Montana Field Guide

This National Vegetation Classification Group is composed of herbaceous-dominated wet meadows (wet prairie) and freshwater marshes as well as localized areas of riparian or wetland shrub communities throughout areas of the Great Plains region. This is a minor group in Montana with a sporadic distribution and relatively poor documentation. The wet meadows (wet prairie) component of this group occurs along drainages, in basins and lowland sites in areas flooded for brief periods during the growing season via runoff or that flood after snowmelt or heavy rains. These lowland sites often have standing water for several weeks each year and they are commonly dominated by Sedges (Carex spp), Western Wheatgrass (Elymus smithii), Prairie Cordgrass (Spartina pectinata), or Switchgrass (Panicum virgatum).

Prairie marshes 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, and at the margins of, 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 throughout the Great Plains region and is separable from the related G531 Arid West Freshwater Marsh & Wet Meadow primarily by geography.

Wet or riparian shrublands usually dominated by Sandbar Willow (Salix exigua, Salix interior) are found along rivers and streams, typically in alluvial sand or gravel. Heights of these shrubland communities are less than 15ft tall. They also occur along irrigation ditches, and other low wet areas that are not subject to frequent flooding and scouring.

This group encompasses portions of the Emergent Marsh, the Great Plains Closed Depressional Wetland, the Great Plains Open Freshwater Depressional Wetland and the Great Plains Prairie Pothole Ecological Systems.

Wetlands; Marsh and Wet Meadow; Shrubby wetlands; Herbaceous or Shrub Dominated; Great Plains Region; Seasonally, Vernally or Permanently Saturated; Hydric Soils

Typical Dominants: Sedges (Carex spp), Western Wheatgrass (Elymus smithii), Prairie Cordgrass (Spartina pectinata), Switchgrass (Panicum virgatum), Spikerushes (Eleocharis), Cattails (Typha sp), Bulrushes (Schoenoplectus spp, Scirpus spp); Rushes (Juncus spp); Sandbar Willow (Salix exigua, Salix interior)

This wetland group occurs sporadically throughout the Great Plains Region in Montana, excluding areas in or adjacent to the island mountain ranges that are more appropriately classified as G521, G526, or G531.

In Montana, G1213 occurs in Level III Ecoregions: 42 (Northwestern Glaciated Plains) and 43 (Northwestern Great Plains).

In Montana, G1213 occurs or potentially occurs within these Major Land Resource Areas: 52 - Brown Glaciated Plains, 53A - Northern Dark Brown Glaciated Plains, 53B - Central Dark Brown Glaciated Plains, 54 - Rolling Soft Shale Plain, 58A,B,C,D - Northern Rolling High Plains, 60A,B - Pierre Shale Plains.

Small Patch

The wet meadows (wet prairie) component of this group occurs along drainages, in basins and lowland sites in areas flooded for brief periods during the growing season via runoff or that flood after snowmelt or heavy rains. These lowland sites often have standing water for several weeks each year. The water may be fresh or mildly saline. Soils can be mineral but mucks often form through the buildup of organic material (Looman 1982).

Marshes 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 is 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.

Wet or riparian shrublands usually dominated by Sandbar Willow (Salix exigua, Salix interior) are found along rivers and streams, typically in alluvial sand or gravel. They also occur along irrigation ditches, and other low wet areas that are not subject to frequent flooding and scouring.

The wet meadows (wet prairie) component of this group are commonly dominated by short to tall species such as Sedges (Carex spp), Western Wheatgrass (Elymus smithii), Prairie Cordgrass (Spartina pectinata), or Switchgrass (Panicum virgatum). The vegetation of these communities is usually moderate to dense and the dominant vegetation is typically 0.5-1.0 m tall. Forbs can be common, but shrubs are rarely found in this type. In wetter sites, the most abundant species are often Calamagrostis stricta, Carex pellita, Carex sartwellii, Anemone canadensis, Apocynum cannabinum, Symphyotrichum lanceolatum, Eleocharis spp, Juncus arcticus ssp. littoralis, Phalaris arundinacea, Polygonum amphibium, and Schoenoplectus americanus. These wetter sites are similar to G325 Great Plains Freshwater Marsh but have standing water for a much shorter amount of time each year.

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 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), and Common Water-milfoil (Myriophyllum sibiricum).

Sandbar Willow (Salix exigua, Salix interior) is the dominant shrub and often the only woody species present. Other shrubs that may be present include Salix eriocephala (syn S. famelica, S. lutea) and Cornus sericea. Stands can have other woody species such as saplings of Salix amygdaloides and Populus deltoides. The understory is usually moderate to lush but can be sparse if subject to a recent major flood. The herbaceous layer is typically dominated by mid and tall graminoids such as Carex spp., Western Wheatgrass, Switchgrass, Prairie Cordgrass, and Schoenoplectus spp. in wetter areas. Other common herbaceous species include Horsetails (Equisetum hyemale), Xanthium strumarium, Polygonum spp., and Ambrosia artemisiifolia.

In Montana, this group is represented by vegetation communities classified into 7 Alliances and 12 Associations within the National Vegetation Classification. Additional vegetation types may occur, and further review is needed.

Communities in this group are dependent on hydrological factors from groundwater recharge, snow melt, surface flows and rain events during the growing season. 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.

Focus on maintaining hydrology of these sites and minimizing or eliminating on-site impacts should be the primary consideration. Additionally, impacts to and activities on adjacent sites may detrimentally impact these communities via changes in hydrology, nutrient and pollution runoff, or increased chances of spread of invasive species onto these sites.

In marsh habitats 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 habitats 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.

Vinge-Mazer et al. (2025)

S. Mincemoyer

7/6/2025