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321.
Jessica Spijkers Tiffany H Morrison Robert Blasiak Graeme S Cumming Matthew Osborne James Watson Henrik Österblom 《Fish and Fisheries》2018,19(5):798-806
Conflict over marine fishery resources is a growing security concern. Experts expect that global changes in our climate, food systems and oceans may spark or exacerbate resource conflicts. An initial scan of 803 relevant papers and subsequent intensive review of 31 fisheries conflict studies, focused on subnational and international conflicts, suggests that four substantial scientific gaps need addressing to improve our understanding of the nature and drivers of fisheries conflict. First, fisheries conflict and levels of conflict intensity are not precisely defined. Second, complex adaptive systems thinking is underutilized but has the potential to produce more realistic causal models of fishery conflict. Third, comparative large‐scale data and suitably integrative methodologies are lacking, underscoring the need for a standardized and comparable database of fisheries conflict cases to aid extrapolation beyond single case‐studies. Fourth, there is room for a more widespread application of higher order concepts and associated terminology. Importantly, the four gaps highlight the homogenized nature of current methodological and theoretical approaches to understanding fishery conflict, which potentially presents us with an oversimplified understanding of these conflicts. A more nuanced understanding of the complex and dynamic nature of fishery conflict and its causes is not only scientifically critical, but increasingly relevant for policymakers and practitioners in this turbulent world. 相似文献
322.
Tree mortality is a major force driving forest dynamics. To foresters, however, tree mortality is often considered a loss in productivity. To reduce tree mortality, silvicultural systems, such as selection cuts, aim at removing trees that are more likely to die. In order to identify trees with higher risks of mortality, field classifications are employed that assess vigour based on external characteristics of trees. We used a novel longitudinal approach for estimating survival probabilities based on ring-width measurements, initially developed by Bigler and Bugmann [Bigler, C., Bugmann, H., 2004. Predicting the time of tree death using dendrochronological data. Ecol. Appl. 14 (3), 902–914], to parameterize a survival probability model for sugar maple (Acer saccharum Marsh.) and to test whether field-assessed tree vigour classes are corroborated by survival probabilities determined from radial growth history. Data from 56 dead and 321 live sugar maples were collected in stands in western Quebec (Canada) that had undergone a selection cut ≈10 years prior to sampling. Our results showed that tree vigour established from external defects and pathological symptoms, using the classification of Boulet [Boulet, B., 2005. Défauts externes et indices de la carie des arbres: guide d’interprétation. Publication du Québec, Sainte-Foy, Quebec. 291 pp.], is partially corroborated by growth-driven survival probabilities. Moribund trees had lower survival probabilities than vigorous trees over several years in the period prior to vigour assessment. Intermediate vigour classes showed less obvious tendencies, but this may be due to the growth-independent nature of some defects used for their classification. Although the timing of tree death may not be correctly predicted by the vigour classification (i.e., our results suggest that time of death generally was overestimated), its general agreement with survival probabilities determined from growth series make it a useful tool for tree selection in sugar maple stands under selection management. 相似文献
323.
324.
Faba bean in cropping systems 总被引:1,自引:0,他引:1
The grain legume (pulse) faba bean (Vicia faba L.) is grown world-wide as a protein source for food and feed. At the same time faba bean offers ecosystem services such as renewable inputs of nitrogen (N) into crops and soil via biological N2 fixation, and a diversification of cropping systems. Even though the global average grain yield has almost doubled during the past 50 years the total area sown to faba beans has declined by 56% over the same period. The season-to-season fluctuations in grain yield of faba bean and the progressive replacement of traditional farming systems, which utilized legumes to provide N to maintain soil N fertility, with industrialized, largely cereal-based systems that are heavily reliant upon fossil fuels (=N fertilizers, heavy mechanization) are some of the explanations for this decline in importance. Past studies of faba bean in cropping systems have tended to focus on the effect of faba bean as a pre-crop in mainly cereal intensive rotations, whereas similar information on the effect of preceding crops on faba bean is lacking. Faba bean has the highest average reliance on N2 fixation for growth of the major cool season grain legumes. As a consequence the N benefit for following crops is often high, and several studies have demonstrated substantial savings (up to 100–200 kg N ha−1) in the amount of N fertilizer required to maximize the yield of crops grown after faba bean. There is, however, a requirement to evaluate the potential risks of losses of N from the plant–soil system associated with faba bean cropping via nitrate leaching or emissions of N2O to the atmosphere as a consequence of the rapid mineralization of N from its N-rich residues. It is important to develop improved preventive measures, such as catch crops, intercropping, or no-till technologies, in order to provide farmers with strategies to minimize any possible undesirable effects on the environment that might result from their inclusion of faba bean in cropping system. This needs to be combined with research that can lead to a reduction in the current extent of yield variability, so that faba bean may prove to be a key component of future arable cropping systems where declining supplies and high prices of fossil energy are likely to constrain the affordability and use of fertilizers. This will help address the increasing demand by consumers and governments for agriculture to reduce its impact on the environment and climate through new, more sustainable approaches to food production. The aims of this paper are to review the role of faba bean in global plant production systems, the requirements for optimal faba bean production and to highlight the beneficial effects of faba bean in cropping systems. 相似文献
325.
Annemarie Fejer Justesen Henrik Jørskov Hansen Hans O. Pinnschmidt 《European journal of plant pathology / European Foundation for Plant Pathology》2008,122(2):253-263
A real-time PCR assay was designed to quantify seed-borne infection of Pyrenophora graminea in barley (Hordeum vulgare). Conventional tests such as the freezing blotter method cannot distinguish P. graminea from the closely related P. teres. The seed infection threshold for P. graminea is lower than the one for P. teres and is therefore applied for both species although P. graminea may be absent. This results in unnecessary rejections of seed lots. PCR primers and a TaqMan probe were designed to target
a P. graminea-specific DNA sequence. The potential of the real-time PCR assay for quantifying seed-borne infection of P. graminea was investigated by examining seed lots harvested from P. graminea-infected fields. The major part (84%) of the variation in the amount of P. graminea DNA measured by real-time PCR could be attributed to variation between seed lots while only about 8% was due to variation
within seed lots. DNA quantities of P. graminea were positively correlated with seed infection incidence detected by the freezing blotter method as well as with the infection
incidence of plants examined in the greenhouse. Both correlations were highly significant (P < 0.001) but the DNA quantities accounted only for 59% (R
2 = 0.59) and 56% (R
2 = 0.56), respectively, of the variation in the results obtained by the two conventional methods. Seed lots of varieties resistant
to P. graminea contained considerable amounts of P. graminea DNA but showed no or only few leaf symptoms in the greenhouse test suggesting that the recommended seed infection thresholds
could be raised for resistant varieties. 相似文献
326.
Henrik Eckersten Håkan Marstorp Dennis Collentine Holger Johnsson Thomas Kätterer 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2018,68(3):230-242
To what extent might a crop with increased plant N uptake efficiency and/or N demand increase plant biomass and soil carbon storage, decrease N leaching, and reduce the need for N fertilisation? This was assessed for a fertilised sandy loam site in central Sweden cultivated with spring barley for a four year period using a process based crop and soil simulation model (SOILN) calibrated to fit observations of field experiments with non-modified crops. Crop properties were changed in accordance with previous model applications to other crops with higher N uptake and utilisation efficiencies, to resemble potential effects of breeding. For the modified crops a doubling of daily uptake efficiency of soil mineral N and/or increase of radiation use efficiency by 30%, increased plant biomass by 3%–30%, decreased N leaching by 1%–30% and increased soil organic carbon (SOC) content by 1–12?g?C?m?2 year?1. The larger changes were mainly due to increased uptake efficiency. Fertilisation of the modified spring barley crop could be reduced while still producing the same plant biomass as the non-modified crop. The plant biomass to N leaching ratio of the modified crops increased. The simulated changes in plant biomass and SOC were sensitive to weather conditions suggesting that in situ experiments would need to cover a large range of weather conditions to evaluate the performance of new crop traits under climatic variability. The study suggests a strong need that field experiments are accompanied with model applications, when exploring the potential of the modified crops under variable conditions. 相似文献
327.
Tanka P. Kandel Alastair J. Ward Lars Elsgaard Henrik B. Møller Poul Erik Lærke 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2017,67(7):670-677
This study evaluated the effects of harvesting managements with two-cuts (2C) and three-cuts (3C) per year for subsequent specific methane yield (SMY) and methane yield per hectare (MYPH) of festulolium and tall fescue cultivated on a riparian fen peatland in a block-designed field experiment (n?=?3). For the 2C managements, three timings of the first cut were implemented corresponding to growth stages of pre-heading (2C-early), inflorescence emergence (2C-mid), and flowering (2C-late). Anaerobic digestion batch assays with biomass samples were run for 68 days, showing that 90% of total methane (CH4) was produced within 38 days. Specific methane yield ranged from 315 to 464?NL?CH4?kg?1 volatile solids (mean, 393?NL). On average, SMY of the final cut biomass was 13% lower than the first cut biomass. Methane yield per hectare ranged from 5277 to 6963?Nm3?CH4?ha?1 (mean, 6265?Nm3) and was predominantly influenced by biomass yield since SMY only deviated modestly in relation to harvest management (crop maturity). Methane yield per hectare of festulolium under 3C and 2C-late management were significantly higher than 2C-early and 2C-mid managements, whereas the harvesting managements did not influence MYPH of tall fescue. The levels of SMY and MYPH in the present study represented high-end of reported values due to a combination of high activity of the biogas inoculum and a high productivity of festulolium and tall fescue at the riparian fen peatland. 相似文献
328.
Kathryn L. Perrin Mads F. Bertelsen Henrik Bartholin Carsten Grøndahl Steffen Heegaard 《Veterinary ophthalmology》2017,20(6):547-550
A 2‐year‐old male ostrich (Struthio camelus) presented with a rapidly growing soft tissue mass protruding from the ventromedial aspect of the right eye (OD). The initial physical examination revealed a soft tissue mass attached to the medial inferior conjunctiva. The mass was excised with cryosurgery, and the conjunctival tissue margins were treated with cryoablation. Histopathological examination diagnosed granulomatous inflammation associated with scattered acid‐fast bacteria. The ostrich recovered uneventfully and appeared healthy until recurrence of a grossly similar mass 2 months later. Gross examination revealed a botryoid mass attached to the inferior palpebral conjunctiva and extending onto the palpebral aspect of the nictitating membrane. Euthanasia was selected, and the histological diagnosis of the second mass was a mixed mucinous adenocarcinoma; however, no acid‐fast bacteria were seen. Granulomatous conjunctival lesions have been previously described in the ostrich, while, to the authors' knowledge, neoplastic conjunctival lesions have not. Neoplasia should be considered as a differential diagnosis for a rapidly recurring, granulomatous conjunctival mass in this species. 相似文献
329.
Veronika Kiseleva Henrik Heräjärvi Maria Riala Anne Toppinen 《Wood material science & engineering》2017,12(2):72-81
Understanding the state of market for modified wood as well as the forces that affect its future development will be essential for those seeking to enter the Russian market. Information on modified wood from websites of companies, research and development organisations, woodworking-oriented magazines and forums, and official Russian statistics were explored, and finally verified by personal contacts with experts. A number of modification methods have been either researched, developed or pre-commercialised during the past 15 years, but only few of them have been adopted by users. Mostly, the modification methods have been copied, further developed and commercialised from variations of thermal modification originally introduced in Western Europe. Modified wood products are still considered premium goods among Russian consumers. Political initiatives aim at increasing the share of wood in construction and renovation but also at import minimisation, which reduces the penetration of foreign producers into the markets. There are approximately 20 producers of thermally modified timber (TMT) with an overall annual capacity of 60,000–65,000 m3. The current annual market for TMT is estimated to be approximately €35–40 million. In contrast to the European mainstream end uses of TMT, there is also a market for massive and glued thermally modified logs in Russia. 相似文献
330.
Binary repeated measures data are commonly encountered in both experimental and observational veterinary studies. Among the wide range of statistical methods and software applicable to such data one major distinction is between marginal and random effects procedures. The objective of the study was to review and assess the performance of marginal and random effects estimation procedures for the analysis of binary repeated measures data. Two simulation studies were carried out, using relatively small, balanced, two-level (time within subjects) datasets. The first study was based on data generated from a marginal model with first order autocorrelation, the second on a random effects model with autocorrelated random effects within subjects. Three versions of the models were considered in which a dichotomous treatment was modelled additively, either between or within subjects, or modelled by a time interaction. Among the studied statistical procedures were: generalized estimating equations (GEE), Marginal Quasi Likelihood, likelihood based on numerical integration, penalized quasi-likelihood, restricted pseudo likelihood and Bayesian Markov Chain Monte Carlo. Results for data generated by the marginal model showed autoregressive GEE to be highly efficient when treatment was within subjects, even with strongly correlated responses. For treatment between subjects, random effects procedures also performed well in some situations; however, a relatively small number of subjects with a short time series proved a challenge for both marginal and random effects procedures. Results for data generated by the random effects model showed bias in estimates from random effects procedures when autocorrelation was present in the data, while the marginal procedures generally gave estimates close to the marginal parameters. 相似文献