Figure 4.

Seedling growth response to elevation, soil source and seed source. Effect of (a) planting site, regardless of soil source, and (b–d) soil and seed source on seedling height. Soil source effects are separated by planting sites (b) within, (c) at the edge and (d) beyond sugar maple's natural distribution, thus the effects of elevation are negligible within each of the three lower panels. Seed came from populations within and at the edge of sugar maple's distribution within the study area. Missing boxes indicate that no seedlings emerged and/or survived in that experimental treatment. Letters indicate significant differences as in figure 2, with letters in (b–d) indicating differences between soil source treatments. Seed source differences are not indicated in the figure but were detected where seedlings germinated from seed collected within sugar maple's distribution were significantly taller than those using seed from the range edge. (Online version in colour.)