Chapter 2: Emergent Wetlands

Emergent Wetlands

Emergent wetlands are what many people imagine when they think of marshes that fringe lakes and ponds. They are characterized by a mix of open water and vegetation that grows in, but emerges from, the surface of the water. Over the course of a year, emergent wetland water levels can fluctuate considerably between deeply flooded and dry.39 The emergent wetlands surrounding Great Salt Lake (GSL) are often located near large submergent wetlands and encompass approximately 520 km² (129,693 ac). Emergent wetlands are dominated by stout, fast-growing bulrushes, cattails, and large grasses.

Plants

Alkali bulrush (Bolboschoenus maritimus, p. 39), hardstem bulrush

(Schoenoplectus acutus, p. 40), and Olney’s threesquare (Schoenoplectus americanus, p. 41) are three species of bulrushes that provide essential migratory bird habitat. Each thrives under slightly different flooding and water chemistry conditions, but all reproduce by rhizomes as well as by seeds.40 Rhizomes allow stands of bulrushes to persist under stressful drought or flooding conditions that are characteristic of emergent wetlands.12 Alkali bulrush, the shortest and most valuable bulrush species, grows in expansive, loose stands.34 While it grows best in 5–15 cm (2–6 in) of water, it also benefits from seasonally fluctuating water levels and is capable of withstanding both temporary, deep flooding and

short-term drought.27 This hardy species can tolerate highly alkaline soils up to 9.0 pH, and while it grows most robustly when salinity is below 6 ppt, it can tolerate extended periods of time at salinities near 10 ppt with no increase in plant mortality.51 Hardstem, the tallest bulrush, grows in dense stands of deeply flooded wetlands (up to 30 cm or 12 in deep); however, it has lower drought and salinity tolerances than alkali bulrush.13 Adult plants can tolerate salinities near 6 ppt with very little reduction in growth, but mortality increases at salinities above that level.29 During periods of drawdown, the soil must remain saturated for long-term maintenance of hardstem bulrush.52 Olney’s threesquare, another dense, stand-forming bulrush, gets its name from its concave, triangular stem. Thriving best in shallow water of at least 10 cm (4 in), Olney’s threesquare can tolerate water depths up to 30 cm (12 in).19 Olney’s threesquare can also tolerate brackish conditions, around 6 ppt for up to 2 months, but will grow shorter as salinity approaches 12 ppt.26 In addition to bulrushes, cattails (Typha spp., pp. 64–65) are common in GSL emergent wetlands. Although native, cattails are often viewed as undesirable species because they can colonize wetlands after a disturbance or when water stagnates, forming dense monocultures that outcompete habitat-forming plants like bulrushes.10 Without proper management of water flow, salinity, and nutrients, cattails will form dense, monotypic stands that waterfowl and other large birds cannot use.47 Water management, herbicide application, mowing, disking, grazing, burning, or a combination of those techniques can be useful in preventing cattails from growing too densely.31