Ecological interaction of little bluestem and vesicular–arbuscular mycorrhizal fungi

The percentage of vesicular–arbuscular mycorrhizal (VAM) colonization of little bluestem (Schizachyrium scoparium) (Michx.) Nash.) and VAM spore populations in the rhizosphere of little bluestem from four prairie areas in Illinois were studied. At Goose Lake Prairie, a significant positive correlation (r = 0.77, p < 0.01) was found between soil moisture and density of VAM spores, but soil moisture and percent VAM colonization were not significantly correlated at any of its sites. Percentage of VAM colonization tended to be higher at study areas where little bluestem was a dominant species. However, spore numbers and abundance of little bluestem tended to be inversely related. Colonization decreased from May to July at all areas and this trend frequently continued into September. Month of sample collection had no significant effect on spore numbers except at Reavis Hill Prairie. The endophyte isolated at all areas was Glomus fasciculatum (Thaxter sensu Gerd.) Gerd. & Trappe. Other species, such as Gigaspora heterogama (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe, were more restricted in their distribution.

Lower Pennsylvanian (Morrowan) Ammonoids from the North American Midcontinent

The Lower Pennsylvanian Hale Formation, which comprises the lower portion of the type Morrowan Series, in northwestern Arkansas, is subdivided into the Cane Hill and overlying Prairie Grove Members. The Cane Hill Member includes interbedded shale and sandstone with a basal conglomerate containing clasts reworked from underlying, truncated Mississippian formations. The Prairie Grove Member is highly variable, but includes sandy biosparite and calcareous sandstone. Highly fossiliferous pebble conglomerate and calcirudite lenses occur sporadically throughout the Hale Formation. Ammonoids and conodonts show that the Cane Hill-Prairie Grove boundary is unconformable.Several thousand ammonoids collected from more than 100 localities in the Hale Formation show that four ammonoid zones and two subzones are recognizable in the Hale succession, and consequently in the redefined Halian Stage of the Morrowan Series. These are, in ascending order, the Retites semiretia, Quinnites henbesti, Arkanites relictus (including the Arkanites relictus relictus and overlying Cancelloceras huntsvillense Subzones) and Verneuilites pygmaeus Zones. Halian Stage ammonoids are known primarily from northern Arkansas, but an upper Arkanites relictus Zone (Cancelloceras huntsvillense Subzone) ammonoid assemblage occurs in the Primrose Member of the Golf Course Formation in south central Oklahoma.Conodont-ammonoid associations in the Hale sequence provide a basis for integration of independently based zonal information. Rhachistognathus primus Zone conodonts occur in the Retites semiretia Zone; the Idiognathoides sinuatus Zone ranges through the Quinnites henbesti and Arkanites relictus relictus Subzone. The overlying Cancelloceras huntsvillense Subzone and Verneuilites pygmaeus Zone both contain conodonts of the Neognathodus symmetricus Zone.The Hale ammonoid succession has few, if any, species in common with the type Namurian of Europe, but numerous genera are common to both sequences and the generic successions coincide and are equivalent in degree of development. The Retites semiretia Zone is equivalent to the Reticuloceras circumplicatile Zone (R1a); the Quinnites henbesti and lower Arkanites relictus Zones correspond to some portion of the R2b–R2c interval; and the upper Arkanites relictus Zone and the Verneuilites pygmaeus Zone correlate to Zone G1. The Retites semiretia Zone correlates to the lower Reticuloceras-Baschkortoceras Genozone (Nm2b1) of the upper Namurian in the south Urals; the Quinnites henbesti Zone is equivalent to some portion of the Nm2b2–3 intervals of this zone; the lower Arkanites relictus Zone is equivalent to the lower Bilinguites-Cancelloceras Genozone (Nm2c1) and the upper Arkanites relictus and Verneuilites pygmaeus Zones correspond to the uppermost interval (Nm2c2) in the south Urals sequence.Systematic descriptions of biostratigraphically significant Halian taxa, including Reticuloceras tiro Gordon, R. wainwrighti Quinn, Retites semiretia McCaleb, Arkanites relictus relictus (Quinn, McCaleb, and Webb), A. relictus redivivus n.subsp., Quinnites n.gen. (type species Q. henbesti (Gordon)), Q. textum (Gordon), Bilinguites eliasi n.sp., Cancelloceras huntsvillense n.sp., and Verneuilites pygmaeus (Mather) are also presented.

Changing Holocene Environments at the Koster Site: A Geo-Archaeological Perspective

Geomorphologic and sediment-stratigraphic study of the Koster site has been carried out in the broader context of the lower Illinois Valley. Accumulation of reworked loess in an overdeepened tributary valley began at Koster shortly after 10,000 B.P., and continued through Holocene times with major sedimentary breaks. The Illinois floodplain began to stabilize ca. 5000 B.P. after rapid aggradation, but remained a dynamic environment that developed its present patterns after 2500 B.P. Valley-margin hillside vegetation was considerably more xeric during the periods 1200-950 B.P., 2100–1900 B.P., and ca. 9700–5000 B.P., with hillside woodland reduced to hill prairie or parkland ca. 8500–7700 B.P. These dramatic Holocene environmental changes suggest that interpretative archaeological models for cultural adaptations through time must consider the environment as a critical variable, rather than as a constant.

Hill Prairies of Illinois

Hill prairies are grasslands on pronounced slopes. Of the many hill prairies in Illinois, 61, with a combined area of more than 200 acres, were visited by the writer inthe course of this study. In Illinois, hill prairies occur on the exposed upper or brow slopes of the generally southwest- and west-facing bluffs east of the Mississippi River for most of the length of the state and on similar slopes along the Illinois River from Putnam County southward into Jersey County, where the valley of the Illinois enters the Mississippi valley. Hill prairies are present also along the Sangamon and Rock rivers. The observed flora of Illinois hill prairie was 394 species and varieties. Of these, 390 were vascular plants distributed in 209 genera and 70 families. The largest family was Compositae, with 26 genera and 71 species and varieties. Aster was the largest genus, with 12 species. Thirty species were of foreign origin.