North American Prairies Grassland

These grasslands can be roughly divided into tall grass prairie in the east, short grass prairie in the west and mixed grass prairie between the two. This reflects increasing aridity from east to west. For thousands and possibly millions of years, fire has been an important natural factor. Consequently many of the plant species are adapted to tolerate fire. In fact, tall grass prairie tends to be replaced by forest when protected from fire. Also prior to man’s intervention, prairie provided grazing for literally millions of buffalo and other grazing animals.  Tall-grass prairie is largely composed of bunchgrass and sod forming grasses. The dominant species are Andropogon gerardii, Panicum virgatum, Schizachyrium scoparium and Sorghastrium nutans. Before man’s interference tall-grass prairie formed a dense cover commonly reaching heights of up to 3 m, but most of the canopy today is less than 1 m. In short-grass prairie Bouteloua gracilis and Buchloe dactyloides are the dominant sod forming species, while other important grasses are Agropyron smithii, Hilaria jamesii, Koeleria cristata, Muhlenbergia torreyi, Sporobolus crytandus and Stipa comata. These short-grass prairies are thought to be more of a true climax community than tall-grass prairies, and many of the species are draught resistant. The dryness of this habitat was shown in the 1930s when the so-called ‘dust bowls’ were created as a result of trying to plow short-grass prairie. Mixed-grass prairie is a blend of tall and short grass prairie species, and in fact, represents a large ecotone between this two prairie types. Typical dominants are species of Agropyron, Bouteloua, Colamovilfa, Schizachrium, Sporobolus and Stipa.

Although grasses dominate the prairies and characterize the landscape there are also large numbers of other, often colourful, flowering plants from other families. The Asteraceae are particularly prominent with different taxa characterizing each of the seasons - Gaillardia and Senecio in spring, Helianthus, Ratibida, Rudbeckia and Silphium in midsummer and Aster and Solidago in the fall. Most of the endemic species are also forbs such as Amorpha nana (Fabaceae), Astragalus barrii, A. gracilis, A. hyalinus, A. pectinatus, A. plattensis (Asteraceae), Lespedeza leptostachya (Fabaceae), Psoralea cuspidata, P. hypogaea, P. linearifolia (Fabaceae), Carex hookerana (Cyperaceae), Daucosma laciniatum, Eryngium leavenworthii, Eurytaenia texana (Apiaceae), Eriogonum correllii, E. vischeri (Polygonaceae), Haplopappus engelmannii (Asteraceae), Lesquerella angustifolia, L. arenosa, L. auriculata, L. calcicola, L. engelmannii, L. ovalifolia, L. recurvata, L. sessilis (Brassicaceae), Oenothera fremontii (Onagraceae), Phlox andicola, P. oklahomensis (Polemoniaceae), Tomanthera densiflora (Scrophulariaceae), Valeriana texana (Valerianaceae) and the moss Aschisma kansanum (Pottiaceae).

The prairies are not completely treeless - Populus deltoides var. occidentalis (Great Plains Cottonwood) and sometimes other species form gallery forests along many of the large streams, and dwarf stands of Quercus macrocarpa var. depressa occur in some of the wetter areas. Also Pinus ponderosa, Picea glauca and other species can be found in the Black Hills, but these represent a dome-like outlier of western American cordillera.

A type of prairie also extends on to Edwards Plateau in south central Texas where grass taxa such as Andropogon, Bouteloua and Buchloe can be found. However it also shares a number of species with the Chihauhuan and Tamarlipan deserts and as such represents a transition zone to the Sonoran BioProvince. Nevertheless, the area is important in its own right and supports a number of endemic species such as Anemone edwardensis (Ranunculaceae), Quercus texana (Fagaceae), Streptanthus bracteatus (Brassicaeae), Styrax platanifolia, S. tenax (Styracaceae), Lythrum ovatum (Lythraceae), Galium correllii (Rubiaceae), Matelea edwardsensis (Asclepiadaceae), Forestiera reticulata (Oleaceae), Physostegia correllii (Lamiaceae), Buddleja racemosa (Loganiaceae), Campanula reverchonii (Campanulaceae), Erigeron mimegletes (Astereaceae), Verbesina lindheimeri (Asteraceae), Dasylirion heteracanthium (Nolinaceae), Yucca rupicola (Liliaceae) and Tridens buckleyanus (Poaceae).

North American Prairies Salmarsh (Big Salt marsh, Kansas)

The saltmarsh vegetation here radiates out in zones from a central barren salt flat devoid of vegetation. However, there is no sequence of community zonation as found in coastal saltmarsh, but there are local patterns caused by local variations in topography, drainage, and salinity. The following vegetation types have been described.

Tall Distichlis stricta Salt Meadow
This salt marsh vegetation type is located on the eastern border of the salt flats and in wetter saline areas throughout the marsh. The vegetation comprised about 13 species of vascular plants but just three of these, Pluchea purpurascens, Polygonum hydropiperoides and Rumex maritimus var. fueginus, were confined to this zone. However, the most characteristic and abundant plant was Distichlis stricta. Other typical species included Hordeinn jubatum, Poa arida, and Scirpus paludosus, while less common species were Aster ericoides, Aster exilis, Atriplex patula var. hastata, Bassia hyssopifolia and Suaeda depressa.

Sporobolus airoides Saltmarsh
Situated bewteen the Tall Distichlis stricta stands and Sandhill Mixed Prairie this community comprised just 11 species of vascular plants, all of which occurred in other parts of the marsh. Typical species apart from Sporobolus airoides included Ambrosia psilostachya var. coronopijolia, Atriplex patula var. hastata, Conyza canadensis, Desmanthits illinoense, Elymus canadensis, Euphorbia marginata and Poa arida.

Sandhill Mixed Prairie
Occurring on the higher, sandy hummocks within the moist, saline zones of Big Salt Marsh are stands of mixed prairie supporting over 100 species, 41 of which are not found elsewhere on the marsh. In the late summer tall prairie grasses such as Andropogon scoparius, Panicum virgatum and Sorghastrum nutans dominate together with species such as Ambrosia psilostachya var. coronopijolia, Bouteloua gracilis, Eragrostis trichodes, Froelichia campestris, Solidago altissima, Sporobolus asper and Sporobolus cryptandrus.  However, in early spring the vegetation has a very different character with species such as Androsace occidentalis, Cerastium brachypodum, Lappida redowskii, Lithospermum incisum, Veronica peregrina var. xalapensis and Viola kitaibeliana var. rafinesquii in flower. Then in late spring through early summer flowers of Achillea lanidosa, Agropyron smithii, Callirhoe involucrata, Elymus canadensis, Erigeron strigosis var. beyrichii, Festuca octoflora, Monarda citriodora, Panicum lanuginosum var. fasciculatum, Panicum scribnerianum, and Plantago purshii become conspicuous. Finally during summer Artemesia ludoviciana, Cassia fasciculata, Coreopsis tinctoria, Cyperus filiculmis, Oenothera rhombipetala, Setaria geniculata, Solidago missouriensis and Strophostyles leiosperma become the main flowering species.

Suaeda depressa Saltmarsh
Directly bordering the open salt flats and in other areas this vegatation was mainly composed of widely scattered stands Suaeda depressa. Other less common succulents included Salicornia rubra and Sesuvium verrucossum.

Distichlis stricta-Suaeda depressa Saltmarsh
This, the most extensive saltmarsh type, was almost entirely composed of Distichlis stricta and the upright growth form of Suaeda depressa. Other species played only small part of the overall vegetation cover but could be of local importance. These include Heliotropium curassavicum, Poa arida, Polygonum ramoisissimum, Scirpus paludosits, Sesuvium verrucossum, Sporobolus airoides, Tamarix gallica and Spartina pectinata.

Scirpus paludosus-Distichlis stricta Saltmarsh
Covering relatively small areas this vegetation comprised up to nine species, all except Atriplex argentea occurring in other parts of the marsh. Other species included Atriplex patula var. hastata, Heliotropium curassavicum, Hordeum jubatum, Poa arida, Polygonum ramosissumum and Suaeda depressa.

Spartina pectinata-Distichlis stricta Saltmarsh
In this vegatation Spartina pectinata is the tall dominant species (up to 130 cm) while Distichlis stricta represented a short co-dominant. Among the other 24 taxa recorded Eustoma grandiflora appeared to be limited to this zone. In the spring, species such as Amorpha fruticosa, Apocynum sibiricum, Hordeum jubatum, Juncus interior and Juncus torreyi are the most conspicuous flowering species. These were succeeded by Asclepias incarnata, Distichlis stricta, Eustoma grandiflora, Spartina pectinata, Verbena hastata and Vernonia fasciculata in summer and in late summer by Aster exilis, Iva annua and Flaveria campestris.

Scirpus americanus-Eleocharis rostellata Salmarsh
This sedge-meadow was limited to the western edge of the marsh. Scirpus americanus forms the tall dominant, (up to 160 cm.) and Eleocharis rostellata the short dominant. Other characteristic species included Agrostis alba, Asclepias incarnata, Aster ericoides, Aster exilis, Carex annectans, Carex lanuginosa, Carex praegracilis, Cicuta maculata, Eleocharis tenuis, Helianthus maximilliani, Juncus interior, Juncus torreyi, Lippia lanceolata var. recognita, Lobelia siphilitica, Scirpus lineatus, Scirpus paludosus, Sphenopholis obtusata, Spiranthes cernua, Verbena hastata and Vernonia fasciculata.

Freshwater Seepage Marsh
In the center of a freshwater seepage zone where salinity levels were low the vegetation was dominated by Sagittaria latifolia and Typha latifolia. Among the other 30 species recorded here, 5 were not found in any other part of the marsh. These were Berula pusilla, Mimulus glabratus var. fremontii, Myosurus minimus, Ranunculus sceleratus and Spirodela polyrhiza. Other characteristic species, often found in slightly elevated, dryer zones, included Carex annectans, Carex praegracilis, Cicuta maculata, Eleocharis macrostachya, Eleocharis rostellata, Eleocharis. tenuis, Flaveria campestris, Lycopus americanus, Scirpus americanus and Scirpus paludosis.

Saline Lake Vegetation
Only two species of flowering plants, Eleocharis acicularis and Potamogeton foliosus, could tolerate these brackish or saline aquatic systems.  In stead, the greatest density of vegetation was made up of coralline algae (Charophyceae) including Chara canescens, Chara evoluta, Chara globularis, Chara hornemani, Nitella opacu and Tolypella intricata. These species can not only tolerant of a wide range of salinity; they can also withstand large fluctuations.

References

Hazlett, D. L. 2004. Vascular plant species of the Comanche National Grassland in southeastern Colorado. United States Department of Agriculture.

McKell, C. M. & Garcia-Moya, E. 1989. North American Shrublands. In: The Biology and Utilization of Shrubs. Ed. C. M. McKell. Academic Press, Inc.

Moss, E. H. 1971. The parkland or grove belt of Alberta. In: World Vegetation Types. Ed. S. R. Eyre. Macmillan.

Qian, H. 1999. Floristic analysis of vascular plant genera of North America north of Mexico: characterization and phytogeography.  Journal of Biogeography, 26: 1307-1321.

Ricketts, T. h. et al. 1999. Terrestrial Ecosystems of North America - a conservation assessment. World Wildlife Fund, USA and Canada. Island Press, Washington.

Sims, P. L. 1989. Grasslands.  In: North American Terrestrial Vegetation. Eds. M. G. Barbour and W. D. Billings. Cambridge University Press.

Ungar, I. A. 1965. An ecological study of the vegetation of the Big Salt Marsh, Stafford County, Kansas. The University of Kansas Science Bulletin, XLVI: 1-99.

Vanderhorst, J., Cooper, S. V. & Heidel, B. L. 1998. Botanical and vegetation survey of Carter County, Montana. United States Department of the Interior Bureau of Land Management.

Watt, F. B. 1969. The Natural Vegetation of the Southern Great Plains of Canada. In: Vegetation, Soils and Wildlife. Eds. J. G. Nelson & M. J. Chambers. Methuen.