Search

In February 1963, a huge landslide (ca. 1,950,000 m3) blocked the Visočica River and, thus, formed Zavoj Lake. The primary objective of this research was to investigate the importance of snowmelt in relation to landslide occurrence and to define the critical climatic conditions that may trigger massive winter landslides. We used monthly precipitation and average monthly maximum temperature data from meteorological and precipitation stations in the Visočica River basin (Dojkinci) and in the immediate proximity of Lake Zavoj (Pirot, Dimitrovgrad and Topli Do) as data inputs to the Snow-Melt Landslide (SML) index. It considers the summed monthly precipitation for previous months that continuously have an average maximum temperature below 0 °C. According to this method, the event at Zavoj Lake stands out among all other precipitation and snowmelt values for the past 72 years. After applying the SML index, all stations showed values of >300 mm for February 1963, which we consider as the threshold value for potential landslides appearance. In addition to meteorological data, we applied the SML index to data from the Coordinated Regional Downscaling Experiment (CORDEX) regional climate model outputs for the region from 2022 to 2100. As expected, climate change will have influenced the temperature values, especially during the winter. Conversely, the study area is experiencing drastic changes in land use caused by depopulation, leading to a reduced risk of winter landslides in the Visočica basin. We suggest that future climatic conditions in the area will make it more likely to experience extreme summer precipitation events, which might trigger large landslides. The SML method can be implemented for all landscapes that experience snowy winters, providing information in a timely manner so that local residents can react properly when the probability of landslide occurrence rises. The SML index, grounded in essential meteorological principles, provides a tailor-made, data-driven methodology applicable across varied geographical settings. Its utility extends to mitigating hydro-meteorological hazards on scales ranging from local to national scales, offering diverse and effective early warning solutions. [ABSTRACT FROM AUTHOR]

Among the numerous factors that trigger landslide events, the anthropogenic impact caused by inadequate planning and faulty land use in urban areas is increasing. The Zemun settlement on the northern outskirts of Belgrade has experienced a number of landslides in the last three decades, endangering buildings and roads, and claiming human lives, particularly in the case of the 2010/2011 landslides. Selected meteorological parameters were used to calculate rainfall erosivity indices such as Precipitation Concentration Index and Modified Fournier Index over the period 1991-2015. Drought indices, Lang aridity index and Palfai Drought Index were calculated as well. Mann-Kendall trend test was applied to identify potential rising and/or declining trends both in meteorological parameters and calculated indices. Trend analysis of the annual and seasonal scales yielded a statistically significant trend in the spring time series. Stable arid and pronounced drought conditions were recorded. The modified Fournier index based on monthly mean values yields moderate aggressiveness, with several extreme values indicating very high erosivity classes, especially for 2010/2011. The geological substrate is predominantly loess and hence highly susceptible to erosion and slope failure when climatological conditions are suitable. Accelerated urbanization at the end of the last century reduced vegetation cover, intensified pressure on the vertical loess slope, and lacked suitable rain drainage systems so that surface-water runoff was directed into the porous loess, thereby endangering slope stability. We proposed a geomorphic model to describe the nature of the erosional processes on the loess cliffs of the Zemun loess plateau. Results from this study have implications for mitigation strategies. [ABSTRACT FROM AUTHOR]

We report on pollen, plant macrofossils, and associated lithostratigraphy of a sediment core extracted from the base of Silver Lake, a kettle lake in northern Lower Michigan, USA, which reveal a complex deglacial scenario for ice block melting and lake formation, and subsequent plant colonization. Complementary multivariate statistical and squared chord distance analyses of the pollen data support these interpretations. The basal radiocarbon age from the core (17 540 cal years BP) is rejected as being anomalously old, based on biostratigraphic anomalies in the core and the date's incongruity with respect to the accepted regional deglaciation chronology. We reason that this erroneous age estimate resulted from the redeposition of middle-Wisconsin-age fossils by the ice sheet, mixed with the remains of plants that existed as the kettle lake formed at ca. 10 940 cal years BP by ice block ablation. Thereafter, the kettle lake became a reliable repository of Holocene-age fossils, documenting a mature boreal forest that existed until 10 640 cal years BP, followed by a pine-dominated mixed forest, an early variant of the mixed conifer–hardwood forest that persists to the present day. Our study demonstrates that researchers investigating kettle lakes, a common depositional archive for plant fossils in deglaciated landscapes, should exercise caution in interpreting the basal (Late Pleistocene/early Holocene-age) part of lake sediment cores. [ABSTRACT FROM AUTHOR]

• Integrated remote sensing and geochronology approaches have been applied. • OSL and radiocarbon dating indicate an earlier than expected retreat of the Saginaw Lobe. • Revisiting the timing of the LIS retreat is required. Understanding the behavior of paleo-ice sheets in response to past climate change and land surface processes can provide insights into the interplay between the atmosphere, ocean surface, and the cryosphere, which helps update current climate models and understand landscape evolution. The timing of the advancement and retreat of ice lobes along Quaternary ice sheet margins and their link to ocean surface temperature fluctuation are of particular interest. The Saginaw lobe along the southern margin of the Laurentide Ice Sheet (LIS) was bound by the Lake Michigan and Huron-Erie lobes. It flowed out of Saginaw Bay, across Lower Michigan, and into northern Indiana. All three of these lobes retreated across the region asynchronously, with the Saginaw lobe retreating first. The asynchronous behavior of the lobes allowed the Lake Michigan and Huron-Erie lobes to overprint and alter landscapes once occupied by Saginaw lobe ice. Lacustrine sediments within the Sturgis Moraine, deposited during the Saginaw lobe retreat in extreme southwestern Michigan, yielded optically stimulated luminescence (OSL) ages of 30.1 ± 1.8, 28.7 ± 1.5 and 25.2 ± 1.9 ka. An additional radiocarbon date (22.22 ± 0.8 cal ka) was measured from bryophytes sampled near the base of an ice-walled lake plain atop the moraine. These dates indicate that deglaciation of the Saginaw lobe could have been underway in southwestern Michigan between ∼ 30 and 22 ka, while ice margins of the Huron-Erie and Lake Michigan lobes were further south in Indiana and Illinois. The new dates indicate that southwestern Michigan may have witnessed ice-free conditions four thousand years earlier than previously thought. Moreover, the paleo-hydrological analyses of southwestern Michigan using detailed surficial geology mapping, Lidar-based longitudinal and terrace profiles along meltwater channels, and OSL data indicate that meltwater originating from the Saginaw—Huron-Erie interlobate area drained westward across the Saginaw lobe terrain between ∼ 18.0 to 14.6 Ka ago. The findings call for revisiting the current understanding of the timing and behavior of the southern margins of the LIS and the Holocene landscape evolution in Michigan. [ABSTRACT FROM AUTHOR]

Uprooting represents a key disturbance process in forests, forming pit-mound microtopography, which can then dramatically impact pedogenesis and the forest ecology. At our study sites in northern Michigan, where well-drained, sandy Spodosols dominate, pit-mound microtopography tends to persist for millennia. Because of its persistence, the influence of this type of microtopography is greater here than in most forests. In that respect, our sites represent an end member along a continuum of forest soil disturbance by uprooting. We studied post-uprooting pedogenesis (at 14 dated pit-mound pairs), mapped and characterized the pit-mound topography (over 2.8 ha), the soils below (within 317 soil profiles), and the trees above, to better understand the complex interactions among this type of disturbance regime and forest dynamics. We used a pair correlation function and chi-square test approach to study the relationships between treethrow features and the living trees at one of these sites. Soil variability as affected by microtopography, was studied using geostatistics. Pit-mound microtopography here covers 17% of the surface and are generally randomly distributed across the forest floor. Mounds are more prominent features of the forest floor than are pits. Pits infill with sediment and litter, obscuring them, whereas mounds persist for millennia in the sandy sediment because runoff is limited, and litter forms a protective armor. Treethrow features had volumes of roughly 214–225 m 3 /ha, and on average, each uprooting event translocated 0.6 m 3 of soil about 0.8 m laterally and 0.1–0.2 m vertically. Areas of the pit-mound features did not differ between slope aspects, supporting an idea that on the gentle slopes of the study sites, uprooting does little to affect the movement of sediment downslope. The exceptional longevity of the treethrow features is probably a factor in the statistical randomness with which treethrow features are distributed on the forest floor, as footprints of many uprooting events are interlaced across the forest floor. As reported elsewhere, soil development was accelerated in pits, leading to increasingly greater differences in soil development between pits and mounds, over time, and illustrating the concept of locally divergent pedogenesis. In older pits, the abnormally thick soil profiles extent so far below the depth of rooting that they are unlikely to be disturbed by future uprooting events. On the coarser spatial scale of the forest stand, uprooting decreased the ranges and increased the sills of spatial autocorrelation for O, E and Bhs horizon thicknesses. The effect of treethrow dynamics on soil characteristics was greatest and statistically most significant for E horizon thicknesses, where the range was decreased from 13 m to 10 m, whereas the maximal level of semivariance (sill) increased by 42%. All tree species preferred treethrow mounds to pits or undisturbed microsite for regeneration, especially Acer saccharum . [ABSTRACT FROM AUTHOR]

Abstract Magnetic properties of soils formed in and on loess substrate and their relation to climate are of general interest in paleoclimate and pedological research. The loess-paleosol sequences (LPS) in the Vojvodina region (Serbia) have been the subject of intensive study. On the Bačka loess plateau (BLP), covering approximately 2500 km2, six different soil types are observed. While the stratigraphy of the LPS has been investigated the relation between climatic factors and magnetic properties of surface soil have not yet been examined. In this study we analyze 50 samples of chernozem soils, which have been dominated by climatic factors during their formation. Previous studies have confirmed that the formation of magnetic properties in soils is related to climate, and especially rainfall, because of the response of hematite and goethite to different, climatically-driven regimes. The sensitivity of certain iron-bearing minerals to climate has also been documented in the literature. Climatic variables for the BLP were derived from six-decade national meteorological datasets. Low frequency magnetic susceptibility (χ) and frequency dependent magnetic susceptibility (χ fd) were determined for each site and compared to the mean annual precipitation (MAP), mean annual temperature (MAT) and the De Martonne aridity index (I DM). The meteorological variables were interpolated to sampling points by Kriging method in ArcMap 10.1. Our results suggest that values of χ and χ fd both decrease from south to north and so does the precipitation. Thus, our work provides new evidence for the relationship between precipitation, temperature, aridity and magnetic properties of modern top soils. The obtained and analyzed data may help in the future to improve transfer functions of the relationship between magnetic susceptibility and climatic data. [ABSTRACT FROM AUTHOR]

Abstract In this study, we compare two independent paleoenvironmental proxies for a loess sequence in northern Serbia, in the southern Carpathian Basin: novel n -alkane biomarkers and traditional land snail assemblages. Both are associated with other, more widely used proxy data for loess sections, such as environmental magnetism, grain size, and geochemical indices. Together, these paleoenvironmental proxy records provide evidence for the continued dominance of grasslands during the Late Pleistocene in the Southern Carpathian Basin. It is contrary to other European loess provinces, which are characterized by high diversity of Late Pleistocene environments (ranging from tundra-like to deciduous forest habitats). These findings highlight the southeastern part of Carpathian Basin as an important, but still insufficiently investigated, biogeographical refugium, and biodiversity preservation zone. The reason for this is a mostly stable paleoclimate for much of the Late Pleistocene. Highlights • Comparison of two independent paleoenvironmental proxies: novel n -alkane biomarkers and traditional land snail assemblages • Evidence of continuous dominance of grasslands during the Late Pleistocene in the Southern Carpathian Basin • Much reduced diversity of Late Pleistocene environments than in other European loess provinces [ABSTRACT FROM AUTHOR]

• Many parts of Iceland are affected by the severe aeolian erosion. • Dendrochronological analyses of dwarf shrubs provided reliable data on rates and timing of aeolian erosion. • Erosion rates (post-1990′s) ranged from 1.0 cm yr−1 in the 1970 s to 4.4–5.4 cm yr−1. • Reconstructed erosion rates in NE Iceland compared well to observations of dusty conditions (from the 1970′s to the present) • Increased erosion rates of small erosional escarpments coincide with dust storm activity. Iceland is known for having strong aeolian erosion events, as evidenced by erosional escarpments on the soil surface; these are known locally as rofabards. The aim of the study was to estimate aeolian erosion rates at two research plots affected by severe erosion, using anatomic features of the roots of Arctic, woody, dwarf shrubs. Ours is the first study to utilize dendrochronological analyses of exposed roots of dwarf willows (Salix herbacea L.) as an indicator of aeolian erosion. When dwarf shrub roots are exposed to the atmosphere by erosion, cell sizes are reduced by >50 %, with maximum changes in individual plants exceeding 150–200 %. We detected the erosion signal by analyzing changes in cell-size and width of growth rings in the roots. Using this relationship, were able to estimate erosion rates (the retreat of escarpments) since the 1970s for the study area. During the 1970s and 1980s, erosion rates were fairly constant, with retreat ranging from 1.0 to 2.5 cm yr−1. Rapid increases in erosion rates were observed after the late 1990s, occasionally as much as 4.4–5.4 cm yr−1. Increased aeolian erosion rates may be linked to continuous heavy grazing by sheep and climate change, as this period coincides with increased numbers of hot and warm, and dusty days. Our results indicate that dendrochronological methods can be highly useful in determining past geomorphic activity, due to modern environmental changes observed in the Arctic. The methods employed here can be applied even in treeless areas. [ABSTRACT FROM AUTHOR]

Soils on many of the outwash plains in southwestern Michigan have loamy upper profiles, despite being underlain by sand-textured outwash. The origin of this upper, loamy material has long been unknown. The purpose of this study is to analyze the spatio-textural characteristics of these loamy-textured sediments to ascertain their origin(s). The textural curves of this material have distinct bimodality, with clear silt and sand peaks. Because the sand peaks align with those in the outwash below, we conclude that the upper material is a mixture of an initially silty material with the sand from below, forming loamy textures. By applying a textural filtering operation to the data, we determined its original characteristics; nearly all of the soils originally had silt loam upper profiles, typical for loess. Field data showed that the loamy material is thickest east of a broad, north-south trending valley (the Niles-Thornapple Spillway) that once carried glacial meltwater. The material becomes thinner, generally better sorted, and finer in texture eastward, away from this channel. We conclude that the loamy mantle on many of the adjacent outwash plains is silt-rich loess, derived from the Niles-Thornapple Spillway and its tributary channels and transported on mainly westerly winds. The spillway was active between ca. 17.3 and 16.8 k cal. years ago. At this time, a large network of tunnel channels existed beneath the stagnant Saginaw lobe ice. Meltwater from the lobe funneled silt-rich sediment into the spillway, rendering it a prodigious silt source. [ABSTRACT FROM AUTHOR]