Weed cover in hybrid poplar (Populus) plantations on Quebec forest soils under different lime treatments

Fast-growing trees such as hybrid poplars (Populus) have the potential to decrease rotation length (time to harvest) and thus produce wood products more quickly from smaller areas of land. Several forest companies in Quebec currently plant hybrid poplar on formerly logged forest sites, rather than on agricultural land as is more common elsewhere. The forest sites often have acidic soils, and lime addition has been proposed to improve hybrid poplar growth. In addition, forest sites present challenges with regard to control of competitive vegetation, particularly in jurisdictions such as Quebec where use of herbicides in forests is banned or restricted.     

Linear woody landscape elements may help to mitigate leaf surface loss caused by the cereal leaf beetle

Landscape Ecology - Woody semi-natural habitats serve as permanent habitats and hibernation sites for natural enemies and, through spillover processes, they play an important role in the biological...     

Tracing Groundwater Flow Systems with Hydrogeochemistry in Contrasting Geological Environments

The importance of the chemical composition in evaluating groundwater flow is discussed. Two different geological environments, a felsic volcanic region around San Luis Potosí (SLPB), Mexico, and a sedimentary basin, part of the Pannonian Basin (PB), in Hungary, were chosen to explore the effect of local, intermediate and regional groundwater flows on the chemical evolution of water in different geological circumstances. In the study areas contrasting stable isotopes and groundwater temperature values, as well as the chemical composition of groundwater were convenient tools to propose groundwater flow direction and to study contamination processes in the different groundwater flow systems. Results indicate that regardless of the geological framework variability of the chemical composition of the shallow (<100 m) groundwater is significant; at depth the chemical content of groundwater becomes homogeneous, and the concentrations are smaller than at shallow depths. The Cl^– and NO^– ₃ concentrations indicate mainly up- and downward vertical flow directions suggesting local flow systems in the shallow layers. The linear regression between Cl^– and Na⁺ suggests that evaporation processes are the main control of the Cl^– concentration. Deviations from the regression line suggest processes such as pollution at shallow depths in both study areas. Based on the distribution of Ca⁺², Mg⁺² and Na⁺, a lateral flow can be traced. The large dimensions of the geological units involved with the regional flow systems implies a long groundwater flow path, also these flows remain isolated from anthropogenic contamination, then groundwater has not been altered by human influence, although in the SLPB a communication between the local and intermediate flows has been found. Recharge areas of the local and intermediate flow systems are more vulnerable to contamination processes than the discharge areas, where the expected low dissolved oxygen content of ascending water could play a control. Differences in the lithology between the PB (sedimentary basin) and the SLPB (felsic volcanic basin) explain the contrasting saturation indices calculated for chalcedony and calcite and the lack of the expected development of HCO^– ₃, SO^–2 ₄ Cl^– facies and contrasting aerobic/oxidizing conditions.     

Where do we go from here? Dispersal simulations shed light on the role of landscape structure in determining animal redistribution after reintroduction

Reintroduction projects represent viable options for animal conservation. They allow the establishment of new local populations and may contribute to recreating functional networks within a metapopulation. In the latter case, landscape connectivity may be a major determinant of the phase of spread of the reintroduced populations. Here, we deal with an example of a red deer (Cervus elaphus) translocation planned to enable the connection among existing isolated populations of the species in the Italian Alps. Our aim was to assess whether the analysis of landscape suitability and the simulation of dispersal of released individuals could shed light on the actual process of population spread. For these purposes, we adopted a modelling approach using radiotracking data to develop a habitat suitability map. On the basis of this map, we simulated the dispersal of the animals after release and we then compared the simulation results with the outcome of null models and with the observed population redistribution. The results suggest that the spread of the subpopulation was easier north-westward than southward. Taking into account landscape suitability, our simulations produced a reliable estimate of the ease of colonization of the valleys neighbouring the release-site and they allowed the identification and validation of a potential pathway for animal dispersal. The suitability model based on the monitoring of individuals in the earliest phase of establishment shed light on the spread of the population and on its potential connections with other deer subpopulations.     

Understory succession in post-agricultural oak forests: Habitat fragmentation affects forest specialists and generalists differently

The herbaceous understory forms the richest stratum in temperate broadleaved forests in terms of plant diversity. Understanding the process of understory succession is thus of critical importance for the development of management guidelines for biodiversity restoration in post-agricultural plantation forests.We studied effects of stand age, forest fragmentation, and soil and canopy conditions on species richness and abundance of four species groups in the understory of post-arable oak plantations in southern Sweden: herbaceous forest specialists, habitat generalists and open-land species, and woody species.The group of forest specialists may approach the richness of continuously forested sites after 60-80 years in non-fragmented plantations, but many forest species were sensitive to habitat fragmentation. Open-land species richness decreased during succession, while the richness of woody species and of generalists remained stable, and was not affected by fragmentation. Abundance of generalists gradually decreased in non-fragmented plantations, probably due to competition from colonizing forest specialists. Soil pH in post-arable stands remained consistently higher than in continuously forested stands, which maintained differences in species composition. The development of a shrub layer seemed to imply a competitive advantage for forest specialists compared to generalist species.For successful recovery of a rich understory, we suggest that post-arable plantations should be established on loamy soils of intermediate to high pH proximate to older forest with source populations, and that a continuous overstory canopy cover of 70-80% is maintained by regular light thinnings and promotion of a shrub layer.     

Endotracheal tube placement during computed tomography of brachycephalic dogs alters upper airway dimensional measurements

Computed tomography (CT) is used to document upper airway lesions in dogs with brachycephalic obstructive airway syndrome. The presence of an endotracheal tube during CT scanning is often required for general anesthesia. We hypothesized that the endotracheal tube placement would change the soft tissue dimensions of the upper airway. The aims of this prospective, method comparison study were to evaluate the reliability of the previously reported upper airway CT measurements with endotracheal tube placement, and to propose measurements that are minimally affected by the endotracheal tube. Twenty brachycephalic dogs were included in this study. Each dog underwent head/neck CT with an endotracheal tube, followed by a second scan without the endotracheal tube. Ten measurements of the soft palate, nasopharynx, and trachea were performed. Tracheal dimension was significantly larger with the endotracheal tube compared to without, whereas the soft palate cross‐sectional area was significantly smaller with the endotracheal tube than without the endotracheal tube. The influence of the endotracheal tube on the caudal nasopharynx cross‐sectional (transverse‐sectional) area varied with a mean proportional absolute difference of 35%. Rostral soft palate thickness, tracheal perimeter, and cross‐sectional area of the rostral nasopharynx were the measurements least affected by the endotracheal tube (intraclass correlation coefficient = 0.964, 0.967, and 0.951, respectively). Therefore, we proposed that these three measurements may be most useful for future brachycephalic obstructive airway syndrome studies that require CT scanning of intubated animals. However, with endotracheal tube placement, measurements of soft palate length, caudal nasopharyngeal cross‐sectional area, and trachea height and width may not be reliable.     

Simulation Analysis of Variation among Seasons in Winter Wheat Yields in Northern Italy

Winter wheat growth and yield was observed in two sets of field experiments performed at the Experimental Farm of Padova University in Legnaro, over seven years beginning in 1981. A spring wheat model in which leaf area development was calculated as a function of temperature and biomass accumulation was utilized. The final number of leaves in each season was calculated based on a previous winter wheat model and the biomass accumulation was decreased when average daily temperature was below 10 °C. In addition to the two modifications described above, the soil/crop nitrogen submodels were modified so that denitrification was a function of temperature and plant nitrogen uptake rate was sensitive to variations in daily temperature. Nitrogen leached below 60 cm was assumed to be no longer available to the winter wheat crop. The winter wheat model with the soil/crop nitrogen budged resulted in good agreement between the simulated and observed yields (less than 14 % difference existed in 12 of 14 environments). A strong negative correlation (r = -0.74) existed between the simulated yields and the simulated amount of nitrogen leached out of the root zone. Under the conditions of nothern Italy, retention of root zone nitrogen appears to be particularly important in achieving high winter wheat yields.     

Reciprocal performance of winter wheat in Hungary and Oklahoma, USA

International wheat ( Triticum aestivum L.) performance trials have revealed adaptive responses in vernalization and photoperiod for certain Eastern European cultivars when field-tested in Oklahoma in south central USA. Common experiments were conducted in Hungary and Oklahoma with 12 elite germplasm varieties or lines from each locale to uniformly and directly compare the agronomic potential of hard red winter (HRW) North American wheat and Hungarian bread wheat and to identify potential benefits or hazards for introducing germplasm into reciprocal breeding programmes. Results from four Oklahoma and six Hungarian environments showed that non-native cultivars were 14% and 25% lower in grain yield than native ones in Hungary and Oklahoma, respectively, although one HRW cultivar (2163) exhibited exceptional yield potential in both locations. The lower grain yield potential of Hungarian genotypes in Oklahoma was reflected primarily in lower spike production at harvest. Yield performance in one location did not correlate with performance in the other. Greater consistency between locales was found for test weight (r = 0.6, P < 0.05) and heading date (r = 0.9, P < 0.01); thus, screening for those traits prior to introduction of parent material may be useful. Although some recovery of the genetic yield potential of native material will be necessary, intergroup crossing between these apparently distinct gene pools should provide a new and valuable resource for bread wheat cultivar development.     

Behaviour of the Root Nodules in Soybean in the Presence of Nitrogen: The Use of a Statistical Simulation Model

Two varieties of soybean were grown in large pots out of doors. At the R2 stage, a state of temporary root anoxia appeared caused by a heavy rainfall and in R3, nitrogen was applied. The nitrogenase activity of the nodules was measured at weekly intervals (ARA test).
During the vegetative stage, the number of nodules and their weight increased rapidly, although the anoxia caused a slowing down followed by a recovery in the successive stages (R3–5). The same effect was apparent in consequence of a late nitrogen fertilization; both varieties attaining values close to those of the control 15 days after the treatment. Nitrogenase activity also showed an inhibition caused by the anoxia but it appeared earlier. During the latest stages of the cycle (R6–7), the nitrogen treatment increased the rate of nitrogen fixation in Hodgson 78 only. The use of a multiple regression model allowed a verification that the parameters controlling nitrogen fixation acted in a similar way in both varieties. In the field, the weight of the nodules, both single and total, appeared to be particularly important in determining the total nitrogen fixation rate.     

Assessment of clinical criteria to diagnose scrapie in Italy

A reliable ante-mortem test for the detection of scrapie in all genotypes has not yet been developed and clinical diagnosis remains a useful tool for surveillance purposes. This paper describes the results of a three-year study in which clinical signs consistent with scrapie were recorded according to standardized criteria in 245 sheep from 21 outbreaks in Italy in order to identify helpful criteria for the diagnosis of the disease. Thirty-seven sheep were scrapie-positive at post-mortem rapid testing, 23 showed weight loss, 20 had proprioceptive deficits, 17 demonstrated ataxia and nibble reflex, and some sheep had a combination of signs. Six scrapie-positive sheep were asymptomatic. The clinical protocol was easy to handle and appears to be a useful tool for improving passive surveillance. The data suggested that positive clinical history, nibble, and nibble combined with proprioceptive positioning deficit have a quite high negative predictive value. The protocol will be proposed as a tool for field inspection in passive surveillance in Italy.