Direct and indirect effects of ocean acidification and warming on a marine plant–herbivore interaction

The impacts of climatic change on organisms depend on the interaction of multiple stressors and how these may affect the interactions among species. Consumer–prey relationships may be altered by changes to the abundance of either species, or by changes to the per capita interaction strength among species. To examine the effects of multiple stressors on a species interaction, we test the direct, interactive effects of ocean warming and lowered pH on an abundant marine herbivore (the amphipod Peramphithoe parmerong), and whether this herbivore is affected indirectly by these stressors altering the palatability of its algal food (Sargassum linearifolium). Both increased temperature and lowered pH independently reduced amphipod survival and growth, with the impacts of temperature outweighing those associated with reduced pH. Amphipods were further affected indirectly by changes to the palatability of their food source. The temperature and pH conditions in which algae were grown interacted to affect algal palatability, with acidified conditions only affecting feeding rates when algae were also grown at elevated temperatures. Feeding rates were largely unaffected by the conditions faced by the herbivore while feeding. These results indicate that, in addition to the direct effects on herbivore abundance, climatic stressors will affect the strength of plant–herbivore interactions by changes to the susceptibility of plant tissues to herbivory.     

Direct and indirect effects of ant–trophobiont interactions on the reproduction of a hummingbird-pollinated mistletoe

Plant Ecology - Fluid-feeding herbivores directly affect host plants through sap consumption. Moreover, they establish mutualistic relationships with ants, which might generate additional...     

Paths to last in mixed crop–livestock farming: lessons from an assessment of farm trajectories of change

Mixed crop–livestock systems, combining livestock and cash crops at farm level, are considered to be suitable for sustainable intensification of agriculture. Ensuring the survival of mixed crop–livestock systems is a challenge for European agriculture: the number of European mixed crop–livestock farms has been decreasing since 1970. Analysis of farming system dynamics may elucidate past changes and the forces driving this decline. The objectives of this study were (i) to identify the diversity of paths that allowed the survival of mixed crop–livestock farming and (ii) to elucidate the driving forces behind such survival. We analysed the variety of farm trajectories from 1950 to 2005. We studied the entire farm population of a case study site, located in the ‘Coteaux de Gascogne’ region. In this less favoured area of south-western France, farmers have limited specialisation. Currently, half of the farms use mixed crop–livestock systems. The data set of 20 variables for 50 farms on the basis of six 10-year time steps was collected through retrospective surveys. We used a two-step analysis including (i) a visual assessment of the whole population of individual farm trajectories and (ii) a computer-based typology of farm trajectories on the basis of a series of multivariate analyses followed by automatic clustering. The European Common Agricultural Policy, market globalisation and decreasing workforce availability were identified as drivers of change that favoured the specialisation process. Nevertheless, farmers’ choices and values have opposed against these driving forces, ensuring the survival of some mixed crop–livestock farming systems. The trajectories were clustered into five types, four of which were compatible with mixed crop–livestock systems. The first type was the maximisation of autonomy by combining crops and livestock. The second type was diversification of production to exploit economies of scope and protect the farm against market fluctuations. The other two types involved enlargement and progressive adaptation of the farm to the familial workforce. The survival of mixed crop–livestock systems in these two types is largely dependent on workforce availability. Only one type of trajectory, on the basis of enlargement and economies of scale, did not lead to mixed crop–livestock systems. In view of the current evolution of the driving forces, maximising autonomy and diversification appear to be suitable paths to deal with current challenges and maintain mixed crop–livestock systems in Europe.     

Mixed crop–livestock farming systems: a sustainable way to produce beef? Commercial farms results,questions and perspectives

Mixed crop–livestock (MC–L) farming has gained broad consensus as an economically and environmentally sustainable farming system. Working on a Charolais-area suckler cattle farms network, we subdivided the 66 farms of a constant sample, for 2 years (2010 and 2011), into four groups: (i) ‘specialized conventional livestock farms’ (100% grassland-based farms (GF), n=7); (ii) ‘integrated conventional crop–livestock farms’ (specialized farms that only market animal products but that grow cereal crops on-farm for animal feed, n=31); (iii) ‘mixed conventional crop–livestock farms’ (farms that sell beef and cereal crops to market, n=21); and (iv) organic farms (n=7). We analyse the differences in structure and in drivers of technical, economic and environmental performances. The figures for all the farms over 2 years (2010 and 2011) were pooled into a single sample for each group. The farms that sell crops alongside beef miss out on potential economies of scale. These farms are bigger than specialized beef farms (with or without on-farm feed crops) and all types of farms show comparable economic performances. The big MC–L farms make heavier and consequently less efficient use of inputs. This use of less efficient inputs also weakens their environmental performances. This subpopulation of suckler cattle farms appears unable to translate a MC–L strategy into economies of scope. Organic farms most efficiently exploit the diversity of herd feed resources, thus positioning organic agriculture as a prototype MC–L system meeting the core principles of agroecology.     

The management of crop structure: a general approach to reversing the impacts of agricultural intensification on birds?

Agricultural intensification is accepted widely as a cause of bird population declines on farmland in Europe and North America. Although intensification is multivariate, one common theme is the impact on variation in crop structure, both within and between fields. Intensification creates simpler, more homogeneous and denser swards in both tillage crops and grassland. This influences predation risk, exposure to weather extremes and the diversity, abundance and accessibility of food. Birds trade off these pressures in different ways, so that the more uniform and dense the vegetation, the fewer the number of birds and range of species that are able to nest and forage successfully. Reversing recent trends towards dense, simplified and homogeneous swards will improve nesting and foraging habitat conditions for a wide range of species across farming systems, and may represent a cost-effective mechanism for the further improvement of agri-environment scheme options designed to assist the recovery of farmland bird populations.     

Biotic resistance on coral reefs? Direct and indirect effects of native predators and competitors on invasive lionfish

Coral Reefs - Biotic resistance is the ability of an ecological community to prevent or limit the establishment or success of non-indigenous species. Native species can confer resistance by...     

Solvent-responsiveness of PS–PEO binary mixed polymer brushes: a coarse-grained molecular dynamics study

Abstract

Systems of mixed polymer brushes (polystyrene–polyethylene oxide, PS–PEO) uniformly grafted on solid substrate were investigated by coarse-grained molecular dynamics simulations. The effects of grafting density and relatively degree of polymerisation of PS and PEO on the switching property of PS–PEO mixed polymer brushes in water and solvent are explored and discussed. Simulation results indicate that PS dominated the thickness of PS–PEO mixed polymer brushes in different solvents, which can be controlled by adjusting the grafting density. Brush heights of mixed PS–PEO polymer brushes fluctuate in different solvents when grafting density varies. The chemical composition of the very top surface of these mixed polymer brushes are largely determined by the relative polymerisation degree of PS and PEO.     

Comparing direct land use impacts on biodiversity of conventional and organic milk—based on a Swedish case study

Purpose

Halting the loss of biodiversity while providing food security for a growing and prospering world population is a challenge. One possible solution to this dilemma is organic agriculture, which is expected to enhance biodiversity on the farmland. However, organic products often require larger areas. This study demonstrates how we can quantify and compare the direct land use impacts on biodiversity of organic and conventional food products such as milk.

Material and methods

This study assessed direct land use impacts of 1 l of milk leaving the farm gate. Inventory data on land occupation were extracted from a life cycle assessment study of 15 farms in southern Sweden. Direct land use change data were derived from the FAO statistical database. Spatially differentiated characterization factors of occupation (CF_Occ) and transformation (CF_Trans) were calculated based on the relative difference of plant species richness on agricultural land compared to a (semi) natural regional reference. Data on plant species richness and regeneration times of ecosystems (for calculating transformation impacts) were derived from a literature review. To account for differences in biodiversity value between regions, a weighting system based on absolute species richness, vulnerability and irreplaceability was applied.

Results and discussion

Organic milk had a lower direct land use impact than conventional milk, although it required about double the area. Occupation impacts dominated the results and were much smaller for organic than conventional milk, as CF_Occ of organic land uses were considerably smaller. For transformation impacts, differences between the two farming practices were even more pronounced. The highest impacts were caused by soymeal in concentrate feeds (conventional milk) due to large-scale deforestation in its country of cultivation (i.e. Brazil and Argentina). However, lack of reliable data posed a challenge in the assessment of transformation impacts. Overall, results were highly sensitive to differences in land occupation area between farms, the CF_Occ and assumptions concerning transformed area. Sensitivity and robustness of results were tested and are discussed.

Conclusions

Although organic milk required about twice as much land as conventional, it still had lower direct land use impacts on biodiversity. This highlights the importance of assessing land use impacts not only based on area but also considering the actual impacts on biodiversity. The presented approach allows to quantify and compare hot- and coldspots in the agricultural stage of milk production and could potentially also be applied to other agricultural products. However, more research is needed to allow quantification of indirect land use impacts.     

Human impacts on hydrological health and the provision of ecosystemservices: a case study of the eMthonjeni–Fairview Spring Wetland,Grahamstown, South Africa

Wetland hydrological health and the provision of indirect ecosystem services in the eMthonjeni–Fairview Spring Wetland, Grahamstown, South Africa, were assessed in 2008, using the newly developed wetland assessment tools WET-Health and WET-EcoServices. Variation in health and ecosystem services were assessed over time, based on aerial photograph interpretation and the use of the score sheets in these assessment tools. Hydrological health and indirect ecosystem services of the wetland have been altered since 1949, due to human activities both in the catchment and the wetland. The most significant human intervention on the wetland's hydrological health was the result of road construction and invasion by alien plants. Water use by local residents had an unmeasurable effect on hydrological health. Wetland health is related to the provision of wetland ecosystem services, and cumulative impacts in the catchment and wetland have reduced the provision of many indirect wetland ecosystem services.     

Influence of co-inoculation of bacteria-cyanobacteria on crop yield and C–N sequestration in soil under rice crop

The performance of three selected bacterial strains—PR3, PR7 and PR10 (Providencia sp., Brevundimonas sp., Ochrobacterium sp.) and three cyanobacterial strains CR1, CR2 and CR3 (Anabaena sp., Calothrix sp., Anabaena sp.), and their combinations was evaluated in a pot experiment with rice variety Pusa-1460, comprising 51 treatments along with recommended fertilizer controls. Highest yield enhancement of 19.02% was recorded in T12 (CR2), over control, while significant enhancement in nitrogen fixing potential was recorded in treatments involving combination of bacterial-cyanobacterial strains—T37 (PR3 + CR1 + CR3) and T21 (PR7 + CR1). Organic carbon was significantly increased in all microbe-inoculated treatments, which could be correlated with microbial biomass carbon values and activities of all the enzymes tested in our study. Also, panicle weight and plant biomass were highly correlated with soil microbial carbon. Comparative evaluation revealed the superior performance of strains CR2, CR1 (both Anabaena sp.) and PR10 (Ochrobacterium sp.) in increasing the growth and grain yield of rice and improving soil health, besides N (nitrogen) savings of 40–80 kg ha⁻¹. The study for the first time illustrated the positive effects of co-inoculation of bacterial and cyanobacterial strains for integrated nutrient management of rice crop.     

Effect of parity on productivity and sustainability of Lotka–Volterra food chains

Hairston, Slobodkin, and Smith conjectured that top down forces act on food chains, which opposed the previously accepted theory that bottom up forces exclusively dictate the dynamics of populations. We model food chains using the Lotka–Volterra predation model and derive sustainability constants which determine which species will persist or go extinct. Further, we show that the productivity of a sustainable food chain with even trophic levels is predator regulated, or top down, while a sustainable food chain with odd trophic levels is resource limited, which is bottom up, which is consistent with current ecological theory.     

Prey subsidy or predator cue? Direct and indirect effects of caged predators on aquatic consumers and resources

The non-consumptive effects of predators on prey can affect prey phenotypes, potentially having important consequences for communities due to trait-mediated indirect interactions. Predicting non-consumptive effects and their impacts on communities can be difficult because predators can affect resources directly through nutrient cycling and indirectly by altering prey resource use, which can lead to complex interactions among resources and consumers. In this study we examined the effects of caged dragonfly predators on aquatic resources in the presence and absence of two focal herbivores, the tadpoles of Neotropical tree frogs Agalychnis callidryas and Dendropsophus ebraccatus. We crossed the presence/absence of caged dragonflies with four tadpole treatments: no tadpoles, each tadpole species alone, and both species together to examine interactions among tadpole composition, predator presence, and time on tadpole growth, resources, and zooplankton abundances. Predator effects on growth changed through ontogeny and was species-dependent. Predators initially reduced then dramatically increased A. callidryas growth, but had no effect on D. ebraccatus. Predators also increased the abundances of both periphyton and phytoplankton. However, there was no evidence of a trait-mediated trophic cascade (i.e., tadpole by predator interaction). Instead, nutrients from prey carcass subsidies likely played an increasingly important role in facilitating resources, and shaping tadpole growth, competitive interactions, and zooplankton abundances through time. In nutrient-poor aquatic systems the release of nutrients via the consumption of terrestrially derived prey items by aquatic predators may have important impacts on food webs by facilitating resources independent of the role of trait-mediated trophic cascades.     

Simultaneous production of mixed electron–photon beam in a medical LINAC: A feasibility study

PurposeThe electron or photon beams might be used for treatment of tumors. Each beam has its own advantage and disadvantages. Combo beam can increase the advantages. No investigation has been performed for producing simultaneous mixed electron and photon beam. In current study a device has been added to the Medical Linac to produce a mixed photon–electron beam.MethodsFirstly a Varian 2300CD head was simulated by MCNP Monte Carlo Code. Two sets of perforated lead sheets with 1 and 2 mm thickness and 0.2, 0.3, and 0.5 cm punches then placed at the top of the applicator holder tray. This layer produces bremsstrahlung x-ray upon impinging fraction electrons on it. The remaining fraction of electrons passes through the holes. The simulation was performed for 10 × 10, 6 × 6, and 4 × 4 cm² field size.ResultsFor 10 × 10 cm² field size, among the punched targets, the largest penumbra difference between the depth of 1 and 7 cm was 72%. This difference for photon and electron beams were 31% and 325% respectively. A maximum of 39% photon percentage was produced by 2 mm target with 0.2 cm holes diameter layer. The minimum surface dose value was 4% lesser than pure electron beam. For small fields, unlike the pure electron beam, the PDD, penumbra, and flatness variations were negligible.ConclusionsThe advantages of mixing the electron and photon beam is reduction of pure electron's penumbra dependency with the depth, especially for small fields, also decreasing of dramatic changes of PDD curve with irradiation field size.     

Edaphic factors and plant–insect interactions: direct and indirect effects of serpentine soil on florivores and pollinators

Edaphic factors can lead to differences in plant morphology and tissue chemistry. However, whether these differences result in altered plant–insect interactions for soil-generalist plants is less understood. We present evidence that soil chemistry can alter plant–insect interactions both directly, through chemical composition of plant tissue, and indirectly, through plant morphology, for serpentine-tolerant Mimulus guttatus (Phrymaceae). First, we scored floral display (corolla width, number of open flowers per inflorescence, and inflorescence height), flower chemistry, pollinator visitation and florivory of M. guttatus growing on natural serpentine and non-serpentine soil over 2 years. Second, we conducted a common garden reciprocal soil transplant experiment to isolate the effect of serpentine soil on floral display traits and flower chemistry. And last, we observed arrays of field-collected inflorescences and potted plants to determine the effect of soil environment in the field on pollinator visitation and florivore damage, respectively. For both natural and experimental plants, serpentine soil caused reductions in floral display and directly altered flower tissue chemistry. Plants in natural serpentine populations received fewer pollinator visits and less damage by florivores relative to non-serpentine plants. In experimental arrays, soil environment did not influence pollinator visitation (though larger flowers were visited more frequently), but did alter florivore damage, with serpentine-grown plants receiving less damage. Our results demonstrate that the soil environment can directly and indirectly affect plant–mutualist and plant–antagonist interactions of serpentine-tolerant plants by altering flower chemistry and floral display.     

Direct and indirect regulation of derrière,a Xenopus mesoderm-inducing factor,by VegT

One candidate for an endogenous mesoderm-inducing factor in Xenopus is derrière, a member of the TGFbeta family closely related to Vg1. In this paper we first show that derrière is able to exert long-range effects in the early Xenopus embryo, reinforcing the view that it functions as a secreted factor required for proper formation of posterior structures. Analysis of the derrière promoter shows that expression of the gene is controlled through a complex inductive network involving VegT and TGFbeta-related molecules and also, perhaps, FGF family members. The work confirms that derrière plays an important role in mesoderm formation and it illustrates the complex regulation to which inducing factors are subject.     

Direct and indirect effects of human interferon α on renal cell carcinoma: a new in vitro assay system for evaluating cytokine-mediated antitumor effects

A highly purified natural -interferon (nIFN) was tested in vitro for direct and indirect antiproliferative activity against renal cell carcinoma (RCC), using a modified human tumor clonogenic assay and clinically achievable concentrations. In preclinical experiments, the indirect (cytokine-mediated) antiproliferative activity of nIFN was investigated using ACHN cells (established human RCC cell line). Continuous exposure to nIFN at concentrations of more than 5 IU/ml in the presence of feeder cells (a mixture of 5×10⁴ monocytes/dish and 5×10⁵ lymphocytes/dish, obtained from healthy donors) significantly inhibited colony formation of ACHN cells in comparison with growth inhibition in the absence of feeder cells (P<0.05). Various cytokines were measured in the supernatants lying over the medium on the feeder-layer agarose containing the same conditioned feeder cells. With IFN at 500 IU/ml, tumor necrosis factor (TNF) and IFN were detected at markedly high levels for 2–24 h. Neutralizing anti-TNF monoclonal antibody significantly reduced the indirect antiproliferative activity. Using our modified human tumor clonogenic assay technique, sufficient numbers of colonies for drug testing were observed in 19 of 31 surgical specimens (61.3%). In these clinical materials, nIFN at a clinically achievable concentration (50 IU/ml) significantly inhibited colony growth in the presence of feeder cells consisting of 5×10⁴ monocytes/dish and 5×10⁵ lymphocytes/dish, obtained from the patient whose tumor was examined (P<0.05). In colony-forming cases, a significant correlation between the percentage colony survival and TNF concentration in the supernatant was observed (r=–0.95,P<0.01). These results suggest that this assay system may be an appropriate technique for evaluating the antiproliferative activities of nIFN involving cytokine-mediated action, and that TNF may play an important role in this cytokine-mediated activity.This work was supported in part by a grant-in-aid for promoting research (no. 02771010) from the Ministry of Education     

180 Integrating structural and systems biology: structure-based prediction of protein–protein interactions on a genome-wide scale

The genome-wide identification of pairs of interacting proteins is an important step in the elucidation of cell regulatory mechanisms. To date, structural information has had only limited impact on genome-scale efforts to predict protein–protein interactions (PPIs). A new algorithm, PrePPI, will be introduced that combines structural information with nonstructural clues and that is comparable in accuracy to high-throughput experiments. The surprising effectiveness of three-dimensional structural information can be attributed to the use of homology models and the exploitation of both close and remote geometric relationships between proteins. More generally, the “structural BLAST” approach encapsulated in PrePPI significantly expands the range of application of protein structure in the annotation of protein function.     

Adsorption of HCN on reduced graphene oxides: a first–principles study

Journal of Molecular Modeling - Over the past few years, time-dependent ultrafast fluorescence spectroscopy method has been applied to the study of protein dynamics. However, observations from...     

The opening of Pandora’s Box: climate change impacts on soil fertility and crop nutrition in developing countries

Feeding the world’s growing population is a serious challenge. Food insecurity is concentrated in developing nations, where drought and low soil fertility are primary constraints to food production. Many crops in developing countries are supported by weathered soils in which nutrient deficiencies and ion toxicities are common. Many systems have declining soil fertility due to inadequate use of fertility inputs, ongoing soil degradation, and increasingly intense resource use by burgeoning populations. Climate models predict that warmer temperatures and increases in the frequency and duration of drought during the 21st century will have net negative effects on agricultural productivity. The potential effects of climate change on soil fertility and the ability of crops to acquire and utilize soil nutrients is poorly understood, but is essential for understanding the future of global agriculture. This paper explores how rising temperature, drought and more intense precipitation events projected in climate change scenarios for the 21st century might affect soil fertility and the mineral nutrition of crops in developing countries. The effects of climate change on erosion rates, soil organic carbon losses, soil moisture, root growth and function, root-microbe associations and plant phenology as they relate to mineral nutrition are discussed. Our analysis suggests that the negative impacts of climate change on soil fertility and mineral nutrition of crops will far exceed beneficial effects, which would intensify food insecurity, particularly in developing countries.