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Pale swallow-wort, Vincetoxicum rossicum (Kleopow) Barbar., is an invasive weed in the lower Great Lakes Basin of North America. We investigated the relationship between V. rossicum productivity and several environmental variables across 54 established V. rossicum populations in southern Ontario. Variables included climate measurements, soil characteristics (pH, texture, and nutrient status), habitat type, plant community, and the diversity of root-associated fungi. Vincetoxicum rossicum roots were collected at all 54 sites, and associated fungi were compared using terminal restriction fragment length polymorphism. Aboveground biomass of V. rossicum was measured at 23 sites with similar light regimes, allowing comparison between populations. Results suggested that abiotic soil variables, and habitat type have little effect on V. rossicum productivity. Aboveground biomass production was significantly correlated with precipitation, and the presence of fungal pathogens and dark septate endophytes. Annual precipitation and soil clay content were also positively correlated with the abundance of soil pathogens. Accumulation of these microbes may negatively affect co-occurring native plants and associated fungal partners. The presence of these fungal species in soil could be used as an indicator of site susceptibility to invasion by V. rossicum and assist in the development of management plans for this exotic vine. [ABSTRACT FROM AUTHOR]

Wood density, an important parameter for evaluating forest biomass productivity and wood product quality control, is influenced by a complex combination of variables of forest plantations, including environmental conditions and the management practices adopted. In this paper, we demonstrate that three site variables (annual rainfall, temperature, and soil texture) and 10 plantation variables (e.g., age and genetic material) are associated with basic wood density (evaluated in two situations: with and without bark) in 936 trees of different species of Eucalyptus L'Hér across five distinct edaphoclimatic regions in Brazil. A canonical correlation analysis was used to identify the most contributory variables affecting wood density. The variables globally associated with high basic wood densities were, in order of importance, the genetic material and area per tree (both under direct control of plantation managers), as well as mean annual temperature and soil texture of the site. These results confirmed the advantage of using clonal material (instead of seedling origin material) planted in larger spacings in sites with higher mean annual temperatures and clayey soils to obtain higher basic wood densities. Conversely, low basic wood densities were associated with high-productivity sites, higher rainfall, and plantations with a higher basal area per stem in second rotation. [ABSTRACT FROM AUTHOR]

The permanent deformation of the road subgrade soil accumulated during passage of the cyclic loads is mainly due to the post-compacting and plastic flow mechanisms according to a study by the National Cooperative Highway Research Program in 2004. The main objective of the paper is to develop a relationship between the parameters a an d b of a power model and the usual physical properties of subgrade soils. The parameters a and b are assumed to represent the post-compacting and plastic deformation, respectively. Highlighting the link between the parameters a and b and the mechanisms of permanent deformation was the basic assumption which helped developing correlations. Data collected on nine different samples of soils characterized and having undergone cyclic triaxial tests permanent deformation were used to develop relationships. A distinction was made between the relationship parameter for clay and sandy soils. Indeed, clay soils with lower air permeabilities behave differently when compared to post-compaction sandy soils. However, a single relationship was developed for the parameter b, because the observed behavior appears similar for clay and sandy soils. Both correlations have coefficients of determination about 0.6. Also, comparison of the measured and predicted permanent deformation was done on the clay of St-Narcisse and sand of Fossambault. The results are generally good, despite a case of discrepancy observed. [ABSTRACT FROM AUTHOR]

Small angle neutron scattering (SANS) data are reported from a system that models the contamination of a clay - organic matter soil from a fuel spillage. The soil was represented as an aqueous dispersion of the synthetic clay mineral Laponite coated with lysine, and the contaminant was a representative jet fuel, quadricyclane, mixed with the detergent cetyltrimethylammonium bromide (CTAB). The adsorbed surface coverage on the clay was estimated. It is shown that the presence of adsorbed lysine considerably enhances the subsequent adsorption of both CTAB and quadricyclane. It is demonstrated that the SANS technique can contribute to the general problem of environmental remediation and retention by probing the interactions of pollutants and clay surfaces. [ABSTRACT FROM AUTHOR]

Asbestos cement (AC) water mains were installed extensively in North America, Europe, and Australia from the late 1920s to the early 1980s and still form a significant component of water distribution networks of many cities. These water mains are ageing and some water systems have experienced a high breakage rate in AC mains in recent years. It is essential that a clear understanding be developed of the factors contributing to their failure to ensure that municipalities and water authorities can manage their AC water-main assets. In this paper, the historical failure data of AC water mains from the City of Regina were collected and correlated with their corresponding environmental setting, including soil type, water quality, climate, and construction and maintenance practices. The predominant factors that influence the AC pipe breaks were identified. It was observed that pipe age, diameter, climate, clay soil, and construction and maintenance methods all influence the failure of AC water mains in the city, with climate and clay soil conditions being the two critical factors. Some chemical attack from the conveyed water and soil pore water may have occurred and detrimentally affected the structural integrity of the AC water mains. [ABSTRACT FROM AUTHOR]

Clayey soils are stabilized with various percentages of volcanic ash (VA), finely ground natural lime (NL), Portland cement, and their combinations. The influence of stabilizers and their combinations is evaluated through standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity, and California bearing ratio (CBR) tests. The durability of stabilized soil mixtures is judged based on drying shrinkage and the influence of water immersion on strength. Correlations between compressive strength, modulus of elasticity, and CBR are also established. Stabilized soil mixtures can be used in various constructions, including road pavements and low-cost housing. [ABSTRACT FROM AUTHOR]

This study examined the effect of soil type on burrowing behaviour and cocoon formation during aestivation in the green-striped burrowing frog, Cyclorana alboguttata (Günther, 1867). Given a choice, frogs always chose to burrow in wet sand in preference to wet clay. Frogs buried themselves faster and dug deeper burrows in sandy soil. However, under my laboratory conditions, there was little difference in the pattern of soil drying between the two soil types. Frogs in both sand and clay soil experienced hydrating conditions for the first 3 months and dehydrating conditions for the last 3 months of the 6-month aestivation period, and cocoons were not formed until after 3 months of aestivation. After 6 months, there were more layers in the cocoons of frogs aestivating in sand than those aestivating in clay. Frogs were able to absorb water from sandy soil with water potentials greater than –400 kPa, but lost water when placed on sand with a water potential of –1000 kPa. [ABSTRACT FROM AUTHOR]