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排序方式: 共有7482条查询结果,搜索用时 265 毫秒
1.
Sarah M. Collier Sophie M. Green Alex Inman David W. Hopkins Hazel Kendall Molly M. Jahn Jennifer A. J. Dungait 《Soil Use and Management》2021,37(1):49-62
There are few reliable data sets to inspire confidence in policymakers that soil organic carbon (SOC) can be measured on farms. We worked with farmers in the Tamar Valley region of southwest England to select sampling sites under similar conditions (soil type, aspect and slope) and management types. Topsoils (2–15 cm) were sampled in autumn 2015, and percentage soil organic matter (%SOM) was determined by loss on ignition and used to calculate %SOC. We also used the stability of macroaggregates in cold water (WSA) (‘soil slaking’) as a measure of ‘soil health’ and investigated its relationship with SOC in the clay‐rich soils. %SOM was significantly different between management types in the order woodland (11.1%) = permanent pasture (9.5%) > ley‐arable rotation (7.7%) = arable (7.3%). This related directly to SOC stocks that were larger in fields under permanent pasture and woodland compared with those under arable or ley‐arable rotation whether corrected for clay content (F = 8.500, p < .0001) or not (F = 8.516, p < .0001). WSA scores were strongly correlated with SOC content whether corrected for clay content (SOCadj R2 = .571, p < .0001) or not (SOCunadj R2 = 0.490, p = .002). Time since tillage controlled SOC stocks and WSA scores, accounting for 75.5% and 51.3% of the total variation, respectively. We conclude that (1) SOC can be reliably measured in farmed soils using accepted protocols and related to land management and (2) WSA scores can be rapidly measured in clay soils and related to SOC stocks and soil management. 相似文献
2.
Shelley J. Newman Stephen A. Smith Kurt Zimmerman 《Journal of veterinary diagnostic investigation》2021,33(3):566
A large, firm, multi-cystic mammary gland mass grew slowly over 4 y in a 12-y-old, female Finn–Shetland cross sheep. A diagnosis of epithelial malignancy was suspected following fine-needle aspiration cytology at 30 mo after initial observation. The sheep was euthanized when the flock was downsized 18 mo later. A field postmortem examination revealed a large mammary mass, but an absence of metastases to internal organs. Imprint cytology of the mammary tissue supported a benign proliferative process. Histologically, mammary tissue was obliterated by cystic, tubular, and papillary adenomatous arrangements of mammary epithelium, with an anaplastic component, consistent with mammary carcinoma arising in an adenoma. IHC showed strong nuclear positivity to the antibody against progesterone receptor and minimal positivity to the antibody against estrogen receptor alpha expression. Intrinsic subtyping for basal or luminal epithelial origin was attempted through adaptation of companion animal IHC classification panels; high- and low-molecular-weight cytokeratins (CK5, CK8, CK18) failed to stain, but p63 expression for basal epithelium was positive. 相似文献
3.
The release and uptake of metals from potential biofilm inhibition products during spiny lobster (Sagmariasus verreauxi,H. Milne Edwards 1851) culture 下载免费PDF全文
Gregory G Smith Andrew J Poole Peter C King Stephen Battaglene Quinn Fitzgibbon Rocky de Nys 《Aquaculture Research》2017,48(2):608-617
Zinc (Zn) and copper (Cu) are strong inhibitors of bacterial biofilms in aqueous solutions, but are known toxins of crustaceans. A new metal application method; cold‐sprayed metal embedment, known to modulate metal release, was tested for its applications in crustacean larval culture systems. Cold‐spray technology allows metal particles to bond to plastics, while modulating metal ion release and biocide activity to the substrate boundary. In this study, Eastern spiny lobster (Sagmariasus verreauxi) larvae (phyllosoma) were cultured in the presence of cold‐sprayed Zn and Cu metal surfaces. Metal loss was monitored gravimetrically on embedded surfaces, assessment of water ion concentrations and analysis of phyllosoma body content were undertaken. Phyllosoma moulting, deformity and mortality patterns were monitored. Cold‐sprayed Zn‐ and Cu‐embedded surfaces were depleted with losses of 0.69% and 31.2% noted respectively. Culture water concentrations of these metals were elevated and accumulation by phyllosoma occurred. Water Zn concentrations of 18.5 μg L?1 were associated with chronic eyestalk moult deformities; the first report of Zn causing a non‐lethal moult deformity in crustacean larvae. The Cu surface lost a third of its metal mass with a water concentration of 40 μg L?1 causing acute toxicity and localization of composite granules in the midgut gland. Cu associated mortality was noted by Day 2 of culture with a LD 50 experienced by Day 9. Future work on the use of bioactive metals in aquaculture systems will focus on a range of different metal alloys, and improved modulation of ion release mechanisms through increased particle embedment depth and separation. 相似文献
4.
Reproductive resilience: a paradigm shift in understanding spawner‐recruit systems in exploited marine fish 下载免费PDF全文
Susan Lowerre‐Barbieri Greg DeCelles Pierre Pepin Ignacio A Catalán Barbara Muhling Brad Erisman Steven X Cadrin Josep Alós Andres Ospina‐Alvarez Megan M Stachura Michael D Tringali Sarah Walters Burnsed Claire B Paris 《Fish and Fisheries》2017,18(2):285-312
A close relationship between adult abundance and stock productivity may not exist for many marine fish stocks, resulting in concern that the management goal of maximum sustainable yield is either inefficient or risky. Although reproductive success is tightly coupled with adult abundance and fecundity in many terrestrial animals, in exploited marine fish where and when fish spawn and consequent dispersal dynamics may have a greater impact. Here, we propose an eco‐evolutionary perspective, reproductive resilience, to understand connectivity and productivity in marine fish. Reproductive resilience is the capacity of a population to maintain the reproductive success needed to result in long‐term population stability despite disturbances. A stock's reproductive resilience is driven by the underlying traits in its spawner‐recruit system, selected for over evolutionary timescales, and the ecological context within which it is operating. Spawner‐recruit systems are species specific, have both density‐dependent and fitness feedback loops and are made up of fixed, behavioural and ecologically variable traits. They operate over multiple temporal, spatial and biological scales, with trait diversity affecting reproductive resilience at both the population and individual (i.e. portfolio) scales. Models of spawner‐recruit systems fall within three categories: (i) two‐dimensional models (i.e. spawner and recruit); (ii) process‐based biophysical dispersal models which integrate physical and environmental processes into understanding recruitment; and (iii) complex spatially explicit integrated life cycle models. We review these models and their underlying assumptions about reproductive success vs. our emerging mechanistic understanding. We conclude with practical guidelines for integrating reproductive resilience into assessments of population connectivity and stock productivity. 相似文献
5.
Hilary Ford John R. Healey Bid Webb Tim F. Pagella Andrew R. Smith 《Soil Use and Management》2019,35(4):576-584
Hedgerows have the potential to influence ecosystem function in livestock‐grazed pasture. Despite this, they are often ignored when quantifying farmland ecosystem service delivery. In this study, we assess the contribution of hedgerows to the ecosystem function of carbon (C) storage, with a particular emphasis on soil organic carbon (SOC). We measured SOC stock (kg C m?2), on an equivalent soil mass basis, at 0–0.15 m depth in pasture adjacent to 38 hedgerows (biotic) and 16 stone walls or fences (abiotic controls) across ten farms in the county of Conwy, Wales, UK. Pasture SOC stock (~7 kg C m?2) was similar adjacent to biotic and abiotic field boundaries, positively associated with soil moisture and negatively with soil bulk density (BD). For biotic boundaries, two further variables were significantly associated with SOC stock, distance from hedgerow (decrease in SOC stock) and slope orientation (upslope SOC stock greater than downslope). For pasture adjacent to hedgerows, a model combining the aforementioned variables (BD, soil moisture, distance from hedgerow, slope orientation) explained 78% of variation in SOC stock. This study demonstrates that whilst hedgerows do have subtle positive effects on SOC stock in adjacent pasture, SOC storage adjacent to field boundaries is influenced more by soil moisture content and BD than field boundary type. 相似文献
6.
Alexander Jarryd Ehlers Smith David A. Ehlers Smith Yvette C. Downs Colleen T. 《Landscape Ecology》2019,34(3):537-549
Landscape Ecology - The effects of changing land use, and especially urbanisation, on species and functional diversity are of global concern. Eco-estates are a form of urban housing development... 相似文献
7.
Ecology of Salmonids in Estuaries around the World: Adaptations,Habitats and Conservation Colin D. Levings University of British Columbia Press 2016. Vancouver, 388 pp,ISBN‐13: 978‐0774831734, CDN 75; USD 83; GBP 71 (hardcover).
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Lia Chalifour Morgan J. Black Kieran Cox Sarah Schroeder Francis Juanes 《Fish and Fisheries》2017,18(4):790-791
8.
Luc Doyen Christophe Béné Michel Bertignac Fabian Blanchard Abdoul Ahad Cissé Catherine Dichmont Sophie Gourguet Olivier Guyader Pierre‐Yves Hardy Sarah Jennings Lorne Richard Little Claire Macher David Jonathan Mills Ahmed Noussair Sean Pascoe Jean‐Christophe Pereau Nicolas Sanz Anne‐Maree Schwarz Tony Smith Olivier Thébaud 《Fish and Fisheries》2017,18(6):1056-1072
Reconciling food security, economic development and biodiversity conservation is a key challenge, especially in the face of the demographic transition characterizing many countries in the world. Fisheries and marine ecosystems constitute a difficult application of this bio‐economic challenge. Many experts and scientists advocate an ecosystem approach to manage marine socio‐ecosystems for their sustainability and resilience. However, the ways by which to operationalize ecosystem‐based fisheries management (EBFM) remain poorly specified. We propose a specific methodological framework—viability modelling—to do so. We show how viability modelling can be applied using four contrasted case‐studies: two small‐scale fisheries in South America and Pacific and two larger‐scale fisheries in Europe and Australia. The four fisheries are analysed using the same modelling framework, structured around a set of common methods, indicators and scenarios. The calibrated models are dynamic, multispecies and multifleet and account for various sources of uncertainty. A multicriteria evaluation is used to assess the scenarios’ outcomes over a long time horizon with different constraints based on ecological, social and economic reference points. Results show to what extent the bio‐economic and ecosystem risks associated with the adoption of status quo strategies are relatively high and challenge the implementation of EBFM. In contrast, strategies called ecoviability or co‐viability strategies, that aim at satisfying the viability constraints, reduce significantly these ecological and economic risks and promote EBFM. The gains associated with those ecoviability strategies, however, decrease with the intensity of regulations imposed on these fisheries. 相似文献
9.
Endenburg Sarah Mitchell Greg W. Kirby Patrick Fahrig Lenore Pasher Jon Wilson Scott 《Landscape Ecology》2019,34(10):2385-2399
Landscape Ecology - Agricultural expansion is a principal driver of biodiversity loss, but the impacts on community assembly in agro-ecosystems are less clear, especially across regional scales at... 相似文献
10.
Thoroughbred racehorses perform exercise at maximal intensities and typically display a hyperthermic exercise response, which can drive core body temperature to critical levels. Despite extremely efficient thermoregulatory mechanisms, certain weather conditions may affect the horse’s ability to cool and result in a syndrome referred to as exertional heat illness (EHI). This is characterised by central nervous system dysfunction, as well as cytotoxic effects of heat on cells, which can produce deleterious consequences. Early detection of exertional heat illness (EHI) in Thoroughbred racehorses can be difficult because signs are often vague and the measurement of rectal temperature as an indicator of hyperthermia is not practical. Best practice in the treatment of EHI in horses, as in human subjects, centres on early detection, rapid assessment and aggressive cooling. Research in human subjects has shown that EHI is manageable when recognised early and appropriate treatment provided. The aim of this study was to investigate the measurement of skin surface temperature (SST) by an infrared thermometer as an aid in the early detection of EHI. A skin surface temperature ≥39°C in the immediate postrace period is considered to be hot. It reflects the interaction of exercise-related metabolic heat production, physiological adjustments to the skin surface such as vasodilation and sweating, together with the effect of high ambient temperature. Most importantly, high SST is associated with a reduced core-to-skin temperature difference, which retards heat transfer from the deep body tissues to the skin and can hinder heat dissipation. Identification of horses with high SSTs can prioritise them for rapid cooling and curtail possible progression to EHI. 相似文献