Search

Cave carbonate minerals are an important terrestrial paleoclimate archive. A few studies have explored the potential for applying carbonate clumped isotope thermometry to speleothems as a tool for constraining past temperatures. To date, most papers utilizing this method have focused on mass-47 clumped isotope values (Δ47) at a single location and reported that cave carbonate minerals rarely achieve isotopic equilibrium, with kinetic isotope effects (KIEs) attributed to CO2 degassing. More recently, studies have shown that mass-47 and mass-48 CO2 from acid digested carbonate minerals (Δ47 and Δ48) can be used together to assess equilibrium and probe KIEs. Here, we examined 44 natural and synthetic modern cave carbonate mineral samples from 13 localities with varying environmental conditions (ventilation, water level, pCO2, temperature) for (dis)equilibrium using Δ47-Δ48 values, in concert with traditional stable carbon (δ13C) and oxygen (δ18O) isotope ratios. Data showed that 19 of 44 samples exhibited Δ47-Δ48 values indistinguishable from isotopic equilibrium, and 18 (95 %) of these samples yield Δ47-predicted temperatures within error of measured modern temperatures. Conversely, 25 samples exhibited isotopic disequilibria, 13 of which yield erroneous temperature estimates. Within some speleothem samples, we find Δ47-Δ48 values consistent with CO2 degassing effects, however, the majority of samples with KIEs are consistent with other processes being dominant. We hypothesize that these values reflect isotopic buffering effects on clumped isotopes that can be considerable and cannot be overlooked. Using a Raleigh Distillation Model, we examined carbon and oxygen isotope exchange trajectories and their relationships with dual clumped isotope disequilibria. Carbon isotope exchange is associated with depletion of both Δ47 and Δ48 relative to equilibrium, while oxygen isotope exchange is associated with enrichment of both Δ47 and Δ48 relative to equilibrium. Cave rafts collected from proximate locations in Mexico exhibit the largest average departures from equilibrium (ΔΔ47¯ = −0.032 ± 0.007, ΔΔ48¯ = −0.104 ± 0.035, where ΔΔi is the measured value – the equilibrium value). This study shows how the Δ47-Δ48 dual carbonate clumped isotope framework can be applied to a variety of tcave carbonate mineral samples, enabling identification of isotopic equilibria and therefore quantitative application of clumped isotope thermometry for paleoclimate reconstruction, or alternatively, constraining the mechanisms of kinetic effects.

Oxygen isotopes (δ18O) are the most commonly utilized speleothem proxy and have provided many foundational records of paleoclimate. Thus, understanding processes affecting speleothem δ18O is crucial. Yet, prior calcite precipitation (PCP), a process driven by local hydrology, is a widely ignored control of speleothem δ18O. Here we investigate the effects of PCP on a stalagmite δ18O record from central Vietnam, spanning 45 – 4 ka. We employ a geochemical model that utilizes speleothem Mg/Ca and cave monitoring data to correct the δ18O record for PCP effects. The resulting record exhibits improved agreement with regional speleothem δ18O records and climate model simulations, suggesting that the corrected record more accurately reflects precipitation δ18O (δ18Op). Without considering PCP, our interpretations of the δ18O record would have been misleading. To avoid misinterpretations of speleothem δ18O, our results emphasize the necessity of considering PCP as a significant driver of speleothem δ18O. This study finds that in-cave processes affect speleothem oxygen isotope records. Correcting for these processes improves agreement with other regional records and climate models, providing a more accurate reflection of past hydroclimate change. [ABSTRACT FROM AUTHOR]

The present study contributes to the morphogenesis of the Miresii Cave, located in Cheia Mare of Dâmbovița in the area of the Bran—Dragoslavele Corridor, an important tourist axis in Romania. The main aim of the research is the proposal to the Scientific Council of Piatra Craiului National Park to bring to the attention of the national decision-making commissions that the cave be declared a natural monument. The inventory of this speleological geomorphosite suggested its inclusion in a thematic geotouristic circuit integrated into national and EU-protected natural areas. The novelty of the present research lies in the fact that the cave has never been studied before, being difficult to access. This cave, spatially found in the strict protection zone of the national park, is not included in its management plan. When being integrated into other nature protection areas, it is necessary to exclude any form of recreational tourism so that the cave can be exploited as a geotouristic resource strictly for research and educational purposes. The morphogenetic analysis of the cave, based on the information synthesized from geomorphological and geological literature, allowed us to decipher the morphological individualization of Miresii Cave in the local and regional geocronomorphological context, in accordance with the chronological separation of the karstification phenomenon manifested first in phreatic and later in vadose karst. The diversified typology of speleothems has been rendered according to the geomorphologic generating processes. The identification of the Rhinolophus ferrumequinum chiropteran colony and observations of its biotope highlighted the ecological significance of the cave. The inventory of the individuals of the colony led to the conclusion that the cave harbors one of the first two largest bat communities of this species in the national park and the adjacent depressional corridor. The present study may allow the documentation of the photographs and description of the geomorphosite integrated into the proposed thematic circuit to be included on billboards and in promotional brochures. Thus, it could also be useful for the decision-making authorities of Rucar and Podu Dâmboviței villages, which are interested in making decisions related to the promotion of geotourism, especially due to the existence of numerous geological and geomorphological tourist resources in the administrative territories. [ABSTRACT FROM AUTHOR]

Variations in speleothem calcium isotope ratios (δ44Ca) are thought to be uniquely controlled by prior carbonate precipitation (PCP) above a drip site and, when calibrated with modern data, show promise as a semi‐quantitative proxy for paleorainfall. However, few monitoring studies have focused on δ44Ca in modern cave systems. We present a multi‐year comparative study of δ44Ca, carbon isotopes (δ13C), and trace elemental ratios from cave drip waters, modern calcite, and host rocks from two cave systems in California—White Moon Cave (WMC) and Lake Shasta Caverns (LSC). Drip water and calcite δ44Ca from both caves indicate PCP‐driven enrichment, and we used a simple Rayleigh fractionation model to quantify PCP variability over the monitoring period. Modern calcite trace element and δ44Ca data positively correlate at WMC, but not at LSC, indicating a shared PCP control on these proxies at WMC but not at LSC. At both WMC and LSC, we observe an inverse relationship between PCP and rainfall amounts, though this relationship is variable across individual drip sites. Our modeled data suggest that WMC experiences ∼20% more PCP than LSC, consistent with the fact that WMC receives less annual rainfall. This work supports speleothem δ44Ca as an independent constraint on PCP that can aid in the interpretation of other hydrologically sensitive proxies and provide quantitative estimates of paleorainfall. Additional, long‐term monitoring studies from a variety of climate settings will be key for understanding δ44Ca variability in cave systems more fully and better constraining the relationship between PCP and rainfall. Plain Language Summary: Chemical analyses on the minerals that make up stalagmites can provide useful information about how rainfall varied in the past, but most of the chemical parameters measured in stalagmites can respond to several complex environmental influences in addition to rainfall amount. Stalagmite calcium (Ca) isotope ratios can provide more direct information about past rainfall variability but haven't been closely studied in modern cave systems. In this study, we present new Ca isotope measurements of cave drip waters and modern calcite mineral samples collected at a seasonal‐to‐annual resolution from two sites in California that experience different amounts of yearly rainfall. We find that periods of less rainfall at each individual cave generally correspond to higher Ca isotope ratios and that the drier of the two caves experienced less water infiltration overall during the study period. These findings support the idea that Ca isotope ratios in cave systems are controlled by the amount of water infiltrating the cave and can be used in combination with other data from stalagmites to reconstruct rainfall variability in the past. This type of information about past rainfall patterns can help planners assess future water availability, which is especially important in drought‐prone regions such as California. Key Points: Drier periods correspond to higher Ca isotope ratios and more prior calcite precipitation, though there is variability between drip sitesModern calcite trace element ratios positively correlate with Ca isotope data at one of the two cave sitesCa isotope data provides an independent constraint on water infiltration to aid the interpretation of other hydrologically sensitive proxies [ABSTRACT FROM AUTHOR]

Speleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high‐resolution paleomagnetic records of short‐term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10−11 Am2), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm3, averaging tens to hundreds of years of magnetic variation. Nonetheless, smaller samples (∼1–10 mm3) can be measured using superconducting quantum interference device (SQUID) microscopy, with a sensitivity better than ∼10−15 Am2. To determine the application of SQUID microscopy for obtaining robust high‐resolution records from small‐volume speleothem samples, we analyzed three different stalagmites collected from Lapa dos Morcegos Cave (Portugal), Pau d'Alho Cave (Brazil), and Crevice Cave (United States). These stalagmites are representative of a range of magnetic properties and have been previously studied with conventional rock magnetometers. We show that by using SQUID microscopy we can achieve a five‐fold improvement in temporal resolution for samples with higher abundances of magnetic carriers (e.g., Pau d'Alho Cave and Lapa dos Morcegos Cave). In contrast, speleothems with low abundances of magnetic carriers (e.g., Crevice Cave) do not benefit from higher resolution analysis and are best analyzed using conventional rock magnetometers. Overall, by targeting speleothem samples with high concentrations of magnetic carriers we can increase the temporal resolution of magnetic records, setting the stage for resolving geomagnetic variations at short time scales. Plain Language Summary: Earth has a magnetic field that is generated in the outer core, and through paleomagnetism we can retrieve information about the evolution of the field from rocks. Different types of rocks have been used to determine how Earth's magnetic field has changed over time. In this study, we use magnetic microscopy to analyze the magnetic record of speleothems, which are rocks that form inside caves and that can record magnetic fields in annual scales. This allows us to obtain magnetic records with higher resolution than previous studies. This is important because Earth's magnetic field changes in timescales ranging from thousands of years to a few years, and obtaining records from speleothems using magnetic microscopy can help us track these variations. We provide data demonstrating how the technique can be used and showing its limitations, and we discuss how the geologic context of the cave influences the robustness of the magnetic record. We also provide protocols for future studies using magnetic microscopy in speleothems. Key Points: Magnetic microscopy can be used to produce a 5× improvement in temporal resolution of magnetic records from speleothemsVariations in magnetic properties across speleothems can affect the temporal resolution of the magnetic recordProtocols for conducting high‐resolution magnetic measurements of speleothems with magnetic microscopy are presented [ABSTRACT FROM AUTHOR]

In recent years, the application of real scene 3D technology has become widespread in urban planning and cultural heritage protection. However, there has been relatively little attention paid to the construction of real scene 3D models for special natural landscapes such as caves. Given the global distribution of karst topography and the large number of naturally developed caves with diverse types, unique landscape styles, and significant scientific value, this paper enriches the research in this field. By combining ground-based and aerial remote sensing techniques, and based on 3D laser scanning and photogrammetry, we have successfully constructed a real scene 3D model of the internal structure of a karst cave with a precision better than 4 cm. Utilizing Unmanned Aerial Vehicle (UAV) oblique photography, we established a real scene 3D model of the external karst landform with a precision better than 2 cm. We also integrated the internal and external 3D models of the cave, developing a new, complete, and high-precision method for constructing real scene 3D models of karst cave landscapes. Furthermore, we proposed a method for texture reproduction in the dark environment inside the caves, enhancing the reproduction and visual appeal of the real interior. The establishment of high-precision real scene 3D models can not only serve as an effective tool for scientific research on caves but also, as replicas of the real world, play a crucial role in public dissemination and education, thereby enhancing public understanding of cave geological landscapes. [ABSTRACT FROM AUTHOR]

Dating the onset of ancient (>1 Ma) karstification is a challenge. One approach is to date the earliest calcite cements in speleothems. We show the benefits of in situ U-Pb dating directly on thin sections from ancient (ca. 30 Ma) thin (<1 mm) speleothems in the karstified Lower Oligocene lacustrine-palustrine carbonates of the Paris Basin (France), which cannot be dated using other methods. We dated 32 calcite rafts (a type of speleothem), one geopetal cement, and 10 calcite cements precipitated along the karstic walls. The ages of the calcite rafts and cements at 29 ± 1 Ma (Lower Oligocene) fall within the age range of the host deposits (≈29 Ma) previously deduced from palaeontological evidence. We demonstrate that cementation of the carbonate host rock, its dissolution, and the speleothem precipitation occurred within 2 m.y. after deposition. Ostracods and intraclasts trapped within Rupelian calcite rafts clearly indicate that the karst developed deep underground shortly before a phase of lacustrine-palustrine sedimentation at the surface. This very early dissolution episode is attributed to the uplift of the Paris Basin as a result of the far-field intraplate deformation induced by the alpine orogenesis. This study shows that in situ U-Pb geochronology on ancient calcite rafts is a promising technique for the indirect dating of karstification and, more broadly, for dating geodynamic events and diagenetic evolution of sedimentary basins. [ABSTRACT FROM AUTHOR]

Paleoclimatological field reconstructions are valuable for understanding past hydroclimatic variability, which is crucial for assessing potential future hydroclimate changes. Despite being as impactful on societies as temperature variability, hydroclimatic variability – particularly beyond the instrumental record – has received less attention. The reconstruction of globally complete fields of climate variables lacks adequate proxy data from tropical regions like South America, limiting our understanding of past hydroclimatic changes in these areas. This study addresses this gap using low-resolution climate archives, including speleothems, previously omitted from reconstructions. Speleothems record climate variations on decadal to centennial timescales and provide a rich dataset for the otherwise proxy-data-scarce region of tropical South America. By employing a multi-timescale paleoclimate data assimilation approach, we synthesize climate proxy records and climate model simulations capable of simulating water isotopologs in the atmosphere to reconstruct 2000 years of South American climate. This includes surface air temperature, precipitation amount, drought index, isotopic composition of precipitation amount and the intensity of the South American Summer Monsoon. The reconstruction reveals anomalous climate periods: a wetter and colder phase during the Little Ice Age (∼ 1500–1850 CE) and a drier, warmer period corresponding to the early Medieval Climate Anomaly (∼ 600–900 CE). However, these patterns are not uniform across the continent, with climate trends in northeastern Brazil and the Southern Cone not following the patterns of the rest of the continent, indicating regional variability. The anomalies are more pronounced than in previous reconstructions but match trends found in local proxy record studies, thus highlighting the importance of including speleothem proxies. The multi-timescale approach is essential for reconstructing multi-decadal and centennial climate variability. Despite methodological uncertainties regarding climate model biases and proxy record interpretations, this study marks a crucial first step in incorporating low-resolution proxy records such as speleothems into climate field reconstructions using a multi-timescale approach. Adequately extracting and using the information from speleothems potentially enhances insights into past hydroclimatic variability and hydroclimate projections. [ABSTRACT FROM AUTHOR]

Lava caves are home to a stunning display of secondary mineral speleothems, such as moonmilk and coralloids, as well as highly visible microbial mats. These features contain diverse and under-characterized groups of bacteria. The role of these bacteria in the formation of secondary mineral speleothems is just beginning to be investigated. The lava caves of the Big Island of Hawai'i and in El Malpais National Monument, New Mexico (USA), share many morphologically similar speleothems. This study focused on investigating the overlap in bacteria across a wide range of speleothems in these two geographically distant sites. Through scanning electron microscopy (SEM) and 16S rRNA gene analysis, we found that Hawaiian caves have a greater alpha diversity and beta diversity separated by cave and speleothem type. Many Actinobacteriota were in higher abundance in New Mexico caves, while Hawaiian caves contained more bacteria that are unclassified at the genus and species level. Discovering the diversity in bacteria in these secondary speleothems will assist in identifying cave secondary mineral formations that may be good candidates for finding life on extraterrestrial bodies. [ABSTRACT FROM AUTHOR]

In order to study the influence of multiple karst cave factors on surface settlement during tunnel boring machine (referred to TBM hereinafter) tunnelling, a three-dimensional numerical model is built by taking a subway project as an example and combining it with MIDAS GTS NX finite element software. Secondly, the influence of the radius, height, angle, vertical net distance and horizontal distance of the karst cave on maximum surface settlement is studied and sorted under the two working conditions of treatment and lack of treatment using the gray correlation analysis method. Additionally, a multi-factor numerical model of the untreated karst cave is established. Finally, based on the preceding research, a multi-factor prediction model for maximum surface settlement is proposed and tested. The results reveal that when the karst cave is not treated, the radius and height of the karst cave have a significant effect on maximum surface settlement. Following cave treatment however, the influence of the cave parameters on maximum settlement of the surface is greatly reduced. The calculating model created in this study offers excellent prediction accuracy and good adaptability [ABSTRACT FROM AUTHOR]

This study investigated the effect of nitrogen application on the rhizosphere soil microenvironment of sunflower and clarified the relationship between ammonium assimilation and the microenvironment. In a field experiment high (HN, 190 kg/hm²), medium (MN, 120 kg/hm²) and low nitrogen (CK, 50 kg/hm²) treatments were made to replicate plots of sunflowers using drip irrigation. Metagenomic sequencing was used to analyze the community structure and functional genes involved in the ammonium assimilation pathway in rhizosphere soil. The findings indicated that glnA and gltB played a crucial role in the ammonium assimilation pathway in sunflower rhizosphere soil, with Actinobacteria and Proteobacteria being the primary contributors. Compared with CK treatment, the relative abundance of Actinobacteria increased by 15.57% under MN treatment, while the relative abundance decreased at flowering and maturation stages. Conversely, the relative abundance of Proteobacteria was 28.57 and 61.26% higher in the MN treatment during anthesis and maturation period, respectively, compared with the CK. Furthermore, during the bud stage and anthesis, the abundance of Actinobacteria, Proteobacteria, and their dominant species were influenced mainly by rhizosphere soil EC, ammonium nitrogen (NH+4-N), and nitrate nitrogen (NO- 3-N), whereas, at maturity, soil pH and NO-3-N played a more significant role in shaping the community of ammonium-assimilating microorganisms. The MN treatment increased the root length density, surface area density, and root volume density of sunflower at the bud, flowering, and maturity stages compared to the CK. Moreover, root exudates such as oxalate and malate were positively correlated with the dominant species of Actinobacteria and Proteobacteria during anthesis and the maturation period. Under drip irrigation, applying 120 kg/hm² of nitrogen to sunflowers effectively promoted the community structure of ammonium-assimilating microorganisms in rhizosphere soil and had a positive influence on the rhizosphere soil microenvironment and sunflower root growth. [ABSTRACT FROM AUTHOR]

Natural dissolved organic matter (DOM) is ubiquitous in aquatic environments and is an essential component in the carbon cycle in karst areas. To improve understanding of the carbon cycle in karst caves with heterogeneous hydrological processes, we examined the spatiotemporal variability of DOM composition and further uncovered its source and fate. Results may also provide insights into the feedbacks of organic carbon to carbon sinks in karst regions. In this study, concentrations and compositions of DOM, partial pressure of aqueous carbon dioxide (pCO2), dissolved inorganic carbon, and other physicochemical parameters were investigated in a karst cave at Mahuang, Southwest China. Ultraviolet-visible absorption spectroscopy was coupled with multiple statistical analyses to identify the compositional variations and potential fates of DOM in cave waters. The results showed that DOM dynamics were regulated by both terrigenous and biogenic drivers under the control of meteorological conditions. With higher air temperature, precipitation, and microbial activity, fulvic fractions were consumed to generate CO2, leading to the accumulation of refractory DOM in cave waters and changing the hydrochemical features. When temperature and precipitation decreased, DOM was dominated by lignin fractions, which served as an indicator of terrestrial inputs and vascular plants, suggesting variation in the preferential fraction of biological consumption. In addition, different hydrological path patterns influenced DOM properties in cave waters due to differences in recharging, the leaching process, and subsurface reworking. Thus, hydrology could serve as an important constraint on the coupling between dissolved organic and inorganic carbon. [ABSTRACT FROM AUTHOR]

The study of foraging behaviour is crucial for understanding several ecological and adaptive processes, as well as for developing conservation measures. While extensive research has been completed on birds and mammals, few studies have been conducted on the learning capabilities of amphibians, particularly those pertaining to foraging behaviour. Amphibians may detect potential prey through distinct sensory systems including visual detection, chemoreception, and mechanoreception. In this study, we tested whether fire salamander larvae shift their prey recognition depending on the prey stimulus typology. We performed behavioural assays to better understand the roles of visual and chemical cues in prey recognition and how a continuative visual stimulus may change behavioural patterns. For this assessment, larvae from different habitats (cave and stream) were reared under laboratory conditions and fed while exposed to accompanying sensory stimuli. Their responses to visual and olfactory cues were measured before and after rearing. Both visual and chemical cues significantly affected the time of approach to the stimulus. The period of rearing significantly interacted with the time of approach for both cues. After rearing, when visual cues occurred, the time of approach was much lower than before rearing. These findings provide a basis for further studies on the role of plasticity in the predator–prey interactions of fire salamander larvae. [ABSTRACT FROM AUTHOR]

Aim: Quantifying the relative contribution of environmental filtering versus limiting similarity in shaping communities is challenging because these processes often act simultaneously and their effect is scale‐dependent. Focusing on caves, island‐like natural laboratories with limited environmental variability and species diversity, we tested: (i) the relative contribution of environmental filtering and limiting similarity in determining community assembly in caves; (ii) how the relative contribution of these driving forces changes along environmental gradients. Location: Europe. Time period: Present. Major taxa studied: Subterranean spiders. Methods: We used data on distribution and traits for European cave spiders (n = 475 communities). We estimated the trait space of each community using probabilistic hypervolumes, and obtained estimations of functional richness independent of the species richness of each community via null modelling. We model functional diversity change along environmental gradients using generalized dissimilarity modelling. Results: Sixty‐three percent of subterranean spider communities exhibited a prevalence of trait underdispersion. However, most communities displayed trait dispersion that did not depart significantly from random, suggesting that environmental filtering and limiting similarity were both exerting equally weak or strong, yet opposing influences. Overdispersed communities were primarily concentrated in southern latitudes, particularly in the Dinaric karst, where there is greater subterranean habitat availability. Pairwise comparisons of functional richness across caves revealed these effects to be strongly scale‐dependent, largely varying across gradients of cave development, elevation, precipitation, entrance size and annual temperature range. Conversely, geographical distance weakly affected trait composition, suggesting convergence in traits among communities that are far apart. Main conclusions: Even systems with stringent environmental conditions maintain the potential for trait differentiation, especially in areas of greater habitat availability. Yet, the relative influence of environmental filtering and limiting similarity change with scale, along clear environmental gradients. The interplay of these processes may explain the assembly of species‐poor subterranean communities displaying high functional specialization. [ABSTRACT FROM AUTHOR]

The Carajás region is home to the largest number of iron caves in Brazil, but studies that integrate elements of biological diversity and landscape characteristics are scarce. We present the first study based on the bat cave vulnerability index (BCVI), which uses bats as a key species for prioritizing caves in South America, whose objective was to assess the biotic potential and vulnerability of caves in the Carajás region, determining priority sites and the most effective conservation actions. The study took place from August 2021 to March 2023, where an inventory of the chiropterofauna of 12 caves was carried out. We recorded 16 bat species, two of which are vulnerable to extinction – Furipterus horrens (Cuvier, 1828) and Natalus macrourus (Gervais, 1856) – and two endemics to the Amazon region – Hsunycteris aff. thomasi (Allen, 1904) and Phyllostomus latifolius (Thomas, 1901); as well as one species with insufficient data to delimit its endemicity or threat status (Lonchophyllinae sp.). Mining is the main anthropogenic activity in the region, but tourism is also present and acts as a potential source of disturbance to the caves. The BCVI revealed three high priority caves for conservation and four with medium priority, indicating that these habitats are vulnerable to species loss and population decline due to exposure to anthropogenic activities and habitat destruction, thus requiring more effective conservation strategies. Considering the uniqueness of the subterranean habitats, we recommend re‐evaluating the proposals for expanding mining activities, implementing controlled tourist visitation plans and conducting ecological studies and long‐term monitoring. [ABSTRACT FROM AUTHOR]

Speleogenesis in hypogene karst settings may be closely tied to regional tectonic dynamics and concomitant hydrochemical evolution of karst waters. However, placing temporal constraints on these processes can require a wider array of field observations and techniques than for typical karst systems. Herein, we present a comprehensive study of Novoafonskaya Cave (Western Caucasus, Abkhazia). The updated speleogenetic history of the cave comprises four stages: (1) the most ancient, a low-T hydrothermal (ca. 40-50°C) priming stage; (2) the main stage enabled by mixing of upwelling thermomineral and locally recharged common karst waters; (3) the late sulfuric-acid speleogenesis (SAS) stage, which left significant mineralogical overprint (gypsum and a suite of minerals resulting from the alteration of silicate sediments) but did not alter the morphology of the cave appreciably; and (4) the contemporary stage, occurring predominantly in the phreatic and epiphreatic zones. Ages of speleogenetic stages were constrained by radiometric dating (230Th-U and 40Ar/39Ar) and paleomagnetic data, alongside the Quaternary geological history of the region and paleodynamics of the Black Sea level. Conditions for the low-T hydrothermal karstification occurred from Miocene-Middle Pliocene. The main stage, which created the main volumes of the cave, took place from Late Pliocene-Middle Pleistocene. The cave emerged from the phreatic into the vadose zone after ca. 400 ka ago, due to the combined effect of the Black Sea regression and intensification of tectonic uplift in the Caucasus. The presence of sulfidic waters during dewatering led to the development of transient SAS processes during Middle to Late Pleistocene. Dating of calcite underlying SAS-associated overgrowths constrains the cessation of this SAS activity to within the last 147 ka. In its present state, the cave has no connection with thermomineral waters; however, such waters are found deeper in the southern parts of the karst massif (based on the hydrochemistry of Psyrtskha spring), implying that hypogene karstification, primarily driven by mixing corrosion, may still be active deep in the phreatic zone. [ABSTRACT FROM AUTHOR]

We chose to study the bottom structure stress evolution law in the process of undercut area advancement via the block caving method, reveal the influence law of the undercut rate on the effect of the ore body caving process, and assess the floor stress evolution law in the process of the undercut area with a different undercut rate in order to guide the production of a natural disintegration method under horizontal ground stress and also provide some reference value for rock damage assessment. According to the actual engineering and physical parameters of the mine, a numerical simulation model was created by using finite discrete element software GPI-3D-FDEM, and the Neo–Hookean hyperelastic constitutive model was adopted for calculation purposes. The simulation process follows a backward bottoming approach and monitors and analyses the stress state of the substructure after each bottoming step. The indoor physical model is employed to conduct similar two–dimensional simulation experiments on similar materials, investigating the motion laws of overlying rock layers. The research findings indicate that as bottom blasting progresses, a gradual concentration of compressive stress occurs in the foundation structure ahead of the advancing line. If this stress surpasses the rock mass's shear failure limit, ground pressure failure may ensue. During mineral extraction from the bottom, internal stress within the fractured fault zone significantly diminishes compared to adjacent rock and ore deposits. [ABSTRACT FROM AUTHOR]

To explore the solution of the two-step method applied in the rapid construction of super large cross-section tunnels passing through IV-and V-grade surrounding rock sections in karst cave areas, based on an engineering example of the Lianhuashan Tunnel, we use the numerical calculation method to analyze the stability of surrounding rock and the design parameters of the control measures for super large cross-section tunnels during the construction of the step method. The calculated results show that the working face of IV-grade surrounding rock can be stabilized by an advanced small pipe, and the stability of the supporting structure should be controlled mainly by IV-grade surrounding rock. In order to control the stability of the tunnel face, it is necessary to use an advanced large pipe shed in the surrounding V-grade rock. The reinforcement range of the advanced large pipe shed is 120° and the length is 20 m. This is the most economical design parameter of the advanced large pipe shed, ensuring the deformation control effect. For control of the stability of the supporting structure, under the condition that the working space is suitable for large machinery, the settlement of the arch of the supporting structure can be obviously reduced by shortening the step cycle footage and reducing the step length, and the peripheral convergence of the supporting structure can be obviously reduced by reducing the step height. After comprehensive analysis and considering the development of karst caves, the advanced support measures, design parameters, bench excavation design parameters, initial support measures, karst cave treatment measures, and bench construction process of IV- and V-grade surrounding rock is determined. The application verification shows that the research results have a good control effect on the stability of the surrounding rock and cave and are suitable for large-scale mechanical operations, which can significantly improve the excavation speed of the super large cross-section tunnel passing through the IV- and V-grade surrounding rock sections in the karst cave area. [ABSTRACT FROM AUTHOR]

Copyright of Carsologica Sinica is the property of Institute of Karst Geology, CAGS and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The irrigation systems require modernization and management by evaluating water system prerequisites precisely. A study was carried out at Srinagar during kharif 2022 to determine the crop water demands, irrigation scheduling and simulation of moisture movement under different irrigation regimes on tomato crop in open field conditions using CROPWAT and HYDRUS-1D models. The results revealed that the average crop water requirement at 100% ETC per plant per day was 0.24 l plant-1 day-1 during the initial stage, 0.37 l plant-1 day-1 during development stage, 0.85 l plant-1 day-1 during mid-stage and 0.74 l plant-1 day-1 during the end stage. Soil water content was simulated by HYDRUS-1D model in 0 to 30 cm of soil profile. Higher values (0.86 to 0.95) of coefficient of determination (R² ) indicated that observed and simulated values of moisture content are highly correlated and the model predicts that lower values of mean absolute error (MAE) and root mean square error (RMSE) indicates that the HYDRUS-1D model is more accurate at simulating the movement of moisture under different irrigation regimes. [ABSTRACT FROM AUTHOR]

The 8.2 ka event has been extensively investigated as a remarkable single event but rarely considered as a part of multi-centennial climatic evolution. Here, we present absolutely dated speleothem multi-proxy records spanning 9.0–7.9 ka from Beijing in North China, near the northern limit of the East Asian summer monsoon (EASM) and thus sensitive to climate change, to provide evidence of the intensified multi-decadal climatic oscillations since 8.52 ka. Three extreme excursions characterized by inter-decadal consecutive δ18 O excursions exceeding ±1σ are identified from 8.52 ka in our speleothem record. The earlier two are characterized by enriched 18 O at ∼8.50 and 8.20 ka, respectively, suggesting a prolonged arid event, which is supported by the positive trend in δ13 C values, increased trace element ratios, and lower growth rate. Following the 8.2 ka event, an excessive rebound immediately emerges in our δ18 O and trace element records but moderate in the δ13 C, probably suggesting pluvial conditions and nonlinear response of the local ecosystem. Following two similar severe droughts at 8.50 and 8.20 ka, the different behavior of δ13 C suggests the recovering degree of resilient ecosystem responding to different rebounded rainfall intensity. A comparison with other high-resolution records suggests that the two droughts–one pluvial pattern between 8.52 and 8.0 ka is of global significance instead of being a regional phenomenon, and is causally linked to the slowdown and acceleration of the Atlantic Meridional Overturning Circulation that was further dominated by the freshwater injections in the North Atlantic. [ABSTRACT FROM AUTHOR]

Abstract Speleothems are mineral deposits capable of recording detrital and/or chemical remanent magnetization at annual timescales. They can offer high‐resolution paleomagnetic records of short‐term variations in Earth's magnetic field, crucial for understanding the evolution of the dynamo. Owing to limitations on the magnetic moment sensitivity of commercial cryogenic rock magnetometers (∼10−11 Am2), paleomagnetic studies of speleothems have been limited to samples with volumes of several hundreds of mm3, averaging tens to hundreds of years of magnetic variation. Nonetheless, smaller samples (∼1–10 mm3) can be measured using superconducting quantum interference device (SQUID) microscopy, with a sensitivity better than ∼10−15 Am2. To determine the application of SQUID microscopy for obtaining robust high‐resolution records from small‐volume speleothem samples, we analyzed three different stalagmites collected from Lapa dos Morcegos Cave (Portugal), Pau d'Alho Cave (Brazil), and Crevice Cave (United States). These stalagmites are representative of a range of magnetic properties and have been previously studied with conventional rock magnetometers. We show that by using SQUID microscopy we can achieve a five‐fold improvement in temporal resolution for samples with higher abundances of magnetic carriers (e.g., Pau d'Alho Cave and Lapa dos Morcegos Cave). In contrast, speleothems with low abundances of magnetic carriers (e.g., Crevice Cave) do not benefit from higher resolution analysis and are best analyzed using conventional rock magnetometers. Overall, by targeting speleothem samples with high concentrations of magnetic carriers we can increase the temporal resolution of magnetic records, setting the stage for resolving geomagnetic variations at short time scales.

Mg/Ca ratio in stalagmites primarily serves as an indicator of past hydrological conditions rather than temperature variations. Here, we present an Mg/Ca ratio record in a stalagmite from northern China, spanning ice age termination II. A unique finding is that Mg/Ca ratio shows a moderately strong positive correlation with cave air temperature obtained from clumped isotopes data in the same stalagmite. The stable hydrogeochemistry of source water and high temperature sensitivity of Mg partition coefficient plausibly explain this temperature dependence. Furthermore, we establish an Mg/Ca‐temperature calibration for stalagmites from mid‐latitudes, encompassing a temperature range between ∼2 and ∼15°C, where Mg/Ca = 14.221 × e0.073×T (R2 = 0.40). Applying this function to Mg/Ca ratio from similar stalagmites could tentatively provide a quantitative regional temperature record over millennial and centennial timescales. This research highlights Mg/Ca ratio in stalagmites as a potential palaeo‐temperature proxy and introduces, for the first time, a tentative Mg/Ca‐temperature calibration function for speleothems. Plain Language Summary: Stalagmite is one type of speleothems that grow from the floor of caves. The geochemical indexes within stalagmites, such as Mg/Ca ratio, can help us to understand the past climate changes. Here, we conducted a study on a stalagmite from northern China during ice age termination II. Traditionally, Mg/Ca ratios in stalagmites have been used to investigate past hydrological conditions. However, we found that Mg/Ca ratio matches the cave air temperature obtained from clumped isotopes data within the same stalagmite. This correlation was explained by the stable chemistry of the source water and the sensitivity of Mg partition coefficient to temperature. We also developed a tentative formula to calculate past temperature from Mg/Ca ratio in similar speleothems. Key Points: A Chinese stalagmite at termination II shows moderately strong positive correlation between Mg/Ca ratio and clumped isotopes‐temperatureStable drip water hydrogeochemistry and high temperature sensitivity of Mg partition coefficient may explain this temperature dependenceWe tentatively establish, for the first time, an Mg/Ca‐temperature calibration function for speleothems [ABSTRACT FROM AUTHOR]

The carbon isotopic composition of dissolved organic carbon (δ13CDOC) in speleothems, based on high-precision U-Th ages, has great potential to reconstruct past ecology, microbial activity, and carbon cycling. Identifying the reliability of the pretreatment and measurement of speleothem δ13CDOC is therefore essential to putting it into practice. Actually, we have previously verified the reliability of the method for speleothem δ13CDOC measurements. However, it was only based on the final δ13CDOC values of homogeneous speleothem powder and is unable to evaluate the effects of different experimental conditions and the impacts of adding acid on δ13CDOC if using speleothem as the study samples. In this study, we used an organic reagent (potassium sorbate) as the study sample and designed a conditional experiment that simulates the protocols for speleothem δ13CDOC analysis and presented the resulting data to inspect the effects of the experimental processes on the analysis of δ13CDOC. The results show that the standard deviation of duplicate samples is 0.1‰, which is close to that of the previous work for organic reagents and water samples, and the results were not affected by different experimental conditions and operation steps (such as adding orthophosphoric acid, digestion time, and storage duration of resulting CO2 in storage vessels), suggesting that this method is robust to detect the speleothem δ13CDOC. Considering the range and standard deviation of results, we proposed that the δ13CDOC record could be used in various studies when the amplitudes of the δ13CDOC record are larger than 0.1‰, especially greater than 0.4‰. [ABSTRACT FROM AUTHOR]

Speleothem δ13C in monsoonal China differs from speleothem δ18O, which is widely used as a climatic proxy for several complex control reasons. Nevertheless, δ13C records have the potential to reveal the implications of hydroclimatic changes. This study reports a speleothem δ13C record from Didonghe (DDH) Cave in central China spanning 34 to 13 kyr BP. After we investigated the factors that influence speleothem δ13C, we found that the δ13C record showed that DDH Cave can prompt directional shifts via local hydroclimatic changes, such as in vegetation types, biomass, and rock–water interaction processes, suggesting that δ13C is mainly controlled by the local hydroclimate. Ensemble empirical mode decomposition (EEMD) results revealed a coupling relationship between δ18O and δ13C on multiple timescales, which suggested that changes in precipitation caused by large-scale monsoonal circulation are controlled by regional hydrological conditions to a great extent. However, the hydrological conditions of the cave were relatively mild and humid during the last glacial maximum (LGM), which revealed the impact of evaporation on changes in the region's hydrological conditions. We also found that the δ18O and δ13C profiles decoupled when δ13C changed with a shift in the location of the westerly during HS1. The δ13C record correlates well with other paleoclimate records, suggesting that regional hydrological conditions are also modulated by the Earth's internal and external driving factors. [ABSTRACT FROM AUTHOR]

The Slovenian climate has undergone significant fluctuations, and an understanding of the past climate is necessary to improve models and recognise long-term patterns. The cryosphere environment, such as ice core samples, provides valuable palaeoclimate data. Palynology and dendroclimatology are also effective ways to study long-term changes in vegetation and reconstruct past climates using pollen and tree proxies. Sediment cores from various locations in Slovenia have been studied to understand past environmental changes. Borehole temperature profiles as well as historical records were also used to reconstruct past climate conditions. Studies have shown specific periods when climatic changes likely played a major role, but a complete timeline of the Slovenian climate throughout the Holocene has not yet been fully developed. [ABSTRACT FROM AUTHOR]

Caves serve as time capsules, preserving significant markers of tectonic activity and offering insights into geological history. Fault geometries and past activations found in caves can be correlated with known deformational events in the broader area, temporally delimiting the speleogenesis. More specifically, cave passage formation is suggested to be affected by the regional stress-field. The Asprorema Cave in Northern Greece is a typical example of a fracture guided cave, with passage geometry influenced by relative sidewall movements, revealing these discontinuities as faults. This study constructs the timeframe and conceptual model of speleogenesis in relation to tectonic events, geomorphological evolution and hydrological zones, and verifies its relation to the stress-field. Active tectonics, mineralogy and cave geomorphology are investigated. Results suggest syntectonic speleogenesis under phreatic and epiphreatic conditions. The absence of corrosion on fault slip surfaces implies recent activations post cave's shift to the vadose zone. Structural analysis identifies three main neotectonic phases: NNW-SSE striking faults (oldest group of structures), NE-SW striking faults with dextral strike-slip movement (post-middle Miocene), and NE-SW striking normal faults indicating extensional stress-regime (Quartenary). The last two phases affect cave passage shape causing wall displacement, highlighting passage formation along discontinuities perpendicular to the horizontal minimum stress axis. [ABSTRACT FROM AUTHOR]

Storm Babet (18–21 October 2023) brought heavy and persistent rain (80–100 mm) to the English Peak District, causing widespread surface and underground flooding. The village of Castleton experienced groundwater flooding from springs that drain a complex mixed allogenic–autogenic karst catchment. Transmission of the flood pulse was monitored using high-resolution (2 and 4 min intervals) logging of (a) the hydraulic head at five underground locations in the karst conduits and (b) the water depth at three springs and in the surface river fed by the springs. Underground, there were large increases in the hydraulic head (9–35 m), which resulted in two types of flow switching. Firstly, the increased head at the input end of a phreatic (water-filled) conduit system removed an underwater permeability barrier in a relatively low-elevation conduit, resulting in a dramatic increase in flow out of the conduit and a corresponding decrease in flow from a linked higher-elevation conduit that had dominated before the storm. Secondly, the increased head upstream of two conduits with limited hydraulic conductivity allowed water to spill over into conduits that were inactive prior to the storm. As expected, the conduits fed by sinking streams from the allogenic catchment responded rapidly to the recharge, but there was also a rapid response from the autogenic catchment where there are no surface streams and only a small number of dolines. The complex signals measured underground are not apparent from the spring hydrographs. [ABSTRACT FROM AUTHOR]

Leakage in underground structures, especially tunnels, may cause seepage erosion in the surrounding soil, which in turn leads to ground subsidence, posing a great threat to urban safety. The current literature mainly focuses on seepage erosion in the sand but lacks a systematic study on the development process of seepage erosion induced by tunnel leakage in different strata. To investigate the different seepage erosion modes induced by tunnel leakage in different stratum types, a series of reduced-scale model tests were carried out. A coupled fluid–solid numerical model was further established to analyze the fine-scale characteristics of different seepage erosion modes. The results show that (1) the soil seepage erosion modes can be divided into three categories: no soil cave, unstable soil cave, and stable soil cave; (2) the adopted coupled fluid–solid numerical model based on DEM, which takes into account the degradation of clay during seepage erosion, can effectively simulate the erosion process of soil with different seepage erosion modes; (3) the phenomena of the three erosion modes are different in the process of erosion development; and (4) the micro-mechanisms of the three seepage erosion modes are different, which are manifested in the erosion range, soil arching effect, and displacement. [ABSTRACT FROM AUTHOR]

Understanding past fire regimes and how they vary with climate, human activity, and vegetation patterns is fundamental to the mitigation and management of changing fire regimes as anthropogenic climate change progresses. Ash‐derived trace elements and pyrogenic biomarkers from speleothems have recently been shown to record past fire activity in speleothems from both Australia and North America. This calls for an empirical study of ash geochemistry to aid the interpretation of speleothem palaeofire proxy records. Here we present analyses of leached ashes collected following fires in southwest and southeast Australia. We include a suite of inorganic elemental data from the water‐soluble fraction of ash as well as a selection of organic analytes (pyrogenic lipid biomarkers). We also present elemental data from leachates of soils collected from sites in southwest Australia. We demonstrate that the water‐soluble fraction of ash differs from the water‐soluble fraction of soils, with trace and minor element concentrations in ash leachates varying with combustion completeness (burn severity) and sample location. Changes in some lipid biomarker concentrations extracted from ashes may reflect burn severity. Our results contribute to building a process‐based understanding of how speleothem geochemistry may record fire frequency and severity, and suggest that more research is needed to understand the transport pathways for the inclusion of pyrogenic biomarkers in speleothems. Our results also demonstrate that potential contaminant loads from ashes are much higher than from soils, with implications for the management of karst catchments, which are a critical water resource. Plain Language Summary: Understanding past fire activity is necessary to develop effective land management strategies to manage activity. Recently, stalagmites (naturally forming cave decorations) have been shown to record past fire information through chemical changes. The chemical changes are due to post‐fire leaching of wildfire ash. By investigating wildfire ash chemistry, we will be able to improve our interpretations of the stalagmite past fire signal. Our results show that ash chemistry from Australian fires varies with burn severity and sample location, and that the ash chemistry and soil chemistry differ. Results suggest that stalagmites may record burn severity as well as fire frequency. We also suggest that the potential impact of high concentrations of potential contaminants in wildfire ash on karst aquifers should be further investigated. Key Points: Stalagmites record past fire activity through changes in inorganic and organic chemistry sourced from ashesWildfire ash leachate chemistry will aid interpretation of proxy fire dataResults show that inorganic chemistry varies with burn severity and sample location, and the pyrogenic biomarker signal is less clear [ABSTRACT FROM AUTHOR]

Clearing and construction activities related to the Maya Train (Tren Maya) project resulted in potential and inevitable impacts to archaeological caves sites in largely undeveloped areas of Quintana Roo. An effort coordinated by Mexico's National Institute of Anthropology and History (INAH) involved accelerated digital documentation of two caves – via SLAM-enabled mobile LiDAR scanning and targeted photogrammetry – to facilitate prompt visualization and evaluation of terrestrial and subterranean geospatial relationships. Mobile LiDAR is well suited to the challenges of capturing the complex, multilevel morphology of caves and was readily deployed across and through priority environments. Specific archaeological features – such as ancient Maya rock art and masonry shrines – were documented via photogrammetry, and the resulting higher-resolution models co-referenced with the georeferenced mobile LiDAR-generated point clouds of each cave and the surrounding topographic context. This integrative approach contributed to a more informed decision-making process, with respect to conservation and construction, and provided baseline data for future monitoring of the affected cave sites. [ABSTRACT FROM AUTHOR]

High‐resolution records from past interglacial climates help constrain future responses to global warming, yet are rare. Here, we produce seasonally resolved climate records from subarctic‐Canada using micron‐scale measurements of oxygen isotopes (δ18O) in speleothems with apparent annual growth bands from three interglacial periods—Marine Isotope Stages (MIS) 11, 9, and 5e. We find 3‰ lower δ18O values during MIS 11 than MIS 5e, despite MIS 11 likely being warmer. We explore controls on high‐latitude speleothem δ18O and suggest low MIS 11 δ18O values reflect greater contribution of cold‐season precipitation to dripwater from longer annual ground thaw durations. Other potential influences include changes in precipitation source and/or increased fraction of cold‐season precipitation from diminished sea ice in MIS 11. Our study highlights the potential for high‐latitude speleothems to yield detailed isotopic records of Northern Hemisphere interglacial climates beyond the reach of Greenland ice cores and offers a framework for interpreting them. Plain Language Summary: Few climate records pre‐dating the last ice age exist from high‐latitude North America, which inhibits our understanding of how regions with permafrost responded to past warming and how they might change in the future. Here, we help fill this data gap by using six speleothems (cave mineral deposits) from a cave in the Northwest Territories, Canada to produce climate records that span thousands of years during former warm periods of Earth's history. We find that speleothems that grew during an exceptionally warm super‐interglacial period 400,000 years ago have 3‰ lower oxygen isotope (δ18O) values compared to those that grew during a likely cooler interglacial 125,000 years ago. We explore potential explanations for the difference in δ18O across interglacials, and suggest that lower δ18O values during warmer periods reflect greater infiltration of cool‐season precipitation with longer annual ground thaw durations. This study highlights the importance of high‐latitude speleothems to provide detailed climate records beyond the range available from Greenland ice cores. Key Points: Long high‐latitude terrestrial climate records are rare in the Northern HemisphereHigh‐latitude speleothems can provide ultra‐high‐resolution climate records beyond the reach of Greenland ice coresMean oxygen isotopes of Arctic and subarctic speleothems likely are controlled by annual ground thaw durations [ABSTRACT FROM AUTHOR]

Background: Moonmilk represents complex secondary structures and model systems to investigate the interaction between microorganisms and carbonatic rocks. Grotta Nera is characterized by numerous moonmilk speleothems of exceptional size hanging from the ceiling, reaching over two meters in length. In this work we combined microbiological analyses with analytical pyrolysis and carbon stable isotope data to determine the molecular composition of these complex moonmilk structures as well as the composition of the associated microbiota. Results: Three moonmilk structures were dissected into the apical, lateral, and core parts, which shared similar values of microbial abundance, richness, and carbon isotopes but different water content, microbiota composition, and organic matter. Moonmilk parts/niches showed higher values of microbial biomass and biodiversity compared to the bedrock (not showing moonmilk development signs) and the waters (collected below dripping moonmilk), indicating the presence of more complex microbial communities linked to carbonate rock interactions and biomineralization processes. Although each moonmilk niche was characterized by a specific microbiota as well as a distinct organic carbon profile, statistical analyses clustered the samples in two main groups, one including the moonmilk lateral part and the bedrock and the other including the core and apical parts of the speleothem. The organic matter profile of both these groups showed two well-differentiated organic carbon groups, one from cave microbial activity and the other from the leaching of vascular plant litter above the cave. Correlation between organic matter composition and microbial taxa in the different moonmilk niches were found, linking the presence of condensed organic compounds in the apical part with the orders Nitrospirales and Nitrosopumilales, while different taxa were correlated with aromatic, lignin, and polysaccharides in the moonmilk core. These findings are in line with the metabolic potential of these microbial taxa suggesting how the molecular composition of the preserved organic matter drives the microbiota colonizing the different moonmilk niches. Furthermore, distinct bacterial and archaeal taxa known to be involved in the metabolism of inorganic nitrogen and C1 gases (CO2 and CH4) (Nitrospira, Nitrosopumilaceae, Nitrosomonadaceae, Nitrosococcaceae, and novel taxa of Methylomirabilota and Methanomassiliicoccales) were enriched in the core and apical parts of the moonmilk, probably in association with their contribution to biogeochemical cycles in Grotta Nera ecosystem and moonmilk development. Conclusions: The moonmilk deposits can be divided into diverse niches following oxygen and water gradients, which are characterized by specific microbial taxa and organic matter composition originating from microbial activities or deriving from soil and vegetation above the cave. The metabolic capacities allowing the biodegradation of complex polymers from the vegetation above the cave and the use of inorganic nitrogen and atmospheric gases might have fueled the development of complex microbial communities that, by interacting with the carbonatic rock, led to the formation of these massive moonmilk speleothems in Grotta Nera. [ABSTRACT FROM AUTHOR]

Subsurface karst caves provide unique opportunities to study the deep biosphere, shedding light on microbial contribution to elemental cycling. Although ammonia oxidation driven by both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) is well explored in soil and marine environments, our understanding in the subsurface biosphere still remained limited to date. To address this gap, weathered rock and sediment samples were collected from the Xincuntun Cave in Guilin City, an alkaline karst cave, and subjected to high-throughput sequencing and quantification of bacterial and archaeal amoA, along with determination of the potential nitrification rates (PNR). Results revealed that AOA dominated in ammonia oxidation, contributing 48-100% to the PNR, and AOA amoA gene copies outnumbered AOB by 2 to 6 orders. Nitrososphaera dominated in AOA communities, while Nitrosopira dominated AOB communities. AOA demonstrated significantly larger niche breadth than AOB. The development of AOA communities was influenced by deterministic processes (50.71%), while AOB communities were predominantly influenced by stochastic processes. TOC, NH4 +, and Cl- played crucial roles in shaping the compositions of ammonia oxidizers at the OTU level. Crossdomain co-occurrence networks highlighted the dominance of AOA nodes in the networks and positive associations between AOA and AOB, especially in the inner zone, suggesting collaborative effort to thrive in extreme environments. Their high gene copies, dominance in the interaction with ammonia oxidizing bacteria, expansive niche breadth and substantial contribution to PNR collectively confirmed that AOA better adapted to alkaline, oligotrophic karst caves environments, and thus play a fundamental role in nitrogen cycling in subsurface biosphere. [ABSTRACT FROM AUTHOR]

Neoteny is a developmental strategy wherein an organism reaches sexual maturity without associated adult characteristics. In salamanders, neoteny takes the form of individuals retaining aquatic larval characteristics such as external gills upon maturation. Mole salamanders (Ambystoma) occupy a wide range of habitats and areas across the North American continent, and display examples of non‐neotenic, facultatively neotenic and obligate neotenic species, providing high variation for investigating the factors influencing the evolution of neoteny. Here, we use phylogenetic comparative methods to test existing hypotheses that neoteny is associated with elevational and latitudinal distribution, cave‐associated isolation, and hybridisation‐related polyploidy. We also test if neoteny influences the diversity of habitats a species can occupy, since the restriction to an aquatic life should constrain the availability of different niches. We find that neoteny tends to occur in a narrow latitudinal band between 20–30° North, with particularly narrow latitudinal ranges for obligate compared to facultative neotenic species (16–52° North). We also find that facultatively neotenic species occur at elevations more than twice as high as other species on average, and that species with a higher frequency of neoteny typically have lower habitat diversity. Our results suggest that evolutionary transitions between non‐neotenic and facultative neoteny states occur at relatively high and approximately equal rates. Moreover, we estimate that obligate neoteny cannot evolve directly from non‐neotenic species (and vice versa), such that facultative neoteny acts as an evolutionary 'stepping stone' to and from obligate neoteny. However, our transition rate estimates suggest that obligate neoteny is lost >4‐times faster than it evolves, partly explaining the rarity of obligate species. These results support the hypothesis that low latitudes favour the evolution of neoteny, presumably linked to more stable (aquatic) environments due to reduced seasonality, but once evolved it may constrain the diversity of habitats. [ABSTRACT FROM AUTHOR]

Introduction: The presence of brackish water resources is significant in addressing the scarcity of freshwater resources, particularly in the Xinjiang region. Studies focused on reducing adverse effect of brackish water irrigation based on using ionized brackish water, as well as on investigating its effects on fibre and oil plant production processes, remain incipient in the literature. Some benefits of this technique are the optimization of the quality and quantity of irrigation water, economy of water absorbed by the plants, improvement in the vegetative growth and productivity compared to irrigation using conventional brackish water. Thus, the aim of the current study is to assess the effect of different nitrogen application rates on soil water and salinity, cotton growth and water and nitrogen use efficiency. Methods: The experimental design consisted of completely randomized design with two water types (ionized and non-ionized) and six nitrogen application rates with four replications. Results: Irrigation conducted with ionized brackish water and different nitrogen application rates had significant effect on the plant height, leaf area index, shoot dry matter, boll number per plant and chlorophyll content. The study also demonstrated significant effects of ionized brackish water on soil water content and soil salinity accumulation. The highest cotton production was achieved with the use of 350 kg·ha-1 of ionized brackish water for irrigation, resulting in an average increase of 11.5% compared to the use of non-ionized brackish water. The nitrogen application exhibits a quadratic relationship with nitrogen agronomic use efficiency and apparent nitrogen use efficiency, while it shows a liner relationship with nitrogen physiological use efficiency and nitrogen partial productivity. After taking into account soil salinity, cotton yield, water and nitrogen use efficiency, the optimal nitrogen application rate for ionized brackish water was determined to be 300 kg·ha-1. Discussion: It is hoped that this study can contribute to improving water management, reducing the environmental impact without implying great costs for the producer. [ABSTRACT FROM AUTHOR]

Quaternary stable isotope records of marine and lacustrine carbonate deposits as well as speleothems were extensively studied to reconstruct global and regional climatic evolution. This study demonstrates how stable isotope records of travertine provide fundamental information about climate and the consequences of its evolution on groundwater level fluctuations. The deposition of the Lapis Tiburtinus travertine succession occurred during the Late Pleistocene (150-30 ka), coeval with the last activity of the Colli Albani volcanic complex. Two boreholes (Sn1 and Sn2) were drilled into the Acque Albule Basin (23 km E of Rome), crossing the entire Lapis Tiburtinus succession. The Sn1 borehole in the central part of the basin crosscuts a travertine succession of 62.1 m in thickness, while the Sn2 borehole in the southern part of the basin is characterized by a travertine succession 36.3 m in thickness. Carbon and oxygen stable isotope ratios were analysed on 118 samples (59 samples both for Sn1 and Sn2 boreholes) representative of the entire Lapis Tiburtinus travertine succession crossed by the boreholes. Values, measured and correlated in the two drilled boreholes, permitted determination of the sensitivity of the travertine depositional system to glacial and interglacial cycles, unravelling the complex oxygen and carbon cycle dynamic recorded in such sedimentary succession. Moreover, the results obtained correlated with available pollen curves of the Mediterranean area (from the Castiglione crater, 25 km E of Rome). Regional and global oxygen isotope continental and marine curves, calibrated with the stratigraphy of the Acque Albule Basin, and available U/Th dating allow the identification of at least three phases of the last interglacial (Marine Isotope Stage 5-MIS5). The carbon isotope record, compared with CO2 flux reconstructed and associated with the volcanic activity of the Colli Albani volcanic complex, instead shows an influence from groundwater level changes. In particular, positive shifts that occurred during arid phases are associated with a lower groundwater level and increased CO2 degassing, inducing a major fractionation effect on carbon isotopes. Instead, the negative shifts occurring during more humid periods indicate the inhibition of CO2 degassing and increase in pressure, attesting to a rise in groundwater level. In this view, travertine deposits, frequently studied to define the tectonic setting and activity of the area where they develop, can thus also be used as a tool to understand climate changes and groundwater variations apparent in their stable oxygen and carbon isotope signature. [ABSTRACT FROM AUTHOR]

Understanding the distribution of water and nitrate nitrogen in the soil profile is crucial for the reasonable operation of fertigation, and it is also fundamental for controlling and regulating nitrate nitrogen in the root zone, thereby meeting a crop's requirements. The application rates of fertilizer and water directly influence this distribution of water and nitrate nitrogen. However, the effects in Aeolian sandy soil, a type of developing soil bordering deserts, remain ambiguous. In this study, field experiments for different drip fertigation treatments in Aeolian sandy soil were conducted to investigate the soil water distribution, as well as that of nitrate nitrogen. A completely randomized experimental design was implemented, encompassing three levels of irrigation amount: low (W1), medium (W2), and high (W3), and three levels of nitrogen application rate: low (F1), medium (F2), high (F3). After the completion of each irrigation treatment, soil samples were extracted at 10–20 cm intervals. The soil water and nitrate nitrogen contents in the profiles of these samples were measured. The experimental results revealed that increasing the nitrogen application rate facilitated the retention of greater amounts of water and nitrate nitrogen in the soil profile. However, with an increase in the nitrogen application rate, both soil water and nitrate nitrogen exhibited a radial tendency to move away from the drip emitter. Some moved upward and accumulated in surface soil near a ridge furrow, while some moved downward and remained in a deeper area approximately 30 cm horizontally from the emitter at depths of 40–60 cm. The uniformity of the water distribution decreased with increasing nitrogen application under low water conditions, with a reversal of this trend observed in medium and high water treatments. The effect of nitrogen application level on the uniformity of the nitrate nitrogen distribution was not significant. There was no significant correlation between the average soil water content and nitrate nitrogen content along the horizontal direction, however, a positive correlation existed in the vertical direction. In the whole profile, increasing the nitrogen application enhanced the correlation under low water conditions, but under medium and high water conditions, this trend was the opposite. This implies that, to avoid nitrate nitrogen leaching or limiting in a specific area, a moderate nitrogen application level is advisable. Under low water conditions, nitrogen application showed a positive effect on the nitrate nitrogen content, and a higher application is recommended. In cases of substantial water irrigation or rainy years, the nitrogen application rate should be decreased. [ABSTRACT FROM AUTHOR]

Studies on the development of the root system can provide important information about responses to different management strategies, such as the use of lower quality water, also evaluating the interaction between plants and the physical properties of the soil. This study tested the hypothesis that irrigation with treated sewage effluent (TSE) supplies the water needs of sugarcane plants, increasing root growth and improving the physical properties of the soil. We evaluated the effects of subsurface dripping with TSE or surface reservoir water (SRW) on the root development of first ratoon cane (Saccharum officinarum L.) and the physical properties of dystrophic red latosol. Irrigation treatments were applied at 20 and 40 cm and soil properties were evaluated at soil depth layers of 0–20, 20–40, 40–60, and 60–80 cm. We verified that under irrigation with TSE and SRW, shallower soil layers present better porosity, soil aggregation, and aggregate stability conditions, parameters that improve the root system development and plant growth. On the other hand, deeper soil layers have lower macroporosity and higher total clay volume, indicating the possibility of compaction and greater limitations for sugarcane root growth. These results are important for understanding soil quality and provide significant information for agricultural management and for the implementation of sustainable soil conservation practices. This study shows the efficiency of TSE as an alternative water source for sugarcane crops. [ABSTRACT FROM AUTHOR]

Over 3000 iron formation caves (IFCs) have formed in erosion-resistant Fe(III)-rich rocks throughout Brazil. Microbial Fe(III) reduction occurs in IFCs, where a microbe-rich, Fe(III)-depleted paste (sub muros) is found behind an Fe(III)-(hydr)oxide crust in the ceiling/walls. Microbial Fe(III) reduction in sub muros appears to be responsible for the transformation of Fe(III) to more soluble Fe(II), which is removed, leading to cave formation. This process of biospeleogenesis is likely controlled by O2 availability, which is linked to seasonal changes. Here, we studied the effects of alternating anoxia/oxia on the microbial community and on Fe solubility in banded iron formation (BIF), a rock type consisting of layered Fe(III)-oxide and silicate. Incubations of synthetic pore water, pulverized BIF, and sub muros were prepared and incubated under anoxia, during which BIF-Fe(III) reduction proceeded. During the Fe(III) reduction period, Firmicutes and/or Alphaproteobacteria were enriched, and genes involved in Fe(III) and sulfate reduction were detected in the metagenomes. Fe(II) oxidation genes, which were detected in the fresh sub muros, were not found. Upon the addition of atmospheric O2, Fe(III) reduction was arrested, and incomplete Fe(II) oxidation occurred. Betaproteobacteria, Gammaproteobacteria, and Chloroflexi increased in relative abundance following aeration, and Fe(III) reduction genes were still identified. Our results demonstrate that the sub muros microbial community retains the ability to reduce Fe(III) and drive speleogenesis despite fluctuations in O2 levels. [ABSTRACT FROM AUTHOR]

The Asian monsoon (AM) has direct and profound effects on the livelihoods of residents in South Asia and East Asia. Modern observations have shown multi-decadal alternations of flood and drought periods in these regions, likely influenced by climatic processes such as the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation. However, our understanding of the multi-decadal variability of the AM under different climatic conditions remains uncertain. In this study, we collected an annually laminated and 780-mm stalagmite (sample number: BJ7) from Binjia (BJ) Cave in southwestern China, which is deeply influenced by the Asian monsoon system. Based on this sample, we established 6-year resolution and multi-proxy records for the Asian summer monsoon (ASM) variabilities during the early last termination, spanning from 18.2 to 16.1 ka BP. Measurements of five pairs of uranium and thorium solutions for 230Th dating were conducted using a multi-collector inductively coupled plasma mass spectrometer (MC-ICP- MS), and 374 pairs of stable isotope (δ18O and δ13C) analyses were run on a Kiel Carbonate Device connected with Finnigan MAT-253 at Nanjing Normal University. The chronology for this sample was established by annual layer counting anchored with 230Th dating results. Our BJ7 δ18O record replicates well with other Chinese δ18O records on the general trend, all of which are superimposed by frequent multidecadal-scale fluctuations at approximately 60 years periodicity. Inspection of the 60-year band in BJ7 δ18O and δ13C records and results of the cross-wavelet analysis indicate coherent changes in the ASM and biomass production/karst processes during most of the studied period. In addition, the 60-year band of BJ7 and NGRIP δ18O records are consistent, implying the impacts of the high-latitude North Atlantic or Atlantic Multidecadal Oscillation on the ASM. Our study suggests that the 60-year variability should be an intrinsic feature of the climate system regardless of glacial or interglacial backgrounds. [ABSTRACT FROM AUTHOR]

Mediterranean marine caves have been categorized as both biodiversity reservoirs and vulnerable habitats. However, only a few studies have focused on Porifera assemblages within marine caves along the Adriatic Apulian coast (southern Italy). In this study, the sponge fauna of the Rondinella cave, a semi-submerged marine cave along the coast of Bari (Southern Adriatic Sea), was investigated for the first time. The use of advanced image analysis in combination with targeted sampling has made it possible to determine the spatial distribution and diversity of Porifera along a transect from the entrance to the end of the cave. Data analysis clustered the stations into two groups, separated according to the distance from the entrance and corresponding to the cave entrance and the semi-dark zone. Sponges were found at all stations covering a considerable part of the substrate, with the highest cover values occurring in the semi-dark zone. A total of 54 sponge taxa were identified: 49 Demospongiae, 3 Homoscleromorpha, and 2 Calcarea. Six species are new records for the Apulian marine caves, one species represents a new record for marine caves, and two species are new findings for the southern Adriatic Sea. [ABSTRACT FROM AUTHOR]

Geodiversity elements contribute significantly to local and global hydrological, biogeochemical and ecosystem services and as such, fire is a potentially disruptive force with long-term implications. from limiting karstic speleothems formation, to compounding impacts of peat-fire-erosion cycles. Geodiversity elements additionally possess important cultural, aesthetic, and environmental values, including the support of ecosystem services. Hence, assessments of potential fire damage should consider implications for land users, society, and culture, alongside the geomorphic impacts on geodiversity elements. With a view to providing a concise set of descriptors of the response of geodiversity elements to fire, we qualify and in places, quantify, how fire may degrade geosystem function. Where possible, we highlight the influence of fire intensity and frequency gradients, and cumulative fire, in the deterioration of geodiversity values. Geoconservation is integral to protected areas with implications from fire effected geodiversity functions and values presenting issues for management, with potential consequences extending through to delisting, degazetting, and resizing of protected areas. Future research in reserve systems should concentrate on understanding the synergistic and compounding effects of fire on the geophysical landscape. Geodiversity provides valuable benefits through its existence and function. Fire can degrade geodiversity elements in several ways, on vast spatial and temporal scales, with implications for geoconservation and protected areas management. Understanding recovery rates of geodiversity elements, and the cumulative impact of fire on geodiversity, requires further research. [ABSTRACT FROM AUTHOR]

Caves are ubiquitous subterranean voids, accounting for a still largely unexplored surface of the Earth underground. Due to the absence of sunlight and physical segregation, caves are naturally colonized by microorganisms that have developed distinctive capabilities to thrive under extreme conditions of darkness and oligotrophy. Here, the microbiomes colonizing three frequently studied cave types, i.e., limestone, sulfuric acid speleogenetic (SAS), and lava tubes among volcanic caves, have comparatively been reviewed. Geological configurations, nutrient availability, and energy flows in caves are key ecological drivers shaping cave microbiomes through photic, twilight, transient, and deep cave zones. Chemoheterotrophic microbial communities, whose sustenance depends on nutrients supplied from outside, are prevalent in limestone and volcanic caves, while elevated inorganic chemical energy is available in SAS caves, enabling primary production through chemolithoautotrophy. The 16S rRNA-based metataxonomic profiles of cave microbiomes were retrieved from previous studies employing the Illumina platform for sequencing the prokaryotic V3-V4 hypervariable region to compare the microbial community structures from different cave systems and environmental samples. Limestone caves and lava tubes are colonized by largely overlapping bacterial phyla, with the prevalence of Pseudomonadota and Actinomycetota, whereas the codominance of Pseudomonadota and Campylobacterota members characterizes SAS caves. Most of the metataxonomic profiling data have so far been collected from the twilight and transient zones, while deep cave zones remain elusive, deserving further exploration. Integrative approaches for future geomicrobiology studies are suggested to gain comprehensive insights into the different cave types and zones. This review also poses novel research questions for unveiling the metabolic and genomic capabilities of cave microorganisms, paving the way for their potential biotechnological applications. [ABSTRACT FROM AUTHOR]

The karst cave serves as the primary storage space in carbonate reservoirs. Simultaneously connecting multiple karst caves through hydraulic fracturing is key to the efficient development of carbonate reservoirs. However, there is lack of systematic research on the mechanisms and influencing factors of fracture propagation in carbonate rocks. This paper established models including karst cave models, single natural fracture-cave models, and multiple natural fracture-cave models based on the discrete lattice method. It thoroughly studied how geological and operational factors affect the fracture propagation and the connectivity of karst caves. The final step involved establishing a prototype well model and optimizing operation parameters. The research indicates that an increase in the Young's modulus and pore pressure of karst cave could facilitate hydraulic fracture connecting with caves. When the pore pressure is lower than that in the matrix, it will generate a repulsive effect on hydraulic fractures. The natural fracture along the hydraulic fracture path significantly facilitates the connection with caves. When the wellbore azimuth is less than 60°C, the fracture's diversion radius is small, and hydraulic fractures primarily connect with karst cave through natural fractures. When the wellbore azimuth exceeds 60°C, the fracture's diversion radius increases. Under the combined action of hydraulic fractures and natural fractures, the stimulated volume of the karst cave noticeably increases. Under the same liquid volume, increasing the injection rate could enhance the cave stimulated volume. Combining the findings from numerical simulation studies resulted in the development of a diagram that depicts the connectivity of karst caves, providing valuable insight for hydraulic fracturing operations in carbonate reservoirs. [ABSTRACT FROM AUTHOR]

The timing and geographic extent of a potential "4.2 ky event" remain highly contested. Here we present records of ENSO variability at 3.8 kyBP and 4.1 kyBP derived from a Borneo stalagmite, which suggest a significant change in ENSO properties between these time intervals. The Borneo records show evidence of significantly reduced ENSO activity at 4.1 kyBP, relative to other measured windows within the Holocene. This reduced ENSO activity coincides with a period of drier conditions and enhanced dust events in the Middle East that took place ∼4.0–4.3 kyBP. The Borneo records show evidence of enhanced ENSO activity at 3.8 kyBP. Various hydroclimate changes attributed to the "4.2 ky event" in many regions may thus be reflecting a shift from reduced to enhanced El Niño activity that occurred between 3.8 kyBP to 4.0 kyBP. Plain Language Summary: Research suggests that a significant climate shift may have occurred around 4,000 years ago, though the exact timing and global extent of the event remain uncertain. A change in the frequency or magnitude of the El Niño‐Southern Oscillation (ENSO) is one hypothesized cause, however there are currently few high‐resolution records which resolve ENSO variability 4,000 years ago. We present a new western tropical Pacific stalagmite‐based record of ENSO activity, which shows a significant minimum in ENSO variability around 4,100 years ago. This reduced ENSO activity coincides with a centennial‐scale climate event in the Middle East characterized by drier conditions and enhanced dust events. The Borneo record also shows a significant increase in El Niño/La Niña activity that took place by 3,800 years ago. Hydroclimate changes around 4,000 years ago found in records from multiple regions around the world may therefore reflect a shift from reduced to enhanced El Niño activity. Key Points: Borneo stalagmite record shows anomalously low El Niño‐Southern Oscillation variability in a 135‐year‐long window, centered at 4.1 kyBPBorneo stalagmite record suggests an abrupt shift from low to high El Niño‐Southern Oscillation variability between 3.8 and 4.0 kyBPRecords of tropical hydroclimate change ∼4,000 years ago may reflect a significant increase in El Niño variability [ABSTRACT FROM AUTHOR]

When a super-large diameter shield tunnel passes through a strongly karst-developed area, in order to ensure the stability of the tunnel and economy of karst reinforcement, the reasonable treatment range for a huge number of karst caves needs to be researched. Based on a karst treatment project of a shield tunnel with a diameter of 14.5 m, this paper studies the influence of intrusive fully filled karst caves on the stability of the lining and excavation face by using theoretical calculation. In addition, the safe distance between the tunnel and karst caves outside the tunnel is proposed through numerical simulation, and the corresponding treatment range is obtained. The results show that the bearing capacity of the lining has a certain reserve when the intrusive cave is smaller than a certain size, and the caves filled with plastic or hard plastic clay have sufficient antifracturing ability. Therefore, some small fully filled caves inside the tunnel profile can be left unreinforced. On the other side, the critical safe distance is only 1–2 m for the caves with a size of 3 m, so the outside caves with a size less than 3 m can be left unreinforced in the treatment range farther away from the tunnel. The proposed treatment range is close to similar projects that have been built, indicating that analysis results are reasonable. [ABSTRACT FROM AUTHOR]

The Malagasy Summer Monsoon is an important part of the larger Indian Ocean and tropical monsoon region. As the effects of global warming play out, changes to precipitation in Madagascar will have important ramifications for the Malagasy people. To help understand how precipitation responds to climate changes we present a long-term Holocene speleothem record from Anjohibe, part of the Andranoboka cave system in northwestern Madagascar. To date, it is the most complete Holocene record from this region and sheds light on the nature of millennial and centennial precipitation changes in this region. We find that over the Holocene, precipitation in northwestern Madagascar is actually in phase with the Northern Hemisphere Asian monsoon on multi-millennial scales, but that during some shorter centennial-scale events such as the 8.2 ka event, Anjohibe exhibits an antiphase precipitation signal to the Northern Hemisphere. The ultimate driver of precipitation changes across the Holocene does not appear to be the meridional migration of the monsoon. Instead, zonal sea surface temperature gradients in the Indian Ocean seem to play a primary role in precipitation changes in northwestern Madagascar. [ABSTRACT FROM AUTHOR]

Introduction: Quinoa a crop with high nutritional value has the widespread adaptability to different climates and there is an increased demand for this product in the world. Characterized by roots with extensive penetration capabilities and wide, alternate leaves giving rise to diverse inflorescences, quinoa plants exhibit variable heights ranging from 20 to 300 cm. The duration of their growth phase spans 95 to 125 days' contingent upon cultivar selection and prevailing climatic conditions. Materials and methods: In order to reduce chemical fertilizers consumption through using organic fertilizers a two-year study was conducted at the Research Farm of the University of Kurdistan, Iran, during the 2021-2022 growing seasons. In this study the effects of varying levels of irrigation and vermicompost application on soil characteristics and quinoa (Chenopodium quinoa) yield were investigated. The experiments were arranged as split plots within a randomized complete block design. The main factor consisted of four irrigation levels (50%, 75%, 100%, and 125% of quinoa's water requirement), while the sub-factor encompassed four vermicompost application rates (0, 5, 10, and 15 tons per hectare). The irrigation method employed was a drip-tape irrigation system with a seven-day interval between irrigations, and water quantities were measured using a volumetric meter on the main pipeline. Results: The results demonstrated that the highest levels of available soil phosphorus (21.83 mg kg-1) and soil ammonium (36.08 mg kg-1) were observed in the treatment receiving 50% of quinoa's water requirement combined with 15 tons per hectare of vermicompost. Additionally, the application of 15 tons per hectare of vermicompost led to the highest concentrations of soil nitrate (14.16 mg kg-1), available potassium (144.62 mg kg-1), and quinoa seed yield (1784.01 kg ha-1)). Over both years, the greatest activity of alkaline and acid phosphatase enzymes was noted in the treatment receiving 125% of quinoa's water requirement in combination with 15 tons per hectare of vermicompost. Vermicompost application was found to enhance yield and ameliorate drought stress by enhancing soil physical and chemical properties and improving soil moisture retention. [ABSTRACT FROM AUTHOR]