Search Results (77)

Ice wedges, which are ubiquitous in permafrost areas, play a significant role in the evolution of permafrost landscapes, influencing the topography and hydrology of these regions. In this paper, we combine a detailed multi-generational, interdisciplinary, and international literature review along with our own field experiences to explore the development of low-centered ice-wedge polygons and their orthogonal networks. Low-centered polygons, a type of ice-wedge polygonal ground characterized by elevated rims and lowered wet central basins, are critical indicators of permafrost conditions. The formation of these features has been subject to numerous inconsistencies and debates since their initial description in the 1800s. The development of elevated rims is attributed to different processes, such as soil bulging due to ice-wedge growth, differential frost heave, and the accumulation of vegetation and peat. The transition of low-centered polygons to flat-centered, driven by processes like peat accumulation, aggradational ice formation, and frost heave in polygon centers, has been generally overlooked. Low-centered polygons occur in deltas, on floodplains, and in drained-lake basins. There, they are often arranged in orthogonal networks that comprise a complex system. The prevailing explanation of their formation does not match with several field studies that practically remain unnoticed or ignored. By analyzing controversial subjects, such as the degradational or aggradational nature of low-centered polygons and the formation of orthogonal ice-wedge networks, this paper aims to clarify misconceptions and present a cohesive overview of lowland terrain ice-wedge dynamics. The findings emphasize the critical role of ice wedges in shaping Arctic permafrost landscapes and their vulnerability to ongoing climatic and landscape changes. Full article

Artificial reservoirs formed by hydroelectric dams are young ecosystems requiring water quality monitoring, as they often serve local populations. Traditionally, this is performed through hydrochemical and sanitary assessments, alongside phytoplankton composition analysis. This study aimed to assess the seasonal dynamics of microbial communities—both bacterioplankton and microeukaryotes including phytoplankton—in the Irkutsk Reservoir (IR), which is fed by the cold oligotrophic waters of Southern Baikal (SB). Using parallel metabarcoding of 16S and 18S rRNA gene fragments, we analyzed community composition during the open-water season and evaluated the ecological connectivity between these two freshwater systems. We demonstrated that seasonal changes in microeukaryotic communities were closely linked between SB and IR, with the greatest divergence observed in early summer and progressive convergence by autumn. Metabarcoding confirmed microscopy-based observations while providing higher taxonomic resolution and detecting otherwise overlooked groups. Bacterioplankton communities also exhibited seasonal variation and were shaped by environmental gradients and reservoir characteristics. Cyanobacteria peaked in SB in late summer but did not dominate communities, unlike in mesotrophic lowland reservoirs. These findings demonstrate the value of metabarcoding for freshwater monitoring and provide new insights into microbial community dynamics in river–reservoir systems influenced by oligotrophic lake inflow. Full article

Unique, small-scale tectonic and geological systems are occasionally vulnerable to natural hazards. Although the combination of such systems with rapid socio-ecological change can enhance the risk of disasters, such synergistic impacts have not been well studied. The primary goal of this study was to investigate the potential synergistic impact of land deformation and rapid socio-ecological changes on disaster risk in lowland alluvial regions of a collision zone in the Gorontalo Regency of Gorontalo Province, Indonesia. In this region, socio-ecological changes such as urbanization and rapid lake shrinkage are significant. Frequent occurrence of flood hazards threatens local livelihood. Differential interferometric synthetic aperture radar analysis of Sentinel-1 C-band data from April 2020 to April 2023 was applied to assess land deformation. Thereafter, supervised classification of moderate and high spatiotemporal resolution optical satellite time series was used to assess the relationship between land deformation and built-up area. The findings revealed both significant land deformation and rapid socio-ecological changes. Vertical deformation rates were as high as ~6 cm/year and were primarily attributable to tectonic activity; they were particularly apparent in rapidly developing and highly populated residential areas. Rapid shrinkage of a lake resulted from the local geological system and socioeconomic changes in the region, which together possibly exacerbated the hazard risk because of their effects on land deformation. These results indicate the potential danger to both infrastructure and human inhabitants at a regional level due to the synergistic effects of natural processes and socio-ecological changes. The study design and data that were used facilitated a comprehensive assessment of the potential impacts on disaster risk. These findings are expected to be integrated into locally specific hazard (e.g., flood inundation and ground fissuring) risk mitigation and management strategies. Full article

Angling tourism is becoming increasingly important at Central Europe’s largest lowland reservoir, Lake Tisza. The lake, created in the 1970s, covers 127 km² and has been increasingly used for recreational and nature conservation purposes recently. This study seeks to identify anglers’ site selection preferences at Lake Tisza, considering hydrological and ecological aspects, in support of sustainable site management. In order to achieve this, an in-person questionnaire survey was carried out covering the whole area during springtime 2024. During the survey period, a total of 224 anglers provided answers about their preferred location and recreational characteristics. Data processing was carried out using SPSS 26 and ESRI ArcGIS version 10.4.1. Based on the created catchment area map, it was found that a significant proportion (74%) of anglers arrive from within a 50 km radius, but the lake also has appeal outside the country. A total of 53.1% of respondents visit the lake several times per month, typically for fishing purposes. In addition, cycling, walking and picnicking are popular recreational activities among anglers. The respondents considering different landscapes (pictures showed by the interviewers) for angling prefer shaded areas with vegetation and a narrow view of the wide expanse of water (62%). The results of the open-ended questions indicate that site selection is primarily based on the existence of a shadow (49.5%), and suitability for fishing is only the second aspect (40.6%). Our study also highlighted the international trend that anglers are more interested in leisure activities in a green environment. In addition, the results have practical significance for more successful recreation planning and sustainable site management. Full article

Baskunchak is a large drainless, highly saline lake located in the Caspian lowland. The chemical and gas composition of water (brine) and bottom sediments lying under a 10 cm layer of salt in the lake has been studied; specific fluxes of CH₄ and CO₂ at the water–atmosphere interface have been measured. The lake’s sodium chloride brine is characterized by high mineralization (313.5–334.7 g/L) and a slightly acidic–neutral pH (5.75–6.80). Bottom sediments are characterized by a slightly acid–neutral pH (6.27–6.64) and a reducing condition (Eh from −104.7 to +22.0 mV). Specific fluxes of CH₄ into the atmosphere were low (0.11–0.12 mg CH₄/(m² h)) due to its low concentrations in the brine of the lake (0.91–2.66 µL/L). The appearance of an excess of HCO₃ during the anaerobic oxidation of CH₄ in the bottom sediments of the lake contributes to the formation of autigenic gypsum and calcite. Specific CO₂ fluxes into the atmosphere ranged from 12.2 to 73.1 mg CO₂/(m² h). The probable source of CO₂ in the brine of the lake and its emission into the atmosphere, in addition to the process of organic matter cycling and uptake by microorganisms, is the chemogenic precipitation of sulfates and calcium carbonates. Full article

The Dzungaria Basin is located north of Xinjiang and is one of the largest inland basins in China. The eastern coalfields in the Dzungaria Basin contain a large amount of coal resources, and the thickness of the coal seams is significant. Therefore, the aim of this study was to classify the paleovegetation types and develop paleoclimate succession models of the extra-thick coal seams. We conducted the sampling, separation, and extraction of spores and pollen and carried out microscopic observations in the Wucaiwan mining area of the eastern coalfields in the Dzungaria Basin. The vertical vegetation succession in the thick seam (Aalenian Stage) in the study area was divided into three zones using the CONISS clustering method. The results show that the types of spore and pollen fossils belong to twenty families and forty-five genera, including twenty-three fern, twenty gymnosperm, and two bryophyte genera. The types of paleovegetation in the study area were mainly Lycopodiaceae and Selaginellaceae herb plants, Cyatheaceae, Osmundaceae, and Polypodiaceae shrub plants, and Cycadaceae and Pinaceae coniferous broad-leaved trees. The paleoclimate changed from warm–humid to humid–semi-humid and, finally, to the semi-humid–semi-dry type, all within a tropical–subtropical climate zone. The study area was divided into four paleovegetation communities: the nearshore wetland paleovegetation community, lowland cycad and Filicinae plant community, slope broad-leaved and coniferous plant mixed community, and highland coniferous tree community. This indicates that there was a climate warming event during the Middle Jurassic, which led to a large-scale lake transgression and regression in the basin. This resulted in the transfer of the coal-accumulating center from the west and southwest to the central part of the eastern coalfields in the Dzungaria Basin. Full article

Foresters and natural resource managers are increasingly exploring opportunities for the early detection of emerging forest health concerns. One of these emerging concerns is the eastern larch beetle (ELB, Dendroctonus simplex LeConte), a native insect of tamarack (Larix laricina (Du Roi) K., Koch). Historically, the ELB attacked only dead or dying trees, but with climate change, it is now becoming a damaging disturbance agent that affects healthy trees as well. This shift creates a need to evaluate the methods used to detect and quantify the impacted areas. In northern Wisconsin, USA, 50 tamarack stands or aerial detection polygons were surveyed in the field during the 2023 growing season to explore different detection tools for ELBs. We visited 20 polygons identified by aerial sketch map surveys as having ELB mortality, 20 tamarack stands identified by the Astrape satellite imagery algorithm as disturbed, and 10 randomly selected stands from the Wisconsin forest inventory database (WisFIRs) for landscape-level context. For each of the detection methods and the Random stands, information on species composition, mortality, signs of ELB, invasive species, and water presence was quantified. ELBs were common across the landscape, but were not always associated with high levels of mortality. While overstory tree mortality was frequently observed in both aerial sketch map surveys and Astrape, it was not always linked to tamarack mortality. Current methods of detection may need to be re-evaluated in this environment. Tamarack stands in northern Wisconsin were highly heterogeneous in species, which is likely contributing to the difficulties in identifying both tamarack mortality and tamarack mortality specifically caused by ELBs across the two detection methods. Given the evolving impacts of climate change and the shifting dynamics between forests and insects, it is essential to evaluate and innovate detection methods to manage these ecosystems effectively. Full article

In this study, long-term lake surface water temperature (LSWT) data were used to investigate the impact of climate change on thermal conditions in 25 Polish lowland lakes. The results show that the warming rate of the annual mean LSWT ranges from 0.14 °C per decade to 0.69 °C per decade with an average value of 0.44 °C per decade. The annual maximum LSWT presented the strongest warming trend, with the warming rate varying between 0.26 °C per decade and 1.06 °C per decade (average value of 0.65 °C per decade). Warming rates were observed in all seasons but with different intensities, with warming rates increasing from spring to autumn and then to summer. The warming rate of the summer LSWT varied between 0.29 °C per decade and 0.87 °C per decade with an average value of 0.56 °C per decade. Conversely, winter and annual minimum LSWTs did not present clear increasing trends. The increase in the annual maximum, annual average, and seasonal LSWTs correlated well with the inter-annual variability in air temperature. To understand the relationship between LSWT and air temperature, the non-linear regression model (S-curve) was used in this study. The results indicate that the non-linear regression model can help to present the relationship between LSWT and air temperature in the studied lakes (the average values of the root mean squared error (RMSE), the mean absolute error (MAE), and the Nash–Sutcliffe efficiency coefficient (NSE) are 1.68 °C, 1.28 °C, and 0.95, respectively). The warming trends of LSWTs observed for the studied lakes in Poland are coherent and in some cases larger than the data from other lakes worldwide, and should be seriously considered by policy makers. Full article

Polder landscapes, as a representative of lowland agriculture landscapes, possess diverse natural and cultural values. However, polder landscapes are facing multiple challenges arising from economic and climate changes, including increasing flood threats and the fragmentation of landscape patterns. These issues have severely threatened the safety and regional characteristics of the polder landscape. Therefore, this study aims to preserve the regional characteristics of polder landscapes while promoting the sustainable development of lowland environments, and the objective is to provide a foundation and baseline for the management and planning of polder landscapes. In this study, the Dongting Lake Area (DLA) was selected as a representative case of polder landscapes. To identify the landscape character and delineate the landscape management zones, this study employed the Landscape Character Assessment (LCA) method in conjunction with a polder typology method at two scales. As a result, the polder landscape types were identified and visualized at two different scales. At the Lake Scale, a comprehensive identification method for polder unit types and polder landscape regions was established, achieving a stepwise transition from polder areas to polder clusters and ultimately to individual polder units. At the Local Scale, an integrative analysis of landscape character diversity (LCD) and land construction suitability (LCS) was employed to establish five landscape management zones for polder landscapes, thereby realizing a balance between the conservation of polder landscape diversity with the sustainable development of wetland environments. This study contributes a set of cross-scale ideas and methods for identifying landscape characters and delineating management zones in polder landscapes, which could be expanded to other lowland agricultural landscapes. Full article

Rainbow trout, or mykiss (Oncorhynchus mykiss), is one of the most popular species used in aquaculture and has been naturalized worldwide, including in the Central Asian Balkhash basin, which has unique aboriginal fish fauna. Both rainbow trout from European farms and wild mykiss from Kamchatka were introduced to some mountain lakes and rivers of the Balkhash basin about 50 years ago. This study investigates the current distribution and life history traits of the alien species and its possible impact on the local fish fauna. This study showed that the rainbow trout occupies various habitats in the Ili River basin: mountain lakes, fast-flowing mountain rivers, and lowland rivers with slow currents and warm water (up to +27 °C). Rainbow trout from European fish farms dominate the mountain Middle Kolsay Lake, while the wild trout from Kamchatka occupies the small Ulken Kokpak River. Both co-occur in the Chilik River. Contrary to that in other regions, the distribution of rainbow trout in the Balkhash basin remained almost the same after their introduction. Broad intrapopulation variability in terms of size, growth rate, and maturation age was revealed, apparently as a result of adaptation to the new environment and intrapopulation competition. In particular, the growth rate has decreased, but life span, surprisingly, has increased as compared to the originally introduced fish. Intrapopulation variation in growth and maturity patterns was also noted. Differences in skin coloration between highland (cold-water) and lowland (warm-water) populations were discovered. The feeding mode of naturalized trout is insectivorous (insect imago), indicating that it occupies its own niche in the local fish communities. The largest population of rainbow trout was recorded in the Lower Kolsay Lake, lowering the population of native fish species, while in other localities, no negative impact on local fish communities was recorded. Full article

Reservoirs serve functional purposes such as irrigation and power generation. However, concerns are raised due to the alterations of the connected riverine ecosystems. Chironomidae (Diptera), a diverse aquatic macroinvertebrate group, are vital to the functioning of ecosystems and serve as water quality indicators. Their holometabolous development includes the pupal stage after four larval stages. The chironomid pupal skin (exuvia) is used in environmental assessments, where the Chironomid Pupal Exuvial Technique (CPET) is a recognized standard. The CPET method is adaptable to different freshwater environments and here was applied in the study of 28 man-made lakes in the Pannonian Lowlands and Dinaric Western Balkan Ecoregion in Croatia to obtain information on chironomid diversity and analyze the potential influence of environmental factors on the chironomid community. The lake surface was skimmed with an exuvial hand net (mesh size of 300 µm) along the lake edge with a transect length of 10 m in the area of accumulated debris of organic and inorganic matter. Individual exuviae were mounted in a Berlese mounting medium and identified by morphological characteristics to the lowest taxonomic level. During the study, 5698 chironomid pupal skins were collected, and 141 taxa (including 97 species) belonging to five subfamilies were identified. The tribe Tanytarsini comprised 40% of the identified taxa, with Paratanytarsus spp. being the most abundant. In the Dinaric ecoregion, Paratanytarsus bituberculatus dominated, while Microchironomus tener and the genus Cricotopus were the dominant taxa in the Pannonian ecoregion. Community structure in the Pannonian ecoregion was influenced by total organic carbon (TOC) and orthophosphates (PO₄³⁻), indicating higher anthropogenic pressure compared to the Dinaric ecoregion, where water conductivity influenced Chironomidae assemblages. The research has provided valuable and useful information on the chironomid diversity in man-made and highly altered water bodies, as some of the most vulnerable aquatic habitats to anthropogenic influence. The CPET method could be a useful tool for the ecological studies and bioassessment of water quality in Croatia. Full article

Natural or artificial selection causes animals to adapt to their environment. The adaptive changes generated by the rumen population and metabolism form the basis of ruminant evolution. In particular, the adaptive drive for environmental adaptation reflects the high-quality traits of sheep that have migrated from other places or have been distant from their origins for a long time. The Hu sheep is the most representative sheep breed in the humid and low-altitude environments (Tai Lake region) in East Asia and has been widely introduced into the arid and high-altitude environments (Tibetan Plateau and Hotan region), resulting in environmental adaptive changes in the Hu sheep. In this study, a joint analysis of the rumen microbial metagenome and metabolome was conducted on Hu sheep from different regions (area of origin and area of introduction) with the objective of investigating the quality traits of Hu sheep and identifying microorganisms that influence the adaptive drive of ruminants. The results demonstrated that the growth performance of Hu sheep was altered due to changes in rumen tissue and metabolism following their introduction to the arid area at relatively high altitude. Metagenomic and metabolomic analyses (five ramsper area) revealed that 3580 different microorganisms and 732 different metabolites were identified in the rumen fluid of arid sheep. Among these, the representative upregulated metabolites were 4,6-isocanedione, methanesulfonic acid and N2-succinyl-L-arginine, while the dominant microorganism was Prevotella ruminicola. The downregulated metabolites were identified as campesterol, teprenone and dihydroclavaminic acid, while the disadvantaged microorganisms were Dialister_succinatiphilus, Prevotella_sp._AGR2160, Prevotella_multisaccharivorax and Selenomonas_bovis. The results of the Pearson analysis indicated that the rumen microbiota and metabolite content of sheep were significantly altered and highly correlated following their relocation from a humid lowland to an arid upland. In particular, the observed changes in rumen microorganisms led to an acceleration of body metabolism, rendering sheep highly adaptable to environmental stress. Prevotella_ruminicola was identified as playing an important role in this process. These findings provide insights into the environmental adaptation mechanisms of sheep. Full article

The backwater lowland habitats of large rivers, like the Mississippi River in North America, present complex and often inaccessible environments for traditional capture-based fish biodiversity sampling. Our knowledge of the assemblages of the fishes that occupy such habitats is often incomplete, and this can compromise management efforts. We employed environmental DNA (eDNA) metabarcoding methods to sample a Mississippi River bottom wetland system to assess the ichthyofaunal diversity and the assemblage structure across habitat types, and we compared our results with capture-based survey records for the same habitats. We collected water samples in the spring and fall of 2022 from slough, ditch, shallow lake, and bayou habitats that varied in depth, vegetation, seasonal variability, and connectivity to the Mississippi River channel. We detected a diverse array of fish species that included 51 taxa. Nearly all the species previously documented in the habitats were detected using eDNA metabarcoding, and we increased the number of documented species by more than a third. Most of the species were ubiquitous across the range of habitats, but there was also a substantial assemblage structure, with some species exhibiting clear habitat specificity. Fall sampling was limited to the deeper bayou habitats where seasonal variation between the spring and fall was minimal. eDNA metabarcode sampling was demonstrated to be effective at detecting invasive species as well as uncommon species, which included several species of conservation concern. Full article

Recently, as global climate change and local disturbances such as wildfires continue, long- and short-term changes in the high-latitude vegetation systems have been observed in various studies. Although remote sensing technology using optical satellites has been widely used in understanding vegetation dynamics in high-latitude areas, there has been limited understanding of various landscape changes at different spatiotemporal scales, their mutual relationships, and overall long-term landscape changes. The objective of this study is to devise a change monitoring strategy that can effectively observe landscape changes at different spatiotemporal scales in the boreal ecosystems from temporally sparse time series remote sensing data. We presented a new post-classification-based change analysis scheme and applied it to time series Landsat data for the central Yakutian study area. Spectral variability between time series data has been a major problem in the analysis of changes that make it difficult to distinguish long- and short-term land cover changes from seasonal growth activities. To address this issue effectively, two ideas in the time series classification, such as the stepwise classification and the lateral stacking strategies were implemented in the classification process. The proposed classification results showed consistently higher overall accuracies of more than 90% obtained in all classes throughout the study period. The temporal classification results revealed the distinct spatial and temporal patterns of the land cover changes in central Yakutia. The spatiotemporal distribution of the short-term class illustrated that the ecosystem disturbance caused by fire could be affected by local thermal and hydrological conditions of the active layer as well as climatic conditions. On the other hand, the long-term class changes revealed land cover trajectories that could not be explained by monotonic increase or decrease. To characterize the long-term land cover change patterns, we applied a piecewise linear model with two line segments to areal class changes. During the former half of the study period, which corresponds to the 2000s, the areal expansion of lakes on the eastern Lena River terrace was the dominant feature of the land cover change. On the other hand, the land cover changes in the latter half of the study period, which corresponds to the 2010s, exhibited that lake area decreased, particularly in the thermokarst lowlands close to the Lena and Aldan rivers. In this area, significant forest decline can also be identified during the 2010s. Full article

The 2012 satellite ASTER geoscience maps of Australia were designed to provide public, web-accessible, and spatially comprehensive surface mineralogy for improved mapping and solutions to geoscience challenges. However, a number of the 2012 products were clearly compromised by variable green and/or dry vegetation cover. Here, we show a strategy to first estimate and then unmix the contributions of both these vegetation components to leave, as residual, the target surface mineralogy. The success of this unmixing process is validated by (i) visual suppression/removal of the regional climate and/or local fire-scar vegetation patterns; and (ii) pixel values more closely matching field sample data. In this process, we also found that the 2012 spectral indices used to gauge the AlOH content, AlOH composition, and water content can be improved. The updated (new indices and vegetation unmixed) maps reveal new geoscience information, including: (i) regional “wet” and “dry” zones that appear to express “deep” geological characters often expressed through thick regolith cover, with one zone over the Yilgarn Craton spatially anti-correlated with Archaean gold deposits; (ii) a ~1000 km wide circular feature over the Lake Eyre region defined by a rim of abundant “muscovite” that appears to coincide with opal deposits; (iii) a N–S zonation across the western half of the continent defined by abundant muscovite in the south and kaolinite in the north, which appears to reflect opposing E ↔ W aeolian sediment transport directions across the high-pressure belt; (iv) various paleo-drainage networks, including those over aeolian sand covered the “lowlands” of the Canning Basin, which are characterized by low AlOH content, as well as those over eroding “uplands”, such as the Yilgarn Craton, which have complicated compositional patterns; and (v) a chronological history of Miocene barrier shorelines, back-beach lagoons, and alluvial fans across the Eucla Basin, which, to date, had proved elusive to map using other techniques, with potential implications for heavy mineral sand exploration. Here, we explore the latter three issues. Full article