Medicine Lake Sandhills 



(Part of Medicine Lake Wilderness Area) 



ENVIRONMENT: 



The Medicine Lake Sandhills are of recent Holocene 

 geological development, formed when prevailing winds 

 from the northwest scoured sediments from dried 

 Pleistocene lake beds. The lacustrine beds contained 

 all particle size classes. Silt and clay fractions were 

 carried far downwind but the sand-sized particles were 

 deposited immediately to the southeast, and partially 

 reworked by the winds to form sand dunes. Much of the 

 landscape is rolling but portions have typical choppy 

 dune features, with blowouts and associated stages of 

 dune stabilization. Not all of the springs and seeps were 

 developed for livestock use, and they contribute 

 significantly to species and habitat diversity. The semi- 

 arid continental climate has peak precipitation in June 

 followed by July and May, and a mean annual 

 precipitation of 13.25 inches (Climate data from 

 Medicine Lake, Western Regional Climate Center, 

 1911-1997). 



Note: This area and two others in Medicine Lake are 

 part of the 11,366 acres designated as Medicine Lake 

 Wilderness Area. This report is a very preliminary 

 description of the refuge portion (about 2,300 acres of 

 the Wilderness Area) of the entire sandhills area that 

 in the aggregate covers about 2 1 square miles, the 

 largest dune complex in Montana. 



VEGETATION: 



The sandplains and sand dunes harbor community 

 types that are possibly unique in Montana, 

 underdocumented, and pending classification review in 

 the northern Great Plains states and provinces. The 

 landscape is primarily composed of graminoid- 

 dominated vegetation, especailly in blow-out areas, 

 though in swales and bottomlands shrub-dominated 

 vegetation types are common. 



Calamovilfa longifoUa - Stipa comma Herbaceous 



Vegetation 



[GALLON -STICOM] 



Prairie sandreed (-) needle-and-thread grassland 



Stabilized sites constitute the vast majority of the 

 landscape, particularly the more planar areas while the 

 blow-out patches are very scattered. Tlie more 

 stabilized states have high canopy coverages of needle- 

 and-thread (Stipa comata) usually in excess of 50%. 

 There are far lesser amounts of the next most prevalent 

 grass, prairie sandreed (Calamovilfa longifolia) , with 



lemon scurf-pea {Psoralea lanceolata) as the most 

 common species among a weakly represented forb 

 component (total cover not exceeding 10%). It was 

 tentatively place in the Calamovilfa longifoUa - Stipa 

 comata Herbaceous Vegetation type (prairie sandreed — 

 needle-and-thread grassland) . This plant association 

 may in turn be an early and long-persisting serai stage 

 of to Stipa comata - Bouteloua gracilis - Carex filifoUa 

 Herbaceous Vegetation, but no examples of the latter 

 were found in either the choppy or the gently rolling 

 terrain. Additional field sampling may be required to 

 adequately describe the plant associations, their 

 relation to successional processes, and the site 

 variables. [Plots NHMTECRA97SC0004. 

 NHMTECRA97SC0005, NHMTECRA97SC0006] 



Symphoricarpos occidentalis Shrubland 



[SYMOCC] 



western snowberry shrubland 



Shrubland dominated by western snowberry 

 (Symphoricarpos occidentalis) is a recurrent community 

 type within the Sandhills, usually occurring in swales 

 but extending upslope in the area, though with reduced 

 stem density. In the physiognomic portion of the 

 classification it is referred to as a temporarily flooded 

 type which could hardly be the case for the Sandhills 

 sites; there have to be some unappreciated 

 circumstances that favor the establishment of 

 Symphoricarpos occidentalis and other shrubs on such 

 seemingly droughty sites. The undergrowth is 

 dominated by western wheatgrass (Pascopyrum smithii) 

 and very few herbaceous species (usually fewer than 

 five). 



Elaeagnxis commutata / Stipa comata Shrubland 



[ELECOM/ STICOM] 



silverberry / needle-and-thread shrubland 



This is community type has not been previously named 

 or described. A rare silverberry/westem wheatgrass 

 shrubland {Elaeagntis commutata I Pascopryrum smithu 

 Shrubland; G2) has been named and cited as occurring 

 in MT, SK, ND, and MB. The combination of 

 ElaeagTMS commiaata and Stipa comata is unique in that 

 Elaeagnus commutata is usually associated with moist 

 sites in the landscape and Stipa comata with drier, sandy 

 soils. Quite possibly the deeper-rooting E. commutata is 

 tapping a watertable unavailable to the herbaceous 

 component. This is supported by the fact that common 

 chokecherry (Prunus vir^ruana) and western snowberry 

 (Symphorricarpos occidentalis) occur as community 

 dominants adjacent to the Elaeagnus commutata- 

 dominated community, ostensibly on the same site. 



47 



