. The Canadian field-naturalist. B. Early Post-Glacial C. Recent Grassland, tundra, or bare ground ^^^ Pinus banksiana and Picea glauca Picea glauca. [O o u oj „. )oooc Picea enqelmannii Q Q Q Ql — Picea glauca and engelmannii Other montane conifers Laurentide Ice Sheet Figure 9. Diagrammatic representation of the probable sequence of post-Wisconsin vegetation changes in the northern Great Plains. retreating glacier. For various reasons, other taiga conifers, including Pinus banksiana, did not expand westward into Montana with the Picea glauca forests. As the glacier retreated north and east o
. The Canadian field-naturalist. B. Early Post-Glacial C. Recent Grassland, tundra, or bare ground ^^^ Pinus banksiana and Picea glauca Picea glauca. [O o u oj „. )oooc Picea enqelmannii Q Q Q Ql — Picea glauca and engelmannii Other montane conifers Laurentide Ice Sheet Figure 9. Diagrammatic representation of the probable sequence of post-Wisconsin vegetation changes in the northern Great Plains. retreating glacier. For various reasons, other taiga conifers, including Pinus banksiana, did not expand westward into Montana with the Picea glauca forests. As the glacier retreated north and east of the Cypress Hills (Figure 9B), this entire area of the northern Great Plains was overrun with coni- fers, Picea glauca forest following immediately behind the ice sheet and montane forest ad- vancing farther south. As the melting Lauren- tide ice sheet opened a corridor to the Arctic, cold arctic air moved into northern Montana (Bryson et al. 1970), allowing montane conifers to persist at elevations as low as 1000 m. Montane mammals, including Phenacomys in- termedius, Sorex palustris, and S. nanus (Thompson, unpublished data), and land snails (Russell 1952) followed the montane forests, also colonizing the island mountain ranges of the Plains region. Presumably, although Picea glauca colonized the Sweetgrass Hills, the Cypress Hills, and the Black Hills of South Dakota, only the leading edge of the montane forest reached the Cypress Hills. Species such as Pinusponderosa, Pseudo- tsuga menziesii, and Pinus flexilis, which require more moderate climates than existed during this stage in the history of the Cypress Hills, did not arrive as far north as the Cypress Hills, although the latter two reached the Sweetgrass Hills. It is unlikely that Pinus ponderosa ever extended as far north as the Sweetgrass Hills, which appear to remain above the cold limits of this species even today. The more cold-tolerant montane species, including Abies lasiocarpa, Picea engel- mannii, Pinus
Size: 2241px × 1115px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorottawafieldnaturalistsclub, bookcentury1900, bookcolle
