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Mechanisms of Post-Glacial Revegetation
After the glaciers receded, plants used several different methods for colonizing the recently exposed bare land. Pioneer species, such as lichens and mosses start to grow on the exposed rocky surface.
Next, the cycles of growth and decay in the pioneer species begin to create a basic soil, comprised of the dead organic material from the pioneer species. This allows vascular plant species that require some soil in order to grow to colonize an area.
Foliage from the fallen leaves of shade intolerant vascular plants begins to build up even more and begin to form a thicker organic layer. This allows vascular plants requiring higher amounts of nutrients to colonize the area such as shrubs and trees.
Refugia
The maximum rate of northward spread of Picea spp. (after the end of the last glacial period) are estimated to be 376 m/yr in eastern North America. Maximum migration rate for northern pines (Pinus banksiana, P. strobus, P. resinosa) has been estimated to be 613 m/yr in east north America as well.
Fossil pollen records have been used to provide reconstructions of past geographical changes in Boreal tree species. The most pivotal of these shifts are the northward expansion of various tree species. Below are two examples of common Boreal tree species and their modeled refugia during deglaciation.
Buildup of moss.
Retrieved from http://www.mountainmoss.com/assets/images/MossinAnnieGarden-Top%20of%20Hill.jpg
Scarce Moss On Rock.
Retrieved from http://www.bambooandmore.info/2010/12/where-did-all-this-moss-come-from.html
→→→
Seed Dispersal of Spruce Sp. from Refugia.
Retrieved from http://www.fao.org/docrep/u6850e/u6850e04.htm
Seed Dispersal of Pine Sp. from Refugia.
Retrieved from http://www.fao.org/docrep/u6850e/u6850e04.htm
Primary Sucession.
Retrieved from http://people.eku.edu/ritchisong/317notes2.html
BOREAL @ MEMORIAL