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A warming global climate will elicit changes in the distribution of plant species around the planet, and this will become most apparent where biomes converge. Climate exerts the strongest control over the geographic location of ecotones at the continental scale and many, including the boreal forest - temperate forest ecotone (BTE), are expected to shift to higher latitudes under climate change. Fine-scale drivers that define biome boundaries at the sub-continental scale are less well understood for many ecotones. We assembled studies addressing whether a modern distributional shift is occurring at the BTE and what biotic and abiotic factors are driving such a shift. Current research suggests a northward shift is occurring; yet, scant data are available to identify the processes involved. Abiotic and biotic factors are repeatedly identified as key drivers of change, though not all claims are evidence-supported and the interacting effects of these non-climatic factors are poorly understood. [ABSTRACT FROM AUTHOR]

Plant species distribution and plant community composition vary along environmental gradients. At the continental scale, climate plays a major role in determining plant distribution, while at the local and regional scales vegetation patterns are more strongly related to edaphic and topographic factors. The projected global warming and alteration of the precipitation regime will influence tree physiology and phenology, and is likely to promote northward migration of tree species. However the influence of soil characteristics on tree species migration is not as well understood. Considering the broad tolerance of most tree species to variations in soil factors, soils should not represent a major constraint for the northward shift of tree species. However, locally or regionally, soil properties may constrain species migration. Thus, while climate change has the potential to induce a northward migration of tree species, local or regional soil properties may hinder their migratory response. These antagonistic forces are likely to slow down potential tree migration in response to climate change. Because tree species respond individualistically to climate variables and soil properties, new tree communities are likely to emerge from climate change. [ABSTRACT FROM AUTHOR]