East-central Montana Research Articles

Grazing and defoliation timing effects in Great Plains ponderosa pine woodland following a large summer wildfire

There remains a high level of ambiguity around post-fire grazing management. The Lodgepole Complex fire burned 109,346 ha in east-central Montana in July 2017, including areas previously burned in 2003 by the Bureau of Land Management for fuels mitigation. We hypothesized that herbaceous productivity and species composition in ponderosa pine woodlands are resistant to moderate grazing and timing of defoliation the first growing season after fire. Eight exclosures (25 × 15 m) were built, 4 on reburned area and 4 on wildfire area. To determine grazing effects, a 15 × 10 m sampling area in each exclosure was paired with a grazed section outside the exclosure. Additionally, four 5x10-m plots were established within each exclosure and were mowed to 10 cm in June, July, August, or not mowed to determine seasonal defoliation effects. Differences between grazed and nongrazed sites in 2019 were limited. There was a trend for less old dead biomass in grazed than nongrazed treatments. Species richness was greater on grazed sites than nongrazed or reburn sites. Native species richness was greater on grazed sites than nongrazed sites and reburn sites had an intermediate level of native species richness. Standing crop was reduced by defoliation, with current year and perennial grass biomass being unaffected. The reduction in standing crop was driven by less old dead biomass on defoliated plots. June defoliation reduced C3 grasses and increased C4 grasses, and June and July defoliation each reduced annual grasses. Simpson’s and native Simpson’s diversity were greater on defoliated plots. Results indicate ponderosa pine woodland is resilient to moderate post-fire grazing.

Large Scaphitid Ammonites (Hoploscaphites) from the Upper Cretaceous (Upper Campanian–Lower Maastrichtian) of North America: Endless Variation on a Single Theme

We describe three species of large scaphitid ammonites (Ammonoidea: Ancyloceratina) from the Upper Cretaceous (upper Campanian–lower Maastrichtian) of the Western Interior of North America. Each species occurs as two dimorphs, referred to as macroconch and microconch. All three species share a similar pattern of ornamentation consisting of long, thin, nonbifurcating ribs on the adoral part of the phragmocone, suggesting that they constitute a single monophyletic clade. Macroconchs of Hoploscaphites crassus (Coryell and Salmon, 1934) are characterized by a globose whorl section, with closely spaced ventrolateral tubercles on the body chamber, usually persisting to the aperture. Macroconchs of Hoploscaphites plenus (Meek and Hayden, 1860) differ from those of H. crassus in having a more subquadrate whorl section with flatter flanks, and fewer, larger, and more widely spaced ventrolateral tubercles. Macroconchs of Hoploscaphites peterseni, n. sp., closely resemble those of H. crassus, but differ in being nearly circular in side view with a more compressed whorl section. All three species lived at approximately the same time in the same general area and depositional environment. They are abundant in the Baculites baculus Zone but also occasionally occur in the B. eliasi Zone and possibly lower part of the B. grandis Zone. They are present in the Pierre Shale of east-central Montana and east-central Wyoming, the Lewis Shale of south-central Wyoming, and the Bearpaw Shale of northeast Montana. It is possible that these three species represent subspecies within a single species or a “flock” of very closely related species, similar to the “species flocks” observed in modern cichlid fishes.

Palaeoecological analysis of a methane seep deposit from the Upper Cretaceous (Maastrichtian) of the U.S. Western Interior

Methane seeps were a common feature in the Late Cretaceous Western Interior Seaway of the United States. We document the occurrence of methane seep deposits in the Pierre Shale on the Cedar Creek Anticline in east-central Montana for the first time. The seep deposits occur in the lowermost part of the Baculites baculus Zone (the Endocostea typica Zone), corresponding to the lowermost Maastrichtian. They are therefore the youngest seeps yet described from the Western Interior Seaway. We conducted a detailed faunal analysis of a single seep deposit, together with geochemical investigation of both seep carbonates and molluscan shell material to determine palaeoenvironmental conditions. Oxygen isotope analysis of well-preserved molluscan shell material reveals water temperatures of between 19 and 27°C, while depleted carbon isotope values of seep carbonates are indicative of the anaerobic oxidation of methane. The morphology of the seep deposit suggests a strong advective flux of methane to the sediment–water interface. Comparison to a nearby contemporaneous non-seep site reveals that similar groups of organisms occur in both settings, albeit with varying relative abundances – the seep is numerically dominated by the lucinid bivalve Nymphalucina occidentalis. Substrate appears to be the major control on the diversity and palaeoecological composition of both seep and non-seep sites.

Nautilid nurseries: hatchlings and juveniles of Eutrephoceras dekayi from the lower Maastrichtian (Upper Cretaceous) Pierre Shale of east‐central Montana

The nautilid Eutrephoceras dekayi (Morton 1834) is relatively abundant in the lower Maastrichtian (Upper Cretaceous) Pierre Shale of east-central Montana. We analysed the morphology, size frequency distribution, and isotope composition of a large collection of 220 well-preserved specimens including hatchlings, juveniles and adults. The newly hatched shell is approximately 14 mm in diameter with a body chamber one-third whorl in angular length terminating in the nepionic constriction. Internally, the embryonic shell contains five septa. Juveniles are abundant and comprise two-thirds of the sample whereas sub-adults, defined by the incipient flattening of the venter, are rare. Adults comprise approximately one-third of the sample and average 100 mm in diameter. The co-occurrence of newly hatched shells, small juveniles and adults suggests that the eggs were laid in the same area in which the hatchlings developed. Based on the excellent preservation of the juveniles, we conclude that they did not float into the area after death, but lived in the region, implying that this area served as a nursery for young animals. The calculated temperatures of the embryonic shells are similar to those of the post-embryonic shells and generally range from 16 to 18 °C. Upon hatching, the nautilids probably followed a demersal mode of life and lived in well-oxygenated water ≤50 m deep. An examination of lethal injuries (puncture holes) suggests that all ontogenetic stages were equally vulnerable to predation. The proximity of the site to the Sheridan Delta suggests that the specimens were smothered by sudden pulses of sediment transported into the area by major storms.

Encrustation of inarticulate brachiopods on scaphitid ammonites and inoceramid bivalves from the Upper Cretaceous U. S. Western Interior

AbstractThe inarticulate brachiopodDisciniscais a rare faunal element in the Upper Cretaceous of the U.S. Western Interior. We report two occurrences of encrustation ofDisciniscaon a scaphitid ammonite (scaphite) and several inoceramids from the lower MaastrichtianBaculites baculus/Endocostea typicaBiozones of the Pierre Shale at two localities. Six specimens ofDisciniscaare present on a single specimen ofHoploscaphites crassusfrom east-central Montana. They occur along the furrow at the mature apertural margin. Because the brachiopods are restricted to the margin and do not occur on the rest of the shell, it is likely that they encrusted the ammonite during its lifetime. If so, this implies that the soft body of the scaphite did not cover the outside surface of the aperture, leaving this area vulnerable to epizoan attachment. A total of 13 specimens ofDisciniscaare also present on four specimens ofCataceramus?barabinifrom east-central Wyoming. The brachiopods occur in crevices on the outside of the shells and may have encrusted the inoceramids after their death as the shells began to break down and delaminate, resulting from the decomposition of the organic matrix holding them together. Based on the faunal assemblages at both localities, the presence ofDisciniscamay indicate environments with either low oxygen levels and/or few predators or competitors.

Helminth Parasites of the Western Willet, Tringa semipalmata inornata, From Montana and Texas with a Checklist of Helminth Parasites

In total, 26 western willets, Tringa semipalmata inornata , were examined for helminth parasites, including 8 spring migrating hosts from the Chihuahua Desert, Rio Grande Valley, Texas, and 18 post-breeding hosts from east central Montana. Sixteen species of helminth parasites were present in component communities for both spring migrants and post-breeding birds. There were 9 species of trematodes, 2 cestodes, and 5 of nematodes, with a total of 1,593 individual specimens (X = 99.6, ±SE = 57.9, M = 9) present in migrating willets, and 5 species of trematodes, 8 cestodes, and 3 nematodes for a total of 1,148 individual specimens (X = 71.8, ±SE = 34.4, M = 12) present in post-breeding hosts. Species richness in infracommunities ranged from 2 to 10 (X = 5.1, ±SE = 0.95, M = 5.3) for spring migrants, and from 1 to 4 (X = 2.8, ±SE = 0.26, M = 3) for post-breeding birds. Diversity and evenness were 0.72 and 0.23 for spring migrants and. 0.62 and 0.17 for post-breeding hosts. Trematodes were the dominant taxa in spring migrants and cestode taxa in post-breeding hosts. Helminths with marine-associated life cycles were present in larger numbers in spring migrants from the Rio Grande Valley (11 of 16 species) than in post-breeding hosts from Montana hosts (4 of 16 species). The higher number of marine species in spring migrants was probably related to their more recent association with a marine habitat. Several species of Anomotaenia were major contributors to the component communities in both localities. Four species of nematodes with large prevalence, i.e., Schistorophus skrjabini, Sciadiocara umbellifera, Skrjabinoclava inornatae, and Sobolivicephalus lichtensfelsi, observed in spring migrants from the Rio Grande Valley were absent from Montana hosts. There was only a 2% similarity between the Rio Grande Valley and Montana. All helminth species, except for the possibility of Anomotaenia spp., were generalists. A checklist of helminth parasites of the willet is included.

Range Expansion of Barred Owls, Part I: Chronology and Distribution

During the past century, Barred Owls (Strix varia) expanded their range from forests east of the Great Plains to forests throughout most of central and western North America. Here in Part I, I map more than 12,500 records of Barred Owls in their expanded range from the earliest records to the present, draw the species' distribution in its expanded range and infer the general timing and flow of the range expansion. Evidently, Barred Owls originally traveled across the northern Great Plains via the forested riparian corridors of the Missouri, Yellowstone and Musselshell rivers into east-central Montana by 1873. From there, they accessed western forests in southwestern Montana (1909), moved to northwestern Montana (1922) and then expanded their range in two general directions. They moved north and east to northern Alberta (1934) and Saskatchewan (1948) where they apparently encountered other Barred Owls coming westward from Manitoba. They also moved north to northern British Columbia (1943), southeastern Alaska (1967) and Northwest Territories (1977), and west and south to Washington (1965), Idaho (1968), Oregon (1972) and California (1976). In Part II (Livezey, in press), I explore what prevented Barred Owls from expanding their range westward during recent millennia and what allowed them to do so during the past century.

Incidence of Perenniporia fraxinophila and its effects on green ash ( Fraxinus pennsylvanica) woodlands in eastern Montana, USA

Green ash ( Fraxinus pennsylvanica) woodlands are declining throughout the Northern Great Plains of North America. The heart rot disease of ash caused by Perenniporia fraxinophila is common in these woodlands, but its importance in woodland decline is not known. We sampled the visible incidence of P. fraxinophila stem decay on green ash in 17 native woodland stands in east-central Montana, USA. Randomly chosen trees with and without P. fraxinophila sporocarps were measured for age, height and girth. Incidence of sporocarps on green ash trees ranged from 0 to 67% within stands with a mean of 38%. Sporocarps of other wood-rotting basidiomycetes were not observed in sample stands. P. fraxinophila sporocarps were more frequent on larger, faster growing trees. Rot was detected in basal cores from 23% of the sample trees; 74% of these also had sporocarps. Trees originating from multiple-stump sprouts were not more likely to have sporocarps, suggesting that P. fraxinophila does not usually enter sprouting trees directly from infected stumps. Mean canopy dieback ranged from 22 to 50% and averaged 54% for trees with sporocarps compared with 37% for trees without sporocarps. However, 27% of ash trees lacking both sporocarps and rotten cores had mean canopy dieback ≥50%, indicating that P. fraxinophila is not the primary cause of canopy dieback. Growth rates of ash trees with P. fraxinophila sporocarps declined as the number of sporocarps increased. The incidence of P. fraxinophila is associated with a decline in mean annual precipitation across Nebraska and eastern Montana. These results suggest that this disease may contribute to the decline of ash woodlands, especially where drought stress is common.

Dolomitization patterns in widespread “Bighorn Facies” (Upper Ordovician), Western Craton, USA

There are impressive stratigraphic, paleontologic and petrologic similarities, including dolomitization patterns, among the coeval Upper Ordovician Steamboat Point Member of the Bighorn Dolomite in northwest Wyoming, the burrowed member of the “C” zone of the Red River Formation in east-central Montana, and the lower Upham Dolomite of the Montoya Group in the southern Franklin Mountains near El Paso, west Texas, hundreds of miles to the south. This remarkably widespread “Bighorn Facies” (Zenger and LeMone 1995) extends from El Paso to Greenland (Flower 1961, 1969). Characteristics of this facies are: (1)Thalassinoides-like burrow patterns; (2) similar megafauna, including large receptaculitids, macluritid gastropods, and orthoconic nautiloids; (3) common “matrix” of partly dolomitized (mud-selective) skeletal (primarily echinoderm) wackestone and packstone; (4) fine-centimicron-size, nonplanar, unimodal dolomite completely or nearly completely replacing burrow fills; (5) small “burrows-within-burrows”; (6) essentially stoichiometric dolomite; (7) insignificant differences between δ18O of dolomite within the matrix and that of burrow fills; and (8) relatively high Fe content of the dolomite, suggesting anoxic conditions for at least part of the dolomitization. Petrologic observations and geochemical data (stable isotopes of C and O; trace elements Fe, Mn, Na, and Sr) suggest a relatively early stage of partial dolomitization in near-normal seawater for both the Steamboat Point Member and the Upham Dolomite and in refluxing brines for the burrowed member of the Red River Formation. Later diagenetic stabilization through neomorphism and additional replacement occurred at shallow (Steamboat Point) to intermediate (Upham) to possibly deep (burrowed member) burial environments.

Occurrence of the Upper Cretaceous ammonite Rhaeboceras in the Baculites eliasi Zone of the Pierre Shale

The discovery of a specimen of Rhaeboceras coloradoense Cobban, 1987, in the Baculites eliasi zone in east-central Montana is significant for three reasons: 1) it is the most geologically recent occurrence of Rhaeboceras; 2) it connects more closely than previous specimens the lineage between the genus Rhaeboceras Meek and Ponteixites Warren, its apparent smaller descendant; and 3) it significantly extends the geographical range of the species.

Patterns of Weed Migration in Northwestern U.S.A.

Patterns of spread of 85 weed species alien to the northwestern U.S. were simulated using principal coordinate analysis on primarily herbaria-derived data. The primary pattern detected was a west-to-east migration of weeds. The point of introduction for most weeds following this pattern appeared to be near Portland, OR, an important shipping port in the past. An east-to-west migration represented a secondary pattern. The major cattle and wheat-cropping areas of east-central Montana were the apparent introduction points for weeds following this pattern. The grain and pulse region of eastern Washington represented the point of introduction of species following a third pattern of migration. These weeds subsequently spread southward to Utah and then laterally to the east and west. Historical weed migration patterns provide insight to probable points of origin and routes of currently spreading weeds as well as those that will spread in the future. Such insight may aid in the containment of future spreading weeds.

JORDAN COUNTRY—A GOLDEN ANNIVERSARY LOOK∗

Located on the plains of east-central Montana, and focused on the town of Jordan, Isaiah Bowman's Jordan Country changed considerably in the fifty years following his 1930 study. Gone is the prevailing life of unsettlement and experimentation which characterized that pioneering area. And yet, a revivified Bowman taking his own golden anniversary look would still find largely unchanged a surprising number of the regional characteristics which had attracted him a half-century earlier, especially those relating to transportation, medical care, and schooling. The region has not evolved into the agricultural district Bowman thought possible. The area was then, and remains today, an example of a Great Plains’“yonland.”

Notes on the Quadrant Formation of East-Central Montana

Notes on the Quadrant Formation of East-Central Montana

A Study of Some Upper Cretaceous Sedimentation and Diastrophism in Montana

The presence of a considerable variation in the thickness of the interval from the base of the Eagle sandstone of Montana time to the top of the Kootenai or Cloverly of Lower Cretaceous age has long been recognized over east-central Montana. As far as is known, however, no systematic study has been published showing the regional variation in thickness or the possible causes of such a phenomenon. This article is therefore an attempt to show by discussion and graphical representation the regional variation of the interval previously described, an interval formerly supposed to include only the Colorado formation of Upper Cretaceous age, but now known to embrace, over the southern part of the state at least, sediments of Montana time. There is also shown overloading of sedime ts over certain parts of the area and the resultant effects on diastrophism and sedimentation, from which additional light is shed on the problem of correlation of the sediments grading from Colorado to Montana time. In order to show some effects of the difference in sedimentation, it has been thought advisable to outline roughly the probable conditions immediately prior to Dakota time, as well as the continued deposition into Montana time, as criteria upon which to draw generalized conclusions. It is suggested that more detailed study of isopach lines may throw more light on proper subsurface mapping, especially of relatively large areas, as well as being an aid in the study of the deposition of sediments.