Buried Soils Research Articles

Geomorphological Holocene events as deduced from lithological records of the fluvial basins of Dauria

A conjugate analysis of the processes of morphogenesis and sedimentation within small fluvial basins of Dauria revealed a rhythmic character of change of the Holocene processes which are combined into cycles of a different hierarchical level. It is shown that each cycle begins with an extreme phase of intense fluvial drift and delivery of matter from the system. The fluvial horizons comprise the lower part of deposits of the Holocene macrocycle in the Vesnyanka pad’ (a valley without a permanent watercourse). A disastrous fluvial drift was recorded repeatedly for the period 7–8.5 cal. ka and at the transition time from the Atlantic to Subboreal time. A normal zonal phase of integration of matter within the basins is exhibited by buried humus horizons of soils which give clear evidence of 1800-year cycles. A regional development in Dauria is recorded for the soils with the age of about 8, 6.4 and 4.6 as well as 1.2–1.4 cal. ka. The upper part of the deposits of each cycle is characterized by aeolian horizons of extreme arid phases. The profiles of proluvial trails are indicative of 130-year cycles. Based on results from studying buried soils, data of pollen analysis and radiocarbon dating of the deposits, we determined an enhancement in climate aridization for the last 10 ka and, in general, a decreased of the sedimentation and morphogenesis rate.

Terrace formation in the upper Bengal basin since the Middle Pleistocene: Brahmaputra fan delta construction during multiple highstands

AbstractFloodplains, paleosols, and antecedent landforms near the apex of the Brahmaputra fan delta in north‐central Bangladesh preserve cycles of fluvial sediment deposition, erosion and weathering. Together these landforms and their associated deposits comprise morphostratigraphic units that define the river's history and have influenced its channel position and avulsion behaviour through the Late Quaternary. Previously, temporal differentiation within these units has not been sufficient to decipher their sequence of deposition, an important step in understanding the spatial pattern of migration of the Brahmaputra River. Holocene units in this region are fairly well established by radiocarbon dating of in situ organic material, but pre‐Holocene units are considered Pleistocene‐aged if organic material is dated >48 000 year BP (the limit of radiocarbon dating) or the sediments are positioned beneath a prominent paleosol, interpreted as a buried soil horizon that developed during a previous sea level lowstand. In such cases, these morphostratigraphic units have been broadly interpreted as Pleistocene without knowing their absolute depositional ages or relative evolutionary chronology. Here we use detailed sediment analysis to better differentiate morphostratigraphic units at the Brahmaputra's avulsion node, establishing the sequence of deposition and subsequent weathering of these bodies. We then test this relative chronology by luminescence dating of the sands beneath these landform surfaces. This work provides the first absolute depositional age constraints of terrace sediments for the Middle to Late Pleistocene Brahmaputra River and upper Bengal basin. The luminescence ages are complemented by detailed compositional trends in the terrace deposits, including clay mineralogy and the degree of weathering. Together, these newly dated and carefully described morphostratigraphic units reflect eustasy‐driven cycles of terrace development by way of highstand floodplain deposition and subsequent lowstand exposure and weathering, along with active tectonic deformation. Defining this Late Quaternary history of terrace development and position of the Brahmaputra River is a first step toward an integrated understanding of basin and delta evolution over multiple glacioeustatic cycles and tectonically relevant timescales.

The Method of Microbiological Soil Investigations within the Framework of the Project “Microbiome of Russia”

The methods of Russian soil biology for the purposes of the investigations of soils microbiome were studied. The most important methods are cross-disciplinary investigations of plant and microbial interactions, the role of microbiome in the forming of soil fertility and carbon cycle. For the purposes of the most complete description of soil microbiome functions we suggest to combine the methods of metagenomics (for the purposes of the assessment of the phylogenic diversity of the microorganisms), biomarkers analysis (for the purposes of determination of the functional diversity) and the changes in the enzyme activity (for the purposes of the assessment of the actual functioning of soils). The investigation of correlation of the structural soil hierarchy (from aggregates and microloci to the soil areas) and levels of microbial community organization (from microbial populations to bio-geographic regularities) will allow us to understand better the distribution and common specificities of soil and microorganisms interactions. Along with the investigation of spatial organization we suggest to study the dynamics of the soil microbiomes on different time lines: short-term changes (on the field monitoring areas), transformation during the soil forming process (on the “chronosequences” of the soil of a different age) and at the geologic time scale (on the example of buried soils). In this paper we consider the importance of the investigation of the diversity of the soil microorganisms as a source of the suppressing activity of soils as the largest depository of genetic information, important agent of the emission and fixation of atmospheric carbon. The comparative analysis of microbial diversity of disturbed and undisturbed soils and the assessment of outer impact on the soil microbiome is necessary for the preservation of soil biodiversity as one of the most valuable ecologic and biotechnologic resource.

Reconstruction of a Palaeosurface and Archaeological Site Location in an Anthropogenic Drift Sand Area

AbstractKnowledge of the position of archaeological remains in the surface relief provides important basic information for archaeological survey design and interpretation. Geomorphological processes in (pre)history may have resulted in a modification of the local relief around archaeological sites, especially in areas that are prone to sediment erosion and relocation, such as sheet sand and dune landscapes. In this study, we reconstructed and analysed the palaeorelief of an archaeological excavation site in an inland dune area in southern Brandenburg, Germany. The remains of two Mesolithic sites were documented in the archaeological excavations and found to be associated with a buried soil horizon. To gather information on the relief of the buried soil surface, we used a combination of sedimentological and pedological profile descriptions along archaeological survey trenches and geophysical prospection with ground penetrating radar supplemented with microdrone photography and photogrammetry, global positioning system (GPS) surveys, and analysis of LiDAR‐based elevation models. A digital elevation model of the buried surface was generated and analysed using a geographical information system (GIS). A comparison of the palaeosurface model with the recent surface elevation model shows that sand remobilization resulted in a considerable reshaping of the relief. Further, an analysis of the buried surface model shows that the relief position of the two archaeological sites in the study area was considerably more prominent in relation to the corresponding buried soil surface than in relation to the recent surface morphology. The results affirm the significance of Holocene sediment relocation for the local surface morphology and the importance of considering such relief modifications in archaeological surveys. Copyright © 2017 John Wiley & Sons, Ltd.

Scythian Age Barrows with Burials on the Ground Surface in the Southern Ural Steppes: Features of the Funerary Rite

The article describes burials on the buried soil horizon in southern Ural, dating to 600–300 BC and associated with the culture of nomadic animal breeders. The database includes published data on 37 burial mounds. Instead of digging graves, the nomads built above-ground wooden or adobe structures. Sometimes bodies were placed on wooden fl oors or platforms. Weapons found in burials include swords, daggers, arrowheads, and items of horse harness. In female burials, small stone altars, ornaments, mirrors, and utensils are found. Clay vessels are common. In the late 6th and 5th centuries BC, the tradition of placing bodies on the buried soil level was common in the eastern part of the southern Ural steppes. By ca 400 BC, it had virtually disappeared.

КОНВЕРГЕНЦИЯ РАСТИТЕЛЬНОГО ПОКРОВА И ПОЧВ ПОСТАГРОГЕННЫХ ЭКОСИСТЕМ МЕЖГОРНЫХ КОТЛОВИН ЦЕНТРАЛЬНОГО КАВКАЗА

The study showed that the conventional schemes of the exposition-dependent changes in plant communities and soils in the intermountain basins of North Ossetia do not meet their contemporary distribution. Communities of mountain meadow steppes and subalpine meadows are located regardless of the climatic differences between the slopes of intermountain basins. Soil studies revealed the similarity of properties of soils of different slopes and clear evidences of long agricultural impact. However, buried soils, found in many soil profiles indicate a pronounced expositional differentiation of soils in the past. According to the history of land use, the studied grasslands have experienced a number of stages as agrolandscapes: centuries of agricultural use, subsequent decades of grazing load and weakening or termination of anthropogenic impact in the last 15–20 years. The observed reduction in diversity of ecosystems and their convergence is explained by initial stages of their formation after centuries-long unifying agricultural impact. Made based on satellite and ground-based measurements the assessment of contemporary climate changes in the investigated altitude range showed an increasing temperature and moisture. Improvement of vegetation conditions along with a reduction in anthropogenic load may contribute to the restoration of wood and meadow vegetation, and the gradual progradation of soils.

Природні умови проживання людини на основі вивчення похованих ґрунтів кургану епохи бронзи

Природні умови проживання людини на основі вивчення похованих ґрунтів кургану епохи бронзи

Some aspects of a multidimensional analysis of the evolution of ecological-geochemical soil state

Soil saturation index and its calculating are demonstrating multicollinear correlations between ecological-geochemical soil state and environmental circumstances. There are wood ecosystems on the research area with Phaeozem, Luvisol, Retisol and Fluvisol. We have also studied the buried soil. Their burials occurred as a result of natural processes (about 5000 BP) and as a result of human impact (about 1000 BP). Age of separate genetic horizons (from 360±50 to 1870±160 ВР) indicates soils genesis during the last stage of the Holocene – Subatlantic. In our opinion the dynamics of the climate during last stage of the Holocene is the main cause of the complex structure of the soil cover on quite small area (5 km2). Second reason is difficult geomorphological environment (rough topography). On the basis of factor analysis proved efficiency of soil saturation index by trace elements: analytical work only with the indicated index reveals an unambiguous reduce the number of determining factors (up to two) and, thus, the proportion of the variance, which is determined by two factors is 100 %. While the using in the analysis of the total content, or a mobile forms of trace elements, or of some and the others together as a combined using of content mobile forms and their mobility will lead to an increase factor up to four and the simultaneous decrease in the proportion of the variance which is due to these factors to 74–88 %. We did not find decisive influence of any factor on saturation of studied soil types by trace elements. There is always a combination of processes that contribute to the accumulation of trace elements and processes of their migration. There are illuvial and lower transition to soil parent material horizons of the background content of trace elements for all investigated soil except Fluvisol (S-1). Belong to actual places of trace elements accumulation, which is generally quite small are some lower soil horizons both buried soils and lower transition to horizon of soil parent material (in soil R-3). Thus, the upper parts of the soils which were formed during the last centuries (780 years of age to today dated) are characterized by dissipation of most of trace elements. The genetic features of Fluvisol (S-1) have confirmed very high correlation. These features are the result of the genesis of this soil under the influence both soil and sedimentation processes. This is well illustrated in the analysis of the structure of the soil profile, which have characterized by stratification (during soil formation has not resulted in the development of any diagnostic subsurface horizon) genetic horizons and the presence of buried after the accumulation of alluvial material as a humus, as a transitional horizons. Perhaps, it is partly confirmed by the radiocarbon analysis, this soil should be regarded as younger age, which obviously explains persistent inflow of fresh materials. All other soils including the buried ones were formed under various elementary soil formation processes. These processes have replacing each other in time did not stop, and the normal evolution of the soil profile took place to bottom, in contrast to the fluvisol which evolution was to upper as have happened by the fresh alluvial and probably deluvial sedimentation. Recognizing of the «normal» soil genesis process as a basis for the formation of zonal soils in the Holocene, we are interpreting Factor 1, conducted by the context of factor analysis, as the environmental conditions for such soil formation. The results of factor analysis regarding to ecological-geochemical soil state Factor 1 should be considered as the basic parameters of soils (soil organic matter, pH, indicators of soil absorbing complex, mineralogical composition and particle size distribution). Under this condition Factor 2 is associated with the processes (fluvial, sedimentation, erosion) denudation, or transfer and accumulation of different material that would cause disturbance "normal" soil genesis. For that reason ecological-geochemical soil state is determined by soil formation factors for a specific time stage and dominant conditions for some processes.

About the results of engineering-geological investigation of loess soils massifs of the Northern Eurasia

The results of investigation of morphological, retrospective and prognoses engineering-geological tasks concerning loess soils massifs are formulated. It is shown that maximum values of relative subsidence reach 0,17-0,21, thickness of subsiding soil massif under natural load is about 55 m, maximum amount of loess soils cycles composed of subsiding soils reaches 10, more often the amount of buried soils of loess soils massif cross section doesn’t exceed 4-5 ones. The main result of solution of retrospective engineering-geological tasks is the proposal of hypothesizes and mechanisms of loess soils subsidence formation. They are the base for four special and general theory of subsidence formation. The result of solution of prognoses engineering-geological tasks is the elaboration of methods for calculation the expected subsidence of loess soils massifs under different mode of their wetting and the development of different methods (hydrogeomechanical, geochemical, geotechnical and complex) of improvement of loess soils massifs properties.

Structure and Holocene Rupture of the Morelia Fault, Trans‐Mexican Volcanic Belt, and Their Significance for Seismic‐Hazard Assessment

Abstract The Trans‐Mexican volcanic belt is an active volcanic arc being deformed by an intra‐arc extensional fault network. The Morelia fault, with a length of 14 km and a maximum throw of 260 m, is a major normal fault in the central part of this volcanic arc and forms part of a 36‐km‐long fault array. Slickenlines measured on the primary fault surface indicate north–south extensional dip slip with a minor left‐lateral component. In a well‐exposed cross section in the hanging wall of the Morelia fault, some few meters from the master fault trace, two buried soil layers, containing ceramic shards and stone tools, yielded radiocarbon ages of A.D. 420–660 (prehispanic classic period, Chupicuaro culture) and A.D. 1290–1435 (postclassic period), respectively. The underlying bedrock (Atecuaro ignimbrite) is cut in a staircase pattern by three synthetic secondary normal faults that delimit two colluvial wedges. Three slip events, with displacements ranging between 46 and 185 cm (average 109 cm), can be inferred from this section. The latest of these events must have occurred after A.D. 1290–1435, during the postclassic period or possibly during early novohispanic times. The Morelia fault, which is capable of generating M w 6–7 earthquakes, poses a major seismic ground‐shaking hazard and locally a surface fault‐rupture hazard within the metropolitan Morelia region with a population of more than 900,000 habitants. The foci of a sequence of seven small 2007 earthquakes on the Morelia fault were located below the center of town, at a depth of 11 km, and the fault trace crosses urban residential areas. Moreover, the town repeatedly experienced severe ground shaking during historical earthquakes. The best documented is the 19 June 1858 earthquake, which caused Morelia extensive damage corresponding to a macroseismic intensity of VIII–IX on the modified Mercalli scale. Online Material: Radiocarbon analysis reports, local 1894–1904 and 1909–1911 earthquake catalogs.

Water matters. Geoarchaeology of the city of Adria and palaeohydrographic variations (Po Delta, Northern Italy)

Adria is located in the northern Po delta at the edge of the Venice Lagoon, a sector of the Po Plain that was built by the late Holocene geomorphic activity of the Po, Adige and Tartaro rivers. Early settlements are dated to the Middle Bronze Age, and the city developed as a major urban centre during the Iron Age and Roman times. In the early Middle Ages, Adria survived as a local religious centre in the Venetian area, as evidenced by the existence of a 9th century AD church. The superimposition of archaeological deposits led to the upbuilding of an anthropogenic mound rising up to 5m above the surrounding plain. The aim of this investigation is to understand the evolution of the city of Adria from the 1st millennium BC to the Middle Ages, and its relationships with the rearrangement of the river network and connected palaeogeographic setting.The area was studied through the analysis of historical cartography, aerial photographs, a digital terrain model, archaeological data from the archives of the Soprintendenza Archeologia del Veneto, geological corings and a cone penetration test. New stratigraphic data have been acquired through the execution of 21 manual boreholes up to 5m in depth with an Edelman combination-type auger. Radiocarbon datings were carried out on selected peat samples.The analysis of the elevation above sea level of different stratigraphic data has exposed the stages of the evolution of the city, starting from the 6th century BC through Roman times and post-Antiquity, revealing the extension of the archaeological mound in the southern part of the modern city. The growth of the mound took place in four phases, dated to the 6th–5th centuries BC, 4th–3rd centuries BC, 1st century BC–1st century AD and post-Antiquity. The presence of a buried soil at the top of the Po deposits, coupled with radiocarbon dating of extensive peat layers, has allowed the reconstruction of the stratigraphy of the alluvial succession, and to correlate it with the archaeological record. The buried soil at the top of the Po deposits lies below the 6th century BC archaeological levels in the lowest part of the archaeological mound. On this same palaeosurface the first 9th century AD church was built. Two alluvial events buried this church under about 2m of overbank fines, turning it into an underground hall, known as the ‘crypt’ of the modern San Giovanni church. These alluvial events are attributed to the Tartaro River, with a probable contribution by the Adige River. The first alluvial event took place between the 9th and 11th centuries AD. In the 11th–15th centuries AD, a marshy area extended north, west and east of the city centre, as evidenced by an extensive peat layer that was buried by the second alluvial event later than the 15th century AD.

Erosão hídrica em solos cultivados e sob mata ciliar

Resumo O objetivo deste trabalho foi identificar atributos dos solos e de sedimentos como instrumentos para determinação dos impactos decorrentes da erosão hídrica, bem como propor redução do sobreúso dos solos no Cerrado goiano. Solos e sedimentos da mata ciliar do Córrego Ponte Nova, bem como do cultivo de soja a montante foram avaliados por micromorfometria quanto à morfologia, à granulometria e à porosidade. Na encosta cultivada, o solo foi classificado como Latossolo Vermelho distroférrico, e, na mata ciliar de vereda, como Plintossolo Pétrico Concrecionário êutrico e Gleissolo Melânico Tb distrófico típico. Solos e sedimentos foram predominantemente argilosos, e a fração argila encontrava-se naturalmente agregada em partículas maiores, de tamanho silte e areia. Análises morfológicas, granulométricas e de porosidade, por micromorfometria, possibilitaram distinguir os sedimentos dos solos soterrados, pela diferenciação de coloração, textura e porosidade. Elevada concentração de agregados de argila tamanho areia no Gleissolo Melânico sugere a remoção seletiva de partículas finas, o que indica erosão no solo sob a mata ciliar. A elevada deposição de sedimentos sobre os solos da mata ciliar compromete a função de filtro do solo e também a perpetuidade e a regeneração da floresta por causa do soterramento de sementes e plântulas.

Environmental and climate reconstructions of the Fore-Baikal area during MIS 5-1: Multiproxy record from terrestrial sediments of the Ust-Oda section (Siberia, Russia)

The Ust-Oda section exposes the structure of a 25-m terrace of the Kitoy River. The eroded surface of the Jurassic sandstones is overlain by the heterogeneous (primarily aeolian-alluvial) Upper Pleistocene-Holocene deposits that include buried soils. The Quaternary part of the section exhibits five main stratigraphic subdivisions, ranging from isotopic stage MIS 5 to MIS 1.Reconstructed vegetation composition, of the Unit 1 formation age, is typical for Late Quaternary interglacial periods and suggests moderately cool and moderately humid climate. Unit 2 sediments yielded small mammal remains of taiga, steppe, tundra and hydrophilic species, characterizing the fauna as ecologically mixed or disharmonic, typical of cold Pleistocene epochs in Eurasia. For example, Lagurus lagurus and Dicrostonyx sp. are animal species whose current habitats do not cross and are substantially distant from each other. Microtheriofauna species composition and structure imply Unit 2 formation under the conditions of cold and arid climate, together with 14C dating of the overlying strata suggesting its MIS 4 age. Unit 3 sediments contain spore-pollen spectra typical for MIS 3 interstadial of the Pribaikalye area. MIS 3 climate substantially differed from the modern one. Average January temperatures might have been 15°C lower than the modern ones and the mean July temperatures, 2–3°C lower. Mean annual precipitation value could be lower than the modern one by 100mm/yr. The analysis of the small mammal species ecological requirements suggests domination of tundra-steppe landscapes in the area during the formation of the Unit 3. Theriofauna of the Unit 5 allows reconstruction of paleoecological conditions close to modern ones in humidity and temperature.

Grasslands of intermontane basins of Central Caucasus: land use legacies and present-day state

Abstract Mountain semi-natural grasslands of intermontane basins of Central Caucasus, North Ossetia-Alania and the history of its land use were studied. It was found that post-forest, meadow-steppe and partially subalpine grasslands in the study area had been used as croplands for centuries and have been transformed into grazing lands about 60 years ago. In the last 20 years, the grasslands have been underused. It was revealed that current spatial distribution of grasslands is different from the classic scheme of natural climate-induced vegetation distribution. Species composition of meadow steppes is similar in different locations and does not reflect climatic differences of “dry” leeward and “wet” windward slopes of the intermontane basins. Present-day soils reflect parent material differences and erosion degree, but not topography-induced local climate specificity. However, discovered buried soils showed contrasting soil diversity on the southern and northern slopes. It is assumed that the present convergence of soil cover and vegetation is a result of long homogenising human impact and relatively short grassland development.

The natural-climatic events on the coast of Middle Baikal in the Early Holocene

Presented are the results from pedolithological investigations and reconstructions of the naturalclimatic events in the Early Holocene (radiocarbon age 10.3−8 ka; calendar age 11.7−8.8 ka) on the coast of Middle Baikal, based on data obtained by studying the structure, composition and properties of subaerial deposits and soils in terrestrial sections. A study was made of the numerous soil profiles and sections of geoarchaeological sites. The investigation revealed common features in the layered structure of the Early-Holocene portion of the terrestrial sections and evidence of climate warming represented by buried soils, signals of a cooling in the form of cryogenic fissures, and signals of drying in the form of aeolian drifts and evidence of deflation. It is shown that the Early Holocene was the time of cardinal changes in the nature of subaerial sedimentation (calcareous deposits were replaced by noncalcareous deposits) and the pedogenesis. Considerable cold storage from inherited permafrost and humidification of soils and earth materials with moisture from the thawing of permafrost were responsible for the specific character of soil formation, and for the spread of forest vegetation under a rather low atmospheric humidity. The phases of climate warming were accompanied by an intensification of soil formation with the production of soils of two types: early boreal, and boreal. Deluvial, colluvial and sometimes (in Priol’khonie) aeolian deposits accumulated during the cooling phases (Late Preboreal and Late Boreal). Small cryogenic fissures were generated. The issues of man’s adaptation to the cardinally changed natural conditions at the turn of the Pleistocene and Holocene and over the course of the Early Holocene are associated with the problem of Baikal’s water level and human settlement on its shores. The Lake Baikal stage at the end of the Late Neopleistocene was lower than at present; during the Early Holocene it was rising to reach at the late-boreal period the present-day level (or even exceeded it). The rises of Baikal’s stage at the Mid- and Late-Holocene period were causing scouring and destruction of the Early-Holocene sites that were located at lower elevations.

Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

Abstract A late Pleistocene to Holocene alluvial stratigraphy has been established for the basins of La Paz and San Jose del Cabo, in the southern tip of the Baja California peninsula, Mexico. Six discrete alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development. These criteria were supported using radiocarbon, optically stimulated luminescence and cosmogenic depth-profile geochronology. Major aggradation started shortly after ∼70 ka (Qt2), and buildup of the main depositional units ended at ∼10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units consist of multiple 1–3 m thick alluvial packages deposited as upper-flow stage beds that represent individual storms. Main aggradational units (Qt2-Qt4) occurred across broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are confined to channels of ∼0.5–2 km width. Continuous deposition inside the thicker (>10 m) pre-Qt5 units is demonstrated by closely spaced dates in vertical profiles. In a few places, disconformities between these major units are nevertheless evident and indicated by partly eroded buried soils. The described units feature sedimentological traits similar to historical deposits formed by large tropical cyclone events, but also include characteristics of upper-regime flow sedimentation not shown by historical sediments, like long (>10 m) wavelength antidunes and transverse ribs. We interpret the whole sequence as indicating discrete periods during the late Pleistocene and Holocene when climatic conditions allowed larger and more frequent tropical cyclone events than those observed historically. These discrete periods are associated with times when insolation at the tropics was higher than the present-day conditions, determined by precessional cycles, and modulated by the presence of El Nino-like conditions along the tropical and northeastern Pacific. The southern Baja California alluvial record is the first to document a precession-driven alluvial chronology for the region, and it constitutes a strong benchmark for discrimination of direct tropical influence on any other alluvial record in southwestern North America.

Soil Paleocatenas, Prehistoric Land Use, and Coastal Landscape Dynamics at Druridge Bay, Northeast England

Coastal erosion of sand dune systems along Druridge Bay, northeast England, has progressively exposed parts of the subdune mid‐Holocene landscape, including paleocatenas, indicating former soil hydrosequences with localized wetland habitats, and archaeological evidence of human activities and land use from the Late Mesolithic to the Romano‐British period. Archaeological investigations and pedostratigraphic studies of paleosols provide a unique spatial–chronological framework to interpret soil and land use change over several millennia in the context of a changing coastal environment. Evidence includes dating of archaeological remains, the stratigraphy, morphology and micromorphology of buried soils and sediments, and the palynology and radiocarbon dating of subdune peats. Early Bronze Age burial sites were preferentially located on well‐drained hillocks also used for grazing. Adjacent wetland depressions provided areas of marshy grassland and swamp over deep fen peat soils that started to develop c. 5435 cal. yr B.P. in response to a rising groundwater table stimulated partly by slow sea‐level rise. The backslopes of the paleocatena were occupied by imperfectly to poorly drained soils that supported open oak‐hazel woodland with evidence for progressive clearance and use for agriculture. Windblown sand started to accumulate on the study site sometime between 3930 and 3670 cal. yr B.P., well before the Little Ice Age date for dune formation suggested by previous researchers.

Enhanced summer warming reduces fungal decomposer diversity and litter mass loss more strongly in dry than in wet tundra.

Many Arctic regions are currently experiencing substantial summer and winter climate changes. Litter decomposition is a fundamental component of ecosystem carbon and nutrient cycles, with fungi being among the primary decomposers. To assess the impacts of seasonal climatic changes on litter fungal communities and their functioning, Betula glandulosa leaf litter was surface-incubated in two adjacent low Arctic sites with contrasting soil moisture regimes: dry shrub heath and wet sedge tundra at Disko Island, Greenland. At both sites, we investigated the impacts of factorial combinations of enhanced summer warming (using open-top chambers; OTCs) and deepened snow (using snow fences) on surface litter mass loss, chemistry and fungal decomposer communities after approximately 1year. Enhanced summer warming significantly restricted litter mass loss by 32% in the dry and 17% in the wet site. Litter moisture content was significantly reduced by summer warming in the dry, but not in the wet site. Likewise, fungal total abundance and diversity were reduced by OTC warming at the dry site, while comparatively modest warming effects were observed in the wet site. These results suggest that increased evapotranspiration in the OTC plots lowered litter moisture content to the point where fungal decomposition activities became inhibited. In contrast, snow addition enhanced fungal abundance in both sites but did not significantly affect litter mass loss rates. Across sites, control plots only shared 15% of their fungal phylotypes, suggesting strong local controls on fungal decomposer community composition. Nevertheless, fungal community functioning (litter decomposition) was negatively affected by warming in both sites. We conclude that although buried soil organic matter decomposition is widely expected toincrease with future summer warming, surface litter decay and nutrient turnover rates in both xeric and relatively moist tundra are likely to be significantly restricted by the evaporative drying associated with warmer air temperatures.

Long-stored soil carbon released by prehistoric land use: Evidence from compound-specific radiocarbon analysis on Soppensee lake sediments

Compound-specific radiocarbon (14C) analyses allow studying the fate of individual biomarkers in ecosystems. In lakes with small catchments, terrestrial biomarkers have the potential to be used for the dating of sediments that lack the traditionally targeted terrestrial macrofossils, if the specific organic compounds are deposited soon after production. On the other hand, if the biomarkers have been stored for a significant amount of time in the soils of the catchment before transported to the lake, their age can be used to reconstruct changes in average residence time of organic material on land through time. Here we present a study based on compound-specific 14C analysis of the sedimentary record of Lake Soppensee, Switzerland, targeting long-chain n-alkanes of exclusive terrigenous origin, and comparing them with sediment ages obtained by high-resolution macrofossil dating. Additionally, we measured 14C ages of bulk organic matter and carbonate samples to assess the hard water effect. Prior to 3100 cal BP n-alkanes had about the same age as the sediment or they were slightly older, indicating that the vast majority of the terrestrial organic carbon transported to the lake had a short residence time on land. In the samples younger than 3100 cal BP an increasing offset is observed, indicating liberation of old buried soil organic matter that must have accumulated over the previous millennia. Our results indicate that as long as stable ecosystem conditions have prevailed, the distribution and isotopic composition of the n-alkanes can be used as environmental proxies in small catchments with limited surface runoff, confirming a few earlier studies.

Stratigraphy, morphology, and geochemistry of late Quaternary buried soils on the High Plains of southwestern Kansas, USA

This study investigated two stratigraphic sequences that record the complex interplay of sedimentation and pedogenesis over the past ca. 84ka on the High Plains of southwestern Kansas. Up to eight eolian sand and loess units with associated soils were identified in two cores collected from an upland setting. Soil morphological and geochemical data were used to quantitatively assess and compare soil development between multiple buried soils. Chronostratigraphic relationships indicate that 1) loess and eolian sands were episodically deposited during late Marine Isotope Stage (MIS) 5 (ca. 84–70ka), 2) the Sangamon soil at this site formed between MIS 3/4 (ca. 70–52ka), which is consistent with age estimates for renewed Sangamon pedogenesis in the Mississippi River valley, and 3) soil development in the Gilman Canyon Formation began at ca. 44ka and continued until at least 29.2ka. Multiple lines of evidence, including grain-size distributions, structure, clay content, and chemical weathering index data, indicate that the morphology and chemistry of the Ak horizon developed in the Gilman Canyon Formation is a product of cumulization by slow loess additions. Similar evidence suggests that cumulization processes are also responsible for the morphology and chemistry of other buried soils in the stratigraphic sequence. Overall, loess inputs during pedogenesis complicate the quantification of weathering processes in these soils.