Citation: Boisvert-Marsh, L., C. Périé, S. de Blois. 2014. Shifting with climate? Evidence for recent changes in tree species distribution at high latitudes. Ecosphere 5(7):83. http://dx.doi.org/10.1890/ES14-00111.1Abstract. Warming has been particularly strong at high latitudes in recent decades and bioclimatic models predict northern shifts in optimal conditions for most species. Climate is a strong predictor of site occupancy for trees at broad spatial scales and interacts with other drivers of forest dynamics. Recent changes in distribution and occupancy patterns should therefore provide the best evidence of a tree species' potential to shift in the direction predicted by bioclimatic models. Studies examining recent distribution changes for plants, however, have mostly done so along altitudinal gradients or have used the latitudinal position of juvenile trees relative to adult ones to infer range dynamics. This study provides rare evidence of latitudinal shifts for 11 northern tree species by assessing recent changes in distribution using globally significant inventories from 1970 to 2002. It also compares observed trends with those inferred from the position of juveniles relative to trees in a single survey. Samplings cover 6456 forest plots in temperate and boreal forests up to treeline in eastern North America. The average overall latitudinal shift was 3.07 6 4.37 km northward although responses were species-specific. Shifts were detected more for juvenile than for adult trees and significant northward ones were detected more at northern range limits than at the median. All species demonstrated increased frequency of plot occupancy for saplings while occupancy generally decreased for adult trees. Five out of the 11 species examined (Acer rubrum, Acer saccharum, Betula papyrifera, Fagus grandifolia, and Populus tremuloides) showed significant distributional shifts consistent with northward migration. Saplings of Abies balsamea, Picea glauca, and Picea mariana, on the other hand, showed southward shifting trends. Natural and human disturbances undoubtedly interact with climate to determine forest dynamics; this study shows whether their combined effect can shift distribution in the direction predicted by bioclimatic models. Only continued monitoring will reveal whether these observations are just transient dynamics or indicative of shifting range in this century. Our study provides a benchmark against which to assess future observations of latitudinal shifts for trees.

There is general consensus that wildfires in boreal forests will increase throughout this century in response to more severe and frequent drought conditions induced by climate change. However, prediction models generally assume that the vegetation component will remain static over the next few decades. As deciduous species are less flammable than conifer species, it is reasonable to believe that a potential expansion of deciduous species in boreal forests, either occurring naturally or through landscape management, could offset some of the impacts of climate change on the occurrence of boreal wildfires. The objective of this study was to determine the potential of this offsetting effect through a simulation experiment conducted in eastern boreal North America. Predictions of future fire activity were made using multivariate adaptive regression splines (MARS) with fire behavior indices and ecological niche models as predictor variables so as to take into account the effects of changing climate and tree distribution on fire activity. A regional climate model (RCM) was used for predictions of future fire risk conditions. The experiment was conducted under two tree dispersal scenarios: the status quo scenario, in which the distribution of forest types does not differ from the present one, and the unlimited dispersal scenario, which allows forest types to expand their range to fully occupy their climatic niche. Our results show that future warming will create climate conditions that are more prone to fire occurrence. However, unlimited dispersal of southern restricted deciduous species could reduce the impact of climate change on future fire occurrence. Hence, the use of deciduous species could be a good option for an efficient strategic fire mitigation strategy aimed at reducing fire Propagation in coniferous landscapes and increasing public safety in remote populated areas of eastern boreal Canada under climate change.

Pe´rie´, C. and Ouimet, R. 2008. Organic carbon, organic matter and bulk density relationships in boreal forest soils. Can. J. Soil Sci. 88: 315Á325. Relationships between soil organic carbon (SOC), organic matter (SOM), and bulk density (BD) were established in acidic loamy to sandy loam fine fractions of forest soils in Quebec (Canada). The interest of such relationships rests with the possibility of using simple and rapid techniques to estimate SOC and BD. It is also a crucial step in establishing the correspondence among several data bases when SOC data are obtained using different measurement techniques. In this study, SOC was measured by dry combustion (SOC DC ) and wet digestion (SOC WD ) methods, and organic matter by loss-on-ignition (LOI). Our results suggest that, in these soils: (1) LOI can be used for estimating SOC (r 2 00.95, RMSEP 016%) and SOC DC /SOM significantly decreased with increasing depth from 0.49 to 0.27; (2) SOC DC and SOC WD were highly correlated. Even if SOC WD provided near complete recovery of SOC DC , dry combustion remains the preferred method for SOC analysis since SOC WD recovery decreased with increasing depth from 100 to 83%. (3) BD was also strongly related to SOM (r 2 00.81). We recommend using the organic density approach to estimate BD from SOM because it allows BD to be predicted without significant bias and with a degree of accuracy of 14%.Key words: Forest soils, soil organic carbon, soil organic matter, soil bulk density Pe´rie´, C. et Ouimet, R. 2008. Liens entre le carbone organique, la matie`re organique et la masse volumique apparente dans le sol des foreˆts bore´ales. Can. J. Soil Sci. 88: 315Á325. Les auteurs ont pre´cise´les liens entre le carbone organique (COS), la matie`re organique (MOS) et la masse volumique apparente (MVA) du sol dans les fractions fines de loam et de loam sablonneux des sols forestiers acides du Que´bec. De tels liens pre´sentent un certain inte´reˆt, car on pourrait y recourir comme technique simple et rapide pour e´valuer la concentration de COS et la MVA. Il s'agit aussi d'une e´tape cruciale quand on souhaite e´tablir une correspondance entre des bases de donne´es ou`la concentration de COS e´mane de diverses techniques. Dans le cadre de la pre´sente e´tude, la quantite´de COS a e´te´de´termine´e par combustion se`che (COS CS ) et digestion par voie humide (COS DH ) tandis qu'on a mesure´la concentration de matie`re organique au moyen des pertes par calcination (PPC). Les auteurs ont obtenu les re´sultats que voici pour les sols concerne´s. (1) La me´thode PPC permet d'estimer le COS (r 2 0 0,95, RMSEP 0 16 %) et le ratio COS CS /MOS diminue de manie`re significative, de 0,49 a`0,27, avec la profondeur. (2) Il existe une importante corre´lation entre le COS CD et le COS DH . Bien que la technique COS DH permette de re´cupe´rer la quasi totalite´du COS CS , la combustion se`che demeure la me´thode privile´gie´e pour analyser le COS, la quantite´de carbone re´cupe´re´e par COS DH passant de 100 a`83 % a`mesure qu'augmente la profond...

Anticipating the effects of climate change on biodiversity is now critical for managing wild species and ecosystems. Climate change is a global driver and thus affects biodiversity globally. However, land-use planners and natural resource managers need regional or even local predictions. This provides scientists with formidable challenges given the poor documentation of biodiversity and its complex relationships with climate. We are approaching this problem in Quebec, Canada, through the CC-Bio Project (http://cc‑bio.uqar.ca/), using a boundary organization as a catalyst for team work involving climate modelers, biologists, naturalists, and biodiversity managers. In this paper we present the CC-Bio Project and its general approach, some preliminary results, the emerging hypothesis of the northern biodiversity paradox (a potential increase of biodiversity in northern ecosystems due to climate change), and an early assessment of the conservation implications generated by our team work

Climate change is expected to result in a reorganization of the continental distribution of tree species. Recent shifts in distribution patterns have been reported, but it is not always clear how climate change influences these patterns locally, especially in relation to other disturbances. We investigated latitudinal shifts of four ecologically important tree species between 1970 and 2014 within a study area that encompasses their northernmost range limit in northeastern North America (Quebec, Canada; ~761,000 km2). Changes in latitudinal limits were defined in relation to changes in tree saplings’ occurrence patterns within forest plots resampled over two time periods (1970–1977 and 2003–2014). By examining changes in the frequency of occurrences in different portions of the study area along a latitudinal gradient, we were able to identify spatially explicit patterns of loss or gain (sapling recruitment) resulting in the shifts observed. We then estimated the probability of observing a recruitment event in response to changes in climate, disturbance and their interaction, using a multimodel selection approach. Latitudinal limits of all four species shifted northward, but these shifts resulted from different patterns of plot occurrence changes, depending on the species and the location examined. Greater recruitment at northern locations than at southern ones drove shifts for Acer saccharum Marsh., Fagus grandifolia Ehrh. and Acer rubrum L., but less so for Betula alleghaniensis Britt. Climate variables indicating changes in early or late growing season conditions were most often selected in models. Warming tended to reduce recruitment probability in the south but increase it in the north, leading to divergent responses for a given species across the study area. Disturbance effects were generally less important than climate change effects, as was their interaction. Synthesis. Spatially explicit and divergent responses to climate change and disturbance drive recruitment patterns underlying latitudinal shifts of tree species. The importance of early‐ or late‐season climate variables points towards biological processes being affected at critical stages of the life cycle. Understanding the factors that influence species’ migration capacity in a changing climate is crucial to inform adaptive management and conservation practices.