排序方式： 共有26条查询结果，搜索用时 31 毫秒
1.
Franck Richard Melanie Roy Oula Shahin Christopher Sthultz Myriam Duchemin Richard Joffre Marc-André Selosse 《Annals of Forest Science》2011,68(1):57-68
• Introduction
Millions of hectares of Quercus ilex forests dominate disturbed landscapes in the western part of the Mediterranean basin. Although these forests are very widespread, little is known about the composition and structure of their associated ectomycorrhizal fungal communities. 相似文献2.
Conservation strategies should be based on a solid understanding of processes underlying species response to landscape change.
In forests fragmented by agriculture, elevated nest predation rates have been reported in many forest bird species, especially
near edges. In intensively-managed forest landscapes, timber harvesting might also be associated with negative edge effects
or broader “context” effects on some species when the matrix provides additional resources to their major nest predators.
In this study, we hypothesized that proximity to a forest edge and proportion of cone-producing plantations will increase
nest predation risk in fragments of relatively undisturbed forest. We focused on the Brown Creeper (Certhia americana), an indicator species of late-seral forests. We compared habitat configuration and composition at four spatial scales (0.14,
0.5, 1 and 2 km) around 54 nests and related daily nest survival rate to the distance to the nearest forest edge, mean patch
size of late-seral forest (r = 141 m), proportion of non-forested lands (r = 141 m), density of maintained roads (r = 1 km), proportion of cone-producing spruce plantations (r = 2 km), and year. The best model included distance to the nearest edge and proportion of cone-producing plantations. Distance
of nests to the nearest edge was the best individual predictor of daily nest survival. A larger sample of nests showed a significant
threshold in distance to the nearest forest edge; nests located at least 100 m away were more likely to fledge young. These
results suggest that even in managed forest landscapes, matrix effects can be important and some bird species may exhibit
negative edge effects. 相似文献
3.
Swan Specchi Giuseppe Lacava Marc-André d’Anjou Eric Zini Edoardo Auriemma 《The Canadian veterinary journal. La revue veterinaire canadienne》2012,53(11):1187-1190
A 10-year-old spayed female dalmatian dog developed acute vomiting and abdominal pain. Ultrasound examination of the abdomen showed right hydronephrosis and proximal ureter dilation with mild retroperitoneal free fluid. Computed tomography (CT) of the abdomen confirmed the ultrasonographic findings and revealed, additionally, a right ureteral stone. Spontaneus rupture of the right ureter was confirmed with CT post ultrasound-guided percutaneous antegrade pyelography. Pyeloureteral rupture and the presence of a ureteral stone were confirmed at surgery. 相似文献
4.
D'Anjou MA Carmel EN Blond L Beauchamp G Parent J 《Veterinary radiology & ultrasound》2012,53(1):11-20
Our purpose was to characterize meningeal gadolinium enhancement on magnetic resonance (MR) imaging in dogs with inflammatory and neoplastic diseases, and to assess interobserver variability and the impact of delayed acquisition and chemical fat saturation on its conspicuity. Transverse T1-weighted FLAIR images were acquired prior to, and immediately following gadolinium injection (T0), and at 5 (T5) and 15-20 min delay (TD), with and without fat suppression, in 155 consecutive dogs imaged for suspected brain disease. The agreement on meningeal enhancement was globally substantial (kappa = 0.61) and the likelihood of obtaining a definite diagnosis was significantly increased with the use of fat suppression (P < or = 0.004). Meningeal enhancement was judged definitively present by consensus in 46 of 155 (30%) dogs. Of these, meningeal enhancement was characterized qualitatively and quantitatively in 30 dogs with a clinical diagnosis (18 inflammatory, 11 neoplastic, 1 infarct), and image sequences were compared. Meningeal enhancement was more often diffuse and leptomeningeal in animals with inflammation versus neoplasia (50% vs. 42%, and 69% vs. 48%, respectively), but significant associations were not found. Meningeal thickness and contrast ratio were higher with neoplasia (P < or = 0.02), but results did not vary significantly between series for either group. Yet, images with fat suppression were most useful 50% of the time for definite diagnosis and/or characterization of meningeal enhancement. While delayed image acquisition following gadolinium injection does not improve characterization of meningeal enhancement in dogs, fat suppression is beneficial qualitatively. 相似文献
5.
Techniques for modeling burn probability (BP) combine the stochastic components of fire regimes (ignitions and weather) with
sophisticated fire growth algorithms to produce high-resolution spatial estimates of the relative likelihood of burning. Despite
the numerous investigations of fire patterns from either observed or simulated sources, the specific influence of environmental
factors on BP patterns is not well understood. This study examined the relative effects of ignitions, fuels, and weather on
mean BP and spatial patterns in BP (i.e., BP variability) using highly simplified artificial landscapes and wildfire simulation
methods. Our results showed that a limited set of inputs yielded a wide range of responses in the mean and spatial patterning
of BP. The input factors contributed unequally to mean BP and to BP variability: so-called top-down controls (weather) primarily
influenced mean BP, whereas bottom-up influences (ignitions and fuels) were mainly responsible for the spatial patterns of
BP. However, confounding effects and interactions among factors suggest that fully separating top-down and bottom-up controls
may be impossible. Furthermore, interactions among input variables produced unanticipated but explainable BP patterns, hinting
at complex topological dependencies among the main determinants of fire spread and the resulting BP. The results will improve
our understanding of the spatial ecology of fire regimes and help in the interpretation of patterns of fire likelihood on
real landscapes as part of future wildfire risk assessments. 相似文献
6.
Germain Marion Kneeshaw Daniel De Grandpré Louis Desrochers Mélanie James Patrick M. A. Vepakomma Udayalakshmi Poulin Jean-François Villard Marc-André 《Landscape Ecology》2021,36(10):3013-3027
Landscape Ecology - Although the spatiotemporal dynamics of spruce budworm outbreaks have been intensively studied, forecasting outbreaks remains challenging. During outbreaks, budworm-linked... 相似文献
7.
Multiple novel and prevalent astroviruses in pigs 总被引：3，自引：0，他引：3
Knowledge of porcine astrovirus diversity and epidemiology remains limited. We used a broad range PCR approach to investigate the presence and diversity of astroviruses in healthy pigs of different ages on 20 farms and in 3 slaughterhouses situated in the province of Quebec, Canada between 2005 and 2007. Our study unexpectedly revealed remarkable levels of genetic diversity and high prevalence of astroviruses in pigs of this province. Astroviruses were detected on every farm investigated and in all age groups of pigs, from suckling piglets to adults. In addition, we found that nearly 80% of healthy finisher pigs harbour astroviruses in their intestine at slaughter. Phylogenetic evidence based on partial polymerase and complete capsid sequences, suggests that porcine astroviruses do not form a monophyletic group but are rather found on separate branches across the mamastrovirus tree. In addition to type species strains, we found highly divergent strains that form two additional lineages, one of which falls outside existing taxonomic groups. The presence of diverse astroviruses in a majority of healthy pigs likely represents a continuous source of infection to piglets and possibly to other animal species including humans. Porcine astrovirus strains appeared phylogenetically related not only to prototypical human astroviruses, as was already known, but also to novel human strains recently discovered suggesting multiple cross species transmission events between these hosts and other animal species. Overall, the findings reported in this study suggest an active role of pigs in the evolution and ecology of the Astroviridae. 相似文献
8.
Owing to the economic, social and environmental impacts associated with timber harvesting by small-scale forest owners, a number of studies have characterized their profiles, motivations and activities at a given time. However, little research has focused on how timber production has been affected by changes in the prevalence of types of forest owners over time. A 2012 telephone survey of Quebec (Canada) small-scale forest owners reveals relationships between level of harvesting and socio-demographic factors, and an evolution of these factors by examining the results of surveys conducted in 1973 and 1985. Within the same population, property size, distance between owners’ forest and homes, possession of a forest management plan, gender, education level, the length of ownership are correlated with how likely respondents were to harvest timber on their forest. Furthermore, comparison with results from previous surveys of the same population show an increase in the prevalence of characteristics associated with owners who place less importance on timber harvesting in their management decisions. Overall, since the initial survey of forest owners conducted in 1973, the size of forest holdings in Quebec has decreased, respondents’ education level has improved and the proportion of forests owned by women have increased. However, these changes are occurring at a relatively slow rate, giving government authorities time to implement policies to encourage harvesting among the new generation of forest owners. 相似文献
9.
Gutscher MA 《Science (New York, N.Y.)》2004,305(5688):1247-1248
10.