Marshes

Freshwater marshes

Palustrine wetlands have saturated land dominated by emergent and herbaceous plants

  • Wet meadows, Vernal pools, Playa lakes, and Prairie potholes are examples of marshes

  • Characterized by emergent, floating, or submergent plants that are herbaceous and adapted to saturated soil conditions

  • Receive most of their water from surface water, but also fed by groundwater

  • Frequently occur along streams in poorly drained depressions and in the shallow water along the boundaries of lakes and ponds

  • Nutrients are plentiful; highly organic, mineral rich soils of sand, silt, and clay

  • Neutral pH

  • Most prevalent and widely distributed wetlands in North America

  • Freshwater marshes are one of the most productive ecosystems on earth

  • Characteristic vegetation: cattails, sedges, rushes, pickerelweed, duckweed, bladderworts, and water lilies

Importance of freshwater marshes

  • Recharge groundwater supplies

  • Moderate stream flow

  • Reduce damage caused by floods by storing floodwater

  • Filter pollutants into marsh soil

  • Store excess nutrients in substrate

  • Preserve the quality of surface waters

  • Sustain a vast array of plant communities that in turn support a wide variety of wildlife

Wet meadows

  • Poorly drained areas such as shallow lake basins, low-lying farmland, and the land between shallow marshes and upland areas

  • Some found high in the mountains on poorly drained soil

  • Often resemble grasslands, but drier than other marshes except during periods of seasonal high water

  • Highly fertile soil

  • Importance:

  • Collect water run-off reducing likelihood of flooding

  • Remove the excess nutrients creating fertile soils

  • Habitat for many insects, amphibians, reptiles, birds, and mammals

Vernal pools

  • Seasonal wetlands depressions: small puddles to shallow lakes

  • Occur under the Mediterranean climate conditions of the West Coast

  • Covered by shallow water for variable periods from winter to spring; may be completely dry for most of the summer and fall

  • Underlain by bedrock or hard clay that keeps water in the pool

  • Importance:

  • Provides habitat for numerous rare plants and animals: many spend the dry season as seeds, eggs, or cysts

  • Seasonal source of food and water for egrets, ducks, and hawks

Playa lakes

  • Round, ephemeral hollows in the ground formed by wind or land subsidence

  • Southern High Plains of the United States; west TX, OK, NM, CO, KS

  • Dry lake beds that are surrounded by short-grass prairie and semi-desert regions

  • Most fill with water only after spring rainstorms

  • Few saltwater-filled playas fed by water from underlying aquifers, which brings salt with it as it percolates up through the soil

  • Importance:

  • Store water in a semi-arid region

  • Support an array of wildlife: over-wintering waterfowl, mayflies, dragonflies, salamanders, bald eagles, whooping cranes, jackrabbits and raccoons

  • Support the surrounding agriculture by providing irrigation water and seasonally recharge the Ogallala Aquifer

Prairie potholes

  • Wet depressions formed from glaciation

  • Common in the Upper Midwest, especially ND, SD, WI, and MN

  • The Upper Midwest, because of its numerous shallow lakes and marshes, rich soils, and warm summers, is one of the most important wetland regions in the world.

  • Result from snowmelt and rain in the spring

  • Some temporary, others may be essentially permanent

  • Importance:

  • Shelter and nesting areas for more than 50% of North American migratory waterfowl

  • Absorb surges of rain, snowmelt, and floodwaters

Saltwater marshes

  • Estuarine tidal wetland dominated by salt-tolerant, herbaceous plants

  • Found frequently form on the leeward side of barrier beaches directly across from exposed ocean shore; also found in river deltas directly downstream from brackish tidal marshes

  • Extremely productive communities

    • Salt marshes utilize about 6% of the sunlight they receive

    • By contrast cornfields will capture at most 2% and reefs 3%

  • Not very diverse

    • The inner marsh zone, flooded most of the time, is composed almost entirely of grasses in the genus Spartina (cordgrass).

    • The overwhelming dominance of grasses in the genus Spartina throughout North American's salt marshes is primarily due to the virtually unique capacity for these plants to withstand both continuous inundation and highly saline soil conditions.

  • These grasses are able to do osmosis by increasing the concentration of solutes within its cells to levels in excess of those found in ocean water.

    • In order to avoid the toxic effects of salt-buildup on its cells, its cell membranes actively exclude most types of salt and allow only relatively harmless sodium chloride to accumulate

  • Diversity within the salt marsh community tends to increase with distance from the ocean

  • Eventually the Spartina will be replaced by reeds, sedges, goldenrod, and other species commonly associated with brackish or freshwater marshes