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