Hasil untuk "Natural history (General)"

H. R. Fazlollahi

In this study, by revisiting the quantum interpretation of the cosmological constant, we introduce its formal representation within standard General Relativity. Examining its behavior in a Friedmann-Robertson-Walker spacetime reveals a mechanism in which the symmetry between energy and momentum is dynamically broken. Applying this concept naturally leads to the derivation of the familiar LCDM model, while simultaneously alleviating both the fine-tuning and coincidence problems. Comparison of the ground-state energy behavior in the Friedmann equations with a dust matter field further indicates that large-scale matter exhibits the same symmetry-breaking behavior. Remarkably, due to this broken symmetry, the interactions between local regions of matter in the large-scale structure generate effective pressure, driving late-time acceleration and reproducing the LCDM expansion history without invoking exotic fields or negative-pressure components. This framework provides a self-consistent realization of LCDM within General Relativity, emerging entirely from the intrinsic dynamics of standard matter without fine-tuning and coincidence problems.

Ignaas Verpoest

Jingqing Nian, Yu Zhang, Yu Luo

Abstract Previous studies have found evidence of adaptive suppression mechanisms for physically salient stimuli. However, it remains unclear whether a similar mechanism exists for threat-history stimuli. This study used a threat conditioning task to generate stimuli with and without a history of threat. In the subsequent visual search task, the spatial probability of distractors was manipulated to examine the influence of threat-history stimuli on distractor suppression. The results showed that distractors appearing at high-probability locations were effectively suppressed, and suppression was stronger for threat-history distractors than for no-threat-history distractors. These findings suggest that threat-history distractors are more effectively suppressed when they appear at a predictable location through an adaptive attentional suppression mechanism. Data availability All data supporting the findings are openly available via the Science Data Bank ( https://www.scidb.cn/anonymous/VlpqNm55 ).

Xiao Liu, Xiao Liu, John P. Dunne et al.

Trajectories of >1,600 virtual Argo profiling floats and their sampled variability in key ocean physical and biogeochemical variables are simulated using a 0.125° global ocean physical-biogeochemical model (NOAA GFDL’s MOM6-SIS2-COBALTv2) and an offline Lagrangian particle tracking algorithm. Virtual floats are deployed at 92 locations within 26-50°N, 114-132°W in the California Current System (CCS) during the summers and winters of 2008-2012 with varying sampling strategies adopted (e.g., floats are set to park and drift at different depths, and to profile at different intervals). The overall direction and spatial spreads of simulated float trajectories depend on the latitudes of deployment locations with the largest area and variability sampled by floats deployed in the central CCS. Floats drifting at shallower depths (200 m and 500 m) tend to sample larger variability associated with larger sampled area, while those drifting at 1000 m show the strongest association with eddy-like ocean features. Sensitivity experiments with varying sampling intervals suggest that spatiotemporal variability in float observables are adequately sampled with a typical 5-day or 10-day interval. Furthermore, simulated float trajectories and sampled variability are compared against 3 real float trajectories and along-track observations. Results suggest that the fidelity of both our model simulations and the prevalent Argo float sampling design are generally satisfactory in characterizing interior ocean biogeochemical variability. This study provides new insights to inform optimal float deployment planning, sampling strategies, and data interpretation.

Colin P. Gallagher, Xinhua Zhu, Ellen V. Lea et al.

ABSTRACT Freshwater habitat characteristics are known to affect life history traits of migratory salmonids. Although the life cycle of the anadromous form of Arctic char (Salvelinus alpinus) is typically associated with lakes, there is a small number of anadromous populations in North America that spawn, rear, and overwinter exclusively in rivers. The life history traits of these relatively understudied populations and how they differ from lacustrine Arctic char are poorly documented. We characterized life history tradeoffs expressed by anadromous Arctic char originating from a riverine (Hornaday River) and a relatively nearby lacustrine system (Tatik Lake of the Kuujjua River) in the western Canadian Arctic using a 10‐year dataset. The riverine population attained smaller average size (600 mm vs. 628 mm, fork length) and mean age (7.7 vs. 10.6 years), had a lower longevity (14 vs. 26 years), and expressed a 44% higher growth rate resulting in larger size‐at‐age prior to reaching modeled length asymptote (700 vs. 754 mm). Furthermore, the riverine population had a younger modal age‐at‐maturity (approximately 6–7 vs. 11–13 years) and mean age‐at‐first migration (4.1 vs. 6.4 years), and a higher natural mortality rate (0.31 vs. 0.21 per year). Our results broaden knowledge on the spectrum of life history strategies exhibited by anadromous Arctic char and underscore how freshwater habitat influences vital rates and life history tradeoffs, which have implications for conservation and sustainable harvest (e.g., maximum sustainable yield) of salmonids.

Hang-Fei Liu, Xiaohua Huang, Guoliang Pang et al.

Assessing the current forces exerted on a semi-submersible truss fish cage is crucial for understanding drag force distribution and ensuring the structural safety. The present study employs computational fluid dynamics (CFD) methods and porous media theory to predict the drag forces on a semi-submersible truss fish cage, providing a detailed description of the magnitude and distribution patterns of drag forces on the plane nets, pontoons, columns, and braces. Results indicate that the side plane nets bear the highest forces, contributing 24.3% of the total force. The pontoons and thick columns are the next most affected, contributing 18.7% and 13.8% of the total force, respectively, while the middle cross braces bear the least force at 3.7%. A decrease in current speed leads to reduced drag forces on the downstream side plane nets, columns, pontoons, and braces. However, the projected area of each component in the current direction is a critical factor influencing changes in drag forces. Additionally, the torque generated by the drag forces on the semi-submersible truss fish cage is examined. Center position of the torque can alter the torque direction exerted on the truss net cage, and the transition occurs between 18 cm and 19 cm. The present investigation provides a comprehensive evaluation of the drag force distribution on the semi-submersible truss fish cage, which is significant practical engineering implications.

Giorgi Mamadashvili, Antoine Brin, Maksym Chumak et al.

Abstract The hyperdiverse wood‐inhabiting fungi play a crucial role in the global carbon cycle, but often are threatened by deadwood removal, particularly in temperate forests dominated by European beech (Fagus sylvatica) and Oriental beech (Fagus orientalis). To study the impact of abiotic drivers, deadwood factors, forest management and biogeographical patterns in forests of both beech species on fungal composition and diversity, we collected 215 deadwood‐drilling samples in 18 forests from France to Armenia and identified fungi by meta‐barcoding. In our analyses, we distinguished the patterns driven by rare, common, and dominant species using Hill numbers. Despite a broad overlap in species, the fungal composition with focus on rare species was determined by Fagus species, deadwood type, deadwood diameter, precipitation, temperature, and management status in decreasing order. Shifting the focus on common and dominant species, only Fagus species, both climate variables and deadwood type remained. The richness of species within the deadwood objects increased significantly only with decay stage. Gamma diversity in European beech forests was higher than in Oriental beech forests. We revealed the highest gamma diversity for old‐growth forests of European beech when focusing on dominant species. Our results implicate that deadwood retention efforts, focusing on dominant fungi species, critical for the decay process, should be distributed across precipitation and temperature gradients and both Fagus species. Strategies focusing on rare species should additionally focus on different diameters and on the conservation of old‐growth forests.

Katy R. Goodwin, Alan Kirschbaum, Erin H. Gillam

Abstract Passive acoustic monitoring is a standard technique for studying bat ecology and behavior. However, an issue that has received little attention is how to appropriately analyze data within a long‐term acoustic monitoring dataset when the equipment has been replaced and updated. Equipment changes are often inevitable, especially for microphones, which need to be replaced regularly due to extended weather exposure and associated reductions in recording quality. We compared 2 ultrasonic microphone models (Wildlife Acoustics SMM‐U1 and SMM‐U2) by deploying them side‐by‐side with the same acoustic detector unit. We tested 9 or 10 microphones per model in field deployments lasting an average of 9 nights. We compared triggering frequency, species classification, detection rates, and echolocation call parameters (as indicators of signal quality) from both microphones. The vast majority (97%) of our 25,949 paired recordings were captured simultaneously by both microphones. Yet, the SMM‐U2 outperformed the SMM‐U1 in terms of proportion of files classifiable to the species level (70% versus 61%), rate of bat detections per night (1–6.5 more detections per night depending on species), and recording quality. Based on our results, we propose a correction factor to facilitate direct comparison of datasets collected with these 2 different microphones. Our study will assist bat researchers in selecting appropriate equipment and accounting for potential biases in long‐term acoustic monitoring programs.

Charles Richard Haddad, Wanda Wesołowska

Following a rapid biodiversity assessment of spiders in the arid western interior of South Africa, we report on the occurrence of some poorly known and new species of chrysilline jumping spiders. Helafricanus patellaris (Simon, 1901), Heliocapensis capensis (Wesołowska, 1986), H. mirabilis (Wesołowska, 1986) and Menemerus lesserti Lawrence, 1927 are recorded from the Northern Cape Province for the first time, and Heliocapensis maluti (Wesołowska & Haddad, 2014) (Lesotho) and Heliophanus deformis Wesołowska, 1986 (Angola) are recorded from South Africa for the first time, both also from the Northern Cape. The hitherto unknown females of Heliocapensis mirabilis (Wesołowska, 1986) and Icius pulchellus Haddad & Wesołowska, 2011 and the male of M. lesserti are described for the first time. Three new species are described: Icius jacksoni sp. nov. (♂), Menemerus foordi sp. nov. (♂) and Natta triguttata sp. nov. (♂♀). One new combination, Afraflacilla matabelensis (Wesołowska, 2011), comb. nov. (ex Pseudicius Simon, 1885), is proposed. We present the first comprehensive molecular analysis of South Africa Chrysillini jumping spiders, based on the cytochrome oxidase I (COI) gene, which supports the monophyly of all but two genera (Helafricanus Wesołowska, 1986 and Heliophanus C.L. Koch, 1833), which we briefly discuss.

Jann Zosso

Guided by the Einstein equivalence principle that identifies the phenomenon of gravitation as a manifestation of the dynamics of spacetime in contrast to a localizable force, we review and explore its consequences on formulating a theory of gravity. The resulting space of metric theories of gravity may address open conceptual and observational puzzles through a wealth of effects beyond general relativity, whose traces can be searched for within today's and tomorrow's gravitational testing grounds. Above all, we offer a generic metric theory generalization of Isaacson's approach to the leading-order field equations of physical perturbations with a well-defined notion of energy-momentum carried by the gravitational waves. Within this framework, we identify the backreaction of the Isaacson energy-momentum flux onto the background spacetime with the displacement memory effect that induces a permanent distortion of space after the passage of a gravitational wave. This effect is a well-known prediction of GR whose dominant contribution captures its inherent non-linear nature, manifest in the ability of gravity to gravitate. However, the novel interpretation of memory as naturally arising within the Isaacson approach to gravitational waves comes with two main advantages. Firstly, it allows for a unified understanding of both the null and the ordinary memory effect, which are respectively sourced by unbound energy fluxes that do and do not reach asymptotic null infinity. Secondly, and most importantly, this approach allows for a consistent derivation of the memory formula for a large class of metric theories with considerable lessons to be learned for upcoming future measurements of the memory effect.

Dimitar Atanasov Demerdzhiev, Dobromir Damyanov Dobrev, Zlatozar Nikolaev Boev

Habitat alteration is a widespread threat severely affecting large raptors because of their low density and the huge area they inhabit. In this study, we assessed whether human-driven habitat alterations mediated dietary shifts of apex predators, focusing on the Eastern imperial eagle (<i>Aquila heliaca</i>). Following a bottom-up conception (before–after), we evaluated the effect of grassland change on the eagle’s dietary shift and breeding success. Land use patterns underwent a significant transformation over the study period, creating a large decrease in grasslands. The territories lost an average of 25.79% of their grasslands. Habitat alteration mediated dietary shifts, but had no reproductive consequences for eagles. Eagles became 1.90 times more likely to predate on northern white-breasted hedgehog and 1.62 times more likely to forage on white stork in the period after grassland alteration. The frequency of tortoises also increased, and they were 4.04 times more likely to be predated on in the years after transformation. Conversely, brown hare was 0.51 times less likely to be consumed in the grassland loss period, while this likelihood was 0.54 times lower for rodents and 0.64 times lower for the European souslik. Doves, meanwhile, were 2.73 times more likely to be predated on in the years following grassland destruction. We found that the presence and biomass of songbirds correlated negatively with the breeding success of eagles, and biomass supply from European souslik was negatively associated with breeding success, while the white stork’s presence and biomass resulted positively in more progeny. Diet diversity did not have an effect on the eagle’s reproduction. The responses of these eagles may vary across territories, depending on how they rank their prey, as the territory effect was a powerful factor shaping dietary shifts for this top predator. Our results offer new evidence of the link between habitat alteration, dietary shifts, and reproductive success, contributing to our understanding of the enigmatic mechanism through which an apex predator successfully adapts to large-scale land use pattern transformation by increasing dietary specialization. We recommend restoration of habitat complexity, including preservation of field margins, grassland patches with scattered small shrub formations, and grassland margins between medium-sized arable lands, promotion of measures for traditional grassland management through gradual grazing, and a ban on the use of shredders.

Juliana Tavora, Glauber Acunha Gonçalves, Elisa Helena Fernandes et al.

Turbid coastal plumes carry sediments, nutrients, and pollutants. Satellite remote sensing is an effective tool for studying water quality parameters in these turbid plumes while covering a wide range of hydrological and meteorological conditions. However, determining boundaries of turbid coastal plumes poses a challenge. Traditionally, thresholds are the approach of choice for plume detection as they are simple to implement and offer fast processing (especially important for large datasets). However, thresholds are site-specific and need to be re-adjusted for different datasets or when meteorological and hydrodynamical conditions differ. This study compares state-of-the-art threshold approaches with a novel algorithm (PLUMES) for detecting turbid coastal plumes from satellite remote sensing, tested for Patos Lagoon, Brazil. PLUMES is a semi-supervised, and spatially explicit algorithm, and does not assume a unique plume boundary. Results show that the thresholds and PLUMES approach each provide advantages and limitations. Compared with thresholds, the PLUMES algorithm can differentiate both low or high turbidity plumes from the ambient background waters and limits detection of coastal resuspension while automatically retrieving metrics of detected plumes (e.g., area, mean intensity, core location). The study highlights the potential of the PLUMES algorithm for detecting turbid coastal plumes from satellite remote sensing products, which can have significantly positive implications for coastal management. However, PLUMES, despite its demonstrated effectiveness in this study, has not yet been applied to other study sites.

Piroska Pazonyi, Zoltán Szentesi, Lukács Mészáros et al.

The Süttő 21 site is a fissure fill of the freshwater limestone of the Gazda quarry in Süttő. The material was collected between 2017 and 2019, and the results are summarised in this article, with a special focus on the small vertebrate fauna of the site and its stratigraphic and paleoecological significance. The fissure fill can be placed around the Early/Middle Pleistocene boundary (ca. 1.1 and 0.77 Ma). The paleoecological analysis of the herpeto- and mammal fauna of the sequence indicates the proximity of a permanent water body. The lower part of the sequence is dominated by open habitat indicator taxa indicating a cool, dry climate. Towards the upper part of the sequence, the climate remained cool, but became wetter, and the vegetation gradually changed to forest-steppe/open forest. The fauna of the Süttő 21 site can be compared with the material of sites that are of a similar age, thus revealing taxonomic and paleoecological differences between different areas of the country. While a warm, dry climate and open vegetation can be reconstructed in the Villány Hills around the Early/Middle Pleistocene boundary, the Northern Hungarian areas had a cooler, wetter climate and a slightly more closed (sparse forest, forest-steppe) vegetation during this period.

S. Sørensen, J. Mulvihill, A. Nielsen

A. Kalamchi, Macewen Gd

Pavel S. DMITRIYEV, Ivan A. FOMIN, Jan A. WENDT et al.

To consider the possibility of developing ecological tourism in the districts of the North Kazakhstan region of the Republic of Kazakhstan, based on the conducted sociological research and the available natural and recreational potential. The analysis of the conducted sociological survey is given, using methods of statistical and mathematical processing. Visualization of the presented materials was carried out by means of mapping. The study and analysis of the data obtained allowed us to reveal the natural and recreational potential of the studied areas and determine the degree of their demand as objects for tourism development. The results of the sociological survey determined the possibility and necessity of the development of regional ecological tourism, the uniqueness of local natural and recreational facilities by respondents. A cartographic material has been prepared that clearly reflects the opportunities, problems and prospects for the development of the tourism industry in the region. The natural and recreational potential of the territory of the North Kazakhstan region is certainly of interest. Natural and recreational facilities that are potential for the development of the tourism industry in the North Kazakhstan region have been identified on the territory of the studied areas. The border position of the North Kazakhstan region makes it possible for tourists from Russia to visit it. The results of the sociological survey allow us to conclude that the study of the native land has a positive effect on the patriotic education of the younger generation, and is also one of the factors in the development of eco-tourism.

Jia-Ho Shiu, Che-Hung Lin, Aziz Jabir Mulla et al.

Examining the bacterial communities of offspring is key to understanding the establishment of coral-bacteria associations. Although high sensitivity to the environment is expected, previous studies have only examined bacterial communities of coral offspring in ex situ (laboratory) environments, not in in situ (field) environments. Here, we examined and compared the effect of ex situ and in situ environments on bacterial communities of newly released offspring (eggs and larvae) and their maternal colonies in two phylogenetically distant coral species with different reproductive modes: Dipsastraea speciosa (Scleractinia; spawner) and Heliopora coerulea (Octocorallia; brooder). Our results demonstrated that the spawning environments do not affect the bacterial composition in maternal colonies, but influence that of the offspring (eggs of D. speciosa and larvae of H. coerulea). Dominant bacterial operational taxonomic units (OTUs) varied between in situ and ex situ environments in the eggs of D. speciosa. The composition of bacterial communities among larvae of H. coerulea samples was more diverse in in situ environments than in ex situ environments. This study provides the first information on in situ bacterial communities in coral eggs and larvae and highlights their sensitivities to the local environment. Future studies must take into consideration the influence of ex situ environments on bacterial communities in coral offspring.

Hyeyeon Sarah Jin, Karoline Hemminger, Jonathan J. Fong et al.

Abstract Biodiversity conservation in protected areas requires strict legal limitations to land use. In the Civilian Control Zone (CCZ) of the Republic of Korea (ROK), military control has created an accidental sanctuary for the world's rarest crane species: the white‐naped crane (Antigone vipio) and the red‐crowned crane (Grus japonensis). Yet varying land use demands on the CCZ by stakeholders have caused disagreements in achieving cooperative crane conservation. This paper aims to clarify relevant stakeholders' interconnection and their motives that have led them to either promote or inhibit crane conservation in the Cheorwon Basin of the CCZ. To answer these questions, we conducted participatory Net‐Map interviews and identified stakeholders with a powerful role in crane conservation. Our results identify 44 stakeholders whose trust relations occurred twice as often as conflicts. More than 80% of stakeholders included in this study supported crane conservation initiatives. We attribute local farmers' increased level of environmental stewardship to two key schemes: a community‐led farming project generating financial incentives and a communication channel for stakeholders. Our case study demonstrates that Net‐Map is a valid tool to analyze human‐crane interactions, which is critical to ensure acceptance of legal restrictions to land use as well as crane conservation.

Gerhard Bartzke, Lennart Siemann, Robert Büssing et al.

Framework-forming cold-water corals provide a refuge for numerous organisms and, consequently, the ecosystems formed by these corals can be considered as impressive deep-sea biodiversity hotspots. If suitable environmental conditions for coral growth persist over sufficiently long periods of time in equilibrium with continuous sediment input, substantial accumulations of coral mound deposits consisting of coral fragments and baffled sediments can form. Although this conceptual approach is widely accepted, little is known about the prevailing hydrodynamics in their close proximity, which potentially affect sedimentation patterns. In order to refine the current understanding about the hydrodynamic mechanisms in the direct vicinity of a model cold-water coral colony, a twofold approach of a laboratory flume experiment and a numerical model was set up. In both approaches the flow dynamics around a simplified cold-water coral colony used as current obstacle were investigated. The flow measurements of the flume provided a dataset that served as the basis for validation of the numerical model. The numerical model revealed data from the vicinity of the simplified cold-water coral, such as the pressure field, velocity field, or the turbulent kinetic energy (TKE) in high resolution. Features of the flow like the turbulent wake and streamlines were also processed to provide a more complete picture of the flow that passes the simplified cold-water coral colony. The results show that a cold-water coral colony strongly affects the flow field and eventually the sediment dynamics. The observed decrease in flow velocities around the cold water-coral hints to a decrease in the sediment carrying potential of the flowing water with consequences for sediment deposition.