Growth inhibition by nitrocompounds of selected uric acid-utilizing microorganisms isolated from poultry manure

The overall objective of this study was to evaluate the potential ability of nitrocompounds to reduce ammonia volatilization by inhibiting uric acid-utilizing microorganisms. Experiment I was conducted to evaluate the effects of nitrocompounds on the growth of uric acid-utilizing microorganisms isolated from poultry manure during six-hour incubation. There were five treatments: (1) control, (2) 50 mM nitroethane, (3) 50 mM nitroethanol, (4) 50 mM nitropropanol, and (5) 50 mM nitropropionic acid. Optical density values of nitrocompounds were significantly lower than that of control at two, four, and six hours. Plate counts of uric acid-utilizing microorganisms after six-hour incubation exhibited that nitrocompounds greatly reduced the growth of these microorganisms except for the nitroethane (P < 0.05). The nitropropanol and nitropropionic acid treatments showed significantly higher inhibitory effects compared to the nitroethanol. Experiments II and III were conducted to evaluate inhibitory effects of nitrocompounds on growth of uric acid-utilizing microorganisms compared to non-nitrocompounds such as ethanol, propanol, and propionic acid. Experiments II and III consisted of seven treatments: (1) control, (2) nitroethanol, (3) nitropropanol, (4) nitropropionic acid, (5) ethanol, (6) propanol, and (7) propionic acid. The incubation times of Experiments II and III were 6 and 24 h, respectively. The nitrocompounds were significantly more successful in inhibiting growth of uric acid-utilizing microorganisms compared to those non-nitrocompounds. These results suggest that nitrocompounds exhibit potential to reduce ammonia volatilization in poultry manure by inhibiting growth of uric acid-utilizing microorganisms.     

Predicting the transfer of radiocaesium from organic soils to plants using soil characteristics

A model predicting plant uptake of radiocaesium based on soil characteristics is described. Three soil parameters required to determine radiocaesium bioavailability in soils are estimated in the model: the labile caesium distribution coefficient (kd1), K+ concentration in the soil solution [mK] and the soil solution-->plant radiocaesium concentration factor (CF, Bq kg-1 plant/Bq dm-3). These were determined as functions of soil clay content, exchangeable K+ status, pH, NH4+ concentration and organic matter content. The effect of time on radiocaesium fixation was described using a previously published double exponential equation, modified for the effect of soil organic matter as a non-fixing adsorbent. The model was parameterised using radiocaesium uptake data from two pot trials conducted separately using ryegrass (Lolium perenne) on mineral soils and bent grass (Agrostis capillaris) on organic soils. This resulted in a significant fit to the observed transfer factor (TF, Bq kg-1 plant/Bq kg-1 whole soil) (P < 0.001, n = 58) and soil solution K+ concentration (mK, mol dm-3) (P < 0.001, n = 58). Without further parameterisation the model was tested against independent radiocaesium uptake data for barley (n = 71) using a database of published and unpublished information covering contamination time periods of 1.2-10 years (transfer factors ranged from 0.001 to 0.1). The model accounted for 52% (n = 71, P < 0.001) of the observed variation in log transfer factor.     

Stakeholder involvement facilitates decision making for UK nuclear accident recovery

The importance of major stakeholders participating in the formulation of strategies for maintaining food safety and agricultural production following a nuclear accident has been successfully demonstrated by the UK 'Agriculture and Food Countermeasures Working Group' (AFCWG). The organisation, membership and terms of reference of the group are described. Details are given of the achievements of the AFCWG and its sub-groups, which include agreeing management options that would be included in a recovery handbook for decision-makers in the UK and tackling the disposal of large volumes of contaminated milk, potentially resulting from a nuclear accident.     

The combination of zinc compounds and acidic pH limits aerobic growth of a Salmonella typhimurium poultry marker strain in rich and minimal media

The objective of the present study was to examine the combined effects of zinc compounds with different acidic pH levels on the aerobic growth of a S. typhimurium poultry isolate in either rich or minimal media. When overall main effects of pH levels of medium or concentrations of Zn compounds were compared, growth rates of the S. typhimurium poultry isolate were significantly (p < 0.05) decreased by stepwise increase of pH levels of medium (pH 4, 5, 6, and 7) or concentrations (0.67, 3.35, and 6.03%) of Zn compounds (Zn acetate and Zn sulfate). In general growth rates of S. typhimurium poultry isolate appeared to be more reduced by Zn acetate than by Zn sulfate and more reduced in minimal media compared to rich media.     

Between discrete and continuous: consumer-resource dynamics with synchronized reproduction

In many consumer-resource systems the consumer population has synchronized reproduction at regular intervals (e.g., years) but consumes the resource and dies continuously, while the resource population grows continuously or has overlapping generations that are short relative to the time between consumer reproductive events. Such systems require "semi-discrete" models that have both discrete and continuous components. This paper defines and analyzes a canonical, semi-discrete model for a widespread class of consumer-resource interactions in which the consumer is a discrete breeder and the resource reproduction can be described continuously. The model is the analog of the Nicholson-Bailey and Lotka-Volterra models for discrete and continuous systems, respectively. It thereby develops the basis for understanding more realistic, and hence more complex, semi-discrete models. The model can display stable equilibria, consumer-resource cycles, and single-species-like overcompensation cycles. Cycles are induced by high maximum fecundity in the consumer. If the resource grows rapidly and the consumer has high maximum fecundity, the model reduces to a single-species discrete-time model of the consumer, which can exhibit overcompensation cycles. By contrast, such cycles in discrete consumer-resource models typically occur only in the resource once the consumer is extinct. Also unlike a common class of discrete models that do not display consumer-resource cycles with periods below four years, semi-discrete models can exhibit consumer-resource cycles with periods as short as two years.     

Maternal characteristics and the production and recruitment of sons in the eastern kingbird (<Emphasis Type="BoldItalic">Tyrannus tyrannus</Emphasis>)

Sex allocation theory predicts that if variance in reproductive success differs between the sexes, females who are able to produce high-quality young should bias offspring sex ratio towards the sex with the higher potential reproductive success. We tested the hypothesis that high-quality (i.e., heavy) female eastern kingbirds (Tyrannus tyrannus) that bred early in the breeding season would produce male-biased clutches. A significant opportunity for sexual selection also exists in this socially monogamous but cryptically polygamous species, and we predicted that successful extra-pair (EP) sires would be associated with an excess of male offspring. Although population brood sex ratio did not differ from parity, it increased significantly with female body mass and declined with female breeding date, but was independent of the morphology and display (song) behavior (correlates of reproductive success) of social males and EP sires. Male offspring were significantly heavier than female offspring at fledging. Moreover, the probability that male offspring were resighted in subsequent years declined with breeding date, and was greater in replacement clutches, but lower when clutch size was large. Probability of resighting female offspring varied annually, but was independent of all other variables. Given that variance in reproductive success of male kingbirds is much greater than that of females, and that male offspring are more expensive to produce and have a higher probability of recruitment if fledged early in the season, our results support predictions of sex allocation theory: high-quality (heavy) females breeding when conditions were optimal for male recruitment produced an excess of sons.     

Carcass Provisioning to Support Scavengers: Evaluating a Controversial Nature Conservation Practice

A number of scavenger species have suffered population declines across Europe. In attempts to reverse their decline, some land and wildlife managers have adopted the practice of leaving or placing out carcasses of wild or domestic herbivores to provide a source of carrion. However, this can be a controversial practice, with as yet unclear outcomes for many target species and the ecosystems they are part of. Here we bring out the key aspects of this increasingly common conservation practice illustrated using three contrasting cases studies. We show that the provision of carcasses is often motivated by a desire to benefit charismatic species or to facilitate nutrient cycling throughout an ecosystem. Evidence for the effectiveness of this practice in achieving these objectives, however, is mostly lacking, with ecologists studying “easier” species groups such as beetles and therefore not providing relevant insights. Moreover, conflicts between environmental policies that carcass provisioning is aimed at and other social and economic objectives do occur but these projects are often designed without taking into account this broader context. We conclude that expecting carcasses to simply be “good for biodiversity” may be too naïve a view. A greater knowledge of the impact of carcass provisioning and placement on ecosystems and society at large is required before it can become a more effective conservation tool at a wider scale.     

Niche and fitness differences relate the maintenance of diversity to ecosystem function

The frequently observed positive correlation between species diversity and community biomass is thought to depend on both the degree of resource partitioning and on competitive dominance between consumers, two properties that are also central to theories of species coexistence. To make an explicit link between theory on the causes and consequences of biodiversity, we define in a precise way two kinds of differences among species: niche differences, which promote coexistence, and relative fitness differences, which promote competitive exclusion. In a classic model of exploitative competition, promoting coexistence by increasing niche differences typically, although not universally, increases the "relative yield total", a measure of diversity's effect on the biomass of competitors. In addition, however, we show that promoting coexistence by decreasing relative fitness differences also increases the relative yield total. Thus, two fundamentally different mechanisms of species coexistence both strengthen the influence of diversity on biomass yield. The model and our analysis also yield insight on the interpretation of experimental diversity manipulations. Specifically, the frequently reported "complementarity effect" appears to give a largely skewed estimate of resource partitioning. Likewise, the "selection effect" does not seem to isolate biomass changes attributable to species composition rather than species richness, as is commonly presumed. We conclude that past inferences about the cause of observed diversity-function relationships may be unreliable, and that new empirical estimates of niche and relative fitness differences are necessary to uncover the ecological mechanisms responsible for diversity-function relationships.     

An investigation of the impact of afforestation on stream-water chemistry in the Loch Dee catchment, SW Scotland

The impact of conifer afforestation on stream-water chemistry was investigated in the acidified catchment of Loch Dee, SW Scotland. Long-term trends in stream-water chemistry were evaluated during a period of forest growth from age 6 to 17 years. A significant increase was observed for pH (0.2 units) and a significant decline for aluminium (0.05 mg litre(-1)), sulphate (1.2 mg litre(-1)) and nitrate (0.02 mg litre(-1)) concentrations. The long-term decrease in stream-water acidity was ascribed to the marked reductions in sulphur depositions during the 1970s and early 1980s. There was no evidence that this response had been attenuated by afforestation, the improvements in stream-water chemistry being of a similar magnitude to those recorded in nearby moorland lochs and exceeding that in an adjacent moorland-catchment stream. The lack of a clear forest acidification effect is consistent with deposition-model estimates which show the increased scavenging of occult and dry deposition by the growing forest to be small at this site (相似文献   

Fishing the line near marine reserves in single and multispecies fisheries.

Throughout the world "fishing the line" is a frequent harvesting tactic in communities where no-take marine reserves are designated. This practice of concentrating fishing effort at the boundary of a marine reserve is predicated upon the principle of spillover, the net export of stock from the marine reserve to the surrounding unprotected waters. We explore the consequences and optimality of fishing the line using a spatially explicit theoretical model. We show that fishing the line: (1) is part of the optimal effort distribution near no-take marine reserves with mobile species regardless of the cooperation level among harvesters; (2) has a significant impact on the spatial patterns of catch per unit effort (CPUE) and fish density both within and outside of the reserve; and (3) can enhance total population size and catch simultaneously under a limited set of conditions for overexploited populations. Additionally, we explore the consequences of basing the spatial distribution of fishing effort for a multispecies fishery upon the optimality of the most mobile species that exhibits the greatest spillover. Our results show that the intensity of effort allocated to fishing the line should instead be based upon more intermediate rates of mobility within the targeted community. We conclude with a comparison between model predictions and empirical findings from a density gradient study of two important game fish in the vicinity of a no-take marine-life refuge on Santa Catalina Island, California (USA). These results reveal the need for empirical studies to account for harvester behavior and suggest that the implications of spatial discontinuities such as fishing the line should be incorporated into marine-reserve design.