Physiognomy and Structure: No Data Available

Floristics: Cover is sparse to dense and is dominated by Distichlis spicata, occurring in nearly pure stands. Stands have higher diversity and cover during wet years and near boundaries with other vegetation types. Higher soil salinity favors Distichlis spicata over less salt-tolerant species. However, very high salinity will dwarf the Distichlis spicata and reduce cover. Generally, vegetation height and cover and species diversity tend to vary inversely with salinity on the plains but may increase on very saline sites (Brotherson 1987). Minor cover of associated graminoids may include Muhlenbergia asperifolia, Hordeum jubatum, Pascopyrum smithii, Sporobolus airoides, Carex filifolia, Eleocharis palustris, Puccinellia nuttalliana, and Juncus arcticus ssp. littoralis (= Juncus balticus). Associated forbs, such as Iva axillaris, Helianthus spp. and Asteraceae spp. (from lower salinity sites), Chenopodium sp., Lappula occidentalis, Rumex hymenosepalus, Salicornia rubra, Triglochin maritima, and Suaeda spp., may also be present. Shrubs are rare, but scattered Atriplex canescens, Atriplex confertifolia, Chrysothamnus viscidiflorus, Ericameria nauseosa, Gutierrezia sarothrae, and Sarcobatus vermiculatus may be present. Introduced species are present in some stands and may include Bromus tectorum, Elymus repens, Lepidium latifolium, Lepidium perfoliatum, Bassia scoparia (= Kochia scoparia), and occasionally Tamarix spp.

Dynamics:  The intermittent flooding regime combined with the high evaporation rate in these dry climates causes accumulations of soluble salts in the soil. Total vegetation cover (density and height), species composition, and soil salinity depend on the amount and timing of precipitation and flooding. Growth-inhibiting salt concentrations are diluted when the soil is saturated, allowing the growth of less salt-tolerant species and more robust growth of Distichlis spicata. As the saturated soils dry, the salt concentrates until it precipitates on the soil surface (Dodd and Coupland 1966, Ungar 1968). This osmotic stress of growing in alkaline and saline soils is compensated by the accumulation of proline by some halophytic species including Distichlis spicata. This aids the plants'' water uptake by increasing the osmotic potential of the plant (Shupe et al. 1986). Vegetation forms zones at some saline sites, where species abundance is stratified by salt tolerance (Ungar et al. 1969, Shupe et al. 1986). In playas, the soil salinity at field capacity generally increases from the edge to the center allowing for several different vegetation stands to co-occur (Ungar 1967, 1970, Ungar et al. 1969). Microtopography can also affect vegetation structure. Where soil accumulates to form hummocks, less salt- and alkali-tolerant plants can occur (Ungar 1972, Johnston 1987).

Brotherson (1987) studied species in a saline meadow adjacent to the Great Salt Lake in Utah and found 5 vegetation zones all with Distichlis spicata present. The meadow sloped down and away from the shoreline for the first 4 zones, then up for the last. Soil pH and soluble salt levels followed the slope pattern with the lowest zone (4) having lower pH and salt concentrations and the highest cover of Distichlis spicata (99%) almost exclusively. The other higher salt zones were codominated by other species such as Suaeda calceoliformis, Puccinellia nuttalliana, Salicornia rubra, Triglochin maritima, Glaux maritima, or Eleocharis palustris. Zone 5 was dominated by Eleocharis palustris and had additional moisture from a nearby seep. The salts were concentrated in the higher elevation zones because of evaporation of the salt-laden water that was leached from the lower lying areas.

The warm-season grass Distichlis spicata is rhizomatous, tolerant of moderate grazing, and its roots resist trampling. Although relatively unpalatable, it can provide valuable winter forage for livestock, if needed. When grazed, Distichlis spicata generally increases because of reduced competition from other less grazing-tolerant species. If grazed heavily, Distichlis spicata will decline and may be replaced by less desirable warm-season grasses such as tumblegrass, Schedonnardus paniculatus, or Hordeum jubatum (Costello 1944b, Jones and Walford 1995). Weeds are generally not a problem because few grow well in saline soils. However, severely disturbed sites are susceptible to invasion by introduced species such as Bromus tectorum, Lepidium latifolium, Lepidium perfoliatum, and Bassia hyssopifolia (Franklin and Dyrness 1973).