Ground Pattern Research Articles

Diversity of attachment systems in heelwalkers (Mantophasmatodea) – highly specialized, but uniform

BackgroundHeelwalkers possess a highly modified tarsal attachment system. All extant species lift the distalmost tarsomere permanently off the substrate and primarily use their euplantulae for locomotion. The combination of a smooth adhesive pad (arolium) on the pretarsus and fibrillary attachment pads on the euplantulae offers valuable insights for translational approaches, but its infra-order diversity remains unexplored.ResultsWe explored the morphology of the tarsal attachment apparatus of Mantophasmatodea based on a representative taxon sampling spanning a large fraction of species of this group and compared morphological differences in the specialized morphology of this system across species and sexes. Our scanning electron microscope investigation of the tarsi of 11 species (52% of all described extant species) revealed an overall very consistent ground pattern and almost no specific adaptations. There are only minor, but mostly clade-specific differences in the shape of the adhesive setae on the tarsal euplantulae and in the morphology and density of the acanthae on the pretarsal arolium. Both features differ primarily between Austrophasmatidae in comparison to the remaining Mantophasmatodea taxa.ConclusionWe conclude that the strong specialization of the mantophasmatodean tarsal attachment sufficiently copes with the diversity of substrates the insects are exposed to.

Ultrastructure and functional morphology of the mouthparts in Pterygosoma pseudotrapelus (Bochkov, Melnikov et Nazarov, 2009) (Acariformes, Pterygosomatidae)

ABSTRACT The mouthparts of the pterygosomatid mite, Pterygosoma pseudotrapelus (Bochkov, Melnikov et Nazarov, 2009) (Acariformes, Pterygosomatidae), were studied with light microscopy, scanning (SEM) and transmission (TEM) electron microscopy. The mouthparts are located within the (pseudo)tagma gnathosoma. The gnathosoma is formed of the two frontal body segments with their appendages – chelicerae and pedipalps (palps). The two-segmented chelicerae occupy a dorsal position, whereas the infracapitulum – a derivative of the fused palp coxae – occupies a ventral position. The basal cheliceral segments are widen basally, and contain protractors and retractors of the movable digits and nerve fibres. The distal cheliceral segments, the movable digits, are small and stout, bear a lateral spur, and are provided with tips looking aside. The fixed digits are long and branched. The frontal projection of the infracapitulum, the hypostome, partly envelopes laterally the distal cheliceral portions. The dorsal wall, or the roof of the infracapitulum, consists of the long labrum anteriorly possessing its own muscles and the complexly organized epistome posteriorly. The epistome and its posterior projections – the epistomal apodemes serve for origin of the pharyngeal dilators. The wide cap-shaped pharynx goes along the bottom of the infracapitulum and attaches to it. The two sigmoid pieces articulate posteriorly to the epistome and serve for origin of different sets of muscles performing retraction and protraction of the chelicerae and retraction of the gnathosoma. The peritremes are exceedingly long and protrude freely above the chelicerae. The general architecture of the mouthparts of P. pseudotrapelus corresponds more to the anystid than eleutherengonid ground pattern.

Comparative microscopic anatomy of Schizomida – 2. The rostrosoma and the pharyngeal suction pump

This paper tests hypotheses of independent parallel evolution of the rostrosoma among euchelicerate taxa by analyzing the microscopic anatomy and histology of the rostrosoma of Uropygi (Schizomida and Thelyphonida) and comparing it with the morphology of the snout region in other euchelicerates. The study employs analysis of multiple histological serial sections, μCT-imaging, and graphical as well as computer-based 3D reconstruction. Results of the study are that Thelyphonida and Schizomida share the same morphology of the rostrosoma. The rostrosoma of both groups contains a unique arrangement of musculature that is functionally interpreted as pre-oral suction pump. This is followed by a pharyngeal suction pump. The muscles of the pharyngeal suction pump attach to the epistome and the epipharyngeal sclerite. Neither Schizomida nor Thelyphonida possess a postcerebral suction pump as reported earlier. The microscopic anatomy of the rostrosoma of both taxa is unique and does not compare with any of the other euchelicerates, thus supporting the idea of independent evolutionary origin of the rostrosoma. Thelyphonida, Amblypygi and Scorpiones share the occurrence of a large epipharyngeal/epistomal sclerite with associated musculature, which is a feature that lines up with the Arachnopulmonata concept. A comparison with all Euchelicerata taxa shows that the snout region is formed by homologous morphological elements but the specific arrangement, additions and reductions shape the formation of the rostrosoma, so that parallel evolution of homologous parts of the arachnid ground pattern can be assumed that has formed those elements into convergent morphologies.

A spectral approach to Hebbian-like neural networks

We consider the Hopfield neural network as a model of associative memory and we define its neuronal interaction matrix J as a function of a set of K×M binary vectors {ξμ,A}μ=1,...,KA=1,...,M representing a sample of the reality that we want to retrieve. In particular, any item ξμ,A is meant as a corrupted version of an unknown ground pattern ζμ, that is the target of our retrieval process. We consider and compare two definitions for J, referred to as supervised and unsupervised, according to whether the class μ, each example belongs to, is unveiled or not, also, these definitions recover the paradigmatic Hebb's rule under suitable limits. The spectral properties of the resulting matrices are studied and used to inspect the retrieval capabilities of the related models as a function of their control parameters.

Neuromuscular development in the emerging scyphozoan model system, Cassiopea xamachana: implications for the evolution of cnidarian nervous systems.

The scyphozoan Cassiopea xamachana is an emerging cnidarian model system for studying regeneration, animal-algae symbiotic relationships, and various aspects of evolutionary biology including the early emergence of animal nervous systems. Cassiopea has a life cycle similar to other scyphozoans, which includes the alternation between a sessile, asexual form (polyp) and a sexually reproducing stage, the medusa. The transition between the two forms is called strobilation, where the polyp releases a miniature medusa, the iconic ephyra, that subsequently develops into the adult medusa. In addition, Cassiopea polyps may reproduce asexually by budding off free-swimming so-called planuloid buds. While the development of planuloid buds and polyps has been studied in some detail, little is known about the ontogeny of the sexually produced planula larva. Using immunofluorescence labeling and confocal microscopy, we examined neuromuscular development during metamorphosis of the planula larva into the juvenile polyp in C. xamachana. For this purpose, we used tyrosinated α-tubulin-, FMRFamide- and serotonin-like immunoreactivity together with phalloidin labeling. Our results show a planula nervous system that consists of a basiectodermal neural plexus with mostly longitudinally oriented neurites. This neural meshwork is connected to sensory neurons in the superficial stratum of the ectoderm, which are exclusively localized in the aboral half of the larva. During settlement, this aborally concentrated nervous system of the planula is replaced completely by the orally concentrated nervous system of the polyp. Adult polyps show an extensive nerve net with a loose concentration around the oral disc. These findings are consistent with data from other scyphozoans and most likely constitute a conserved feature of scyphozoan discomedusae. Taken together, the data currently available suggest an aborally concentrated nervous system including sensory cells as part of the neural ground pattern of cnidarian planula larvae. The reorganization of the nervous system from anterior to posterior in planula-to-polyp metamorphosis most likely also constitutes an ancestral trait in cnidarian evolution.

Discovery of a geomorphological analog to Martian araneiforms in the Qaidam Basin, Tibetan Plateau

Araneiforms are spider-like ground patterns that are widespread in the southern polar regions of Mars. A gas erosion process driven by the seasonal sublimation of CO<sub>2</sub> ice was proposed as an explanation for their formation, which cannot occur on Earth due to the high climatic temperature. In this study, we propose an alternative mechanism that attributes the araneiform formation to the erosion of upwelling salt water from the subsurface, relying on the identification of the first terrestrial analog found in a playa of the Qaidam Basin on the northern Tibetan Plateau. Morphological analysis indicates that the structures in the Qaidam Basin have fractal features comparable to araneiforms on Mars. A numerical model is developed to investigate the araneiform formation driven by the water-diffusion mechanism. The simulation results indicate that the water-diffusion process, under varying ground conditions, may be responsible for the diverse araneiform morphologies observed on both Earth and Mars. Our numerical simulations also demonstrate that the orientations of the saltwater diffusion networks are controlled by pre-existing polygonal cracks, which is consistent with observations of araneiforms on Mars and Earth. Our study thus suggests that a saltwater-related origin of the araneiform is possible and has significant implications for water searches on Mars.

Generalized complex variable analysis of shallow tunneling through multi-layered ground

The mechanical analysis of shallow tunnels crossing multiple ground layers is a common problem in urban underground engineering. Since the tunnel boundary intersects multiple ground layers, the challenges of mixed boundary value problem for composite boundary and the conformal mapping of irregular banding computational domain are faced in solving the multi-boundary problem. For this, a new solution strategy regarding the generalized complex variable method to calculate the mechanical responses of the multi-layered ground is proposed. The research object is divided into two independent objects including the complete multi-layered ground without tunnel and the complete tunnel boundary. Firstly, the mechanical responses of the complete multi-layered ground are solved through the superposition of multiple single-boundary contributions. Subsequently, the virtual boundary circle and its corresponding analytic functions are introduced in analyzing the tunnel boundary contribution. Finally, the solution for the stress and displacement field of the multi-layered ground is modified by superimposing the contribution of the virtual boundary circle, so that all the given boundary conditions are satisfied. The self-consistency and accuracy of the proposed method are validated by several examples. The characteristics of the displacement propagation of typical multi-layered ground patterns are analyzed based on the analytical solution. The proposed method can be used to analyze the mechanical responses of multi-layered ground with arbitrary intersections between the tunnel and ground boundaries.

Does atp8 exist in the mitochondrial genome of Proseriata (Metazoa: Platyhelminthes)?

The adenosine triphosphate (ATP) synthase F0 subunit 8 gene (atp8) had been believed to be absent in mitochondrial genomes of platyhelminths until the late 2010s, since when multiple lines of emergent evidence have suggested that this gene is actually present, albeit in highly derived forms, throughout the entire phylum except for the parasitic Neodermata (tapeworms, flukes, and their kin). Of about 11 non-parasitic (turbellarian) major platyhelminth subtaxa, the existence of atp8 has hitherto been documented in five (Catenulida, Macrostomorpha, Polycladida, Rhabdocoela, and Tricladida), while it remains open in the remaining six (Prorhynchida, Gnosonesmida, Proseriata, Fecampiida, Prolecithophora, and Bothrioplanida). Here we report the mitochondrial genome sequence of an undetermined marine interstitial turbellarian species in the genus NematoplanaMeixner, 1938 as the first representative of Proseriata. This circular genome comprises 16,106 bp (but potentially 18,812–19,277 bp when unresolved, non-coding tandem repeats are considered) and includes 38 genes, viz. 23 transfer RNA genes, 13 protein-coding genes (including the putative atp8), and two ribosomal RNA genes. The putative atp8 in Nematoplana sp. was not annotated by a standard automated procedure but was detected by manual inspection. If it encodes a translated product, it consists of 156 bp, with the potential 52-amino-acid-residue product beginning with MPHV, instead of the metazoan-canonical MPQL, and containing a single putative transmembrane region expanding from the 7th to the 29th amino-acid positions. While our finding seemingly strengthens the hypothesis that atp8 is in the ground pattern of flatworm mitochondrial genomes, whether the putative atp8 in flatworms is actually transcribed and translated to form a functional ATP synthetase F0 subunit should be tested in future studies.

First mitochondrial genomes of Anaspidacea (Malacostraca, Crustacea) and the phylogenetic relationships of mountain shrimps (AnaspidesThomson, 1894) and their relatives within Anaspidesidae

AbstractWe present the first complete mitochondrial genomes for Anaspidacea by sequencing 24 specimens from 12 different species in four genera (AnaspidesThomson, 1894; ParanaspidesSmith, 1908; AllanaspidesSwain, Wilson, Hickman & Ong, 1970; and MicraspidesNicholls, 1931). We recovered 20 complete (13 protein coding genes, two ribosomal RNA genes, 22 transfer RNAs), and four partial mitogenomes. The full mitogenomes range in length from 15,213 bp to 17,962 bp. We found five different gene orders and reconstruct the ground pattern of Anaspidacea, which differs from the hypothetical pancrustacean ground pattern by the translocation and reversal of tRNA-L1. The same translocation is also found in Euphausiacea and could represent a synapomorphy of these two taxa. Moreover, we reconstruct the phylogenetic relationships of the Anaspidesidae using a data set consisting of the mitochondrial protein coding genes, the two ribosomal RNAs as well as nuclear 18S and 28S rRNA. Our results strongly corroborate the monophyly of all three anaspidesiid genera, with Paranaspides as the sister group to Anaspides, which together, are sister to Allanaspides. Lastly, we resolve the main phylogenetic relationships within Anaspides.

On latches in biological systems: a comparative morphological and functional study of the retinaculum and the dens lock in Collembola

BackgroundSpringtails have the ability to jump using morphological structures consisting of a catapult, the furca, and a latching system constructed with interaction of the retinaculum and the dens lock. The retinaculum engages in the furca at the dens lock in order to form a spring mechanism. They exhibit diversified morphological traits that serve as adaptations to a variety of terrestrial strata and aquatic surface environments. This comparative morphofunctional study centered on the retinaculum and the furcular region of the dens lock aims to describe the morphological variation between taxa and provide insights into the functional dynamics of the latching mechanism at work in the jumping apparatus. Using SEM, µCT and cLSM, we compared representatives of Collembola taxa, Poduromorpha (Neanura muscorum and Podura aquatica), Symphypleona (Dicyrtomina ornata) and Neelipleona (Megalothorax minimus), and examined extracts of the environment in which they were collected.ResultsA retinaculum is absent in N. muscorum, although vestigial muscles were found. Abdominal musculature varies significantly, being more abundant in springtails with clear segmentation (N. muscorum and P. aquatica), and reduced in springtails with fused segmentation (D. ornata and M. minimus). The M.a-ret varies as regards architecture and point of connection with the ramus, which is lateral in P. aquatica and median in the other species studied. The number of teeth in the retinaculum ramus also varies between three in M. minimus and four in the other species. The dens lock of all species studied has two locks and two furrows.ConclusionsThe retinaculum and dens lock interact in a key-lock relationship. The latching and unlatching mechanism from the retinaculum and dens lock appear to be similar in all the taxa examined, occurring by muscle force. This leads us to question the hypothesis that hemolymph pressure may be a force generator in jumping. We offer a reconstruction of the ground pattern of the retinaculum and dens lock and, in addition, an explanation of their functioning and the interaction between them. Finally, we frame the interaction between the retinaculum and the dens lock as a latch in a biological system, a mechanism which functions by force of physical contact.

Novel gene re-arrangement in the mitochondrial genome of Pisidiaserratifrons (Anomura, Galatheoidea, Porcellanidae) and phylogenetic associations in Anomura.

To improve the taxonomy and systematics of Porcellanidae within the evolution of Anomura, we describe the complete mitochondrial genomes (mitogenomes) sequence of Pisidiaserratifrons, which is 15,344 bp in size, contains the entire set of 37 genes and has an AT-rich region. Compared with the pancrustacean ground pattern, at least five gene clusters (or genes) are significantly different with the typical genes, involving eleven tRNA genes and four PCGs and the tandem duplication/random loss and recombination models were used to explain the observed large-scale gene re-arrangements. The phylogenetic results showed that all Porcellanidae species clustered together as a group with well nodal support. Most Anomura superfamilies were found to be monophyletic, except Paguroidea. Divergence time estimation implies that the age of Anomura is over 225 MYA, dating back to at least the late Triassic. Most of the extant superfamilies and families arose during the late Cretaceous to early Tertiary. In general, the results obtained in this study will contribute to a better understanding of gene re-arrangements in Porcellanidae mitogenomes and provide new insights into the phylogeny of Anomura.

The Complete Mitochondrial Genome of Torix tukubana (Annelida: Hirudinea: Glossiphoniidae).

Torix tukubana is a poorly understood proboscidate leech species, generally an ectoparasite on amphibian species. In this study, the complete mitochondrial genome (mitogenome) of T. tukubana was sequenced using next-generation sequencing (NGS), and the essential characteristics, gene arrangement, and phylogenetic relationship were analyzed. The results showed that the T. tukubana mitogenome was 14,814 bp in length, consisting of 13 protein-coding genes (PCGs), 22 tRNAs, 2 rRNAs, and 1 control region (CR). The mitogenome composition presented a strong A + T bias (73.6%). All tRNAs had the typical clover structure except the trnS1 (TCT), whose dihydrouridine (DHU) arm was short, having only one complementary base pair. Additionally, 8 gene order patterns were identified among 25 known Hirudinea species, and T. tukubana was identical to the Hirudinea ground pattern. A phylogenetic analysis based on 13 PCGs indicated that all the studied species clustered into three main clades. The relationships among Hirudinea species were basically consistent with their gene arrangement results, but different from their morphological taxonomy. T. tukubana was in the monophyletic group of Glossiphoniidae, a finding consistent with previous research. Our results provided the essential characteristics of the T. tukubana mitogenome. As the first complete mitogenome of Torix, it could offer valuable information for a systematic understanding of the Hirudinea species.

Study on the ground fraction of air tankers

Background The ground fraction refers to the ratio of the liquid collected on the ground to the dropped liquid, which is the key index used to assess the drop ground pattern of air tankers when combating wildfires. However, there is no quantitative mechanism model to estimate ground fraction. Aims and methods The current work aims to create a simple model of the ground fraction by directly using full-scale drop test data with different firefighting agents for fitting. Key results and conclusions The result shows that the ground fraction can be estimated by simple quantitative relationships despite significant differences between the conditions of the drop tests. These relationships include factors that can be manipulated during aircraft and release system design as well as during aerial firefighting operations. Implications Based on the presented model, an equation for the maximum coverage level of the mean liquid distribution is solved, and the induced effects of drop velocity, drop height, liquid viscosity and other factors on the ground pattern are revealed, which can provide direct predictions of ground drop distributions.

Integrative taxonomy of the subfamily Orbioninae (Crustacea: Isopoda) based on mitochondrial and nuclear data with evidence that supports Epicaridea as a suborder

Epicaridea is a group of isopods with high morphological diversity, reduction and loss of characters, and strong sexual dimorphism due to their parasitic lifestyles but their systematics is not well understood. Despite the use of nuclear and mitochondrial genes to test the phylogeny of many invertebrate groups, few molecular data from epicarideans are known, especially from the subfamily Orbioninae. Species in this group are obligate penaeoid shrimp parasites and the lack molecular data has hampered studies on the phylogeny of Orbioninae. To rectify this, mitochondrial and nuclear genes of 9 orbionine species are sequenced here. Compared to the isopod ground pattern, the sequences of orbionines seem to be more plastic near the control region and major translocations are located between rrns and cob. A phylogenetic analysis based on three data sets showed strong support for a monophyletic Orbioninae and that Epicaridea should be accepted at the rank of a suborder within Isopoda. The monophyly of Parapenaeon and Orbione is in doubt based on morphological and molecular data. The genus Parapenaeon is revised and a new genus Aparapenaeon is erected for Parapenaeon japonica and three closely related species.

A synthesis of the external morphology of cypridiform larvae of Facetotecta (crustacea: Thecostraca) and the limits of the genus Hansenocaris.

Although the naupliar and cypridiform stages of the enigmatic y-larvae of Facetotecta have been found in the marine plankton worldwide, they still represent the last significant group of crustaceans for which the adult forms are still unknown. From a number of y-cyprids representing different taxa from different locations, we employ scanning electron microscopy to describe fine morphological details of all external structures of this unique larval form. We document different segmentation patterns of the abdomen and presence/absence of the labrum and structural differences in the antennules, labrum, paraocular process, thoracopods, and telson lend support for the erection of several new genera as opposed to the single Hansenocaris. The data presented here emphasize the morphological limits of the genus Hansenocaris and the "bauplan" of cyprydiform larvae of Facetotecta. Although the optimum pathway is a joint analysis of both molecular and morphological characters, we use the morphological characters of y-cyprids to align them cladistically and determine the limits of the genus Hansenocaris s.s. and describe common characters for all y-cyprids including six pairs of the lattice organs instead five pairs considered as a ground pattern for all Thecostraca. We also determine plesiomorphic and apomorphic characters of all known y-cyprids and separate them from other thecostracan cypridiform larvae.

Reconstructing the neuromuscular ground pattern of phylactolaemate bryozoans: new data from the Lophopodidae

BackgroundThe solely freshwater inhabiting Phylactolaemata is a sister taxon to all other bryozoans. Among phylactolaemates, Lophopodidae represents an early branching clade that is therefore crucial for ground pattern reconstruction. While more recent morphological data of most phylactolaemate families are present, data of lophopodids are scarce. The genus Asajirella especially, which was previously assigned to the family Pectinatellidae, lacks any detailed analysis with more recent morphological methods.ResultsThis study provides the first morphological analyses of three lophopodid species using serial-sectioning histology and 3D reconstruction, but also immunocytochemical stainings and confocal laserscanning microscopy. There are several lophopodid-specific traits in the nervous system such as the large ganglion with extensive lumen and two prominent protrusions referred to as epistomial horns. The epistome in all lophopodids is rather small and dome-shaped. Contrary to previous reports, we can confirm that duplicature bands insert at the tentacle sheath rather than the diaphragmatic sphincter in all phylactolaemates. The morphology of the digestive tract of lophopodids is identical to other phylactolaemates and possesses exclusively circular muscles.ConclusionsAltogether, this study fills significant gaps in our knowledge on phylactolaemate neuromuscular systems and general morphology. It shows that the insertion of the duplicature bands at the tentacle sheath and the circular musculature of the digestive tract to be the ground pattern in phylactolaemates. In addition, we found apomorphic characters for lophopodids such as the dome-shaped epistome with its musculature and the voluminous ganglion with its epistomial horns, which aid in defining and delineating the family.

Active Ground Patterns Near Mars' Equator in the Glen Torridon Region of Gale Crater

AbstractOn Mars, near the equator, much of the terrain in Gale Crater consists of bedrock outcrops separated by relatively smooth, uniform regolith surfaces. In scattered sites, however, distinct patterns—in the form and texture of the ground surface—contrast sharply with the typical terrain and with eolian bedforms. This paper focuses on these diverse, intriguing ground patterns. They include ∼1 to >10 m‐long linear disruptions of uniform regolith surfaces, alignments, and other arrangements of similar‐sized rock fragments and shallow, ∼0.1 m‐wide sandy troughs 1–10 m in length. Similar features were recognized early in the Mars Science Laboratory (MSL) mission, but they received only limited attention until Curiosity, the MSL rover, encountered striking examples in the Glen Torridon region. Herein, the ground patterns are illustrated with rover images. Potential mechanisms are briefly discussed in the context of the bedrock composition and atmospheric conditions documented by Curiosity. The evidence suggests that the patterns are active forms of spontaneous granular organization. It leads to the hypothesis that the patterns arise and develop from miniscule, inferred cyclic expansion and contraction of the bedrock and regolith, likely driven by oscillating transfers of energy and moisture between the atmosphere and the terrain. The hypothesis has significant implications for studies of contemporary processes on Mars on both sides of the atmosphere‐lithosphere interface. The ground patterns, as well as ripples and dunes formed by the wind, constitute remarkable extra‐terrestrial examples of granular self‐organization, complex phenomena well known in diverse systems on Earth.

Examining ground and surface water changes in response to environmental variables, land use dynamics, and socioeconomic changes in Canada

Canada's abundant and high-quality water resources support a growing human population, as well as thriving industrial and agricultural economies. However, recent intense drought conditions have raised concerns for current water resource availability. Patterns of long-term ground and surface water (GSW) changes, and their response to environmental conditions, land-use dynamics, and socioeconomic changes are not well-understood across this large and diverse country. To address this crucial gap, we identified regions of ground and surface water (GSW) changes in all the Provinces of Canada between 2002 and 2016 from the Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) datasets. We explored the relationships between GSW changes and environmental, socioeconomic, and land-use dynamics over time. We found that all the Provinces of Canada gained a net 4.46 mm Liquid Water Equivalent (LWE) per year, equivalent to a total increase of 66.9 mm LWE. GSW increases were significantly associated with the normalized difference vegetation index and evapotranspiration rates. In contrast, GSW declines were significantly related to deforestation rate, urban expansion, and economic development (median household income). Despite apparent widespread post-drought recovery detected from 2002 to 2016, the rapid GSW declines were also observed in almost all of Western Canada and part of Ontario, amounting to a net loss of 66.13 mm. This indicates that a pronounced drought had emerged. It is anticipated that Canada will be experiencing more frequent and severe droughts under ongoing climate change and increasing demand for water resources.

One‐dimensional consolidation for multilayered unsaturated ground under multistage depth‐dependent stress

AbstractDue to the phenomenon of stress decay in space, the total vertical stress varies with depth in the layered soil stratum. The physical properties of unsaturated soil stratum and the nonuniformity of external load in vertical direction pose significant effects upon the consolidation process, while related works have viewed modest development at present. Therefore, the main objective of this study is to explore the one‐dimensional (1D) consolidation patterns of multilayered unsaturated ground considering depth‐dependent stress by a semi‐analytical procedure. According to the 1D consolidation theory of unsaturated soils put forward by Fredlund and Hasan, the semi‐analytical solutions of excess pore pressures and settlement are derived with the combination of Laplace transform and matrix transfer method. Crump's method is then adopted to obtain the analytical solutions in the time domain, and the corresponding computing programs are compiled. Furthermore, the validity work of proposed solutions is conducted by comparing the current solutions in this paper with degenerated ones under constant load in existing literature. Concentrating on the double‐layered unsaturated ground, and by considering different physical parameters of separate layer, the 1D consolidation characteristics under depth‐varying stress resulting from two‐stage load are investigated. The major conclusion can be drawn as that the settlement with constantly distributed stress along depth is overestimated compared with that considering the depth‐varying stress.

Assessing the influence of water sampling strategy on the performance of tracer-aided hydrological modeling in a mountainous basin on the Tibetan Plateau

Abstract. Tracer-aided hydrological models integrating water isotope modules into the simulation of runoff generation are useful tools to reduce uncertainty of hydrological modeling in cold basins that are featured by complex runoff processes and multiple runoff components. However, there is little guidance on the strategy of field water sampling for isotope analysis to run tracer-aided hydrological models, which is especially important for large mountainous basins on the Tibetan Plateau (TP) where field water sampling work is highly costly. This study conducted a set of numerical experiments based on the THREW-T (Tsinghua Representative Elementary Watershed - Tracer-aided version) model to evaluate the reliance of the tracer-aided modeling performance on the availability of site measurements of water isotope in the Yarlung Tsangpo river (YTR) basin on the TP. Data conditions considered in the numerical experiments included the availability of glacier meltwater isotope measurement, quantity of site measurements of precipitation isotope, and the variable collecting strategies for stream water samples. Our results suggested that (1) in high-mountain basins where glacier meltwater samples for isotope analysis are not available, estimating glacier meltwater isotope by an offset parameter from the precipitation isotope is a feasible way to force the tracer-aided hydrological model. Using a set of glacier meltwater δ18O that were 2 ‰–9 ‰ lower than the mean precipitation δ18O resulted in only small changes in the model performance and the quantifications of contributions of runoff components (CRCs, smaller than 5 %) to streamflow in the YTR basin. (2) The strategy of field sampling for site precipitation to correct the global gridded isotope product of isoGSM (isotope-incorporated global spectral model) for model forcing should be carefully designed. Collecting precipitation samples at sites falling in the same altitude tends to be worse at representing the ground pattern of precipitation δ18O over the basin than collecting precipitation samples from sites in a range of altitudes. (3) Collecting weekly stream water samples at multiple sites in the wet and warm seasons is the optimal strategy for calibrating and evaluating a tracer-aided hydrological model in the YTR basin. It is highly recommended to increase the number of stream water sampling sites rather than spending resources on extensive sampling of stream water at a sole site for multiple years. These results provide important implications for collecting site measurements of water isotopes for running tracer-aided hydrological models to improve quantifications of CRCs in high-mountain basins.