Landscape Stability Research Articles

Mosaic Landscape Structures in Relation to the Land Use of Nitra District

Abstract Mosaic landscape structures with traditional forms of land use are currently the most important landscape features, especially from the point of landscape and cultural-historical perspective. Their typical features are the alternation of the areas of narrow-field fields, meadow vegetation and permanent cultures, especially vineyards and orchards. Their presence in the territory is mainly related to the rich vineyard and fruit-growing tradition. On the territory of the Nitra district, we record the most extensive mosaic landscape structures from the south to the north-eastern part. These are heterogeneous units, typical of the rotation of small-area land management, scattered by non-woody vegetation and habitat. In the mosaic landscape structures, we also find elements of the traditional settlement architecture of the houses ‘hajloch’. Significant landscape elements in the form of mosaic structures survive thanks to the rich viniculture tradition. In the long run, however, there are changes in their use: they are often the subject of inheritance, they are converted into holiday homes or they are used for the needs of an expanding residential development. The aim of our study is to point out the dynamic and changes that occurred in the mosaic landscape structures between the two-time horizons (the 50s of the 20th century and the present). For this purpose, we use geospatial analysis to evaluate their area representation, spatial characteristics in relation to the surrounding settlement structure and selected properties of relief forms. The analysis and evaluation of the spatial diversity of mosaic landscape structures as important landscape elements play a significant role in protecting the natural and cultural heritage values of the area from the aspect of species diversity and rich gene pool, visual perception of the landscape, preservation of ecological stability of landscape, landscape potential and overall landscape diversity.

Current landscape attributes and landscape stability in breeding grounds explain genetic differentiation in a long‐distance migratory bird

AbstractNumerous studies have highlighted a major role of isolation by both geographic distance and current landscape resistance in controlling bird population genetic differentiation. However, the importance of past landscape features or landscape temporal stability in shaping population genetic structure remains undervalued, particularly in birds. We assessed the role of isolation by landscape resistance – derived from current landscape attributes and measures of landscape stability –, in comparison to geographic isolation, as drivers of genetic differentiation of the Iberian bluethroat (Luscinia svecica azuricollis), a migratory bird whose populations breed in fragmented and dynamic landscapes affected by land use change. First, we characterized bluethroat genetic structure using microsatellite genotypes and evaluated genetic distances. Then, we built species distribution models using as a predictor a time series (two decades) of values of the Normalized Difference Vegetation Index as proxies of recent past landscape stability and current landscape features to ultimately generate landscape resistance values through different functions. Finally, we used maximum‐likelihood population effects models to evaluate the relationships between genetic distances and both geographic and landscape resistance distances. We found a genetic structure of four clusters in the Iberian bluethroats populations, as well as a high level of genetic differentiation. Genetic structure was better associated with landscape resistance, rather than with geographic distance. The highest values of habitat suitability corresponded to areas where vegetation remained mostly stable during the two decades prior to bird surveys, with low annual precipitation and spring temperature, being the relationship between gene flow and presence of intervenient habitat among populations linear or quasi‐linear. Our results suggest that conservation policies and land management practices that promote the maintenance of semi‐open pasture‐shrub mosaics (e.g. through extensive livestock grazing) can strongly benefit Iberian bluethroat populations, improving gene flow and population connectivity.

Land-Use Changes of Historical Rural Landscape—Heritage, Protection, and Sustainable Ecotourism: Case Study of Slovak Exclave Čív (Piliscsév) in Komárom-Esztergom County (Hungary)

The landscape surrounding the village of Čív (Piliscsév in Hungarian) in the north of the Komárom-Esztergom County is part of the cultural heritage of the Slovaks in Hungary. This paper discusses the issue of the Čív landscape changes in the context of its use (historical land use). Between 1701 and 1709, new inhabitants began cultivating the desolated landscape of the Dorog Basin, which is surrounded by the Pilis Mountains. This paper aims to characterize the Slovak exclave Čív land use with an emphasis on the period from the beginning of the 18th century (Slovak colonization of the analyzed territory) to 2019. These findings subsequently lead to the evaluation of the stability of the cultural-historical landscape as an essential condition for the development of ecotourism in the cultural landscape. The study results show that a long-term stable cultural landscape has a similar potential for the development of ecotourism as a natural landscape (wilderness). Research conclusions were aimed at creating three proposals for the cultural landscape management of the study area, conceived by the fundamental pillars of ecotourism, which would lead to its stable and sustainable use in ecotourism.

Evolving a total-evaluation map of flash flood hazard for hydro-prioritization based on geohydromorphometric parameters and GIS–RS manner in Al-Hussain river basin, Tartous, Syria

Floods are one of the most severe hydrological hazards that cause an excessive threat to landscape stability, population welfare, infrastructure and spatial development in the Syrian coastal region. Al-Hussain river basin, like other Syrian coastal basins, is prone to a hazardous, frequent-flooding threat. However, investigating the probable areas of flooding risk is a difficult challenge that results from the almost complete absence of spatially distributed geo-hydrological measurements in Al-Hussain river basin. In this regard, geohydromorphometric parameters (Stream number Nu, Stream length Lu, Bifurcation ratio Rb, Form factor F, Elongation ratio Eb, Drainage density Dd, Stream frequency Fs, Drainage texture Td, Lemniscate ratio K, Compactness index C, Circulatory ratio Rc, Ruggedness number Rn, Basin relief Hr, and Relief ratio Rr) derived from remote sensing data in the GIS environment can provide a comprehensive and objective approach that can be utilized to map the spatial distribution of flood hazards at the level of delineated sub-basins. This being the case, the present research focuses on exploring the spatial distribution of flood risk in ten sub-basins belonging to Al-Hussain river basin by using spatial techniques tools in order to overall determine the hydro-prioritization of conservation. The geo-visualization map of generated flash flood susceptibility evaluates five degrees of the flood risk: very low, low, moderate, high, and very high. The flood risk map indicates that Qalea, and Talaa sub-basins have massive hydrodynamic risk, which, in turn, indicates the urgent need of soil and water maintaining measures. This hydrological dynamic in these sub-basins is explained by high values of Dd, F, Rr, Rn, Rc, and K, respectively. Overall, the spatial outcomes of the current work successfully proved the efficiency of extracted geohydromorphometric layers from RS data in the context of the spatial assessment of flash flood hazard; they also ensure ecological sustainability and productivity of the study basin.

Distribution of silty mantles in soils of the Northcentral Appalachians, USA

Across the northcentral Appalachians, USA, high silt content soils are found as silty mantles or deep, high silt content pedons. The origin of such soils can be attributed to additions of wind-blown dust deposits (WBD) or local parent materials (i.e. shales or siltstone lithology). Previous research on silt soils originating specifically from WBD attributed to late marine isotope stage (MIS) 2 loess has often been isolated to drainageways receiving outwash from deglaciation. We hypothesize that thin (<25–50 cm) silty mantles, and some deep silt soils occurring farther from outwash systems, are also indicative of post MIS 2 WBD and their extent is widespread. To test this hypothesis, we evaluated over 900 pedons from an ~119,280 km2 area of the northcentral Appalachians, USA to: (i) develop a particle size signature indicative of soils largely derived from WBD versus local parent materials, (ii) determine the potential depth of WBD additions to soils, and (iii) document the spatial extent of WBD versus deep, high-silt content soils across part of the region. Results suggest that silty mantles are prevalent across the study area and have a particle size signature indicative of loess and the mean depth of WBD additions to soils is ~50 cm. Below 50 cm, local lithology or pedogenesis more influences particle size trends. Pedon results were applied in a spatial modeling effort using the USA Soil Survey Geographic Database (SSURGO) to document the extent of silty mantles (over non-silt sourced parent materials) and deep, high silt content soils. Model results indicate silty mantles are common on stable landscape positions or positions that accumulate sediments (depressions or valleys). Our finding of silty mantles, or deep high silt content profiles, over lithologies high in sand infers a source other than the underlying lithology. In addition, the presence of such silty mantles on summits and upper slopes suggests the importance of these landforms as stable positions preserving WBD. Our results suggest that stable landforms preserve WBD deposits and where topography is of lesser relief, broader deposition across several aspects is common. Aspect dependent deposition is tied to glaciofluvial sources of WBD, and modeled silty mantles correspond strongly to regional studies of loess.

Ecological network construction of the heterogeneous agro-pastoral areas in the upper Yellow River basin

The increasing landscape heterogeneity in the agro-pastoral areas and the contradiction between the development and biodiversity conservation is becoming more and more prominent, especially in Northwest China. Rational ecological network construction has become an important issue for ecological restoration and ecological security pattern strategy. Taking a typical agro-pastoral ecotone in the upper Yellow River valley as the study area, an ecological network was established using Graphab software based on the integral landscape heterogeneity analysis, in which the morphological spatial pattern analysis (MSPA) and structural equation model (SEM) were used to identify the ecological source regions and determine the resistance surface. The results showed that grazing and agricultural activities are the main reasons for the landscape complexity and heterogeneity. SEM also revealed the interactions between geographical conditions and landscape heterogeneity. The regression coefficients showed that the contribution of various factors on landscape heterogeneity were in order from strong to weak elevation, roads, settlements and slope. The influencing effects on landscape patterns were mainly reflected by the patch density, fractal dimension and landscape division indexes, with coefficients of −0.94, −0.91 and −0.88, respectively. The established ecological network shows that the overall planning of natural habitat and cultivated land will effectively improve the landscape quality. The presence of "stepping stone" patches in the central and eastern regions of the study area increases the landscape connectivity. In addition, the rational planning and utilization of high heterogeneity areas in the landscape are critical for maintaining the structure and function of the landscape. Findings from our study could provide a reference method for maintaining the landscape stability and sustainable development of heterogeneous agro-pastoral ecotones.

SUBSTANTIATION OF THE NEED FOR ORGANIZATION OF A SPECIALLY PROTECTED NATURAL TERRITORY IN THE NEFTECUM CITY DISTRICT OF STAVROPOL REGION

Specially protected natural territories (SPNA) occupy small areas of the Neftekumsky urban district of the Stavropol Territory. In this regard, it is relevant to justify the need to create protected areas on its territory thus making the natural landscapes of the district sustainable. The stability of landscapes was determined on the basis of the ecological-landscape principle. The indicators of landscape stability were obtained by calculating the values of the coefficients of ecological stability of the landscape. For the Neftekumsky urban district of the Stavropol Territory, these studies were conducted for the first time. As a result of the studies, it was established that the representativeness and environmental value of the protected areas existing in the Neftekum urban district do not meet the requirements for the territorial organization of ecosystems of this type, the landscapes are conditionally stable and require the partial transformation of unstable landscape elements into stable ones, which is possible when organizing a new protected area in the territory counties.

The role of defecate and microbial nitrogen-fixing preparations in the formation of alfalfa variety yield in the conditions of the south of Primorsky Krai

Four-year studies revealed a positive role of the effect and aftereffect of the defecate and inoculation of seeds by virulent active strains of Rhizobium Synorhizobium meliloty on the productivity of green and dry alfalfa varieties VEGA 87. The total yield of green alfalfa has varied during four years of life (ten bites) from 142.2 t/ha in the control variant to 153.4-183.2 t/ha in the experimental variants. Total productivity of green mass in variant with application of lime increased by 18.3 %, in the variants with presowing treatment of the seeds with rhizobia strains –by 7.9-11.5 % and their combination – by 23.4-28.8 %. The yield of dry mass in the variant with application of defecate increased by 28.8 %, in the variants with presowing treatment of the seeds with rhizobia strains by 10.7-13.7 % and at their joint action by 37.6-42.0 %. The biggest increase in productivity of green and dry mass is provided by inoculation of the seeds with a promising A4 strain when applying defecate, and without the use of meliorant – inoculation of the seeds with the main production strain 425a. The application of defecate and bacterial preparations for presowing treatment of the alfalfa seeds is agronomically and economically profitable, it promotes to increase the environmental stability of the agricultural landscape and plants to stressful conditions, a balanced level of nutrition, increasing plant productivity and profitability (low cost) of their cultivation.

Paleoenvironments, taphonomy, and stable isotopic content of the terrestrial, fossil-vertebrate–bearing sequence of the El Disecado Member, El Gallo Formation, Upper Cretaceous, Baja California, México

Abstract The Late Campanian (Late Cretaceous), upper part of the El Disecado Member, El Gallo Formation, Baja California, México, preserves a rich fossil assemblage of microvertebrates and macrovertebrates, silicified logs, macroscopic plant remains, and pollen that was likely deposited as the distal part of a subaerial fan. The unit was episodic and high energy, with its salient features deriving from active river channels and sheet, debris-flow deposits. Landscape stability is indicated by the presence of compound paleosol horizons, containing Fe2O3 mottling in B horizons, cutans, and calcium carbonate concretions. All of these features indicate wet/dry cyclicity in subsurface horizons, likely attributable to such cyclicity in the climate. Drainage was largely to the north and to a lesser extent, the west; however, some current flow to the south and east is preserved which, in conjunction with the proximal location of marginal marine deposits, suggest the influence of tides in this setting. The fossil vertebrates preserved in this part of the El Disecado Member are almost exclusively allochthonous, preserved as disarticulated isolated clasts in hydraulic equivalence in the braided fluvial system. A relatively diverse microvertebrate assemblage is preserved, the largest components of which are first, dinosaurs, and second, turtles. Non-tetrapod fossils are relatively uncommon, perhaps reflecting an absence of permanent standing water in this depositional setting. Here we report a high-precision U-Pb date of 74.706 + 0.028 Ma (2σ internal uncertainty), obtained from zircons in an airfall tuff. The tuff is located low within the sequence studied; therefore, most of the sedimentology and fossils reported here are slightly younger. This date, which improves upon previously published 40Ar/39Ar geochronology, ultimately allows for comparison of these El Gallo faunas and environments with coeval ones globally. Primary stable isotopic nodules associated with roots in the paleosols of the terrestrial portion of the El Disecado Member are compared with ratios from similar sources from coeval northern and eastern localities in North America. Distinctive latitudinal gradients are observed in both δ13C and δ18O, reflecting the unique southern and western, coastal geographic position of this locality. These differences are best explained by differences in the floras that populated the northern and eastern localities, relative to the southern and western floras reported here.

A Tale of Grass and Trees: Characterizing Vegetation Change in Payne’s Creek National Park, Belize from 1975 to 2019

The lowland savannas of Belize are important areas to conserve for their biodiversity. This study takes place in Payne’s Creek National Park (PCNP) in the southern coastal plain of Belize. PCNP protects diverse terrestrial and coastal ecosystems, unique physical features, and wildlife. A Support Vector Machine (SVM) classification technique was used to classify the heterogeneous landscape of PCNP to characterize woody and non-woody conversion in a time-series of remotely sensed data from 1975, 1993, 2011 and 2019. Results indicate that the SVM classifier performs well in this small savanna landscape (average overall accuracy of 91.9%) with input variables of raw Landsat imagery, the Normalized Difference Vegetation Index (NDVI), elevation, and soil type. Our change trajectory analysis shows that PCNP is a relatively stable landscape, but with certain areas that are prone to multiple conversions in the time-series. Woody vegetation mostly occurs in areas with variable slopes and riparian zones with increased nutrient availability. This study does not show extensive woody conversion in PCNP, contrary to widespread woody encroachment that is occurring in savannas on other continents. These high-performing SVM classification maps and future studies will be an important resource of information on Central American savanna vegetation dynamics for savanna scientists and land managers that use adaptive management for ecosystem preservation.

Late Holocene geomorphodynamics in the vicinity of Göbekli Tepe, SE Turkey

This study traces the geomorphological development in the environs of the Pre-Pottery Neolithic site Göbekli Tepe by means of radiocarbon dated sediment profiles from its close vicinity. Based on facies interpretation we identify different depositional environments and discuss the involved process dynamics. Our results show that the sediments from the foot slopes are characterized by soil creep and slope wash. Further downstream, in the proximal piedmont zone, fluvial deposition prevails forming a channel and an overbank facies. The sediments at the foot slopes were mainly deposited during Roman and Byzantine times, while those from the proximal piedmont zone cover the period from the Bronze Age to the Roman times. Phases of geomorphological activity and stability can be distinguished in the course of the later Holocene, where organic rich topsoils were buried at c. 4750, 4200, and 3650 cal. a BP documenting phases of landscape stability followed by enhanced geomorphodynamics. These phases fall into the Bronze Age in Anatolia and coincide with an increasing population, pronounced human impact, and climatic aridization that occurred in Turkey around 5.3–4.1 ka BP. Our findings provide among the first insights into the environmental development including the involved process dynamics in the vicinity of the UNESCO World Heritage site of Göbekli Tepe during the later Holocene, also allowing to further develop hypotheses for the period of its occupation.

The drivers of West Nile virus human illness in the Chicago, Illinois, USA area: Fine scale dynamic effects of weather, mosquito infection, social, and biological conditions.

West Nile virus (WNV) has consistently been reported to be associated with human cases of illness in the region near Chicago, Illinois. However, the number of reported cases of human illness varies across years, with intermittent outbreaks. Several dynamic factors, including temperature, rainfall, and infection status of vector mosquito populations, are responsible for much of these observed variations. However, local landscape structure and human demographic characteristics also play a key role. The geographic and temporal scales used to analyze such complex data affect the observed associations. Here, we used spatial and statistical modeling approaches to investigate the factors that drive the outcome of WNV human illness on fine temporal and spatial scales. Our approach included multi-level modeling of long-term weekly data from 2005 to 2016, with weekly measures of mosquito infection, human illness and weather combined with more stable landscape and demographic factors on the geographical scale of 1000m hexagons. We found that hot weather conditions, warm winters, and higher MIR in earlier weeks increased the probability of an area of having a WNV human case. Higher population and the proportion of urban light intensity in an area also increased the probability of observing a WNV human case. A higher proportion of open water sources, percentage of grass land, deciduous forests, and housing built post 1990 decreased the probability of having a WNV case. Additionally, we found that cumulative positive mosquito pools up to 31 weeks can strongly predict the total annual human WNV cases in the Chicago region. This study helped us to improve our understanding of the fine-scale drivers of spatiotemporal variability of human WNV cases.

Late Quaternary vegetation and climate dynamics in central‐eastern Brazil: insights from a ~35k cal a bp peat record in the Cerrado biome

ABSTRACTThe late Quaternary evolution of central‐eastern Brazil has been under‐researched. Questions remain as to the origin of the Cerrado, a highly endangered biome, and other types of vegetation, such as the Capões – small vegetation islands of semi‐deciduous and mountain forests. We investigated the factors that influenced the expansion and contraction of the Cerrado and Capões during the late Quaternary (last ~35 ka), using a multi‐proxy approach: stable isotopes (δ13C, δ15N), geochemistry, pollen and multivariate statistics derived from a peat core (Pinheiro mire, Serra do Espinhaço Meridional). Five major shifts in precipitation, temperature, vegetation and landscape stability occurred at different timescales. Our study revealed that changes in the South Atlantic Convergence Zone (SACZ) seem to have been coeval with these shifts: from the Late Glacial Maximum to mid‐Holocene the SACZ remained near (~29.6 to ~16.5k cal a bp) and over (~16.5 to ~6.1 k cal a bp) the study area, providing humidity to the region. This challenges previous research which suggested that climate was drier for this time period. At present, the Capões are likely to be a remnant of a more humid climate; meanwhile, the Cerrado biome seems to have stablished in the late Holocene, after ~3.1 k cal a bp.

Comparing Uganda's indigenous soil classification system with World Reference Base and USDA Soil Taxonomy to predict soil productivity

This study examines three soil classification systems - Buganda, World Reference Base, and US Soil Taxonomy - in order to evaluate their relative strengths and feasibility for making linkages between them. Nine field sites and 16 pedons were considered across the soil landscapes of the Buganda catena. Each identified field pedon diagnostic horizons and characteristics were described and their soils analyzed using standard pedological techniques and measurements. To document the indigenous use of the Buganda classification system, interviews and discussions were held with farmer groups and local extension specialists. Using this local expertise, five local soil units were identified. We also identified two landscape toposequences with pedons that classified into six WRB Reference Soil Groups and five US Soil Taxonomic Suborders. While four local soil classes each mismatched with international systems' groups, Liddugavu (black) soil corresponded to Phaeozem (WRB) and Udolls (US Soil Taxonomy) and is consistently viewed as the most productive soil due to faster weed growth, diversity of crops it supports and its stable landscape location. Statistical comparisons indicated that the Buganda classes were more homogeneous and effective at separating variability of different soil properties than those of either the WRB Reference Soil Groups or US Soil Taxonomy Suborders. Integrating soil texture, pH and bases information in indigenous system methods could locally complement international classifications and linking the best of both systems would be ideal for the generation of a hybrid system. Our findings show that using the toposequence framework assists in comparing these systems in a way that is useful for scientists and local farmers.

Fluvial activity in major river basins of the eastern United States during the Holocene

In the eastern United States, existing paleo-reconstructions in fluvial environments consist primarily of site-specific investigations of climate and human impacts on riverine processes. This paper presents the first meta-analysis of fluvial reconstructions focused on regional watersheds of the eastern United States, including the Lower Mississippi, Tennessee, South Atlantic–Gulf Coast, Ohio, Mid-Atlantic, and New England regional watersheds. Chronologies of fluvial activity (i.e. alluvial deposition) and stability (i.e. landscape stability) were developed by synthesizing data from existing, published, and site-specific fluvial reconstruction studies conducted across the eastern United States. Overall, regional watersheds show variable patterns of synchronicity across watersheds and did not demonstrate cyclic behavior through the Holocene. During the last millennium, only the Lower Mississippi and Ohio regional watersheds exhibit high rates of fluvial activity active during the ‘Medieval Climate Anomaly’ (650–1050 yr BP), while nearly all other regional watersheds in the eastern United States were active during the ‘Little Ice Age’ (100–500 yr BP). These findings imply that fluvial activity may be more spatially restricted during warmer/drier climatic conditions than during cooler/wetter periods. We find an increase in fluvial activity during the era of Euro-American colonization (400 yr BP to present) in the southeastern United States but not the northeastern United States, implying a heterogeneous response of fluvial systems to human activities in the eastern United States related to climatic, cultural, and/or physiographic variability. These new insights gained from fluvial chronologies in the eastern United States demonstrate the utility of regionally synthesized paleo-records to understand large-scale climate variation effect on rivers.

Late Quaternary landscape evolution and bioclimatic change in the central Great Plains, USA

AbstractA systematic study of floodplains, terraces, and alluvial fans in the Republican River valley of south-central Nebraska provided a well-dated, detailed reconstruction of late Quaternary landscape evolution and resolved outstanding issues related to previously proposed Holocene terrace sequences. Stable carbon isotope (δ13C) values determined on soil organic matter from buried soils in alluvial landforms were used to reconstruct the structure of vegetation communities and provided a means to investigate the relationships between bioclimatic change and fluvial activity for the period of record. Our study serves as a model for geomorphological and geoarcheological investigations in stream valleys throughout the central Great Plains and wherever loess-derived late Quaternary alluvial fans occur, in particular.Holocene alluvial landforms in the river valley include a broad floodplain complex (T-0a, T-0b, and T-0c), a single alluvial terrace (T-1), and alluvial fans that mostly grade to the T-1 (AF-1) and T-0c (AF-0c) surfaces. Remnants of a late Pleistocene terrace (T-2), mantled by Holocene (Bignell) loess, are also preserved, and some Holocene alluvial fans (AF-2) grade to T-2 surfaces.Radiocarbon ages suggest that the T-1 fill and AF-1 fans aggraded between ca. 9000–1000 yr B.P. Hence, nearly all of the Holocene alluvium in the river valley is stored in these landforms. Sedimentation, however, was interrupted by several periods of landscape stability and soil formation. Radiocarbon ages from the upper A horizons of buried soils in the T-1 and AF-1 fills, indicating approximate burial ages, cluster at ca. 6500, 4500, 3500, and 1000 yr B.P. Also, based on the radiocarbon ages, the T-0c fill and AF-0c fans were aggrading between ca. 2000–900 yr B.P. Given that the T-0c fill and upper parts of the T-1 fill were both aggrading after ca. 2000 yr B.P., we suggest that the T-1 surface was abandoned between ca. 4500–3500 yr B.P., but subsequent aggradation of both the T-1 and T-0c fills occurred due to large-magnitude flood events during the late Holocene.The δ13C data indicate a shift from ∼40% C4 biomass at ca. 6000 to ∼85% at ca. 4500 yr B.P. We propose a scenario where (1) a reduction in C3 vegetation after 6000 yr B.P. destabilized the uplands, resulting in an increase in sediment supply and aggradation of the T-1 fill and AF-1 fans, and (2) the establishment of C4 vegetation by ca. 4500 yr B.P. stabilized the uplands, resulting in a reduction in sediment supply and subsequent incision and abandonment of the T-1 and most AF-1 surfaces. The proposed timing and nature of landscape and bioclimatic change are consistent with regional records from the central Great Plains.

The role of eolian-fluvial interactions and dune dams in landscape change, late Pleistocene–Holocene, Mojave Desert, USA

AbstractThe formation of the Kelso Dunes in the eastern Mojave Desert, California, was a landscape-changing event triggered by an increase in sediment supply that followed the incision of Afton Canyon by the Mojave River ca. 25 ka. Eastward migration of sand dunes occurred along a well-defined eolian transport corridor. Dunes temporarily blocked washes resulting in substantial aggradation of eolian and fluvial sediments. Stratigraphic exposures reveal numerous fining-up sequences with interbedded eolian sands that provide evidence of dune dams and subsequent aggradation. Luminescence ages reveal that dune blocking and aggradation correspond to a regional pulse of alluvial fan sedimentation that occurred ca. 14–9 ka. Meanwhile, relative landscape stability occurred downstream of dune dams, resulting in the formation of a moderately developed soil on abandoned fluvial deposits. The next pulse of alluvial fan activity ca. 6–3 ka likely resulted in the breaching of the dune dams, followed by incision. Eolian system sediment state theory suggests that eolian activity in the Mojave Desert is closely tied to enhanced sediment supply, primarily related to the Mojave River–Lake Mojave system. Our data suggests that Intermittent Lake Mojave I, ca. 26–22 ka, triggered a large dune-building event that impounded massive amounts of sediment derived from alluvial fans deposited during the Pleistocene-Holocene transition. Breaching of dune dams and sediment recycling may have also increased sediment supply that contributed to late Holocene eolian activity. This profound impact on the regional geomorphology highlights the critical importance of eolian-fluvial interactions in desert environments.

Stability Assessment of Insular Geosystems of the Empress Eugénie Archipelago (Peter the Great Gulf, Sea of Japan)

A landscape stability assessment is made for the major islands of the Empress Eugenie Archipelago. The landscapes are ranked according to groups of stability on the basis of an integrated numerical score for 17 indicators. It was found that the islands are dominated by landscapes of moderate stability, and by unstable landscapes. The islands are characterized by a significant differentiation with respect to the areas of landscapes belonging in different groups of stability. This is due to the individual features in the landscape organization of the insular geosystems, and to the degree of their economic transformation. Results of cartographic and correlation analyses showed that a considerable contribution to the integrated indicator of landscape stability is made by the geomorphological structure of the territory, and by vegetation cover. However, correlation analysis did not reveal any unambiguous relationship with the other landscape components. This is accounted for by the natural factor (low-mountain relief) and a severe anthropogenic transformation of vegetation, leading to an attenuation of the relationship of the structure of vegetation cover with the other landscape components. A statistical investigation using principal component analysis (PCA) showed the role of the landscape components in the formation of the integrated indicator of stability of insular geosystems. The largest load is experienced by the geomorphological structure, followed by soil and vegetation cover. An individual analysis of island landscape stability by PCA revealed a variation in the loads on the indicators of landscape stability in principal components, which is due to the rate and direction of response of the insular geosystems on homogeneous factors. It is concluded that each insular geosystem has individual characteristics of the formation of an integral landscape matter-energy system, with an inherent set of self-regulation and selforganization mechanisms which arise in accordance with the area of land, physical-geographical conditions and the degree of anthropogenic pressure. Planning of a further development of the insular territories should take into consideration the individual characteristics of the functioning of landscapes and the role of their components in the formation of the integrated stability indicator.

Supergene manganese ore records 75 Myr-long Campanian to Pleistocene geodynamic evolution and weathering history of the Central African Great Lakes Region – Tectonics drives, climate assists

The southeastern part of the Democratic Republic of the Congo locally hosts Proterozoic manganese deposits. The deposits of Kisenge-Kamata are the most significant, but manganese ores are also known to occur at Kasekelesa (former Katanga Province) and Mwene-Ditu (former Kasai Province). For the present study, cryptomelane-rich samples from these two localities were dated, using the 40Ar/39Ar step-heating method with a CO2 laser probe. The ages obtained are within a range of c. 77 Myr to c. 2 Myr. Cryptomelane formation took place at c. 76.4 Ma, c. 59.6 Ma, c. 45 Ma, c. 35 Ma, c. 23.8 Ma, c. 15.4 Ma, and c. 13.3 Ma at Kasekelesa, and it occurred at c. 35 Ma, c. 22.4 Ma, c. 15 Ma, c. 5.5–7.2 Ma, c. 3.6 Ma, and c. 2.1–2.3 Ma at Mwene-Ditu. The Campanian age (c. 76.4 Ma) recorded at Kasekelesa is the oldest 40Ar/39Ar age that has up to now been recorded for Mn ores from Africa. It documents the formation of oxidized ore along a Campanian or older erosion surface, which could be part of the ‘African Erosion Surface’. The complete age record suggests that continent-wide tectonics accounts for most of the recognized supergene ore formation episodes, controlled by vertical lithospheric movements that are ultimately responsible for alternating stages of landscape stability and erosion. Tectonics is thus regarded as the first-order control for secondary ore formation in Central Africa, over the last 80 Myr. Climate is a second-order control, because sufficient water supply is needed for supergene enrichment, whereby climatic conditions are recognized to have been favourable during some relatively cold Late Mesozoic and Paleogene periods, as well as during some humid and warm Neogene stages.

Applications of SAR Interferometric Coherence Time Series: Spatiotemporal Dynamics of Geomorphic Transitions in the South‐Central Andes

AbstractSediment transport domains in mountain landscapes are characterized by fundamentally different processes and rates depending on several factors, including geology, climate, and biota. Accurately identifying where transitions between transport domains occur is an important step to quantify the past, present, and future contribution of varying erosion and sedimentation processes and enhance our predictive capabilities. We propose a new methodology based on time series of synthetic aperture radar (SAR) interferometric coherence images to map sediment transport regimes across arid and semiarid landscapes. Using 4 years of Sentinel‐1 data, we analyze sediment transport regimes for the south‐central Andes in northwestern Argentina characterized by steep topographic and climatic gradients. We observe seasonally low coherence during the regional wet season, particularly on hillslopes and in alluvial channels. The spatial distribution of coherence is compared to drainage areas extracted from digital topography to identify two distinct transitions within watersheds: (a) a hillslope‐to‐fluvial and (b) a fluvial‐to‐alluvial transition. While transitions within a given basin can be well‐constrained, the relative role of each sediment transport domain varies widely over the climatic and topographic gradients. In semiarid regions, we observe larger relative contributions from hillslopes compared to arid regions. Across regional gradients, the range of coherence within basins positively correlates to previously published millennial catchment‐wide erosion rates and to topographic metrics used to indicate long‐term uplift. Our study suggests that a dense time series of interferometric coherence can be used as a proxy for surface sediment movement and landscape stability in vegetation‐free settings at event to decadal timescales.