Illinois Wetland Ecosystems - PowerPoint PPT Presentation

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Wet meadows, composed of sedges, forbs, and grasses
Mudflat annual communities made up of smartweeds, grasses
Emergent communities (plants with roots growing underwater or in water logged soil, while the rest of plant emerges from water into air) - made up of cattails, bulrushes, reeds, bur reeds
Floating leaved communities which feature species such as water-lilies
Free-floating communities made up of duckweeds and watermeals
Submersed communities made up of pondweeds, coontails, naiads, and bladderworts

Dry marsh (also called drawdown phase) - this develops during years of low water caused by below-normal precipitation when all or a large part of the marsh may be nearly dry or at least has no standing water
Mudflat annuals and emergent species are the dominant plants

Regenerating marsh - when normal precipitation resumes, standing water returns, allowing germination of submersed and free-floating plants
The regenerating marsh is characterized by an extensive cover of emergent species with submersed as an understorey

Degenerating marsh - during this phase there is a decline in the populations of emergents due to a variety of interrelated factors which may include anoxia, damage from insects, disease and muskrats
This stage has anywhere from a 25:75 to 75:25 ratio of emergent vegetation to open water and this is the phase with greatest wildlife diversity and density

Lake marsh or "eat out" phase is dominated by submerged plants like coontails, naiads, pondweeds, bladderworts; and floating aquatic plants like duckweed - the few remaining emergent plants may nearly disappear
the lake marsh phase continues until the next drought lowers the water level (which usually occurs on a 5 to 30 year cycle) and returns the marsh to the dry marsh state, starting the cycle over again

Wetland environments are characterized by several environmental stresses that most organisms are ill equipped to handle - Aquatic organisms are not adapted to deal with the periodic drying out that occurs in many wetlands
Terrestrial organisms are stressed by long periods of flooding
Because of the shallow water, temperature extremes on the wetland surface are greater than normally experienced in aquatic environments

But the most severe stress is probably the absence of oxygen in flooded wetland soils, which prevents organisms from respiring through normal metabolic pathways - in the absence of oxygen, the supply of nutrients available to plants is also modified and concentrations of certain elements (iron, sulfur) and organic compounds can reach toxic levels
In coastal wetlands, salt is an additional stress to which organisms must respond

Adaptations can be broadly classified as those that enable the organism to tolerate the stress and those that enable it to regulate the stress
Tolerators have functional modifications that enable them to survive, and often to function efficiently, in the presence of stress
Regulators actively avoid the stress or modify it to minimize its effects