9095 research outputs found
Sort by
Anthropogenic noise limits resource distribution without changing social hierarchies
Get PDFIncreasing evidence demonstrates that anthropogenic noise is a global pollutant that threatens marine ecosystems. Mounting numbers of studies show its diverse effects on individuals and their behaviour. However, little is known about how individual changes in response to anthropogenic noise could cascade through groups and populations affecting resource distribution vital for survival and fitness. Here we test the hypotheses that anthropogenic noise could alter resource distribution, associated hierarchies and consequently individual benefits. We used groups of hermit crabs, a globally distributed model system for assessing impacts of environmental change on wildlife and measured in controlled laboratory conditions the resource distribution of their reusable shelters (gastropod shells) under ship noise and ambient control playbacks. We applied vacancy chain theory to test three predictions about how new resource units create benefits for a population. A new resource unit leads to (i) a cascade of resource abandonments and acquisitions (= chain of vacancy moves) based on an internal (ii) hierarchy (here size-based) which allows (iii) more than one individual to benefit. All three predictions were supported under control sound. Under anthropogenic noise however, fewer individuals benefitted from the arrival of a new, empty shell, while the size-based hierarchy was maintained. The latter was apparent in chain structures, which were concordant between sound treatments. This experiment shows that anthropogenic noise can affect individual behaviours that cascade through groups. This has the potential to disrupt wider resource distribution in populations. [Abstract copyright: Copyright © 2024. Published by Elsevier B.V.
Lateglacial and early Holocene evolution of the Tyne Valley in response to climatic shifts and possible paraglacial landscape legacies
Get PDFNew sedimentological, geomorphological, and geochronological evidence for fluvial evolution of the mid- to lower River Tyne through the Lateglacial to late Holocene. These data reveal a series of fluvial terraces produced by cycles of aggradation and incision, conditioned by glacial inheritance and driven by changing sediment availability and hydrological regime. The distribution and stratigraphy (where available) of nineriver terrace and their associated sediments have been recorded. At two key sites the sediments have been dated using OSL measurements to constrain the fluvial geomorphology. Significant entrenchment of the fluvial system, followed by aggradation formed the earliest fluvial terrace (T1), which encompasses environments spanning the transition from deglaciation into Greenland Interstadial 1 (GI-1). Incision below T1 began towards the end of GI-1, with three terraces (T2 – T4) between the abandonment of T1 and the early Holocene (15.0 – 9.2 ka). Climatic shifts, limited vegetation cover/soil development, and peri-/paraglacial landscape instability conditioned the development of the early postglacial fluvial landsystem. Three further terraces (T5 – T7) developed during the mid- to Late Holocene (6.6 – 3.1 ka), and comprise most of the valley floor. Climatic instability, glacial inheritance, and widespread anthropogenic disturbances are reflected in greater hillslope-channel coupling during this period. The extent of later Holocene terraces (T8 – T9) is limited as the river became isolated from flanking hillslopes entrenched between existing river terraces. Fluvial landscape evolution in formerly glaciated catchments is strongly conditioned by the cold stage legacy that introduced excess sediment and landscape instability into the catchment. Subsequent catchment-wide responses are variable and non-linear, with valley floors operating in a series of reach-wide responses. There is a need for greater chronological control to constrain the Lateglacial and Holocene evolution in the Tyne catchment, but also to further our understanding of region-wide responses to external drivers and local dynamics
Amazon forest biogeography predicts resilience and vulnerability to drought
Get PDFAmazonia contains the most extensive tropical forests on Earth, but Amazon carbon sinks of atmospheric CO are declining, as deforestation and climate-change-associated droughts threaten to push these forests past a tipping point towards collapse . Forests exhibit complex drought responses, indicating both resilience (photosynthetic greening) and vulnerability (browning and tree mortality), that are difficult to explain by climate variation alone . Here we combine remotely sensed photosynthetic indices with ground-measured tree demography to identify mechanisms underlying drought resilience/vulnerability in different intact forest ecotopes (defined by water-table depth, soil fertility and texture, and vegetation characteristics). In higher-fertility southern Amazonia, drought response was structured by water-table depth, with resilient greening in shallow-water-table forests (where greater water availability heightened response to excess sunlight), contrasting with vulnerability (browning and excess tree mortality) over deeper water tables. Notably, the resilience of shallow-water-table forest weakened as drought lengthened. By contrast, lower-fertility northern Amazonia, with slower-growing but hardier trees (or, alternatively, tall forests, with deep-rooted water access), supported more-drought-resilient forests independent of water-table depth. This functional biogeography of drought response provides a framework for conservation decisions and improved predictions of heterogeneous forest responses to future climate changes, warning that Amazonia's most productive forests are also at greatest risk, and that longer/more frequent droughts are undermining multiple ecohydrological strategies and capacities for Amazon forest resilience. [Abstract copyright: © 2024. The Author(s), under exclusive licence to Springer Nature Limited.
Distinct biophysical and chemical mechanisms governing sucrose mineralization and soil organic carbon priming in biochar amended soils:evidence from 10 years of field studies
Get PDFWhile many studies have examined the role of biochar in carbon (C) accrual in short-term scale, few have explored the decadal scale influences of biochar on non-biochar C, e.g., native soil organic C (SOC) and added substrate. To address this knowledge gap, soils were collected from decade-old biochar field trials located in the United Kingdom (Cambisol) and China (Fluvisol), with each site having had three application rates (25-30, 50-60 and 75-100 Mg ha-1) of biochar plus an unamended Control, applied once in 2009. We assessed physicochemical and microbial properties associated with sucrose (representing the rhizodeposits) mineralization and the priming effect (PE) on native SOC. Here, we showed both soils amended with biochar at the middle application rate (50 Mg ha-1 biochar in Cambisol and 60 Mg ha-1 biochar in Fluvisol) resulted in greater substrate mineralization. The enhanced accessibility and availability of sucrose to microorganisms, particularly fast-growing bacterial genera like Arenimonas, Spingomonas, and Paenibacillus (r-strategists belonging to the Proteobacteria and Firmicutes phyla, respectively), can be attributed to the improved physicochemical properties of the soil, including pH, porosity, and pore connectivity, as revealed by synchrotron-based micro-CT. Random forest analysis also confirmed the contribution of the microbial diversity and physical properties such as porosity on sucrose mineralization. Biochar at the middle application rate, however, resulted in the lowest PE (0.3 and 0.4 mg of CO2-C g soil-1 in Cambisol and Fluvisol, respectively) after 53 days of incubation. This result might be associated with the fact that the biochar promoted large aggregates formation, which enclosed native SOC in soil macro-aggregates (2-0.25 mm). Our study revealed a diverging pattern between substrate mineralization and SOC priming linked to the biochar application rate. This suggests distinct mechanisms, biophysical and physicochemical, driving the mineralization of non-biochar carbon in a field where biochar was applied a decade before.SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s42773-024-00327-0.</p
Post-exercise hypotension after exercising in hypoxia with and without tart cherry supplementation
Get PDFBackground: This study investigated the effects of hypoxic exercise with and without tart cherry supplementation on post-exercise hypotension (PEH). Method: In a randomized order, 12 healthy young adults (9 men and 3 women) completed cycle exercise to exhaustion i) in normoxia without any supplementation (Norm), ii) in hypoxia (13% O2) with placebo (Hypo), and iii) in hypoxia with tart cherry supplementation (Hypo+TC). Supplements were supplied for 5 days pre-trial (TC was 200 mg anthocyanin per day for 4 days and 100 mg on day 5). Results: Cycle exercise total energy expenditure was greater in Norm than Hypo and Hypo+TC (P<0.001) with no difference between Hypo and Hypo+TC (P=0.41). Mean arterial pressure (MAP) decreased during recovery in all trials (main effect of time, P<0.001), with no difference in PEH between the trials (P>0.05, change (Δ) in MAP from pre-exercise at 60 min recovery, mean difference, Norm Δ-4.4 mmHg, Hypo Δ-6.1 mmHg, and Hypo+TC Δ-5.2 mmHg). Cardiac baroreflex sensitivity decreased during recovery in all trials (P<0.001) and was lower in Hypo than Norm and Hypo+TC (main effect of trial, P=0.02). Conclusion: Post-exercise hypotension was not increased after exercise in hypoxia, with or without tart cherry supplementation, compared to exercise in normoxia
Generalized Equalization Enhanced Phase Noise in Coherent Optical Transceivers Using Arbitrary Raised Cosine Filters
Get PDFEqualization-enhanced phase noise (EEPN) can degrade the performance of high baud-rate and long-distance coherent optical transmission systems that use electronic dispersion compensation (EDC). Existing theoretical calculations of EEPN are based on the ideal Nyquist filter, which has an unrealizable brickwall response due to its infinite time-domain extent. In this paper, we generalize the EEPN calculation for coherent optical transceivers using arbitrary raised cosine (RC) filters. We demonstrate that when the roll-off factor changes from zero to non-zero, the unitary transmission channel assumption no longer holds in the presence of EEPN. We calculate the resulting energy loss for transceivers using RC filters with arbitrary roll-off factors. The results indicate that while the intra-symbol EEPN remains almost unchanged, the inter-symbol EEPN and the total EEPN decrease with increasing bandwidth. Furthermore, we extend our analysis to high-order modulation formats, where the EEPN distribution varies depending on the moduli of the constellation clusters
The cost-effectiveness of life after stroke services and the impact of these services on health and social care resource use: a rapid review
Get PDFIn the UK, more than 100,000 strokes occur each year, and this is expected to rise to over 2.1 million by 2035. Life after stroke services aim to support peoples physical and emotional state, are complimentary to rehabilitation and take a non-medical holistic approach to living well after a stroke. This rapid review aimed to identify evidence on the cost-effectiveness of life after stroke services, and the impact of these interventions on health or social care resource use. The review included evidence from 12 studies (7 economic evaluations and 5 randomised controlled trials), published between January 2000 and August 2024.The economic evaluations assessed a number of interventions to support stroke survivors, their families and caregivers. Two of the randomised controlled trials were partial economic evaluations, reporting on cost and resource use data related to training caregivers, and an arts and health-based intervention. The other three trials reported on resource use but not cost data, and assessed family support interventions, and a telehealth intervention to assist stroke survivors and their carers. There was a lack of evidence on the cost-effectiveness of life after stroke as a comprehensive service. However, this review identified evidence on the cost-effectiveness and resource utilisation of specific interventions within these services. Findings include that a community-based Individual Management Program for post-stroke survivors was cost-effective from a societal perspective at 24-month follow-up. A carer training intervention, delivered whilst the stroke patient was in hospital, was associated with a reduction in health and social care resource use when evaluated at a single hospital. However, this intervention was not cost-effective when rolled out and assessed across multiple hospitals. Other findings included that a combination of speech and language therapy with voluntary support services had a lower cost per session compared to NHS speech and language therapy alone. Family support organiser interventions for stroke survivors and carers were associated with reduced healthcare utilisation. To fully understand the effectiveness and cost-effectiveness of life after stroke interventions, research is needed to assess potential long-term impacts. A reduction in resource use may be associated with cost savings and reduced burden on the NHS. However, an increase in health care and social care use may also be appropriate due to better signposting or identification of peoples’ needs. Evidence is also needed on the cost-effectiveness of supporting stroke survivors in returning to the workforce. Many of the sample sizes in the included studies lacked ethnic diversity. Stroke trials need strategies to achieve equity of access. This review focused on evidence of cost-effectiveness and resource utilisation. Decisions relating to policy and practice should also consider evidence on clinical effectiveness and patient preferences
Morphological vs. molecular identification of trematode species infecting the edible cockle Cerastoderma edule across Europe
Get PDFIdentifying marine trematode parasites in host tissue can be complicated when there is limited morphological differentiation between species infecting the same host species. This poses a challenge for regular surveys of the parasite communities in species of socio-economic and ecological importance. Our study focused on identifying digenean trematode species infecting the marine bivalve Cerastoderma edule across Europe by comparing morphological and molecular species identification methods. Cockles were sampled from ten locations to observe the trematode parasites under a stereomicroscope (morphological identification) and to isolate individuals for phylogenetic analyses using two gene markers, the small sub-unit ribosomal (18S) RNA gene (SSU rDNA) and the mitochondrial cytochrome c oxidase subunit 1 (cox1). For the first time, we compared both morphological identification and phylogenetic analyses for each of the 13 originally identified species. First, we identified a group of five species for which morphological identification matched molecular results (Bucephalus minimus, Monorchis parvus, Renicola parvicaudatus, Psilostomum brevicolle, Himasthla interrupta). Second, we identified a group of six species for which molecular results revealed either misidentifications or cryptic diversity (Gymnophallus choledochus, Diphterostomum brusinae, Curtuteria arguinae, Himasthla quissetensis, H. elongata, H. continua). Third, our analyses showed that all sequences of two expected species, Gymnophallus minutus and G. fossarum, matched between the two, strongly suggesting that only G. minutus is present in the studied area. Our study clearly demonstrates that molecular tools are necessary to validate the trematode species composition. However, with 17 distinct genetic lineages detected, some of which are not fully identified, future studies are needed to clarify the identity and status (regular vs. accidental infection) of some of these cryptic trematode species
Heterogeneity of phosphorus sources invokes distinct niche partitioning pathways of ectomycorrhizal fungi in forest soils
Get PDFEctomycorrhizal (ECM) fungi are pivotal in acquiring phosphorus (P) in nutrient-deficient soils, especially beyond the rhizosphere. However, the extent to which ECM community structure and function affect the utilization of various P-containing substrates in forest soils is not fully understood. This study explored the influence of different P substrates calcium orthophosphate, phosphate-saturated goethite, fluorapatite, and wheat bran on the release of plant-available P using hyphal in-growth mesh bags. Our results show that these substrates released comparable amounts of plant-available P to the Pinaceae hosts. A significant correlation was observed between the relative abundance of Tylospora (Atheliaceae) and Hourangia (Boletaceae), and their extracellular enzyme activities involved in P acquisition and trivalent iron reduction. This correlation was particularly evident in fungal taxa characterized by long/medium-distance hyphal exploration types. These findings underscore the ECM fungi's distinct preferences for different P-containing substrates, emphasizing the importance of recognizing these preferences to enhance forest management in low P environments