Climate Change Influence On Ontario Corn Farms’ Income

Environmental Modeling & Assessment - Our study quantifies the impact of climate change on the income of corn farms in Ontario, at the 2068 horizon, under several warming scenarios. It is...     

Remediation of s-triazines contaminated water in a laboratory scale apparatus using zero-valent iron powder

Atrazine, propazine and simazine were tested separately and in mixture by batch procedure in a laboratory-constructed apparatus. 3.75 l of a buffered s-triazines pesticide solution was treated at room temperature by 325-mesh zero-valent iron powder (ZVIP) (20 g/l). High performance liquid chromatography was used to separate by-products and study the decline in the pesticide’s concentrations. Results obtained show that the order of degradation was simazine, atrazine and then propazine. The half-lives (t_1/2) of the s-triazines pesticides are, respectively, 7.4, 9.0 and 10.6 min when they are treated separately, and 9.8, 11.2 and 13.7 min when they are treated together under the same conditions. The final by-product obtained after 50 min of contact of simazine with ZVIP shows a shift to longer wavelength in its UV spectrum. A similar phenomenon is shown for atrazine and propazine. Identical primary by-products are produced and subsequently degraded to 4,6-(diamino)-s-triazine, which seems to be the major by-product of the reductive treatment process. Pathways for the degradation of the studied s-triazines by ZVIP are proposed.     

Intrinsic worker mortality depends on behavioral caste and the queens’ presence in a social insect

According to the classic life history theory, selection for longevity depends on age-dependant extrinsic mortality and fecundity. In social insects, the common life history trade-off between fecundity and longevity appears to be reversed, as the most fecund individual, the queen, often exceeds workers in lifespan several fold. But does fecundity directly affect intrinsic mortality also in social insect workers? And what is the effect of task on worker mortality? Here, we studied how social environment and behavioral caste affect intrinsic mortality of ant workers. We compared worker survival between queenless and queenright Temnothorax longispinosus nests and demonstrate that workers survive longer under the queens’ absence. Temnothorax ant workers fight over reproduction when the queen is absent and dominant workers lay eggs. Worker fertility might therefore increase lifespan, possibly due to a positive physiological link between fecundity and longevity, or better care for fertile workers. In social insects, division of labor among workers is age-dependant with young workers caring for the brood and old ones going out to forage. We therefore expected nurses to survive longer than foragers, which is what we found. Surprisingly, inactive inside workers showed a lower survival than nurses but comparable to that of foragers. The reduced longevity of inactive workers could be due to them being older than the nurses, or due to a positive effect of activity on lifespan. Overall, our study points to behavioral caste-dependent intrinsic mortality rates and a positive association between fertility and longevity not only in queens but also in ant workers.     

Incubation time, functional litter diversity, and habitat characteristics predict litter-mixing effects on decomposition

Plant diversity influences many fundamental ecosystem functions, including carbon and nutrient dynamics, during litter breakdown. Mixing different litter species causes litter mixtures to lose mass at different rates than expected from component species incubated in isolation. Such nonadditive litter-mixing effects on breakdown processes often occur idiosyncratically because their direction and magnitude change with incubation time, litter species composition, and ecosystem characteristics. Taking advantage of results from 18 litter mixture experiments in streams, we examined whether the direction and magnitude of nonadditive mixing effects are randomly determined. Across 171 tested litter mixtures and 510 incubation time-by-mixture combinations, nonadditive effects on breakdown were common and on average resulted in slightly faster decomposition than expected. In addition, we found that the magnitude of nonadditive effects and the relative balance of positive and negative responses in mixtures change predictably over time, and both were related to an index of functional litter diversity and selected environmental characteristics. Based on these, it should be expected that nonadditive effects are stronger for litter mixtures made of functionally dissimilar species especially in smaller streams. Our findings demonstrate that effects of litter diversity on plant mixture breakdown are more predictable than generally thought. We further argue that the consequences of current worldwide homogenization in the composition of plant traits on carbon and nutrient dynamics could be better inferred from long-duration experiments that manipulate both functional litter diversity and ecosystem characteristics in "hotspots of biodiversity effects," such as small streams.     

Prediction of germination rates of weed species: Relationships between germination speed parameters and species traits

In fields, the timing of weed emergence flushes is mostly related to the timing and rate of seed germination, which depend on seed dormancy level, soil temperature and water potential conditions as well as soil tillage and crop sowing date. Seed germination parameters are essential in weed dynamics models to account for the effects of soil conditions on weed demography. Since these parameters are difficult to measure, our objective was to test the possibility of estimating them from easily accessible information. Seed germination parameters (germination lag-time, time to mid-germination and mid-germination rate) were measured or collected from the literature for 25 weed species with contrasted seed characteristics. Correlations were then searched for between these parameters and morphological, chemical and physiological seed traits as well as seed dormancy level. The dormancy level was positively correlated with speed of germination parameters. Earliness of germination was positively correlated with seed lipid content and the seed area to mass ratio. Germination was also earlier and faster in species with a high base temperature for germination. These relationships explained about half the observed variability in germination speed parameters but should be further tested before being used to predict the germination behaviour of weed species in the field in different seasons.     

Assessing alpine plant vulnerability to climate change: a modeling perspective

The potential ecological impact of ongoing climate change has been much discussed. High mountain ecosystems were identified early on as potentially very sensitive areas. Scenarios of upward species movement and vegetation shift are commonly discussed in the literature. Mountains being characteristically conic in shape, impact scenarios usually assume that a smaller surface area will be available as species move up. However, as the frequency distribution of additional physiographic factors (e.g., slope angle) changes with increasing elevation (e.g., with few gentle slopes available at higher elevation), species migrating upslope may encounter increasingly unsuitable conditions. As a result, many species could suffer severe reduction of their habitat surface, which could in turn affect patterns of biodiversity. In this paper, results from static plant distribution modeling are used to derive climate change impact scenarios in a high mountain environment. Models are adjusted with presence/absence of species. Environmental predictors used are: annual mean air temperature, slope, indices of topographic position, geology, rock cover, modeled permafrost and several indices of solar radiation and snow cover duration. Potential Habitat Distribution maps were drawn for 62 higher plant species, from which three separate climate change impact scenarios were derived. These scenarios show a great range of response, depending on the species and the degree of warming. Alpine species would be at greatest risk of local extinction, whereas species with a large elevation range would run the lowest risk. Limitations of the models and scenarios are further discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of the presence of ruthenium on the activity and stability of Co–Mg–Al-based catalysts in CO2 reforming of methane for syngas production

Environmental Science and Pollution Research - Hydrogen production by methane dry reforming is an important yet challenging process. A performing catalyst will favor the thermodynamic equilibrium...     

Negative carbon via Ocean Afforestation

Ocean Afforestation, more precisely Ocean Macroalgal Afforestation (OMA), has the potential to reduce atmospheric carbon dioxide concentrations through expanding natural populations of macroalgae, which absorb carbon dioxide, then are harvested to produce biomethane and biocarbon dioxide via anaerobic digestion. The plant nutrients remaining after digestion are recycled to expand the algal forest and increase fish populations. A mass balance has been calculated from known data and applied to produce a life cycle assessment and economic analysis. This analysis shows the potential of Ocean Afforestation to produce 12 billion tons per year of biomethane while storing 19 billion tons of CO₂ per year directly from biogas production, plus up to 34 billion tons per year from carbon capture of the biomethane combustion exhaust. These rates are based on macro-algae forests covering 9% of the world's ocean surface, which could produce sufficient biomethane to replace all of today's needs in fossil fuel energy, while removing 53 billion tons of CO₂ per year from the atmosphere, restoring pre-industrial levels. This amount of biomass could also increase sustainable fish production to potentially provide 200 kg/yr/person for 10 billion people. Additional benefits are reduction in ocean acidification and increased ocean primary productivity and biodiversity.     

Photodegradation and Biodegradation Study of a Starch and Poly(Lactic Acid) Coextruded Material

To simulate the behavior of agricultural mulch coextruded poly(lactic acid)(PLA)/starch films, two stages were carried out. The first was an ultraviolet treatment (UV) at 315 nm, during which glass transition temperature T_g, weight, and molecular weight (MW) decreased and a separation between PLA and starch phase was observed. For the second stage, the mineralization of the carbon of the material was followed using the ASTM (D 5209–92 and 5338–92) and ISO/CEN (14852 and 14855) standard procedures. To measure the biodegradability of polymer material, the assessment of the carbon balance allowed determination of the distribution between the carbon rate used to the biomass synthesis or the respiration process (released CO₂), as well as the dissolved organic carbon into the culture medium and the carbon in the residual insoluble material. The influence of the nature of the medium and the standardized procedures on the final rate of biodegradation was investigated. Whatever the standardized method, the biodegradation percentage was significantly stronger in liquid medium (92.4–93.4) than on inert medium (80–83%). In the case of the compost process, only released CO₂ was measured and corresponded to 79.1–80.3%.