VEGETATION: 



Bisected as it is by a east-west oriented ridge, the 



RNA's predominant vegetation cover includes 



moderately to densely forested north-facing slopes and 



open woodlands and sparsely vegetated south-facing 



slopes. 



Pseudotsuga menziesii I Oryzopsis micrantha Forest 



[PSEMEN/ORYMIC] 



Etouglas fir / little-seed ricegrass forest 



This forest type is of very limited rangewide 

 distribution, found only in the Missouri River Breaks of 

 Montana. It was originally characterized by Roberts and 

 Sibbemsen (1979) as Douglas fir / plains muhly forest 

 (Pseudotsuga menzieTsii I Muhlenberguj cuspidata Forest) 

 as a result of misidentifying the dominant grass in 

 vegetative condition. It occupies moderate to steep 

 slopes with northwest to northeast aspects. This is a 

 major type within the RNA, where it is best-developed 

 on steep north-facing slopes that are very undulating in 

 both the horizontal and vertical. It appears to be 

 developed on the same erodible shale substrate that 

 supports other forested types as well as long-leaved 

 sagewort/indian ricegrass barrens on south exposures. 

 The ground surface has a patchy cover of mosses and 

 lichens, the combined cover of which generally exceed 

 50%; about 40% is contributed by litter and the 

 remaining 10% is bare soil which shows sheet and rill 

 erosion in places. There were no fire scarred trees or 

 buried charcoal which tends to support the contention 

 of Roberts et al. (1979) that these sites experience low 

 fire frequencies. This type usually grades to ponderosa 

 pine woodland on drier/warmer slopes or on flats and 

 toeslopes below. 



The overstory approaches canopy closure with 

 ?seudotsuga mervoesu (Douglas fir) strongly dominant 

 and ?mus ponderosa (Ponderosa pine) scattered. The 

 understory has numerous stems of Pseudotsuga menxiesii, 

 and Rocky Mountain juniper Quruperus icopulorum) in 

 a distinctly shrubby form. The canopy is too dense for 

 Pinus ponderosa reproduction, clearly making 

 ?seudotsuga menziesu the climax dominant and 

 apparently serai dominant as well. 



Further evaluation of old-growth characters may be 

 warranted. Tree ring studies were conducted among 

 Douglas fir at a study site referred to by the nearby 

 "James Kipp Recreation Area" out of the National 

 Laboratory of Tree Ring Research; they documented 

 the oldest age among sampled Douglas fir trees to be 

 491 years (L. Smith pers. commun. to J. McCoUum, 

 1982). 



The rhizomatous western snowberry {Symphoricarpos 

 occiderualis) is present in patches as the dominant 

 shrub; squaw currant (Ribes cereum) is consistently 

 present, as is the intensively browsed common 

 chokecherry (Prunus virgirwma) . The dominant herb, 

 little-seed ricegrass (Oryzopsis micrantha) is highly 

 variable in cover; the sample plot represents the high 

 end (40%) of this species' cover values. Sun sedge 

 {Carex irwps) and bluebunch wheatgrass 

 (Pseudoreogneria spicata) are consistently present with 

 coverages generally not exceeding 5%. Oregon woodsia 

 (Woodsia oregana) is a fern occurring in more than trace 

 amounts; forb cover is lower than this. Yellow 

 sweetclover (Melilotus officinalis) is also present in trace 

 amounts despite the shaded environment, confirming 

 its aggressive nature and broad ecological amplitude. 

 (Plot NHMTECRN98SC0013] 



Pinus ponderosa / Carex inops Woodland 



[PINPON/CARINO] 



Ponderosa pine / sun sedge woodland 



On the steep, south slopes a complex of open pine 

 woodland vegetation encircled the sparse vegetation 

 associations of the long-leaved sagewort / indian 

 ricegrass barrens. The open pine stands represent a 

 wooded shale barrens complex in which there were 

 frequent clumps of sun sedge (Carex irwps) , but 

 undergrowth vegetation was sporadic, sparse over most 

 of the area, and variable in composition. Plains 

 reedgrass (Calamagrostis montanensis) and bluebunch 

 wheatgrass (Pseudoroegneria spicata) were also locally 

 abundant. Multiple plots would be needed to make 

 generalizations and characterize the highly variable 

 structure. This plant association has been documented 

 as a distinct woodland community on isolated shale 

 outcrops such as the War Horse Area of Critical 

 Environmental Concern (Lesica 1987), and on 

 secondary tributaries of the Missouri River such as 

 Woodhawk Creek (Heidel 1996) where it is generally 

 better-developed under less harsh conditions. [No Plot] 



The virtually ubiquitous ponderosa pine of the plains 

 has been employed for reconstructing climate history as 

 indicated by tree ring patterns. Ponderosa pine 

 elsewhere on the Refuge have been cored to document 

 Great Plains drought history (Meko 1982, 1992). 



Artemisia longifolia I Oryzopsis hymenoides Sparse 



Vegetation 



[ARTLON/ORYHYM] 



long-leaved sagewort / indian ricegrass barrens 



34 



