Eleocharis palustris (E. xyridiformis) Community Type 



ELEPAL (ELEXYR); spikerush 

 MTNHP rank: G5/S5 



Environment: This wetland community type was sampled once on BLM land in the Cottonwood 

 Creek drainage in west-central Carter County, where it occurs in a seasonally flooded drainage that 

 floods at other times of the year after major precipitation events. It is an overflow range site and 

 occupies the wettest microsites in low spots and along the drainage channel. It is interpreted to 

 represent a natural type, though the watercourse setting has been altered by ditches, impoundments 

 and a road crossing, and is grazed by cattle in the fall. Elsewhere ELYPAL was observed in small 

 patches in roadside ditches, in the bottoms of intermittent drainages, and around stockponds. 



Vegetation: This shallow marsh community type is dominated by a spikerush, provisionally 

 identified as Eleocharis xyridiformis. The species is included in Flora of the Great Plains (Great 

 Plains Flora Association 1 986) which indicates a Montana distribution based in part on a collection 

 from Carter County. But the taxon is not recognized in other local floras (Booth 1950, Dom 1984, 

 1992, Hitchcock and Cronquist 1973) and is subsumed in Eleocharis palustris by Kartesz (1994). It 

 is part of the Palustres group and distinguished from E. palustris in having flattened, twisted culms. 

 Plants that key to Eleocharis xyridiformis were found to be common by 1 997 surveys in western and 

 southern Carter Coimty. In the floras that do not recognize Eleocharis xyridiformis, these plants key 

 to Eleocharis palustris. Specimens were collected and a specialist is sought to resolve the taxonomy 

 of these plants. Two forms (putative species) of spikerushes of the Palustris group (£. palustris in a 

 broad sense) were observed growing together around stockponds in Carter County. Larger plants 

 with terete culms (typical Montana E. palustris, or in Flora of the Great Plains keying to E. 

 macrostachya) occupied a slightly wetter zone than plants with twisted, flattened culms (putative E. 

 xyridiformis). The latter is more abundant and is the sole dominant spikerush in the community 

 described here. It is possible that the two morphologies are a result of plant water status. 



Vegetation of the sampled plot is dominated by dense patches of the medium height Eleocharis 

 palustris with about 70% total cover. Grasses include Elymus lanceolatus (about 1 0% cover), 

 Hordeumjubatum (about 3% cover) and Beckmannia syzigachne (about 2% cover). The miniature 

 spikerush Eleocharis acicularis is present, and a small patch of cattails, Typha latifolia, has become 

 established. Forb diversity is low, but Polygonum ramosissimum and Rumex crispus are common. 



Wetland margins are dominated by Elymus lanceolatus communities (ELYLAN), a temporarily 

 inundated meadow community with high cover by Hordeumjubatum. 



Soils: Soils are fine textured, seasonally flooded, and extremely poorly drained. 



Sample pH EC, Sand Silt % Clay Texture Organic Matter 

 No. mmhos/cm % % % 



97JV0049 8.5 0.42 - 1.21 



Comments: Carter County stands resemble descriptions o{ Eleocharis palustris communities fi"om 

 Montana (Cooper et al. 1995, Hansen et al. 1995). Taxonomic clarification will either confirm that 



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