Effectiveness and comparison of citronella and scentless spray bark collars for the control of barking in a veterinary hospital setting

This study was designed to evaluate the efficacy of a citronella bark collar and a new, scentless spray bark collar in a veterinary hospital or a similar kennel-type environment. Forty-one dogs were included in the study. The efficacy of each collar was evaluated independently in comparison to control as well as in a crossover design. Thirty of the dogs were evaluated with the citronella collar, with 76.7% showing a reduction in barking. Twenty-nine dogs were evaluated with the scentless collar, with 58.6% showing a reduction in barking. The improvement over the control collars was statistically significant with both the citronella and scentless collars.     

Sugar maple (Acer saccharum Marsh.) growth is influenced by close conspecifics and skid trail proximity following selection harvest

In this study, we quantified the effects of local neighbourhood competition, light availability, and proximity to skid trails on the growth of sugar maple (Acer saccharum Marsh.) trees following selection harvest. We hypothesized that growth would increase with decreasing competition and increasing light availability, but that proximity to skid trails would negatively affect growth. A total of 300 sugar maples were sampled ∼10 years after selection harvesting in 18 stands in Témiscamingue (Québec, Canada). Detailed tree and skid trail maps were obtained in one 0.4 ha plot per stand. Square-root transformed radial growth data were fitted to a linear mixed model that included tree diameter, crown position, a neighbourhood competition index, light availability (estimated using the SORTIE light model), and distance to the nearest skid trail as explanatory variables. We considered various distance-dependent or -independent indices based on neighbourhood radii ranging from 6 to 12 m. The competition index that provided the best fit to the data was a distance-dependent index computed in a 6 m search radius, but a distance-independent version of the competition index provided an almost equivalent fit to data. Models corresponding to all combinations of main effects were fit to data using maximum likelihood, and weighted averages of parameter estimates were obtained using multimodel inference. All predictors had an influence on growth, with the exception of light. Radial growth decreased with increasing tree diameter, level of competition and proximity to skid trails, and varied among crown positions with trees in suppressed and intermediate positions having lower growth rates than codominants and dominants. Our results indicate that in selection managed stands, the radial growth of sugar maple trees depends on competition from close (≤6 m) conspecific neighbours, and is still affected by proximity to skid trails ∼10 years after harvesting. Such results underscore the importance of minimizing the extent of skid trail networks by careful pre-harvest planning of trail layout. We also conclude that the impact of heterogeneity among individual-tree neighbourhoods, such as those resulting from alternative spatial patterns of harvest, can usefully be integrated into models of post-harvest tree growth.     

Beech regeneration of seed and root sucker origin: A comparison of morphology, growth, survival, and response to defoliation

American beech (Fagus grandifolia Ehrh.) reproduces sexually, and vegetatively by root suckers. Although many studies have investigated its regeneration response, most did not account for differences that may exist between its two modes of reproduction. This study was performed in an old-growth Acer - Fagus forest in southern Quebec, where beech bark disease had only a minor effect at the time of the study. We compared the density and frequency of occurrence of beech seedlings and root suckers (height < 30 cm), as well as their morphology, growth, survival, and response to experimental defoliation. Root suckers accounted for 13% of beech regeneration at our site. Density and frequency of occurrence were greater for seedlings than suckers, but did not vary with light availability, which was low at our study site (mean: 2.9%). Seedlings and suckers did not differ in leaf characteristics, but several differences were observed in terms of plant morphology, growth, and survival. Root suckers showed more lateral growth than height growth, and had a lower leaf area index than seedlings. Root suckers had both a greater growth in height and diameter, and a higher survivorship than seedlings (height and diameter growth were, respectively, five and two times greater for suckers than seedlings, and 74% of suckers survived more than 1 year, compared to 52% for seedlings). Defoliation treatments, which included levels of defoliation of 50% and 100% (1) did not affect current-year extension growth of seedlings and suckers; (2) did not affect seedling diameter growth, but had a negative impact on sucker diameter growth; and (3) affected survivorship for both origins, but had a much greater negative impact on seedling survivorship (none of the completely defoliated seedlings survived over one year, while 55% of the suckers did). This study showed that several differences exist between small beech seedlings and root suckers in traits that are important determinants of a species’ competitive ability. We therefore expect that variation in the relative importance of root suckering among sites might have several community-level implications.     

A new bacteriophage of Corynebacterium glutamicum isolated from swine waste

A bacteriophage for Corynebacterium glutamicum strain LP-6 was isolated from swine waste. It belongs to the Siphoviridae family or Bradley morphologic group B, has a narrow host range, and is sensitive to chloroform and resistant to carbon tetrachloride. The phage is unstable (96% inactivation) in swine waste stored for 4 months at 22 C. The DNA has a molecular weight of approximately 20 Md, cohesive ends, and numerous restriction endonuclease sites. The phage differs from other known C glutamicum phages.     

Sugar maple and yellow birch regeneration in response to canopy opening,liming and vegetation control in a temperate deciduous forest of Quebec

We examined how the density, growth and survival of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton) regeneration are influenced by gap size, soil nutrient availability and understory vegetation. We used a factorial combination of (1) three gap sizes (small: <100 m²; medium: 100–300 m²; large: ∼1000 m²); (2) presence/absence of liming (92% CaCO₃ at 500 kg ha⁻¹, 1st year post-harvest); and (3) presence/absence of vegetation control (weeding twice a year; 1st to 3rd year post-harvest). We monitored height increment and survival of 1500 seedlings and saplings of both species from the 3rd to the 6th year post-harvest, and assessed density 6 years post-harvest. Both species exhibited a complex set of density, growth and survival responses across the combination of treatments. Compared to sugar maple, yellow birch had an overall lower density, greater growth, and similar survival rate; the two species attained maximum values in different gap size for density, and similar gap size for growth and survival. Liming had very little or no effect on the species. The growth of yellow birch was slightly but significantly greater when understory vegetation was controlled, particularly in medium and large gaps. These results suggest that a variety of canopy gap sizes can provide the right combination of understory conditions for regenerating these two functionally different tree species.     

Modelling long‐term carbon dynamics in soils reconstituted with large quantities of organic matter

In urban conditions, the widescale availability of organic matter to be recycled and the necessity for soil reconstitution (Technosol) has led to the input of very large quantities of organic matter (up to 50% v/v). The long‐term degradation of these large quantities of organic matter in the soil is not well known. We monitored, over a 60‐month period, the total carbon (C) content and the particulate and biochemical fractions of reconstituted soils placed in 600‐litre boxes under natural conditions. The top layer was a sandy loam amended with 20 or 40% of sphagnum peat or organic compost (sewage sludge, wood chip compost or green waste compost) lying on a layer of sandy loam. We measured C mineralization over time under controlled conditions and built a long‐term model to simulate carbon dynamics where exogenous organic carbon (EOC) was divided into two biodegradable compartments. The model yielded the proportions of EOC that either resisted degradation or contributed to soil organic C storage by mineralization and/or humification. Organic matter degradation was linked to its maturity and to its contents in certain particulate and biochemical fractions but was independent of how much of a given organic matter was introduced. We found a good correlation between the degradable organic compartment and the lignin and cutin‐like, hemicellulose and cellulose‐like fractions larger than 1 mm. The model showed that a large part of initial EOC was still present in the soil after 5 years in a potentially biodegradable but resistant compartment. The degradation of that compartment by mineralization or humification is therefore expected to take longer.     

Prediction of long‐term sustainability of constructed urban soil: impact of high amounts of organic matter on soil physical properties and water transfer

Sustainability of urban soils lies in their ability to facilitate water and air permeabilities. Exogenous organic matter has been shown to have a positive impact on these properties. Under urban conditions, a large one‐time input of an organic amendment was made to the reconstituted soil. Two organic materials, green‐waste compost (gw) or cocompost from sewage sludge and wood chips (sw), were mixed with sandy loam soil (40% v/v) and placed in 600‐L containers. Containers received a 29‐cm thick layer of sandy loam soil–organic matter mix over a 28‐cm thick layer without organic amendment. Volumetric water content, dry bulk density, hydraulic conductivity at saturation and water retention were measured over 5 yrs in the soils and values for the mixes and a control compared. After this time, dry bulk density was greater (1.54 g/cm³) in control than in gw or sw soils (1.31 and 1.11 g/cm³, respectively), whereas hydraulic conductivity at saturation was smaller (4 × 10^?7 m/s) than in gw (3.4 × 10^?6) or sw (3.7 × 10^?6 m/s). HYDRUS 1D water balance model indicated that below 27 cm depth in the control after 5 yrs, there was a high degree of anoxia, lasting >200 days per year, compared with <40 days in gw and sw. Amplification of the risk of anoxia below 27 cm depth after 10 yrs was 323, 151 and 100 days in the control, gw and sw, respectively. Organic matter amendment could support sustainable urban soils for ten years after soil reconstitution.     

Using longitudinal survival probabilities to test field vigour estimates in sugar maple (Acer saccharum Marsh.)

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.