Montana Field Guide

These wetlands occur mostly as small patches on the landscapes and are largely confined to limited areas in suitable floodplain or basin topography. They are seasonally, semi-permanently or permanently flooded habitats. Water is at or above the soil surface for most of the growing season. This group includes shallow, freshwater to slightly brackish waters found in bottomlands along drainages, in river floodplain depressions, along side channels, below seeps and at the margins of lakes, ponds, stock ponds, ditches and slow-moving streams. A consistent source of freshwater is essential to the function of these communities. Vegetation communities include those dominated by Cattails (Typha sp), Bulrushes (Schoenoplectus spp, Scirpus spp), Sedges (Carex spp), Rushes (Juncus spp), Spikerushes (Eleocharis spp). Soils are muck, mineral, or muck over mineral soil, and water is high in nutrients. This wetland group occurs on both sides of the Continental Divide excluding areas of the Great Plains and ranges from valley bottoms to the montane zone.

This Group encompasses portions of the Emergent Marsh Ecological System.

Wetlands; Marsh and Wet Meadow; Herbaceous Dominated; Rocky Mountain and Intermountain Region; Valley Bottoms to the Montane Zone; Seasonally, Vernally or Permanently Saturated; Hydric Soils

Typical Dominants: Cattails (Typha sp), Bulrushes (Schoenoplectus spp, Scirpus spp) Sedges (Carex spp), Rushes (Juncus spp), Spikerushes (Eleocharis spp)

This wetland group occurs on both sides of the Continental Divide from valley bottoms to the montane zone. It potentially occurs in or near all of the island ranges east of the Divide including the foothills of the Rocky Mountain Front and south to the Bighorn Mountains. Similar communities in the Great Plains are included in G325.

In MT, G531 occurs primarily within Level III Ecoregions: 15 (Northern Rockies), 16 (Idaho Batholith), 17 (Middle Rockies), 18 (Wyoming Basin) and 41 (Canadian Rockies) and extending into the western portions of 42 (Northwestern Glaciated Plains) and 43 (Northwestern Great Plains).

In Montana, G531 occurs primarily within these Major Land Resource Areas: 32 - Northern Intermountain Desertic Basins, 43A - Northern Rocky Mountains, 43B - Central Rocky Mountains, and in limited extent within 44A - Northern Rocky Mountain Valleys, 44B - Central Rocky Mountain Valleys, and 46 - Northern and Central Rocky Mountain Foothills.

Small Patch

These wetlands occur mostly as small patches on the landscape and are largely confined to limited areas in suitable floodplain or basin topography. They are seasonally, semi-permanently or permanently flooded habitats. Water is at or above the soil surface for most of the growing season and includes shallow freshwater to slightly brackish waters found in bottomlands along drainages, in river floodplain depressions, along side channels, below seeps and at the margins of lakes, ponds, stock ponds, ditches and slow-moving streams. Sites can have water levels from completely drained (exposed soil) to approximately 1.5 meters deep but are usually less than 1 meter. Water levels can vary by up to 1 m during the year. A consistent source of freshwater is essential to the function of these communities. Soils are muck, mineral, or muck over mineral soil, and water is high in nutrients.

Vegetation in marshy habitats is often patchy or zonal and is driven by the depth of standing water or lack thereof across the growing season. Communities dominated by Cattails (Typha sp), Bulrushes (Schoenoplectus spp, Scirpus spp), Sedges (Carex spp), Rushes (Juncus spp), and Spikerushes (Eleocharis spp) are the most common. Species richness can vary considerably among individual marshes and wetlands and is influenced in part by adjacent land use. Heights of common vegetation types mostly vary from 0.5 meter to 2 meters tall. Vegetation communities occurring in marshes are representative of their hydroperiod; some basins dry to bare soil after seasonal flooding, while others will have a variety of wetland types in a zoned pattern depending on seasonal water table depths and salt concentrations (Kudray and Cooper, 2006). In semi-permanent marshes, typical communities may include annuals in the drawdown zone near the upland edge, with sedges (Carex species) down gradient, and Broadleaf Cattail (Typha latifolia) and Hardstem Bulrush (Schoenoplectus acutus) located in the deeper, central portion of the marsh. Beyond the emergent vegetation, floating-leaved hydrophytes may be present in wetter sites with longer inundation periods, including Water Lilies (Nymphaea species), Yellow Pondlily (Nuphar species), Water Buttercup (Ranunculus aquatilis) and Pondweed (Potamogeton species). Other floating species may be present in shallow water, such as Duckweed (Lemna species), and submergents such as Common Hornwort (Ceratophyllum demersum), Horned Pondweed (Zannichellia palustris), Mare’s Tail (Hippuris vulgaris) and Common Water-milfoil (Myriophyllum sibiricum).

Non-native species, including Reed Canarygrass (Phalaris arundinacea), Yellow Flag Iris (Iris pseudacorus) and Purple Loosestrife (Lythrum salicaria) may invade these habitats, displacing native species.

In Montana, this group is represented by vegetation communities classified into 3 Alliances and 5 Associations within the National Vegetation Classification. Additional vegetation types likely occur, and further review is needed.

Drought cycles, annual fluctuations in precipitation and local changes in hydrology directly affect these sites and will result in changes to the vegetation patterns within these marsh and wetland habitats.

Adjacent land use practices should be considered as they may detrimentally impact these communities through nutrient and pollution runoff.

In marsh systems where water has been drained or altered, the original hydrology of the system must be restored. If water levels are restored, re-growth and re-colonization from dormant rhizomatous root systems of common marsh species often can occur within a few years. Cattle grazing must be eliminated or controlled to allow regrowth, recolonization and resprouting from existing root systems. Many of the characteristic species found in marsh systems are rhizomatous, thus exhibiting excellent erosion control properties. In some cases, if hydric soils are heavily altered due to pugging or compaction, addition of organic material may be needed to facilitate vegetation recolonization.

M.E. Hall, G. Kittel and J. Christy (2015)

S. Mincemoyer, T. Luna, C. McIntyre, L. Vance

12/6/2024