There are many types of wetlands, and several often exist together, making them hard to categorize. Making things even harder, often wetlands don’t all have water year-round! Read below to learn more about the types of wetlands in Ann Arbor.
Wooded Wetlands
Wooded wetlands can be either large (>5 acres) or small (<5 acres), natural or created. When large, they are also called wooded swamps or floodplain forests. When small, they are called vernal ponds. Standing water is typically present during most of the spring, but the soil surface is often dry by mid-summer. They may even be dry before the end of the spring growing season. This dryness limits the number and types of amphibians that are able to breed successfully in them. Wooded wetlands can be rich in amphibian life, chiefly when part of a large undisturbed habitat block. Recurrent drying limits predation on amphibian larvae by fish.
Wooded wetlands in Ann Arbor typically have a tree canopy with some wetland shrubs such as dogwood and buttonbrush. The canopy is often made of red or silver maple, willow, elm, cottonwood, or swamp white oak. The ground may be covered by thick grass, or bare after the standing water dries out. When water is present, it may be covered by duckweed floating on the surface. Wooded wetlands may occur along streams or on floodplains, in flat uplands or on the edges of shallow lakes.
Open Wetlands
Open wetlands are typically filled with sun-loving plants including grass-like and flowering plants. Open wetlands do not have a tree canopy. They may also have mudflats, depending on the season in which they dry out. Other names for these wetlands include wet meadow, emergent marsh, scrub-shrub swamp, fen, or bog. They can look similar to wetlands along lakes or rivers, but their isolation from the predatory fish present in lakes and rivers helps amphibians. Created open wetlands typically have steeper banks and deeper water than natural wetlands. They may also have a narrower band of vegetation around a mostly open-water center. The amphibian habitat provided by created wetlands varies.
When open wetlands have permanent standing water, they are typically called marshes. Marshes have a mix of open water and grass-like plants such as cat-tails and rushes. Wet meadows, fens, bogs and shrub swamps look like a shrubby field, except that the ground is wet during the spring. These wetlands have a mix of grasses, sedges, wildflowers and shrubs with almost no open water.
These wetlands may be highly disturbed because regular drying has allowed them to be farmed or mined. Presence of invasive plant species is not always harmful to the breeding and foraging resources needed by amphibians and reptiles. In some cases, habitat structure can be provided by non-native plants such as reed canary grass. In other cases, invasive plants such as buckthorn and multiflora rose make amphibian movement and foraging harder. These plants can also shade-out more helpful plant species.
Lake and River Wetlands
These wetlands have similar size, structure and look to other wetlands. They may provide different amphibian and reptile habitat because they are close to a large body of open water. Floating-leaved plants such as water-lily may be more prominent here than in isolated wetland. These plants provide habitat for turtles in addition to large amphibians such as green and bull frogs. The presence of fish increases predation on amphibians, reducing the amount and types of frogs, toads, and salamanders.
