Abstract:The combination of biochar (BC) with compost has been suggested to be a promising strategy to promote plant growth and performance, but although "synergistic" effects have been stated to occur, full-factorial experiments are few, and explicit tests for synergism are lacking. We tested the hypothesis that a combination of BC and spent mushroom substrate (SMS) has a positive synergistic effect on plant growth and physiological performance in a nutrient-limited growing media. A greenhouse experiment with a full factorial design was conducted using mixed-wood BC (3.0 kg·m −2 ) and SMS (1.5 kg·m −2 ) (the combination was not co-composted) as organic soil amendments for the annual Abutilon theophrasti and the perennial Salix purpurea. Several measurements related to plant growth and physiological performance were taken throughout the experiment. Contrary to the hypothesis, we found that the combination of BC + SMS had neutral or antagonistic interactive effects on many plant growth traits. Antagonistic effects were found on maximum leaf area, above-and belowground biomass, reproductive allocation, maximum plant height, chlorophyll fluorescence, and stomatal conductance of A. theophrasti. The effect on S. purpurea was mostly neutral. We conclude that the generalization that BC and compost have synergistic effects on plant performance is not supported.

Aim: Species distribution models typically project climatically suitable habitat for trees in eastern North America to shift hundreds of kilometres this century. We simulated potential migration, accounting for various traits that affect species' ability to track climatically suitable habitat.Location: Eastern Canada, covering ~3.7 million km 2 . Methods:We simulated migration-constrained range shifts through 2100 using a hybrid approach combining projections of climatically suitable habitat based on two Representative Concentration Pathways (RCP4.5, RCP8.5) for three time periods and two species distribution modelling approaches with process-based models parameterized using data related to dispersal ability and generation time. We developed a unique "migration kernel" that uses seed dispersal traits and observed migration velocities to obtain kernel shape and dispersal probabilities for each tree species. We then calculated lags between the migration-constrained range limits obtained through simulations and limits of climatically suitable habitat.Results: All species demonstrated northward range shifts at the leading edge of their simulated distribution through 2100, but the magnitude and rate of that shift varied by species and time period. Climatically suitable habitat limits were found to be north of simulated distribution limits across both RCPs, with lags increasing through time.On average, simulated distribution that remained within climatically suitable habitat declined more under RCP8.5 than RCP4.5, with large areas of the rear edge of the simulated distribution becoming partially or completely climatically unsuitable for many species.Main conclusions: Climatically suitable habitat limits projected for 2100 far exceeded migration-constrained range limits for all 10 tree species, particularly for temperate species. This study underlines the limited extent to which tree species will track climate change via natural migration. Integrating observed migration velocities, seed dispersal and generation time with SDM outputs allows for more realistic evaluations | 2331 BOISVERT-MARSH et al.

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