for extended during growing season
Tidal Wetlands
Subtidal permanently flooded with tidal water
Ground Water
Supplies are also linked to wetlands -Wetlands are most commonly groundwater discharge areas, however recharge can also occur
Anaerobic Conditions
THe complete lack of oxygen in the soil because pores are saturated with water -causes stress to plants since roots need oxygen to function (i.e. prevents respiration) -Characterized by lack of oxygen lead to different chemical processes in the soil
Change in Volume/Change in Time
THe water budget measures changes in the volume of water in a wetland over time
Gi
Third, groundwater flows into the Wetland
Compacted soils
Those that have been driven over by tractors/ farm machinery, have reduced pore spaces
Main categories based of Tides
Tidal and Non-tidal
Muck Soils
are characteristics of some wetland types, displaying black color from large quantities of organic matter
The Cation Exchange Capacity Process causes Wetlands to
become a sink for nutrients, pollutants and sediments which become attached to the clay particles
Hydric Soil
is a soil that formed under conditions of saturation, flooding, or ponding long enough during the growing season to develop anaerobic conditions in the upper part
Reduction
occurs when soils are releasing oxygen, or when they are deficient in oxygen
Humus
organic matter that decays -Wetlands often have an abundance of this in the A horizon
Wetland soils are often high in
organic matter; anaerobic conditions show decomposition , so wetland soils often have a thick layer of organic litter
Hydric soils have important (8)
physical geochemical properties high quantities of organic matter and humus saturated soil anaerobic conditions reduced soils Acidic pH Texture: often high in silt and clay, although wetlands sometimes occurs in sandy soils.
Water is necessary in soil for...(5)
plants chemical reactions mixing soil particles for decomposition of organic matter dissolving nutrients (However, when soils become completely saturated, their properties change)
3 Important conditions of soil moisture
saturation field capacit permanent wilting
Surface water
supplied to wetlands through normal stream flow, flooding from lakes and rivers overland flow, ground water discharge, and tides (Surface water amy be permanently, seasonally, or temporarily present in a Wetland
Wetland soils are acidic due to
the decomposition of built up organic materials
Hydroperiod
the seasonal patter of water level in a wetland how deep? How often does it flood? What is the duration of flooding? Termed a Wetland's hydrological signature
Permanent Wilting point
the water content of soil when most plants (corn, wheat and sunflower) growing in the soil wilt and fail to recover in their turer upon rewilting
Irregularly Exposed (Tidal Wetlands)
-Surface exposed by tides less often than daily
What are the hydrological impacts on a Wetland's character? (4)
1. A wetland's particular hydrologic regime leads to a unique vegetation assemblage (remember, plant species vary their ability to tolerate flooded conditions. The amount, frequency and the duration of flooding controls the types of vegetation that will grow. 2. Primary productivity and other ecosystem functions are oftenenhanced by flowing conditions and a pulsing hydroperiod; often stagnated by unvarying conditions. 3. Accumulation of organic material in a wetland is controlled by hydrology through its influence on primary productivity, decomposition and the import/export of organic matter 4. Nutrient cycling and availability are significantly influenced by a wetland's hydrology
Soils have a number of properties (6)
1. Composition 2. Texture 3.Porosity describes the number, size, and connectedness of soil pores (air spaces) 4. Soil moisture potential measure of water 5. Soil Color 6. Soil Horizons
Wetland's 3 basic Characteristics
1. Presence of Shallow water or inundated ground surface 2. Hydric soils 3.Hydrophytes (The hydrology of a wetland directly controls whether hydric soils will form or whether hydrophytes will be present
Wetlands 3 basic characteristics
1. Shallow water or inundated ground surface 2. Hydric soils 3. Hydrophytes
Hydrological functions of a Wetland in a landscape (4)
1. Water storage 2. Improve water quality 3. Recharge surface and ground water supplies 4. the unique hydrology of wetlands can support a diversity of animals
R Horizon (Bed Rock)
Bedrock, such as sandstorm, limestone, or granite
H2CO3 Carbonic acid
Build up of carbon dioxide, when dissolved in water, creates carbonic acid -created when an excess of carbon dioxide is dissolved in water
Tides
Can also influence waterflow in wetland -although tides are typically only an influence in coastal areas where they occur
Permanently flooded (Non-tidal Wetlands)
Flooded throughout the year
Intermittently flooded (Non-Tidal Wetlands)
Flooded throughout year, except in extreme drought
Hydrology
Consist of water level, flow frequency directly effects a wetland's biota and physiochemical environment
Nitrogen Fixation
Converts inorganic N2 to Organic forms Requires presence of oxygen Fixed by lightning bacteria, blue-green algae
Evapotranspiration
Describes the loss of water to the atmosphere (evaporation) and the loss due to transpiration by plants -Solar radiation, windspeed, turbulance relative humidity, available soil moisture and vegetation type and density effect the rate of evapotranspiration
Porosity
Determined in part by texture w/ larger particle sizes generally leading to more porous soils
ET
Fourth, some of the water in the Wetland is loss through ET (Evaporation and Transpiration)
How is a Wetland's physical environment controlled by?
Geomorphology, climate and hydrology
So
Fifth, additional water may be lost due to surface water out flow -For example, a wetland draining into a river
T
Finally, tides (where relevant) bring water in and out of a wetland
Pn
First precipitation (P) inputs water. Net precipitation (Pn) describes the amount that actually reaches the wetland -For example, some water is intercepted by plants before reaching the Wetland
Irregularly Flooded (Tidal Wetlands)
Flooded less often than daily
Classes of Hydroperiods
Hydroperiods are used to classify wetlands into different hydrological types or water regimes
Soil Color
Measure hue, chroma, and value; indicator of different properties as it is influenced by organic matter, minerals and water content -measured using the munsell chart
C Horizon (Parent Material)
Mineral soil, little affected from soil process (no accumulations of minerals or materials from upper layers)
Anaerobic conditions also effect the
Nitrogen cycle
Soil Texture
Texture classes defined using the textural triangle
Field Capacity
The amount of water remaining in the soil a few days after having been wetted and after free drainage has ceased. By definition, it is the amount of water available, stored, or released between field capacity and the permanent wilting point water content.
Wetland Hydrology
The formation, size, persistence and function of a wetland are all directly controlled by hydrological process.
B Horizon (Zone of accumulation)
The subsoil layer, predominantly mineral and accumulations from upper layers
A Horizon (Top Soil)
The top soil laye, mineral soil mized w/ some organic matter
What does Physiochemical environment impacts?
The wetland biota and indirectly impact hydrology.
Hydrograph
Water Levels in a wetland can be measured periodically in the field , often using a staff guage -depicts changes in a wetland's depth overtime (Used for studying and classifying wetlands)
Wetland soils often have high amounts of
clay and silt (although some have a sandy texture)
Regularly flooded (Tidal Wetlands)
flooded and exposed daily
Temporarily flooded (non tidal wetlands)
flooded for brief periods during growing season
Seasonally flooded (non tidal wetlands)
flooded for extended period of growing season, usually dry by the end of growing season
Semipermanently Flooded (non-tidal wetlands)
flooding during growing season of most years
Clay is important because it has a
high cation exchange capacity