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The boundaries around habitat islands in agricultural fields are rather unexamined, although they may be an important part of agroecosystems in some regions. In this study, we surveyed field boundaries in northeastern Brandenburg both at outer field borders and around kettle holes, which are typical habitat islands in the region. We examined, described, and compared the plant species diversity and composition at both the inner and outer field boundaries in the arable fields (crop edge) as well as in permanent vegetation (field margins). Diversity was assessed and compared with Hill diversity values, using the iNext framework. Non‐metric multidimensional scaling and permutational analysis of variance were used to compare species composition at different field boundaries and to search for variables that drive species composition at the local scale. The results revealed that both species diversity and composition differed significantly between the inner and outer boundary along the crop edges and at the field margins. Local site conditions, namely a moisture gradient, influenced the species composition of the field margins, resulting in differences between the inner and outer field margins. Mitigated through crop growth and cover, the moisture gradient influenced also the species composition of the inner and outer crop edges, despite the management practices on the fields were the same. [ABSTRACT FROM AUTHOR]

Abstract Introduction The proximity of semi‐natural habitats and agricultural fields in an agricultural landscape leads to unavoidable biological, chemical, and physical interactions. Fungi can negatively influence, but also support crop growth in agricultural fields. Therefore, in this field study we investigated the colonisation of arbuscular mycorrhizal (AM) fungi and non‐AM fungi in winter‐wheat roots as well as winter‐wheat performance in distance to semi‐natural habitats. Materials and Methods We sampled in an intensively managed agricultural landscape in North‐east Germany along agricultural transition zones, that is, along 50 m‐transects from semi‐natural habitats like hedgerows and glacially created in‐field ponds—so‐called kettle holes—into agricultural fields. Results To our knowledge, we show for the first time that AM fungal colonisation in winter‐wheat roots decreased linearly with increasing distance to semi‐natural habitats while non‐AM fungal root colonisation did not change. Winter‐wheat grain yield and biomass slightly increased with increasing distance to hedgerows but not to kettle holes. This clearly shows that there is a difference between different crop performance parameters. Random forest machine learning algorithms confirmed the particular importance of distance to semi‐natural habitats for AM fungal root colonisation and for winter‐wheat grain yield. Less intensive agricultural management close to semi‐natural habitats, for example, no herbicide and pesticide applications as a result of nature protection regulations, may partly explain this pattern. However, spatial response patterns of AM but not of non‐AM fungi in wheat roots also point to changed ecological interactions close to semi‐natural habitats. Conclusion Semi‐natural and natural habitats in agricultural landscapes are slowly recognised not only to be important for biodiversity conservation, but also for sustainable crop production. Additionally, they may also be a tool for farmers and policy makers to improve sustainable landscape management. And agricultural transition zones are spatially and temporally complex dynamic ecosystems that should be the focus of further investigations.

Agriculture is a leading cause of biodiversity loss and significantly impacts freshwater biodiversity through many stressors acting locally and on the landscape scale. The individual effects of these numerous stressors are often difficult to disentangle and quantify, as they might have nonlinear impacts on biodiversity. Within agroecosystems, ponds are biodiversity hotspots providing habitat for many freshwater species and resting or feeding places for terrestrial organisms. Ponds are strongly influenced by their terrestrial surroundings, and understanding the determinants of biodiversity in agricultural landscapes remains difficult but crucial for improving conservation policies and actions. We aimed to identify the main effects of environmental and spatial variables on α‐, β‐, and γ‐diversities of macroinvertebrate communities inhabiting ponds (n = 42) in an agricultural landscape in the Northeast Germany, and to quantify the respective roles of taxonomic turnover and nestedness in the pondscape. We disentangled the nonlinear effects of a wide range of environmental and spatial variables on macroinvertebrate α‐ and β‐biodiversity. Our results show that α‐diversity is impaired by eutrophication (phosphate and nitrogen) and that overshaded ponds support impoverished macroinvertebrate biota. The share of arable land in the ponds' surroundings decreases β‐diversity (i.e., dissimilarity in community), while β‐diversity is higher in shallower ponds. Moreover, we found that β‐diversity is mainly driven by taxonomic turnover and that ponds embedded in arable fields support local and regional diversity. Our findings highlight the importance of such ponds for supporting biodiversity, identify the main stressors related to human activities (eutrophication), and emphasize the need for a large number of ponds in the landscape to conserve biodiversity. Small freshwater systems in agricultural landscapes challenge us to compromise between human demands and nature conservation worldwide. Identifying and quantifying the effects of environmental variables on biodiversity inhabiting those ecosystems can help address threats impacting freshwater life with more effective management of pondscapes. [ABSTRACT FROM AUTHOR]

Weeds in agricultural landscapes can serve as alternate hosts for phytopathogenic fungi and promote the spatial and long-term distribution of these fungi. Especially, semi-natural habitats such as kettle holes are considered as a source of fungal pathogens because they are a permanent habitat for various weed species in arable lands. In our study, we investigated the suitability of nine different weed species and families at the edges of 18 kettle holes in two consecutive autumn/winter seasons as alternate hosts for Fusarium and Alternaria. We detected a fungal infestation with both genera on every weed species investigated with significantly higher abundances of these fungi in the second, notably wetter season. Eight weed species were described as non-host plants for Fusarium and Alternaria in agricultural landscapes in Brandenburg, Germany for the first time. In both autumn/winter periods, weeds harbored more Alternaria than Fusarium. The study revealed a high Fusarium species diversity in weeds and a community structure of up to 12 Fusarium species at the edges of kettle holes. Grasses showed the highest diversity and often the highest fungal abundances compared to herbaceous plants. Therefore, these habitats in arable lands can act as ecosystem disservice and promote the spread of fungal diseases in the surrounding crop fields. [ABSTRACT FROM AUTHOR]

The intensification of agriculture over the last few decades has caused habitat loss, which poses a significant threat to the survival of populations and species. Where habitats are connected, populations may escape the destruction of their habitat by migrating to another one. Consequently, the functional connectivity of landscapes has become an important focus for species conservation. Kettle holes are hotspots of biodiversity that provide suitable conditions for wildlife species (i.e., amphibians, insects, aquatic plants) and contribute to landscape heterogeneity. They are also considered to function as stepping stone habitats that contribute to habitat connectivity. This study assesses the contribution of kettle holes for (i) habitat provision and (ii) the functional connectivity of three amphibian species with different movement ranges, and (iii) the study identifies areas where the creation of stepping stone biotopes could improve functional connectivity. The contribution of kettle holes was assessed using GIS-based clustering within three research areas in Germany. It was found that the importance of kettle holes for providing amphibian habitats in the three studied areas was equal to or higher than that of other wetland habitats. The state of functional connectivity and the contribution of kettle holes differed strongly depending on the species’ range. For the short-range species, landscapes were highly fragmented, and the contribution of kettle holes was much smaller than that of corridor habitats. For the long-range species, all habitats suited for amphibian reproduction were connected, and the contribution of kettle holes was similar to that of corridor habitats. However, the contribution of both was mostly redundant. Overall, the results showed that kettle holes play a crucial role in habitat provision and function as important stepping stone biotopes in agricultural landscapes. The clustering method applied in this study provides a simple tool for landscape planning and environmental protection agencies, which can be easily adapted to analyze functional connectivity and habitat interactions for different species or landscapes. [ABSTRACT FROM AUTHOR]

In plants, long-distance dispersal is both attenuated and directed by specific movement vectors, including animals, wind, and/or water. Hence, movement vectors partly shape metapopulation genetic patterns that are, however, also influenced by other life-history traits such as clonal growth. We studied the relationship between area, isolation, plant-species richness, reproduction, and dispersal mechanisms with genetic diversity and divergence in 4 widespread wetland plant-species in a total of 20 island-like kettle-hole habitats surrounded by an intensive agricultural landscape. Our results showed that genetic parameters reflect the reproduction strategies with the highest genetic diversity being observed in the non-clonal, outcrossing Oenanthe aquatica compared to the clonal Lycopus europaeus , Typha latifolia, and Phragmites australis. Lycopus showed a positive relationship between genetic diversity and kettle-hole area, but a negative relationship with the number of neighboring kettle holes (less isolation). Genetic diversity increased with plant-species richness in the clonal species Phragmites and Lycopus ; while it decreased in the non-clonal Oenanthe. Finally, genetic divergence and, therefore, connectivity differed between alternative dispersal strategies, where wind-dispersed Typha and Phragmites had a higher gene flow between the analyzed kettle holes compared with the insect-pollinated, hydrochorous Lycopus and Oenanthe. Our study provides information on genetic patterns related to reproduction and dispersal mechanisms of 4 common wetland species contributing to the understanding of the functioning of plant metacommunities occurring in kettle holes embedded in agricultural landscapes. [ABSTRACT FROM AUTHOR]

Kettle holes are common ice decay features in formerly glacial landscapes like those in Southern Scandinavia and Northern Germany. Here the kettle holes are represented either as dry depressions, wetland areas or lakes. However, the majority of these features are silted and part of the present farmland. We investigated a small kettle hole at Tyrsted, near the township of Tyrsted, south of Horsens (Denmark) with the aim to determine the extension and depth of this feature using geophysical methods. A former excavation at Tyrsted carried out from the Horsens Museum in 2017 at a neighboring site revealed Late Palaeolithic flint of the Bromme type and worked reindeer antlers. This connection in a Late Glacial horizon is unique not only in a Danish context and it can help to improve and clarify the dating of the Bromme culture. We used ground penetrating radar (GPR), electromagnetic induction (EMI) and electrical resistivity tomography (ERT) to estimate the extension of the kettle hole (~16 m × 25 m). Shear wave reflection and refraction seismics (SH Seismics) were able to detect the bottom sediment of the former lake at about ~5 m depth. Furthermore, a seismic event at about 1.30 m depth is visible which can be associated to the transition between the Allerød and Younger Dryas sediment making the detection of the Bromme horizon possible. After the non-invasive investigation, a location for an open excavation has been chosen in a way to groundtruth the geophysical results allowing the direct comparison with the stratigraphy. These results allow the archaeologists to identify key excavation areas focused on the investigation of the Allerød and Younger Dryas layers in a way to improve the dating information about the Bromme horizon collected so far. Furthermore, geophysical investigations together with excavations will enable the archaeological and palaeoenvironmental research groups to search large scale palaeolandscapes for these very rare, but highly important finds. • SH-wave seismics enables exploring the kettle hole down to its full depth. • The detection of the Bromme horizon is possible with geophysical methods. • Ground truthing the results with corings allows the reconstruction of the stratigraphy to plan test excavation. [ABSTRACT FROM AUTHOR]

The effects of habitat fragmentation and isolation on plant species richness have been verified for a wide range of anthropogenically fragmented habitats, but there is currently little information about their effects in naturally small and isolated habitats. We tested whether habitat area, heterogeneity, and isolation affect the richness of wetland vascular plant species in kettle holes, i.e., small glacially created wetlands, in an agricultural landscape of 1 km2 in NE Germany. We compared fragmentation effects with those of forest fragments in the same landscape window. Since wetland and forest species might differ in their tolerance to isolation, and because isolation effects on plant species may be trait dependent, we asked which key life history traits might foster differences in isolation tolerance between wetland and forest plants. We recorded the flora and vegetation types in 83 isolated sites that contained 81 kettle holes and 25 forest fragments. Overall, the number of wetland species increased with increasing area and heterogeneity, i.e., the number of vegetation types, while area was not a surrogate for heterogeneity in these naturally fragmented systems. Isolation did not influence the number of wetland species but decreased the number of forest species. We also found that seeds of wetland species were on average lighter, more persistent and better adapted to epizoochory, e.g., by waterfowl, than seeds of forest species. Therefore, we suggest that wetland species are more tolerant to isolation than forest species due to their higher dispersal potential in space and time, which may counterbalance the negative effects of isolation. [ABSTRACT FROM AUTHOR]

Abstract Kettle holes are a circular-shape product of ice decay, and thus are strongly linked with young glacial landscapes. Once glaciation terminates, these holes transform either into wetland and lakes or occasionally into kettle-hole mires. Since an entire sediment sequence preserve in the kettle-holes, these provide an excellent settings to exploit any sensitive paleoenvironmental changes. Here, the kettle-hole mire located onto the Brda River outwash plain (Tuchola Forest) is explored towards a better understanding of local and global environmental trends in the Late Glacial – present day time frame. To fulfill this, multi-proxy study as geochemical, palynological and macrofossils analyses along with the radiocarbon dating are used. Therefore, this study allows to distinguish five phases of steep environmental gradients in the investigated mire, as follows: (1) paludification after glaciation, when dead-ice melted and long-term permafrost was degraded, (2) lake started to disappear in the Late Glacial, followed by a rich vegetation in the first part of the Holocene, (3) vegetation encroachment onto the lake in the first part of the Holocene, which consequently turned into an peat bog, (4) the late Holocene peat bog with a limited human influence, and finally (5) the peat bog with a major human impact along with acidification as related to sandy underlying sediments, leaching of calcium carbonate, recharge from precipitation and pine monoculture. As additionally apparent from this small ecosystem, both local (character of substrate sediments, morphology of the area, rate of permafrost melting, climate conditions and human activity) and regional (climate changes and human activity) are detectable. Nevertheless, the record of these changes is sometimes unclear. Highlights • Multi-proxy study of biogenic kettle-hole sediment in North Central Poland. • Kettle-hole developed in five phases in the Late Glacial – the Holocene time frame. • Record of vegetational and chemical changes in the kettle-hole sediments • Intensive erosion along with acidification took place. • A greater human impact at the end of the Atlantic [ABSTRACT FROM AUTHOR]

Kettle holes, small shallow ponds of glacial origin, represent hotspots for biodiversity and biogeochemical cycling. They abound in the young moraine landscape of Northeast Germany, potentially modulating element fluxes in a region where intensive agriculture prevails. The Rittgarten kettle hole, with semi-permanent hydroperiod and a surrounding reed belt, can be considered as a representative case study for such systems. Aiming to provide insights into the biogeochemical processes driving nutrient and primary producer dynamics in the Rittgarten kettle hole, we developed a mechanistic model that simulates the carbon, nitrogen, phosphorus and oxygen, phytoplankton, and free-floating macrophyte biomass dynamics. After model calibration and sensitivity analysis, our modeling exercise quantified the simulated nutrient fluxes associated with all the major biogeochemical processes considered by the model. Seasonality of nutrient concentrations, magnitude of primary productivity rates, and biogeochemical process characterization in the pond were reasonably reproduced by the model from July 2013 to July 2014. Our results suggest that the establishment of a phytoplankton community well-adapted to low light availability, together with the differential use of N and P from free-floating macrophytes and phytoplankton can explain their coexistence in kettle holes. Sediment nutrient release along with decomposition of decaying submerged macrophyte are essential drivers of internal nutrient cycling in kettle holes. Our results also suggest that the Rittgarten kettle hole act as a net source of CO 2 to the atmosphere on an annual scale, which offers a testable hypothesis for kettle holes with structural and functional similarities. We conclude by discussing the need to shed light on the effects of water level fluctuations on nutrient dynamics and biological succession patterns, as well as the relative importance of external sources and internal nutrient recycling mechanisms. [ABSTRACT FROM AUTHOR]

Kettle hole lakes are a characteristic element of the post-glacial landscape. The paper analyzes the influence of morphometry of kettle holes and the characteristics of their catchments on the accumulation of total nitrogen, total phosphorus, Mg, K, Ni, Fe, Cu, Zn, and Mn. Significantly higher concentrations of nutrients were found in sediment of the lakes located on arable lands than grasslands. Heavy metals contents in the sediments generally did not diverge from natural background. The exception was Cu, for which the geoaccumulation index indicated significant contamination (class IV and V) of the sediments with this metal. All the studied metals created the following decreasing order: Fe > K > Mg > Cu > Mn > Zn > Ni. Results of PCA showed that the enrichment of sediments in metals was strongly influenced by the depth of water body and the lake catchment area. From two groups of kettle lakes distinguished by hierarchical cluster analysis, the group with significantly higher (p < 0.05) levels of K, Mg, Mn, and Fe in the sediments consisted of the deepest reservoirs with biggest capacities and larger catchment areas. Our results showed that the kettles lakes can be considered as reference sites for the need of existing or planned monitoring systems. [ABSTRACT FROM AUTHOR]

Abstract: Kettle holes are glacially created ponds that form within landscape depressions and are numerous across young moraine landscapes. Kettle hole water budgets are based primarily on winter precipitation, and therefore, undergo pronounced short‐term changes in water level fluctuations. Little is known about kettle hole sediment biogeochemistry in NE Germany, especially with regards to hydroperiod. Our objective for this study was to link the abiotic influences demarked by the evaporative isotopic signal from kettle hole water and solute chemistry to sediment organic matter turnover imprinted in the sediment δ13C and δ15N isotopic values. From the 20 kettle holes we sampled, 19 of these completely dried out, but on different dates. This dynamic was partially explained by longitudinal and elevational changes over the catchment area illustrating regional controls of kettle hole water balance. At the scale of an individual kettle hole, we estimated evaporation explained up to 38% of water volume loss. The changes in water levels were weakly related to differences in surface sediment elemental N and C concentrations between kettle hole edge and centre positions. These dynamics were primarily driven by redox conditions, Ca2+, and several nutrient concentrations (dissolved organic carbon, total dissolved nitrogen, total dissolved P, and ammonium) in the water column. Although we did not detect differences in the surface sediment δ13C and δ15N values, the δ15N signature in relation to the C:N ratio highlights the advanced decomposition state of surface sediment OM in temporarily water filled kettle holes. [ABSTRACT FROM AUTHOR]

Kettle holes are small inland waters formed from glacially-created depressions often situated in agricultural landscapes. Due to their high perimeter-to-area ratio facilitating a high aquatic-terrestrial coupling, kettle holes can accumulate high concentrations of organic carbon and nutrients, fueling microbial activities and turnover rates. Thus, they represent hotspots of carbon turnover in the landscape, but their bacterial activities and controlling factors have not been well investigated. Therefore, we aimed to assess the relative importance of various environmental factors on bacterial and biogeochemical processes in the water column of kettle holes and to disentangle their variations. In the water body of ten kettle holes in north-eastern Germany, we measured several physico-chemical and biological parameters such as carbon quantity and quality, as well as bacterial protein production (BP) and community respiration (CR) in spring, early summer and autumn 2014. Particulate organic matter served as an indicator of autochthonous production and represented an important parameter to explain variations in BP and CR. This notion is supported by qualitative absorbance indices of dissolved molecules in water samples and C:N ratios of the sediments, which demonstrate high fractions of autochthonous organic matter (OM) in the studied kettle holes. In contrast, dissolved chemical parameters were less important for bacterial activities although they revealed strong differences throughout the growing season. Pelagic bacterial activities and dynamics might thus be regulated by autochthonous OM in kettle holes implying a control of important biogeochemical processes by internal primary production rather than facilitated exchange with the terrestrial surrounding due to a high perimeter-to-area ratio. [ABSTRACT FROM AUTHOR]

Unlike in deep stratified lakes, the assessment of eutrophication in shallow aquatic systems (i.e., wetlands, marshes, ponds) should be based on the interaction between water and sediment. The availability of P to primary producers is naturally higher in shallow systems, because the sediment plays an active part via adsorption, precipitation and release processes. Thus, many wetlands in protected areas are naturally eutrophic and have a high trophic status due to intrinsic features and thus, display a high concentration of total-P in the water without necessarily implying pollution or poor quality. We have provided a diagnostic tool based on the chemical equilibrium of dissolved reactive P (operationally-defined as o-P) between water and sediment that distinguish anthropogenic eutrophication from a background of natural eutrophy. When the P-binding capacity of the sediment becomes saturated, the o-P concentration increases in the water as long as both the biological uptake and the sediment adsorption are unable to cope with the rate of P-release from the sediment under a long-term P load (or severe anthropogenic eutrophication). In such conditions, we have found that the ratio of total-P/particulate-P exceeds 2.0 in the water, and have used this threshold to validate this tool in other sets of wetlands. [ABSTRACT FROM AUTHOR]

Kettle holes are small depressional wetlands and because of the high variability of site factors they are potential hotspots of biodiversity in the monotone arable land. We investigated eight kettle holes and two agrarian reference biotopes for carabid beetles and spiders. The animals were captured with pitfall traps from May to August 2005, along with surveys of the soil and vegetation. We asked whether each kettle hole has specific ecological properties which match with characteristic carabid beetle and spider coenoses and whether they represent isolated biotopes. Differences in the composition of ecological and functional groups of carabid beetles and spiders between the plots were tested with an ANOVA. The impact of the soil variables and vegetation structure on the distribution of species was analyzed with a Redundancy Analysis. The assemblage similarities between the kettle hole plots were calculated by the Wainstein-Index. Ecological groups and habitat preferences of carabid beetles had maximal expressions in seven different kettle holes whereas most of the ecological characteristics of the spiders had maximal expression in only two kettle holes. High assemblage similarity values of carabid beetle coenoses were observed only in a few cases whereas very similar spider coenoses were found between nearly all of the kettle holes. For carabid beetles, kettle holes represent much more isolated habitats than that for spiders. We concluded that kettle holes have specific ecological qualities which match with different ecological properties of carabid beetles and spiders and that isolation effects affect carabid beetles more than spiders. [ABSTRACT FROM AUTHOR]

Kettle holes as a specific group of isolated, small lentic freshwater systems (LFS) often are (i) hot spots of biogeochemical cycling and (ii) exposed to frequent sediment desiccation and rewetting. Their ecological functioning is greatly determined by immanent carbon and nutrient transformations. The objective of this review is to elucidate effects of a changing hydrological regime (i.e., dry-wet cycles) on carbon and nutrient cycling in kettle hole sediments. Generally, dry-wet cycles have the potential to increase C and N losses as well as P availability. However, their duration and frequency are important controlling factors regarding direction and intensity of biogeochemical and microbiological responses. To evaluate drought impacts on sediment carbon and nutrient cycling in detail requires the context of the LFS hydrological history. For example, frequent drought events induce physiological adaptation of exposed microbial communities and thus flatten metabolic responses, whereas rare events provoke unbalanced, strong microbial responses. Different potential of microbial resilience to drought stress can irretrievably change microbial communities and functional guilds, gearing cascades of functional responses. Hence, dry-wet events can shift the biogeochemical cycling of organic matter and nutrients to a new equilibrium, thus affecting the dynamic balance between carbon burial and mineralization in kettle holes. [ABSTRACT FROM AUTHOR]

Given that water-filled kettle holes are mostly undergo a wet-dry cycle, and are directly fuelled by terrigenous material, it was hypothesized that the downward flux of matter, including P and its binding partners, varies between and within kettle holes, and is closely coupled to the prevalent water regime. Sedimentation was studied in two kettle holes close to Rittgarten (RG) and Kraatz (KR), Uckermark, NE Germany. Pairs of cylindrical traps at three sites in each kettle hole were sampled biweekly (June 2013-July 2014). Mean fluxes decreased with decreasing water level. KR was Fe-dominated binding P, and had submersed macrophytes. RG was Ca dominated and had low Fe concentrations suggesting that both apatite and oxidized Fe compounds equilibrated P release, with finally a surplus in P. Thus, RG was covered by duck weed. The higher C flux fuelled the sulphate reduction at higher rates than in KR, as also favoured by oxygen deficits due to duck weed coverage. Thus, internal eutrophication, i.e. where sulphate reduction and Fe sulphide formation lead to a lower Fe availability for P binding, is an issue for kettle holes increasingly degrading their ecosystem services. [ABSTRACT FROM AUTHOR]

Pollen, plant macroscopic fossil and carbonate analyses supplemented with 14C dating were applied for sediment sections of Lopaičiai Kettle and Pakastuva Lake. The new data obtained from two sediment cores were used to reconstruct vegetation cover and environmental changes during Lateglacial and Holocene in the Samogitian Upland (NW Lithuania). Different burial conditions of dead-ice blocks caused different times of lake sediment start in studied sites. The depositional and vegetation history is traced at the inception of pre-Allerød time in sediment section from the Lopaičiai core. However, sediment section from the Pakastuva core provides paleoenvironmental information starting only from the very beginning of Holocene. The study results shed more light on the environmental development during the Lateglacial and Holocene of the specific ice marginal area, which belongs to interlobate insular upland. [ABSTRACT FROM AUTHOR]

Thirty kettle hole ponds located in agricultural landscape of western Poland were studied with respect to physico-chemical (temperature and pH) and chemical (SC, dissolved oxygen, concentration of nutrients) variables of surface water quality during two subsequent years. Most of the ponds selected for the study host populations of endangered large branchiopod crustaceans, thus the aim of the study was to find out the rules governing these ecosystems and infer the best ways to protect them. Precipitation during the first year of the study was close to the average for the region, whereas severe drought was recorded during the second year. The influence of water regime, morphological parameters, catchment characteristics and vegetation on the parameters of water (pH, conductivity, contents of O 2 , N-NH 4 , N-NO 2 , N-NO 3 , SRP and TP) separately for both years was tested using redundancy analyses (RDA). The results showed that the factors significantly explaining the variance in water chemistry differed between years of the study. In the year of average precipitation, the most important factors were related to the morphology of the pond and its catchment. In contrast, under drought conditions the factors connected with pond vegetation and water depth were significant. However, in general, hydroperiod length of the pond was the most important factor, significant in all the models created. [ABSTRACT FROM AUTHOR]

Excavations were made in the colluvial deposits of seven kettleholes in a sandy esker at Kuttanen, northwestern Finnish Lapland. The Holocene history of forest fires and the associated colluvial activity initiated on the slopes of the kettleholes were reconstructed based on 131 radiocarbon dates from charcoal layers. These dates were supplemented by luminescence dating of colluvial sand layers. The first forest fires occurred ~9000 years ago following the immigration of Pinus sylvestris about 1000 years after deglaciation. Evidence of forest fires and colluvial activity increased with the density of the pine forest, reaching a maximum during the Holocene Thermal Maximum between ~8000 and 4000 cal. a BP, declining thereafter to a minimum in the last ~500 years. This multimillennial-scale pattern corresponds with forest fires being triggered by lightning strikes during the warmest summer weather of the Holocene, which also produced heavy rain and slope wash from convective storms. The 50 forest fires identified over the Holocene indicate a long cycle in fire frequency of 1 in ~200 years, which appears to reflect the average successional recovery time of the forest. Complex interactions amongst vegetation, fire and climate may account for little or no association between 23 centennial- to millennial-scale clusters of forest fires/colluvial events and Holocene temperature or precipitation anomalies. Buried podzols indicate five phases of soil formation and hence low levels of landscape disturbance. The kettleholes and their colluvial deposits therefore provide a unique geo-ecological archive that has led to new insights into the geo-ecological interactions that affect environmental change in the sub-arctic landscape. [ABSTRACT FROM AUTHOR]

Plant invasions are predicted to accelerate in a world with increased anthropogenic disturbance. Non-native species pre-adapted to these disturbances may especially be poised to invade novel communities. Conservation managers therefore need predictions of how to alter disturbances to maximize the persistence of native biodiversity., We tested a multivariate hypothesis about the causal mechanisms underlying plant invasions in an ephemeral wetland in South Island, New Zealand, to inform management of this biodiverse but globally imperilled habitat. Our approach details among the first applications in ecology of Bayesian structural equation modelling, demonstrating its potential to inform management by disentangling the relative importance of strongly intercorrelated processes., We found that invasion by non-native plants was lowest in sites where the physical disturbance caused by flooding was both intense and frequent. This effect was stronger than the positive response of non-native species to high soil N supply, which was positively related to flooding., Sites flooded over a 4-year period had greater reductions in invasion than those associated with floods in the year prior to plot measurement because non-native species lacked traits for long-term persistence beneath water. Grazer exclusion had a small positive effect on invasion, as non-native species were preferentially selected by the herbivores at our site., Our results show that only species adapted to the dominant disturbance regimes at a site may become successful invaders. Species native to ephemeral wetlands have specially evolved traits that allow them to persist and dominate in these sites., Synthesis and applications. Predictions of invasions in a world of multiple disturbances clearly need to consider whether the evolutionary history of non-native species predisposes them to invade novel communities. Maintaining hydrological and nutrient regimes of ephemeral wetlands will limit the number of introduced species that are pre-adapted to become invasive. [ABSTRACT FROM AUTHOR]

Highlights: [•] Semi-natural habitats enhance rodent abundances but not species richness. [•] Grasslands decrease rodent abundances and species richness. [•] High vegetation cover after crop harvest enhances rodent occurrence. [ABSTRACT FROM AUTHOR]

Abstract: Multidisciplinary research on the bottom sediments of a kettle-hole at the Retno site (the Brodnica Lake District, north-central Poland) provided some information about changes in hydroclimatic conditions in the Late Glacial and the Holocene. Detailed analysis (sedimentological, palynological, macroremains, geochemical and radiocarbon dating) helped to identify 6 stages in the development of the depression in the village of Gaj (near Retno Lake) with 11 phases of hydroclimatic conditions. Sediments of the Retno profile with a total thickness of 6.72 m reflected individual, natural stages in the development of the depression from a lake to a peat bog. Most of the environmental changes were gradual. A sequence of Late Glacial and early Holocene lacustrine sediments (mainly gyttja) occurred in the floor of the profile. The upper 4.10 m consisted of paludal deposits (peat of transitional and raised bogs) divided at a depth of 1.56–1.54 m b.g.l. by a thin layer of clay dated late Subboreal/early Subatlantic. The presence of this layer indicates a sudden change in the environmental conditions associated with a water level rise. At that time, denudation processes started within the drainage basin, probably induced by human activity. The important effects related to contemporary anthropopressure included desiccation of the peat bog (muck formation in the uppermost 10 cm layer) and elevated trophic conditions resulting in a change of the vegetation cover. [Copyright &y& Elsevier]

Sediment layers of uniform age within lakes (isochrones) and their patterns reflect accumulation processes which can be correlated with hydrologic conditions in lake basins. The sedimentary archives in three small dystrophic lakes in northeastern Poland are described based on the correlation of local pollen assemblage zones in cores that were collected from the centers and margins of each lake. Past regional groundwater levels could be discerned from the shape of the isochrones, whether plane parallel or concave in configuration in relation to the lake basin shape. The concave configuration of the isochrones in the studied lakes shows that regional groundwater levels remained mostly high and stable throughout their history. The water levels in each lake during the Late Glacial and throughout the Holocene were different and no single, common water-level fluctuation pattern was identified in the three water bodies. The lack of such a finding suggests that the lakes are influenced dominantly by local hydrological factors. [ABSTRACT FROM AUTHOR]

The Kurtna reserve (North-Eastern Estonia) includes about forty lakes of hydro-glacial origin, among which the most are kettle hole lakes. Their level and the quality of water are conditioned by aquifers, which are threatened by industrial activities (sand quarry, peat production and oil shale excavation). The paper presents results of a field campaign in March 2013, for measuring water temperature, dissolved oxygen and salinity in two ice-covered lakes (Martiska and Nõmme). Martiska is a closed lake. A large (from 0 °C to 4 °C) inverse thermal stratification takes place under the ice. The very thick anoxic layer may be caused by the cumulating effect of the ice barrier and the consumption in a rich in organic matter lake. Nõmme fits in a hydrographical chain with tributaries and an emissary. The inverse thermal stratification is disturbed by a well delimited mid-layer. Temperature, dissolved oxygen and salinity show that it is probably the fluvial water body, which has entered the lake. The hypothesis is confirmed by the study of the river plume. This inflow is rich in dissolved oxygen. We may suggest, that the lakes with an affluent are less threatened by the winter lack of oxygen than the closed lakes of the region. [ABSTRACT FROM AUTHOR]

Abstract: Northern peatlands are among the most carbon-rich ecosystems on Earth, but many unanswered questions remain regarding linkages between their long-term developmental processes and climatic variability. In this paper, we present a detailed paleoecological reconstruction of the developmental history of a kettle peatland in northern Wisconsin, USA (Fallison Bog) based on 21 coring locations and temporally constrained by 69 radiocarbon dates. This record of within-basin developmental history is compared to a regional dataset containing estimated ages of peatland establishment for 75 core samples collected from 37 depressional peatlands throughout the Great Lakes Region. Finally, our data are used to develop a spatially explicit model of whole-system carbon accumulation in Fallison Bog, which distinguishes between carbon pools stored in limnic sediments and peat deposits. Results indicate that peatland development in Fallison Bog was episodic and spatially complex. Peatland development was related to the morphology of the underlying basin and characterized by pulses of both terrestrialization and paludification. Major episodes of terrestrialization centered on 4980 and 3180 years before A.D. 1850 (cal yr BP), with less extensive episodes occurring around 3840, 1060, 670, and 410 cal yr BP. Extensive peatland area developed by paludification of shallow portions of the basin around 2040 cal yr BP. The timing of peatland development within Fallison Bog was correlated with the timing of peatland development in other depressional peatlands across the Great Lakes Region (r = 0.70), suggesting a common climatic driver. Comparison of peatland development in Fallison Bog and independent paleoclimate records suggested that both millennial-scale and sub-centennial-scale variability in moisture balance influenced spatiotemporal patterns of peatland development. Model results indicated that Fallison Bog accumulated ∼6655 t of carbon during the Holocene, with 66% of this total stored in peat deposits that have accumulated in only the last ∼5000 years. Collectively, model results and the strong correlation between the timing of within-basin and regional pulses of peatland establishment imply that depressional peatlands likely experienced climate-sensitive and episodic changes in carbon accumulation rates during the Holocene, and similar dynamics could be expected in response to ongoing and future climatic change. [Copyright &y& Elsevier]

Kettle holes, small inland water bodies usually less than 1 ha in size, are subjected to pollution, drainage, and structural alteration by intensive land use practices. This study presents the analysis of spectral signatures from kettle holes based on in situ water sampling and reflectance measurements in application for chlorophyll estimation. Water samples and surface reflectance from kettle holes were collected from 6 ponds in 15 field campaigns (5 in 2007 and 10 in 2008), resulting in a total of 80 spectral datasets. We assessed the existing semi-empirical algorithms to determine chlorophyll content for different types of kettle holes using seasonal and cross-seasonal volume reflectance and derivative spectra. Based on this analysis and optical properties of water leaving reflectance from kettle holes, the following typology of the remote signal interpretation was proposed: Submerged vegetation, Phytoplankton dominated and Mixed type. [ABSTRACT FROM AUTHOR]

In the young moraine landscape in Northeast Germany, small glacially created ponds, the so-called kettle holes, are very abundant. They exhibit large spatial heterogeneity, seemingly rendering each kettle hole unique. However, this would not be consistent with any scientific approach. Thus, a classification scheme has been developed for kettle holes in Northeast Germany based on morphology, hydrodynamics and connection to stream networks of the kettle holes as well as size, topography and land use of the respective catchment. These indices are assumed to be related both to water quality as well as to biological issues of the kettle holes. Starting in the mid-1990s, an extensive monitoring program has been established in the federal state of Brandenburg, Germany. In this study, a subset comprising 1,316 samples from 79 kettle holes was analysed, where 21 parameters had been determined. Sampling intervals varied widely, and were between bi-weekly and three-monthly at most sites. A nonlinear principal component analysis was performed. The first four components explained 90% of the variance. These components seem to provide quantitative measures of phosphorus release from the sediments during hypoxic periods, agricultural solute input, algae primary production, and geogenic compounds. This allowed differentiating between the natural and anthropogenic impact factors on water quality. In addition, scores of single components were related to properties of the kettle holes and their environments. The results contribute to a better understanding of biological and biogeochemical processes and can be used to verify the effects of conservation and management strategies for kettle holes. [ABSTRACT FROM AUTHOR]

One of the limits for the application of constructed wetlands (CWs) in mountain regions (such as the Alps) is associated with the considerable land area requirements. In some mountain areas, the treatment of domestic wastewater at popular tourist destinations is particularly difficult during the summer, when the presence of visitors increases hydraulic and organic loads. This paper aims to evaluate whether a hybrid CW plant designed on the basis of the resident population only, can treat also the additional load produced by the floating population during the tourist period (summer, when temperatures are favourable for biological treatment), without a drastic decrease of efficiency and without clogging problems. The research was carried out by considering two operational periods: the first one was based on literature indications (3.2 m²/PE in the VSSF unit) and the second one assumed higher hydraulic and organic loads (1.3 m²/PE in the VSSF unit). The removal efficiency in the hybrid CW system decreased slightly from 94 to 88% for COD removal and from 78 to 75% for total N removal, even after applying a double hydraulic (from 55 to 123 L m-2 d-1) and organic load (from 37 to 87 g COD m-2 d-1 and from 4.4 to 10.3 g TKN m-2 d-1). The results showed that in the summer period the application of high loads did not affect the efficiency of the hybrid CW plant significantly, suggesting that it is possible to refer the CW design to the resident population only, with subsequent considerable savings in superficial area. [ABSTRACT FROM AUTHOR]

Abstract: Kettle holes are relatively common features of glaciated landscapes and have been widely reported in the literature. The work reported here documents the presence of kettle holes at high altitude and low latitude in the Central Apennines (Italy) and describes the geomorphic and pedogenic processes that originated the soils infilling these depressions. The areas selected for this study were located on three of the main massifs of the Central Apennines (Italy): Gran Sasso, Majella, and Sibillini. The kettle holes on these massifs formed at the end of the Würm glaciation, appear smaller and shallower than those reported from elsewhere in the northern hemisphere, are roughly circular in form and do not contain bogs or lakes. In each area the dimensions of 40 kettle holes were measured and three kettle holes were excavated to examine the soils developed inside them. The size of the kettle holes was highest in the Sibillini massif, where the glaciers reached altitudes as low as 1700m in the very narrow, low-lying valleys. It is hypothesised that at lower elevations the glacier receded more rapidly generating larger blocks of ice and consequently larger kettle holes. Once formed, the kettle hole depressions were very effective as sediment traps and acted as sink for materials washed in from the surrounding slopes or from more distant wind-blown sources. In the kettle holes from Gran Sasso and Majella massifs, small fragments of woody charcoal were found. The material filling the kettle holes accumulated inside them in the form of layers. Soils formed inside the kettle holes showed horizons whose thickness and properties appeared mostly inherited from the amassed layers. The only pedogenic process common to the kettle holes of the three massifs was the incorporation of organic matter that, as expected from the rather cold climatic conditions, was subjected to slow dynamics. In the kettle holes of the Majella massif, the horizons developed from layers rich of materials of volcanic origin, and the formation of short-range order minerals occurred. We conclude that the soils inside the kettle holes are a repository of geomorphic, pedogenic and, in reference to the source of the charcoal, paleo-environmental information. [Copyright &y& Elsevier]

Abstract: This study presents an approach for chlorophyll content determination of small shallow water bodies (kettle holes) from hyperspectral airborne ROSIS and HyMap data (acquired on 15 May and 29 July 2008 respectively). Investigated field and airborne spectra for almost all kettle holes do not correspond to each other due to differences in ground sampling distance. Field spectra were collected from the height of 30–35cm (i.e. area of 0.01–0.015m2). Airborne pixels of ROSIS and HyMap imageries cover an area of 4m2 and 16m2 respectively and their spectra are highly influenced by algae or bottom properties of the kettle holes. Analysis of airborne spectra revealed that chlorophyll absorption near 677nm is the same for both datasets. In order to enhance absorption properties, both airborne hyperspectral datasets were normalized by the continuum removal approach. Linear regression algorithms for ROSIS and HyMap datasets were derived using normalized average chlorophyll absorption spectra for each kettle hole. Overall accuracy of biomass mapping for ROSIS data was 71%, and for HyMap 64%. Biomass mapping results showed that, depending on the type of kettle hole, algae distribution, the ‘packaging effect’ and bottom reflection lead to miscalculations of the chlorophyll content using hyperspectral airborne data. [Copyright &y& Elsevier]

Many environmental variables that are important for the development of chironomid larvae (such as water temperature, oxygen availability, and food quantity) are related to water depth, and a statistically strong relationship between chironomid distribution and water depth is therefore expected. This study focuses on the distribution of fossil chironomids in seven shallow lakes and one deep lake from the Plymouth Aquifer (Massachusetts, USA) and aims to assess the influence of water depth on chironomid assemblages within a lake. Multiple samples were taken per lake in order to study the distribution of fossil chironomid head capsules within a lake. Within each lake, the chironomid assemblages are diverse and the changes that are seen in the assemblages are strongly related to changes in water depth. Several thresholds (i.e., where species turnover abruptly changes) are identified in the assemblages, and most lakes show abrupt changes at about 1-2 and 5-7 m water depth. In the deep lake, changes also occur at 9.6 and 15 m depth. The distribution of many individual taxa is significantly correlated to water depth, and we show that the identification of different taxa within the genus Tanytarsus is important because different morphotypes show different responses to water depth. We conclude that the chironomid fauna is sensitive to changes in lake level, indicating that fossil chironomid assemblages can be used as a tool for quantitative reconstruction of lake level changes. [ABSTRACT FROM AUTHOR]

The coming century is predicted to feature enhanced climatic variability, including increased frequency, intensity, and duration of extreme climatic events. Ecologists are faced with the critical challenge of anticipating potentially nonlinear ecosystem responses to these changes. High-resolution paleoecological data sets that capture past ecosystem responses to climate variability provide valuable long-term perspectives on the sensitivity of ecosystems to climate-forced state shifts. We used a suite of paleoecological analyses at Titus Bog in northwestern Pennsylvania, USA, to test the hypothesis that the development and expansion of floating peatlands in kettlehole basins represents a threshold response to hydroclimate variability. In contrast with expectations of gradual autogenic peat mat expansion, our results indicate that peat mat expansion at Titus Bog was highly episodic and occurred in three distinct pulses centered on 800, 650, and 400 cal yr BP. Each of these expansion events coincided with or immediately followed decadal-to-mutlidecadal droughts recorded in regional paleoclimate reconstructions. These patterns indicate that peatland development in kettlehole basins can follow nonlinear trajectories, with episodes of rapid advancement triggered by climatic forcing. Future climate changes may increase the likelihood of peatland expansion in kettlehole basins, potentially leading to abrupt changes in adjacent lake ecosystems. [ABSTRACT FROM AUTHOR]

Summary: The hummocky post-glacial soil landscapes with kettle holes as internal drainage systems are characterized by ponds that trap lateral fluxes in topographic depressions. A quantitative description is mostly limited by the unknown complexity of hydraulically relevant soil and sediment structures. This paper is focussing on a structure-based approach to identify relevant field-scale flow and transport processes. Illustrative examples demonstrate extreme variations in water table fluctuation for adjoining kettle holes. Explanations require a pedohydrologic concept of the arable soil landscape. Identification of structures is based on geophysical methods and soil hydraulic measurements. Electrical resistivity imaging yields 0.5m-scale spatial structures that correspond with soil texture distributions. Electromagnetic induction provides larger-scale field maps that reflect major soil and sediment features. Results of both methods correspond within the limits of the different spatial resolutions. With geophysical exploration methods, colluvial areas with textural differences between upper and deeper soil layers, coarse-textured sediment lenses, and stony colluvial regions around kettle holes are identified as potentially relevant flow structures. The colluvial fringe around the pond seems to be a sensitive area with important lateral exchange fluxes. Tensiometer measurements perpendicular to this boundary indicate hydraulic gradients directed from the pond towards the partially saturated soil. The localized infiltration of trapped water in kettle holes can control large fractions of ground water recharge and may have implications for the fate of agricultural chemicals in post-glacial landscapes. While surface and subsurface hydraulic structures may be inferred using minimal-invasive techniques, better understanding of processes and properties governing lateral exchange fluxes between pond and surrounding soil are required. [ABSTRACT FROM AUTHOR]

Hättestrand, M. & Robertsson, A.-M. 2010: Weichselian interstadials at Riipiharju, northern Sweden – interpretation of vegetation and climate from fossil and modern pollen records. Boreas, 10.1111/j.1502-3885.2009.00129.x. ISSN 0300-9483. The most complete records of Weichselian ice-free conditions in northern Sweden have been retrieved from kettleholes in the Riipiharju esker. In an earlier study, the Riipiharju I core was described as containing two Weichselian interstadials and Riipiharju was chosen as type site for the second Weichselian interstadial in northern Sweden. Here, we present a palynological investigation of two new sediment cores (Riipiharju II and III) retrieved from Riipiharju. Together, the new cores comprise a late cold part of the first Weichselian interstadial recorded in northeastern Sweden (Tärendö I, earlier correlated with Peräpohjola in Finland) as well as a long sequence of the second Weichselian interstadial (Tärendö II, earlier named Tärendö). The results indicate that the climate during deposition of the Tärendö II sequence was more variable than earlier suggested. According to the present interpretation it was relatively warm in the early part of Tärendö II; thereafter a long cold phase persisted, and finally the climate was warmer again in the late part of Tärendö II. The warm phases are characterized by Betula-dominant pollen assemblages, while the cold phase is characterized by high percentages of Artemisia and Gramineae pollen. Since there is still no firm chronology established of the interstadials in northeastern Sweden, two possible correlations are discussed; either Tärendö I and II are correlated with Brörup (MIS 5c) and Odderade (MIS 5a), or, perhaps more likely, they are correlated with Odderade and early Middle Weichselian (MIS 3) time. [ABSTRACT FROM AUTHOR]

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Abstract: Phytosociological and habitat studies were conducted on the water and swamp vegetation of astatic water bodies within north-eastern Poland. The phytocoenoses were selected on the basis of dominance of species forming the particular communities. The analysis of 147 relevés showed the existence of 10 vegetation types: Lemnetum minoris, Spirodeletum polyrrhizae, Riccietum fluitantis, Elodeetum canadensis, Polygonetum natantis, Typhetum latifoliae, Caricetum elatae, Calletum palustris, Potentilletum palustris, Menyanthetum trifoliatae. Among the properties of water analysed water depth, , pH, total and carbonate hardness, PO4 3−, Ca2+, Mg2+ and Na+ were found to be most important in differentiating the habitats of the vegetation types studied. Substrate properties, which best differentiated the habitats of the associations studied were NO3 −, Na+, water content, pH and total N. In spite of the wide variability of habitat conditions occurring in astatic water bodies, particular phytocoenoses distinguished on the basis of dominance of one species were associated with specific habitats. The particular phytocoenoses or groups of phytocoenoses could be good indicators of various habitat conditions that occur within astatic water bodies or changes taking place in these habitats. [Copyright &y& Elsevier]

Abstract: A peat core from the Barschpfuhl kettlehole mire in north-east Germany was analysed for multiproxy indicators (plant macrofossils, pollen/non-pollen microfossils, testate amoebae, colorimetric humification, carbon/nitrogen ratios, bulk density, loss on ignition), to investigate the effects of climate change and human impact on vegetation and peat accumulation during the last c. 300 years. 14C wiggle-match dating was applied for high-precision dating. Testate amoebae assemblages were used to reconstruct past water table depths and compared with other proxies and instrumental climate data from the mid-18th century onwards. The mire hydrology of this relatively small bog was heavily influenced by forestry changes in the area. The climate signal was therefore obscured. Afforestation with fast-growing conifers and drainage for agricultural purposes resulted in a lowering of the water level, changes in trophic status, changes in mire surface vegetation and increased decomposition of the peat. Variations in the openness and cultivated land indicators in the pollen data of Barschpfuhl reflect regional population density and land use changes. [Copyright &y& Elsevier]

Heat waves, which are projected to be more frequent and intense in a warmer climate, could become a serious threat to plants that rely on water surplus availability, such as bryophytes. Here, I take the advantage of the European summer 2003 climate anomaly to assess the impact of an extreme heat wave on peat mosses of the genus Sphagnum, a group of bryophytes forming the bulk of living and dead biomass in peatlands. With this aim, 20 selected bogs in the Italian Alps were checked for Sphagnum survival in the years following the heat wave. Over the study area, the period May–September 2003 was characterized by higher mean monthly air temperature (13.5 °C) and lower mean monthly precipitation (87 mm) compared with normal climatic conditions (11.5 °C and 117 mm, respectively) so that the heat wave coincided with a drought spell. As a consequence of the unusual water stress, I documented an increased mortality of peat mosses forming high hummocks. In particular, at habitat scale, the distribution of desiccated peat mosses was restricted to the hummock face receiving the greatest amount of solar irradiation. However, at regional scale, the present study identified a climatic threshold, simply defined by the ratio of precipitation to temperature ( P : T), which triggered an irreversible desiccation of peat mosses when mean monthly P : T dropped below 6.5 (mm : °C) during May–September 2003. The absence of any sign of recovery after 4 years since the drought must be seen as a harbinger of the deleterious effects of extreme heat waves on organisms not adapted to cope with abrupt climate anomaly. [ABSTRACT FROM AUTHOR]

Breakdown of woody debris in river and upland habitats as well as the interactions between wood and invertebrates have been well described. Studies of wood in wetlands are rare, and far less is known about breakdown and invertebrate use of wood in these transitional habitats. This study experimentally assessed breakdown and invertebrate colonization of wood in a floodplain wetland and directly related patterns in the wetland to adjacent river and upland habitats. Over a 2.7 year period, we monitored breakdown and invertebrate presence in 10 cm diameter × 150 cm long sweetgum (Liquidambar styraciflua L.) logs in a floodplain wetland (n = 8), river (n = 5), and upland (n = 4) habitat. Mass loss, decay condition change, and C/N ratios of wetland wood more closely resembled upland than river wood. The overall invertebrate assemblage associated with wetland wood was also more similar to that associated with upland than river wood. Breakdown and invertebrate colonization of wood in the floodplain wetland shared more characteristics with upland than river wood, perhaps because of the seasonal nature of flooding in the wetland. However, the ecology of wood in wetlands also had unique characteristics compared with either the uplands or the river. [ABSTRACT FROM AUTHOR]

Abstract: In the Clogher Valley, north-central Ireland, subglacial and proglacial landforms provide evidence for phases of active and inactive subglacial and ice-marginal processes during the Late Devensian (Weichselian) glaciation (∼22–13 kyr BP). Patterns of subglacial Rogen moraines and drumlins record east to west ice flow along the valley axis during maximal ice stages. Eskers, superimposed upon the Rogen moraines and drumlins, record later west to east ice flow and mark the first stages of ice retreat. Areas of large, ice-marginal, non-aligned ridges and mounds are separated by more extensive areas in which no deglacial landforms or sediments are present. The non-aligned ridges and mounds do not show a dominant directional signature, have intricate basal outlines, steep slopes and high relief (<25 m), and are morphologically associated with meltwater channels and deep enclosed depressions (kettleholes). The ridges and mounds are interpreted as ice-marginal moraines formed by a combination of proglacial thrusting and gravity processes (high sediment mobility) during the melting out of buried ice blocks. An alternative model may involve sediment transport by glacially-driven, groundwater fluxes forming so-called ‘extrusion moraines’. Both models suggest that basal ice was polythermal in character and that alternating active (thrusting) and passive (stagnation) processes at the ice margin took place during overall westward ice retreat. [Copyright &y& Elsevier]