Both climatic and edaphic conditions determine plant distribution, however many species distribution models do not include edaphic variables especially over large geographical extent. Using an exceptional database of vegetation plots (n = 4839) covering an extent of ∼55000 km2, we tested whether the inclusion of fine scale edaphic variables would improve model predictions of plant distribution compared to models using only climate predictors. We also tested how well these edaphic variables could predict distribution on their own, to evaluate the assumption that at large extents, distribution is governed largely by climate. We also hypothesized that the relative contribution of edaphic and climatic data would vary among species depending on their growth forms and biogeographical attributes within the study area. We modelled 128 native plant species from diverse taxa using four statistical model types and three sets of abiotic predictors: climate, edaphic, and edaphic-climate. Model predictive accuracy and variable importance were compared among these models and for species' characteristics describing growth form, range boundaries within the study area, and prevalence. For many species both the climate-only and edaphic-only models performed well, however the edaphic-climate models generally performed best. The three sets of predictors differed in the spatial information provided about habitat suitability, with climate models able to distinguish range edges, but edaphic models able to better distinguish within-range variation. Model predictive accuracy was generally lower for species without a range boundary within the study area and for common species, but these effects were buffered by including both edaphic and climatic predictors. The relative importance of edaphic and climatic variables varied with growth forms, with trees being more related to climate whereas lower growth forms were more related to edaphic conditions. Our study identifies the potential for non-climate aspects of the environment to pose a constraint to range expansion under climate change.

The Northern Biodiversity Paradox predicts that, despite its globally negative effects on biodiversity, climate change will increase biodiversity in northern regions where many species are limited by low temperatures. We assessed the potential impacts of climate change on the biodiversity of a northern network of 1,749 protected areas spread over >600,000 km2 in Quebec, Canada. Using ecological niche modeling, we calculated potential changes in the probability of occurrence of 529 species to evaluate the potential impacts of climate change on (1) species gain, loss, turnover, and richness in protected areas, (2) representativity of protected areas, and (3) extent of species ranges located in protected areas. We predict a major species turnover over time, with 49% of total protected land area potentially experiencing a species turnover >80%. We also predict increases in regional species richness, representativity of protected areas, and species protection provided by protected areas. Although we did not model the likelihood of species colonising habitats that become suitable as a result of climate change, northern protected areas should ultimately become important refuges for species tracking climate northward. This is the first study to examine in such details the potential effects of climate change on a northern protected area network.

Differential uptake and translocation of Ca and Sr in organisms have been reported, calling into question the use of Sr to track Ca cycling in the environment. We investigated the relationship between Ca/Sr ratios in soil extracts of various strengths (H 2 O, NH 4 Cl, and NH 4 EDTA) and seedlings of sugar maple (Acer saccharum Marsh.) grown from natural regeneration on 37 sites. Our objectives were to determine if Ca/Sr ratios in soil extracts are correlated with those in sugar maple tissues, and what soil extractant best duplicate plant tissue Ca/Sr ratios. Leaves had higher Ca/Sr ratios than stems and the extractants did not produce equal Ca/Sr ratios: H 2 O had the lowest Ca/Sr, and NH 4 EDTA the highest. The relationships between soil extract Ca/Sr ratios and leaf and stem Ca/Sr ratios were significant and linear, but the slopes differed among extractants. The lowest slope (0.45) was observed for the water extract/leaves and the highest (2.15) for the NH 4 EDTA extract/stem with discrimination factors ranging from 0.22 with NH 4 EDTA to 1.59 for water. Leaf extracts were more strongly correlated with soil Ca/Sr than stem extracts (R 2 of 0.57-0.7 vs. R 2 of 0.45-0.6, respectively). These findings support the use of Ca/Sr ratios in plants to track their source of soil Ca, but they highlight the need to calibrate the relationships for the plant tissue and soil extractant used.

Citation: Beauregard, F., and S. de Blois. 2016. Rapid latitudinal range expansion at cold limits unlikely for temperate understory forest plants. Ecosphere 7(11):e01549. 10.1002Ecosphere 7(11):e01549. 10. /ecs2.1549 Abstract. We ask whether climate warming will be likely to trigger rapid northward range expansion for understory plants in the northeastern forests of North America at the temperate-boreal forest ecotone. We answer this question through a detailed analysis of contemporary occupancy patterns at cold range edges and by looking for patterns consistent with climate or other environmental (e.g., edaphic) limitations. We first identify each species' realized growing degree-day niche to sample zones central, at the tail, or beyond the edge of this niche. We model habitat suitability, based on 11 nonclimate variables, for each species, and compare the availability of, and occupancy on, suitable sites across zones, with the assumption that a limiting climate is likely to result in decreased occupancy or abundance on otherwise suitable sites toward the range limit. We also check for evidence of shifts to warm microclimate conditions at the range limit as a potential indication of climate limitations. Based on our habitat models, we find that the availability of suitable sites declines across these three zones for most species, while occupancy increases on suitable sites at range edge, and abundance does not vary significantly. Some species shifted to sites with warm microclimate conditions; of these, several also declined in abundance suggesting climate limitations. We conclude, however, that for most species studied, suitable site availability appears to determine the northern edges of distribution and, consequently, warming may not necessarily lead to near-term range expansions.

Background and Aims: Reduced availability of calcium (Ca) has been linked to maple forest