78 research outputs found
Effets de la disponibilitĂ© potentielle en nids et en nourriture sur lâabondance du Grand Polatouche (Glaucomys sabrinus) en forĂȘt borĂ©ale mixte de lâest du Canada
Le Grand Polatouche (Glaucomys sabrinus) est un rongeur arboricole et cavicole associĂ© aux gros arbres et aux vieilles forĂȘts non perturbĂ©es. Cette espĂšce est considĂ©rĂ©e non seulement comme une espĂšce clĂ© des forĂȘts de conifĂšres, mais Ă©galement comme une espĂšce indicatrice dâamĂ©nagement durable en AmĂ©rique du Nord. Les rĂ©sultats dâune Ă©tude de 2008 ont cependant montrĂ© que la disponibilitĂ© en cavitĂ©s ne semblait pas limiter la prĂ©sence de lâespĂšce en forĂȘt borĂ©ale quĂ©bĂ©coise. Nous avons donc rĂ©alisĂ© une expĂ©rience dans laquelle nous avons ajoutĂ© des cavitĂ©s artificielles (nichoirs) sur la moitiĂ© des sites Ă©tudiĂ©s en 2008 (n=56), afin de dĂ©terminer par piĂ©geage, 4 ans plus tard, si la disponibilitĂ© de cette ressource influence lâabondance locale de lâespĂšce ainsi que la dynamique de ses populations. Nous supposons que 1) lâabondance initiale augmente selon la disponibilitĂ© potentielle en nourriture (mesurĂ©e par la surface terriĂšre de conifĂšres) et en cavitĂ©s (mesurĂ©e par la surface terriĂšre de chicots) ; 2) lâajout de nichoirs aura une influence positive sur le taux de recrutement et la survie apparente des polatouches et que 3) lâeffet de lâajout de nichoirs dĂ©pendra de la disponibilitĂ© naturelle en nourriture et en cavitĂ©s sur chaque site. En prenant en compte lâeffet de lâannĂ©e, des prĂ©cipitations et de la hauteur des piĂšges sur la probabilitĂ© de dĂ©tection, nous avons analysĂ© les donnĂ©es selon des modĂšles N-mĂ©langĂ©s (N-mixture model). Lâabondance initiale est influencĂ©e par la disponibilitĂ© en nourriture mais pas par la disponibilitĂ© en cavitĂ©s. De plus, ni lâajout de nichoirs, ni les caractĂ©ristiques des sites nâexpliquent lâabondance des populations de polatouches aprĂšs lâajout de nichoirs, bien que tous les sites non occupĂ©s en 2008 sauf un aient Ă©tĂ© colonisĂ©s en 2012. Nos rĂ©sultats confirment lâaspect opportuniste de lâespĂšce et suggĂšrent que le Grand polatouche nâest peut ĂȘtre pas une bonne espĂšce indicatrice de vieilles forĂȘts dans nos forĂȘts borĂ©ales mixtes
Transforming Abandoned Farm Fields to Conifer Plantations Reduces Ruffed Grouse Density
Natural forests likely will be unable to fulfill societyâs needs sustainably for wood fiber in the near future. In an attempt to meet increasing demands while protecting intact forests, producers have increasingly considered alternative sources of timber, such as intensively managed plantations. In regions that are economically dependent on forest harvesting, abandoned farm fields are often targeted for conversion to intensive coniferous plantations. These sites are generally in an early successional stage that is dominated by deciduous stands, which provide an important habitat type for several game species, including ruffed grouse (Bonasa umbellus). Therefore, conversion could represent a loss of habitat for this species and several others that are associated with early successional deciduous stages. We conducted grouse drumming surveys in northwestern Quebec, Canada to evaluate the effects of transforming old fields into conifer plantations on ruffed grouse by comparing densities between two habitat types: abandoned farm fields (n = 22) and old fields converted to conifer plantations (n = 19). To correct anyaudibility bias between habitat types, we located all drumming males that were heard at each site. We then analyzed the number of individuals that were detected in the sites with repeated count models. Our results show that overall drumming males avoided plantations. Overhead cover increased drumming male densities in both habitat types, whereas lateral cover increased drumming grouse densities only in plantations. The density of deciduous stems and fruit-bearing stems also had a tendency to increase drumming male densities, but their effects were marginal. Most ruffed grouse in abandoned farm fields used piles of woody debris on the ground as drumming structures rather than large logs or rock outcrops. Our results suggest that plantations do not have the vegetative cover and quantity of food stems necessary to support high ruffed grouse densities during the drumming season and that conversion of abandoned farm fields to coniferous plantations may exert negative cascading effects for reproduction and population growth
Response of wild bee communities to beekeeping, urbanization, and flower availability
Wild bees provide pollination services and are currently declining at the global scale. A potential cause for this decline is competitive interactions with domestic honey bees. Urban beekeeping, a fairly new activity, is rapidly gaining popularity. In contrast with agricultural and natural areas, the extent of competition between honey bees and wild bees in urban areas is unclear. The objectives of this study were to quantify the impact of honey bees, urbanization, and the availability of floral resources on wild bee communities. We hypothesized that honey bees exert negative impacts on wild bees, that floral resources favor wild bee communities and mitigate the negative impacts of competition with honey bees, and that the influence of heat islands, used as a proxy for urbanization, varies between wild bees with their functional traits (nesting behavior). We tested these hypotheses with a data set of 19,077 wild bee specimens collected using colored pan-traps at 25 urban sites in 2012 and 2013. We investigated community and population patterns after accounting for imperfect detection probability. We found no evidence of competition between wild and domesticated bees. Our analyses indicate mixed effects of urban heat islands across species and positive effects of floral resources. We conclude that cities can allow the coexistence of urban beekeeping and wild bees under moderate hive densities. However, it will remain crucial to further investigate the competitive interactions between wild and honey bees to determine the threshold of hive densities beyond which competition could occur
Variation in Wood Quality in White Spruce (Picea Glauca (Moench) Voss). Part I. Defining the JuvenileâMature Wood Transition Based on Tracheid Length
Estimations of transition age (TA) and juvenile wood proportion (JWP) are important for wood industries due to their impact on end-product quality. However, the relationships between analytical determination of TA based on tracheid length (TL) and recognized thresholds for adequate end products have not yet been established. In this study, we used three different statistical models to estimate TA in white spruce (Picea glauca (Moench) Voss) based on TL radial variation. We compared the results with technological maturity. A two-millimeter threshold, previously suggested for good paper tear strength, was used. Tracheid length increased from pith to bark and from breast height to upper height. Juvenile wood (JW) was conical with the three models. At breast height, TA ranged from 11 to 27 years and JWP ranged from 15.3% to 47.5% across the three models. The linear mixed model produced more conservative estimates than the maximum-quadratic-linear (M_Q_L) model. Both the linear mixed model and the M_Q_L model produced more conservative TA estimates than the piecewise model. TA estimates by the MIXED model, and to a lesser extent by the M_Q_L model, were equivalent to those for real mature wood, whereas TA estimates by the piecewise model were considerably lower, falling into the transition wood area
Effects of Cambial Age and Stem Height on Wood Density and Growth of Jack Pine Grown in Boreal Stands
Jack pine specimens were examined for longitudinal and radial variations in selected wood quality parameters. Wood density and ring width of cross-sections were measured systematically from pith to bark along the merchantable stem using X-ray densitometry. Effects of cambial age and stem height were analyzed using a linear mixed model with two levels of nesting. A strong interaction between the two factors was found in corewood. Tree individual variation increased with cambial age for all studied wood properties and was larger in earlywood than in latewood. Radial patterns in the studied parameters closely approximated published ones in the lower stem but lessened considerably with increasing stem height. By contrast, longitudinal patterns reversed with cambial age in earlywood. High coordination was found between longitudinal patterns in corewood and radial patterns in the stem base, indicating a similar maturation pattern in the apical meristem and cambia. However, with increasing cambial age, this high coordination disappeared rapidly
Using dynamicN-mixture models to test cavity limitation on northern flying squirrel demographic parameters using experimental nest box supplementation
Dynamic N-mixture models have been recently developed to estimate demographic parameters of unmarked individuals while accounting for imperfect detection. We propose an application of the Dail and Madsen (2011: Biometrics, 67, 577â587) dynamic N-mixture model in a manipulative experiment using a before-after control-impact design (BACI). Specifically, we tested the hypothesis of cavity limitation of a cavity specialist species, the northern flying squirrel, using nest box supplementation on half of 56 trapping sites. Our main purpose was to evaluate the impact of an increase in cavity availability on flying squirrel population dynamics in deciduous stands in northwestern Quebec with the dynamic N-mixture model. We compared abundance estimates from this recent approach with those from classic captureâmarkârecapture models and generalized linear models. We compared apparent survival estimates with those from CormackâJollyâSeber (CJS) models. Average recruitment rate was 6 individuals per site after 4 years. Nevertheless, we found no effect of cavity supplementation on apparent survival and recruitment rates of flying squirrels. Contrary to our expectations, initial abundance was not affected by conifer basal area (food availability) and was negatively affected by snag basal area (cavity availability). Northern flying
squirrel population dynamics are not influenced by cavity availability at our deciduous sites. Consequently, we suggest that this species should not be considered an indicator of old forest attributes in our study area, especially in view of apparent wide population fluctuations across years. Abundance estimates from N-mixture models were similar to those from captureâmarkârecapture models, although the latter had greater precision. Generalized linear mixed models produced lower abundance estimates, but revealed the same relationship between abundance and snag basal area. Apparent survival estimates from N-mixture models were higher and less precise than those from CJS models. However, N-mixture models can be particularly useful to evaluate management effects on animal populations, especially for species that are difficult to detect in situations where individuals cannot be uniquely identified. They also allow investigating the effects of covariates at the site level, when low recapture rates would require restricting classic CMR analyses to a subset of sites with the most captures
Utilisation des parcs à résidus miniers par la sauvagine en comparaison avec des étangs de castors en Abitibi-Témiscamingue
Les milieux humides sont essentiels pour un grand nombre dâespĂšces fauniques et vĂ©gĂ©tales. Ces milieux sont cependant dĂ©gradĂ©s par les activitĂ©s humaines, affectant ainsi lâhabitat de groupes dâespĂšces tels que la sauvagine, qui utilise ces milieux aux diffĂ©rentes Ă©tapes de son cycle de vie. Dans ce contexte particulier, certains milieux humides artificiels, tels que des bassins dâĂ©puration ou de rĂ©cupĂ©ration dâeau de pluie, sont parfois utilisĂ©s par ces espĂšces en alternative Ă des habitats naturels perdus. Dans la rĂ©gion de lâAbitibi-TĂ©miscamingue, localisĂ©e dans lâOuest du QuĂ©bec, certains Ă©tangs de parcs Ă rĂ©sidus miniers sont connus par les ornithologistes pour ĂȘtre utilisĂ©s par plusieurs espĂšces aviaires. Dans le cadre de cette Ă©tude, nous nous sommes intĂ©ressĂ©s Ă Ă©valuer la qualitĂ© des parcs Ă rĂ©sidus miniers en comparaison avec un milieu naturel reconnu favorable Ă lâĂ©tablissement de la sauvagine : des Ă©tangs de castors. Nous avons effectuĂ© un inventaire des espĂšces de sauvagine (adultes et couvĂ©es) prĂ©sentes sur 12 Ă©tangs miniers et 38 Ă©tangs de castors situĂ©s en Abitbi-TĂ©miscamingue. Nous avons Ă©galement considĂ©rĂ© les variables environnementales sur les sites pouvant affecter lâoccupation de ces Ă©tangs. Les comparaisons effectuĂ©es entre les deux types de sites ont montrĂ© que les conditions sur les sites miniers semblent aussi favorables Ă lâĂ©tablissement de la sauvagine en pĂ©riode de reproduction que celles observĂ©es sur les Ă©tangs de castors. En utilisant les modĂšles dâoccupation de sites, nous avons trouvĂ© que la plupart des espĂšces utilisaient autant les parcs Ă rĂ©sidus miniers que les Ă©tangs de castors considĂ©rĂ©s. Ces espĂšces semblent Ă©galement se reproduire autant sur les deux types de sites. Les adultes et les couvĂ©es du Garrot Ă oeil dâor semblent mĂȘme utiliser de façon plus importante les Ă©tangs miniers. Bien que nos modĂšles nâaient pas permis de montrer de relation directe entre lâoccupation du garrot et les conditions observĂ©es sur les sites, nous suggĂ©rons que les rĂ©sultats obtenus pour le garrot peuvent sâexpliquer par le fait que les Ă©tangs miniers sont plus ouverts et souvent dĂ©pourvus de poissons compĂ©titeurs. Ces caractĂ©ristiques sont donc Ă favoriser lors de la restauration dâun site minier dans le cas dâun amĂ©nagement pour la sauvagine. Puisque ces Ă©tangs miniers sont Ă©galement utilisĂ©s par plusieurs espĂšces, nous recommandons de conserver ces Ă©lĂ©ments du paysage, qui peuvent reprĂ©senter un nouvel habitat de qualitĂ© pour ce groupe faunique. De futuresĂ©tudes rĂ©alisĂ©es sur lâutilisation des Ă©tangs miniers par la sauvagine devraient ĂȘtre effectuĂ©es afin de confirmer ces conclusions sur le long terme
Habitat, Climate, and Fisher and Marten Distributions
Since the midâtwentieth century, fisher populations (Pekania pennanti) increased in several eastern jurisdictions of North America, particularly in the northern part of the speciesâ range. Changes in fisher distribution have led to increased overlap with the southern portion of the range of American marten (Martes americana), whose populations may be locally declining. This overlap occurs particularly in habitats undergoing natural and anthropogenic modification. The objective of our study was to determine the respective effects of habitat changes and climatic conditions on fisher and marten populations in Quebec, Canada, based on trapper knowledge. We analyzed annual fisher and marten harvest (number of pelts sold/100 km2) between the 1984â1985 and 2014â2015 trapping seasons using linear mixed models. Fisher harvest increased with the increased abundance of mixed forests >12m tall, resulting from decades of forest harvesting. Fisher harvest decreased with increasing spring rains, which can affect survival when rearing young. Marten harvest decreased with increasing winter rains, which lower thermoregulation capacity and hamper movements by creating an ice crust on the snowpack, reducing access to subnivean areas. Decline in marten harvest during the 30âyear study period coincided with an increase in fisher harvest, suggesting possible interspecific competition. Results highlight that managers should strive to maintain mixedwood stands taller than 12m to maintain high quality habitat for fishers. Our study confirms the importance of working with trappers to assess furbearing population trends in response to habitat changes and climatic conditions
Site occupancy by American martens and fishers in temperate deciduous forests of Québec
Anglais
Interspecific interactions can mediate site occupancy of sympatric species and can be a key factor in habitat use patterns. American martens (Martes americana) and Fishers (Pekania pennanti) are two sympatric mesocarnivores in eastern North American forests. Due to their larger size, fishers have a competitive advantage over martens. We investigated site occupancy of martens and fishers in temperate deciduous forests of Québec, an environment modified by forest management and climate change. We formulated hypotheses on the spatial distribution of the studied species based on the knowledge of local trappers and on the scientific literature regarding forest cover composition, habitat fragmentation, and competitive relationships. We used a network of 49 camera traps monitored over two fall seasons to document site occupancy by both species. We used two-species site occupancy models to assess habitat use and the influence of fishers on martens at spatial grains of different sizes. None of the habitat variables that we considered explained site occupancy by fishers. Availability of dense old coniferous stands explained the spatial distribution of martens both at the home range grain size and at the landscape grain size. We identified the characteristics of habitat hotspots based on the knowledge of trappers, which highlighted the importance of stand composition, height, age, and canopy closure. The characteristics of habitat hotspots for martens in temperate deciduous forests refine the habitat suitability model for American martens that was originally developed for boreal forests of Québec.
Français
Les interactions interspĂ©cifiques peuvent affecter lâoccupation de sites par des espĂšces sympatriques et jouer un rĂŽle clĂ© dans leur utilisation des habitats. La martre dâAmerique (Martes americana) et le pĂ©kan (Pekania pennanti) sont deux mĂ©socarnivores sympatriques des forĂȘts de lâest de lâAmĂ©rique du Nord. En raison de sa grande taille, le pĂ©kan est un compĂ©titeur dominant de la martre. Nous avons Ă©tudiĂ© lâoccupation des sites par la martre et le pĂ©kan dans la forĂȘt tempĂ©rĂ©e feuillue du QuĂ©bec, un environnement modifiĂ© par lâamĂ©nagement forestier et les changements climatiques. Nous avons formulĂ© des hypothĂšses sur la rĂ©partition spatiale des espĂšces Ă©tudiĂ©es en nous basant sur les connaissances des trappeurs locaux et sur la littĂ©rature scientifique en ce qui a trait Ă la composition du couvert forestier, Ă la fragmentation de lâhabitat, et aux relations de compĂ©tition. Nous avons utilisĂ© un rĂ©seau de 49 appareils photo Ă dĂ©clenchement automatique pendant deux automnes pour documenter lâoccupation des sites par les deux espĂšces. Nous avons utilisĂ© des modĂšles dâoccupation de sites Ă deux espĂšces afin dâĂ©valuer lâeffet de la prĂ©sence du pĂ©kan sur lâutilisation de lâhabitat par la martre Ă des Ă©chelles spatiales de rĂ©solutions variables. Aucune des variables dâhabitat que nous avons prises en compte nâexplique lâoccupation des sites par les pĂ©kans. La disponibilitĂ© de vieux peuplements denses de conifĂšres explique la rĂ©partition spatiale de la martre aux Ă©chelles spatiales du domaine vital et du paysage. Nous avons dĂ©veloppĂ© un indice dâhabitat potentiel basĂ© sur les connaissances des trappeurs, qui a mis en Ă©vidence lâimportance de la composition, de la hauteur, de lâĂąge et de la densitĂ© des peuplements. Cet indice affine, pour les forĂȘts tempĂ©rĂ©es feuillues du QuĂ©bec, le modĂšle de qualitĂ© de lâhabitat de la martre dâAmĂ©rique originellement Ă©laborĂ© pour la forĂȘt borĂ©ale
Sugar maple (Acer saccharum March.) growth is influenced by close conspecifics and skid trait 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\ud
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 usingmultimodel inference. All predictors had\ud
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 sugarmaple trees depends on\ud
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
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