Loess Bluffs Research Articles

The flora of Fair River Farm, Lincoln County, Mississippi, U.S.A.

Southwest Mississippi is a poorly studied, but biologically diverse region, encompassing the broad transition from the East Gulf Coastal Plain longleaf pine-bluestem ecosystem to the rich hardwood forests of the Loess bluffs and hills. A floristic inventory of an approximately 694.7-hectare privately owned natural area in Lincoln County was conducted. The Fair River Farm is situated in a region of highly dissected terrain around the Little Fair River and Kees Creek, near the transition between two major level III ecoregions, and the boundary between the Pearl River and lower Mississippi River drainage basins. 744 vascular plant taxa and 72 bryophytes were documented. 495 taxa are new to Lincoln County, and 3 are new to the state of Mississippi; 27 species are designated special concern by the Mississippi Natural Heritage Program, 13 are on the watch list and 14 are on the tracking list. Photographic records available on iNaturalist are used for some species as an alternative to physical vouchers. Plant communities present on the tract are discussed and briefly and qualitatively compared to General Land Office records, original county soil surveys, and historic descriptions of the region, with emphasis on the distribution of longleaf pine (Pinus palustris Mill.), now very rare on the tract. The number of county records highlights the need for more survey work and potentially underreported biological diversity and conservation value of the southwest region of Mississippi and other poorly collected areas of the Southeastern U.S.; this inventory may inform land management decisions on the tract and elsewhere in the region.

Age and source of coastal loess in Shandong Peninsula, Bohai Sea, China: Implications for dust aggradation in respond to sea-level change

Coastal loess is a unique and intriguing eolian sediment on Earth, but understanding its formation time, provenance, composition and the geomorphic processes that resulted in its accumulation is very limited compared to its inland counterpart. In this paper, we focused on a loess section at Xiazhupan (XZP) Village, Penglai City in Shandong Peninsula, the only known coastal loess bluffs preserved in China. The coastal loess here not only has characteristics that are common to loess terrains such as being composed of predominantly silt-sized particles and the tendency to stand in vertical exposures, but it also reportedly preserves planktonic foraminifera, sizable pebbles and volcanic glass. In addition to its peculiar near-shore locality, these features make it more unusual compared to other loess deposits. Systematic optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL and pIRIR) and radiocarbon dating reveal it was deposited mostly during 60–20 ka, Marine Isotope Stage (MIS) 4-2, which correlates to the deposition of the Malan loess (L1) in the Chinese Loess Plateau. High-resolution grain size data indicate that the coastal loess is relatively coarse-grained, suggesting a source terrain that is at least partially proximal. Given its proximal source and the geochronological evidence, this coastal loess was sourced from the exposed continental shelf during the sea-level lowstand of the last glacial period, and this hypothesis is further supported by a core collected from the Bohai Sea in which silt was present and would have been subaerially exposed during MIS 4-2. In addition, this source area of exposed continental shelf is comparable to coastal loess in Europe. The coastal loess in Shandong can be regarded as a special type of desert or dryland loess, rather than glacial loess. Finally, future sea level rise will likely increase the erosion potential of these vulnerable coastal loess bluffs, making it urgent to study this special landform.

Holocene loess in Illinois revealed by OSL dating: Implications for stratigraphy and geoarchaeology of the Midwest United States

Most uplands in Illinois are blanketed by late-Wisconsinan Peoria Loess, and the conventional wisdom is that little or no dust accumulation occurred during the Holocene (11.7 ka to present). In a recent effort to investigate if Illinois Holocene loess was deposited and preserved, we applied optically stimulated luminescence (OSL) dating to seven locations where loess is thick. These include four sites along the Mississippi River in westernmost Illinois, and three loess bluffs south of the Illinois River in central Illinois. Our results suggest that Holocene-aged loess is preserved along the Mississippi River in the state of Illinois; in contrast, no Holocene loess was found south of the Illinois River in the central portion of the state. In addition to its spatially limited distribution, Holocene loess thicknesses range only up to 1 m. Nevertheless, loess stratigraphy and OSL dating results provide the first Holocene loess reported east of the Missouri River. Our new finding also resolves the long-time archeological puzzle that a number of artifacts of several thousand years old were buried by upland loess along the Mississippi River.

Hydrologic modeling of the loess bluff in Dunaujvaros, Hungary

The western shoreline of the Danube from Érd to Mohács consists of loess bluffs up to 50 m high. These bluffs can be susceptible to landslides when groundwater conditions weaken the supporting loess. Often this will occur during periods of high rainfall, however morphological, geological and other factors are also important in triggering these movements. Changes in pore water pressures related to precipitation, confined water levels driven by remote catchments, and river level fluctuations are widely recognized as important factors controlling the loess bank stability. This work aims to determine the interaction of rainfall, river level, drainage and local pumping on the pore pressure regime and stability of the bluffs. As a first step, a realistic 2-dimensional infiltration and groundwater model was built that reflects the influence of river levels, rainfall patterns, and local pumping. Based on model results, initial and boundary conditions have a strong influence on seasonal pore pressures. Further study will better define those influences on slope stability along the bluffs.

Artists' Depictions of Catsteps in the Loess Hills of Iowa: Evidence for Mid-Nineteenth Century Climate Change

Catsteps (also known as terracettes) are the staircase-like features common on hillslopes of the Loess Hills of western Iowa. The record of artistic depictions of the Loess Hills was examined to determine when catsteps appeared. Landscape artists George Catlin and Karl Bodmer traveled up the Missouri River in 1832 and 1833, respectively, and between them, produced 30 works of art depicting either the Loess Hills or the loess bluffs on the Nebraska side of the river. Only one painting by Bodmer of Blackbird Hill on the Nebraska side possibly shows catsteps. Moreover, an engraving based on the painting and another painting of the same site by Bodmer do not show catsteps. The Assistant State Geologist, Orestes St. John, produced five sketches of the Loess Hills in 1868, three of which show well-defined catsteps. The appearance of catsteps during the period 1833-1868 may be related to the appearance of gullies during the period 1860-1900. An examination of census data shows that intensive grazing of the Loess Hills did not begin until about 1900 so that climate change is a more likely explanation for the appearance of both catsteps and gullies. Since catsteps are more common on the south- and west-facing slopes, which will dry most quickly, the most probable climate change is a decrease in the periodicity of precipitation cycles. Such a climate change is consistent with tree ring data from eastern South Dakota and eastern Montana, but not central and eastern Iowa.

The significance of the Danube ecological corridor in the proceedings of implementing ecological networks in Serbia

With the modern processes for exploiting land people have altered the original appearance of areas and created cultural environments. The remaining natural environments, whether protected or not, take up a relatively small portion of space and represent isolated islands which in itself can not be sufficient for the preservation of biodiversity or for the fulfillment of national, regional or international goals and commitments related to their preservation. In order to secure the preservation of biodiversity, the strengthening of integrity and the natural processes, such as animal migrations, succession of vegetation and evolution processes, the communication between natural habitats is imperative. Ecological corridors, as integral elements of ecological networks, ensure the preservation of vital ecological interactions by providing a connection between different habitats or areas. Depending on a range of factors, from the fulfillment of demands of different species to the connecting of regions, corridors of local, sub-regional, regional and international importance are identified. The Danube ecological corridor is one of the most significant corridors of international importance which encompasses a large number of habitats which are part of the natural watercourse of the corridor. There are numerous protected areas in the Danube coastal area on Serbia's territory which present themselves as central areas for forming the ecological network, such as: Gornje Podunavlje, Karadjordjevo, Fruska Gora, Titelski Breg hill, Kovalski rit marsh, Dunavski loess bluffs, the Sava mouth, Labudovo okno, Deliblato sands, Djerdap and Mala Vrbica. The diverse and mosaic vegetation of the floodplain, as well as the consistency of the protected areas within the Danube corridor have a direct influence on the quality and functionality of this corridor. The goal of this paper is to show the significance of the Danube ecological corridor in the process of implementing ecological networks, the potential of the area in question for forming corridors, but also to present the limitations which may decrease the functionality of the corridors as well as the guidelines for a sustainable management of the corridor on Serbia's territory.

Long-term population demography of Trillium recurvatum on loess bluffs in western Tennessee, USA

Understanding the demography of long-lived clonal herbs, with their extreme modularity, requires knowledge of both their short- and long-term survival and ramet growth patterns. The primary objective of this study was to understand the dynamics of a clonal forest herb, Trillium recurvatum, by examining temporal and small-scale demographic patterns. We hypothesized: (i) there would be more variability in the juvenile age class compared with non-flowering adult and flowering adult classes due to year-to-year fluctuations in recruitment; (ii) rates of population growth (λ) and increase (r) would be highest in non-flowering ramets due to a combination of transitions from the juvenile stage and reversions from flowering adults; and (iii) inter-ramet distances would be most variable between flowering and juvenile ramets due to a combination of clonal growth, seed dispersal by ants and ramet death over time. Census data were collected on the total number of stems in the population from 1990 to 2007, and placed within one of three life stages (juvenile, three-leaf non-flowering and three-leaf flowering). Modified population viability equations were used to assess temporal population viability, and spatial structure was assessed using block krigging. Correlations were performed using current and prior season weather to current population demography. The first hypothesis was rejected. The second hypothesis was supported: population increase (r) and growth rate (λ) were highest in non-flowering ramets. Finally, the third hypothesis was rejected: there was no apparent density dependence within this population of Trillium and no apparent spatial structure among life stages. Overall population density fluctuated over time, possibly due to storms that move soil, and prior year's temperature and precipitation. However, density remained at some dynamic stable level. The juvenile age class had greater variability for the duration of this study and population growth rate was greatest for non-flowering ramets.

Surface changes on a landslide affected high bluff in Dunaszekcső (Hungary)

Abstract This article presents results from the survey conducted on Dunaszekcső loess bluff after the last major rotational sliding event in 2008. The study area is a region of 25×30 m located on loess bluff close to the recent scarp. The relative elevation change of the surface was surveyed in 2.5×5 m grid network in relation to a marked base point. The survey was conducted using simple equipment such as analogue theodolite and leveller with regular time interval during a year and control measurements were taken after six months. It was assumed that measurements to the nearest cm are sufficient to recognize vertical displacements of the surface. The study focused on identifying the pattern of general vertical movements for the study area by the relative movements of individual points. Our results show significant cm scale vertical displacements. Most of the grid points have a slow decreasing tendency, but close to the scarp a more significant displacement was found. The main character of the spatial pattern is subsidence, which is more definitive on southern part of the study area than the northern part. Our observations correlate with the broader geomorphological characteristics of loess bluffs along the Danube.

Simultaneous determination of terrain correction and local average topographic density

Nettleton’s method is based on the elevation dependence of the surface free-air gravity anomalies and widely used to obtain an optimal average density value by applying e.g. least squares model parameter estimation. Its accuracy, however, strongly depends on how efficiently the regional trends and very local (terrain) effects are removed from the gravity anomalies processed. If the geometry of the topography is fixed then the terrain correction term at the evaluation point P is a linear function of the unknown average topographical density. Therefore it can also be included in the equation system to be solved by adjustment and an estimation of the density can be obtained in one step, without iteration. The results of this simple refinement of Nettleton’s method as well as the distorting effect of the regional trend are demonstrated by a local example. It reviews the gravity survey of a geological structure (known as loess bluff) and its surrounding on the bank of the river Danube. The derived density values increase from ϱt = 1163±543 kg/m3 to ϱt = 1764±113 kg/m3 as the gravity anomalies are gradually reduced by regional and local (terrain) effects during data processing. The lab determination of surface loess samples from the area having only 3.5% water content gives 1610 ± 100 kg/m3.

Geographical variation in male courtship behaviour and sexual isolation in wolf spiders of the genusSchizocosa

We surveyed 12 populations of the wolf spiderSchizocosa crassipes(Walckenaer) andS. nr.crassipesin Tennessee, Mississippi, Louisiana and Florida, in the U.S. to determine the extent of variation in male courtship behaviour when observed in standard laboratory conditions. We observed variation in both the frequency of occurrence and the sequence of the four principal male courtship behaviours and, when compared statistically, most of these behaviours differed between populations. Although there was no clinal pattern in the frequency of courtship behaviour, we observed geographically consistent patterns in the sequence in which male courtship behaviours are displayed. We conducted two subsequent studies to determine whether sexual isolation among selected populations existed. In the first study, we performed male–female reciprocal crosses of brush-legged spiders (S. nr.crassipes) between two populations from the Yazoo–Mississippi Delta physiographical region and one population from the Loess Bluff region of Mississippi and measured mating success, number of matings that produced egg sacs, and the number of egg sacs that hatched young. The results of that experiment suggest that sexual isolation occurs among populations in different physiographical regions but not between populations within regions of the state. In a second crossing study, we paired the brush-legged spiders from one of the Mississippi physiographical regions (Yazoo–Mississippi Delta) withSchizocosa ocreata(Hentz) from Ohio. The results of that cross suggest that the Mississippi Delta population is more similar to the northernS.ocreatapopulations than toS.crassipes. We discuss the results of the crossing experiments in terms of what was revealed about geographical patterns in male courtship behaviour.

HUMAN AND ENVIRONMENTAL INFLUENCES ON FOREST COMPOSITION OF A TENNESSEE LOESS BLUFF

Prior investigations of forests on Mississippi River loess bluffs suggest that their composition is regionally distinct, attributing mesophytic species abundance to atypical physical conditions or Pleistocene history. Owing to the widespread anthropogenic impacts on this landscape, this study examines the relative importance of human and natural factors influencing bluff forest composition. Within the mosaic of former agricultural fields and uncleared areas on the Third Chickasaw Bluff of southwestern Tennessee, 10 transects were placed along the gradient from bottomlands to ridgetops, stratified by former land use. Ordination indicates that the greatest compositional distinction exists between bottomlands and upland positions. Treated separately, the uplands are organized along two primary dimensions: the first distinguishes formerly cleared ridgetops from all other habitats, the second represents a moisture gradient. Three species groups respond differently to these upland conditions: (1) recently disturbed sites favor sweetgum/tulip poplar; (2) sites likely to have been disturbed in the more distant past are oak dominated; (3) mesophytic species prefer undisturbed habitats. The disturbance-related characteristics of each habitat, rather than their direct environmental controls, are a major determinant of bluff composition. The ubiquity of anthropogenic disturbance throughout the region gives rise to the seeming uniqueness of the atypical bluff sites that escaped disturbance. [Key words: human impacts, ordination, vegetation-environment relationships, forest ecology, Tennessee.]

A landslide type occurring frequently along the loess bluff in the Hungarian danube section

The modes of technical intervention as to landslide prevention may differ depending on landslides types. A slab slide type of mass movement occurs along the bluff of the so-called low-lying loess plateaus which are situated on the medium-elevated alluvial fan surface. The thickness of the loess plateau varies between 40 and 60 m, with the loess, paleosol and sandy strata deposited nearly horizontally. A method of protection against slab landslide is discussed in the present paper.

Geomorphological mapping of landslides in Hungary with a case study on mapping Danubian bluffs

Mapping of landslides as a specialized branch of engineering geomorphological mapping aims at providing comprehensive information on landslides for planning and forecasting purposes revealing the role of the main factors controlling the processes. Mapping projects involve survey, inventory, evaluation and mapping of landslides at different scales. A case study dealing with landslide mapping along the Danube loess bluffs provides an understanding of the mapping concept and presents some conclusions on the influencing factors of mass movements.

Additions to the Bryoflora of Iowa

Nineteen county records are reported from collections made in Waubonsie State Park, Fremont County, Iowa, including two species new to the state, Fissidens osmundoides Hedw. and Frullania brittoniae Evans. A series of collections from Waubonsie State Park (Washington twp., T67N,R42W) were made by the junior author in June of 1976 as part of a Fremont County foray cosponsored by the Iowa Ornithological Union and The Iowa State Preserves Board. The park features xeric, loess bluffs with sheltered ravines supporting oak-hickory forest. Identifications of these collections were made by the senior author, and the results were compared with the county flora reported by Conard (1956). The 35 species collected in the park included 19 species not previously reported from the county, of which two species are new to Iowa, as well as the second report of Tortella tortuosa and the third report of Leskeella nervosa in Iowa. Eight records reflect a significant westward extension of the Iowa distribution of that species. In the county records listed below significant extensions are noted with an asterisk (*) and state records with a dagger (t). Specimens are deposited at Conard Bryophyte Herbarium, University of Iowa, Iowa City (IA). The records are as follows: Atrichum angustatum (Brid.) B.S.G., *Barbula fallax Hedw., Bryum lisae DeNot var. cuspidatum (B.S.G.) Marg., *Bryum pseudotriquetrum (Hedw.) Gaertn., Meyer & Scherb., *Callicladium haldanianum (Grev.) Crum, *Desmatodon obtusifolius (Schwaegr.) Schimp., Dicranella varia (Hedw.) Schimp., Entodon cladorrhizans (Hedw.) C.Muell., Entodon seductrix (Hedw.) C.Muell., tFissidens osmundoides Hedw., tFrullania brittoniae Evans, Frullania eboracensis Gott., Leskea obscura Hedw., *Leskeella nervosa (Brid.) Loeske, Phaeoceros laevis (L.) Prosk., *Pohlia nutans (Hedw.) Lindb., Pylaisiella selwynii (Kindb.) Crum, Steere & Anderson, *Rhynchostegiella compacta (C.Muell.) Loeske and *Tortella tortuosa (Hedw.) Limpr. LITERATURE CITED CONARD, H. S. 1956. Mosses and liverworts of Iowa. Iowa Acad. Sci. 63: 345-354. FRANK D. BOWERS, Department of Biology, University of Wisconsin-Stevens Point, Stevens Point, WI 54481. JAMES H. PECK, Department of Biology, University of Wisconsin-La Crosse, La Crosse, WI 54601. 0007-2745/78/448$0.35/0 This content downloaded from 207.46.13.0 on Tue, 17 May 2016 06:01:48 UTC All use subject to http://about.jstor.org/terms

Observations on Endocarpon Pusillum: The Role of Rhizomorphs in Asexual Reproduction

Endocarpon pusillum Hedw. is a common crustose-squamulose lichen occurring on soil and rock in the United States (Fink, 1935). Rhizines, previously reported in this group (Smith, 1921; Bertsch and Butin, 1967; Ahmadjian and Heikkila, 1970), generally are thought to function as a means of anchoring a thallus to a substrate, while there has also been some general discussion of their possible function in water and nutrient uptake (Smith, 1921; Jahns, 1973). While the fungal extensions on the undersurface of these specimens of E. pusillum could be called rhizines, because of their extensive development the term rhizomorph is more appropriate and will be used. As a result of the observations on E. pusillum reported here, the possible involvement of rhizomorphs in asexual reproduction will be discussed. Endocarpon pusillum was observed growing on soil around the bases of prairie grasses at several sites on loess bluffs along the Missouri River in western Iowa. The small lobed thalli were numerous, along with other species of soil-inhabiting lichens, and some areas contained four to five E. pusillum thalli per cm2. Thalli were collected by removing pieces of soil approximately 2 X 5 X 1-2 cm thick. Since whole thalli were to be imbedded for microscopic examination, it was judged expedient for microtomy to remove as much soil as possible. Large pieces of soil with many thalli on them were immersed in water and the soil gently brushed away with small camel-hair brushes. It became apparent that what were superficially separate thalli on the same piece of soil were actually clusters of thalli interconnected by a network of subterranean rhizomorphs (FIG. 1). Some of the rhizomorphs extended laterally outward from the thalli while others traveled vertically into the soil under the thalli. Both lateral and vertical rhizomorphs branched ex-