Freshwater Wetlands and Their Ecology

Freshwater Wetlands

  • Definition and Characteristics

    • Freshwater wetlands are not directly connected to the ocean

    • Found at the edges of streams, lakes, ponds, and shallow depressions filled with rainwater

    • Can remain wet year-round or may dry out in the dry season

  • Types of Freshwater Wetlands

    • Various names for different types can cause confusion

    • Key types include:

    • Marshes

    • Bogs

    • Fens

    • Swamps

    • Mires

    • Sloughs

    • Prairie potholes

  • Common Features

    • All types have wet soil or water covering the soil

    • Wetlands are dynamic and constantly changing ecosystems

    • Long-term changes often involve sediment deposition and peat accumulation

Development and Succession in Wetlands

  • Sedimentation Process

    • Lakes and ponds become filled with sediment as silt and organic matter accumulate

    • Emergent plants, like reeds, slow water movement and promote sediment deposition

    • The density of reeds and suspended material affect sediment accumulation rates

  • Ecological Changes Driven by Plants

    • Presence of plants alters physical conditions, impacting ecosystem development

    • Example: Reeds speed up sedimentation, allowing other plants to colonize

    • Notable ecological processes:

    • Succession: Gradual development over time, involving species replacement

    • Facilitation: One species aids in establishing another by changing conditions

  • Competition and Succession

    • Following facilitation, competition arises as new species outcompete earlier colonizers

    • Example: In drying marshes, trees like willows can overshadow and eliminate reeds

    • These processes often lead to unexpected changes in the ecosystem trajectory

Succession Patterns in Wetlands

  • Stages of Succession

    • Early stages often involve lakes filling with sediment around marsh edges

    • A unique shift can occur with colonization by sphagnum (bog moss), altering water chemistry

    • Sphagnum prevents tree seedlings from establishing, leading to forest decline

  • Biodiversity of Bog Mosses

    • Different species of bog moss have unique ecological requirements

    • Succession gradually allows shade-tolerant species to replace shade-intolerant ones

    • As mosses grow, they accumulate peat, forming raised bogs

Instability and Biodiversity in Wetlands

  • Nature of Wetlands

    • Wetlands are characterized by inherent instability due to their dynamic ecological processes

    • Changes stem from both flora and fauna effects and natural environmental hazards

    • Influences include floods, storms, and the activity of wildlife like alligators and beavers

  • Types of Wetlands

    • Classification includes various types such as shallow freshwater, marshes, fens, swamps, and more

    • All wetlands share the attribute of constant change through succession and unforeseen disturbances

Geographical Distribution of Wetlands

  • Wetland Regions

    • Found in the cool temperate/arctic zone and the tropical zone

    • Their distribution is influenced by atmospheric air movement and rainfall patterns

    • Wetlands require abundant water, often sourced from rainfall or groundwater collection

  • Wetland Types

    • Ambrotrophic Wetlands: Develop under considerably high rainfall

    • Reotrophic Wetlands: Common in drier areas, these are the primary type of terrestrial wetland in such regions

  • Conservation Importance

    • Understanding the ecosystems within wetlands aids in conservation and management efforts for these rich resources.