Evolution in a Glaciated Landscape: Contribution of Endemism to Great Lakes Biodiversity
Catling, Paul M. .
The Restricted and Endemic Flora of Great Lakes Alvars.
Alvars are naturally open areas of thin soil over essentially flat limestone or marble with more or less sparse vegetation cover of shrubs and herbs with trees absent or not forming a continuous canopy. This habitat is a restricted one that occurs sporadically along some Great Lakes shores, and inland primarily along the contact line of granitic and limestone rocks as well as occasionally along certain periodically flooded rivershores. Over 400 native plants have been found in the alvars of the Great Lakes region and 1/4 of these are characteristic based on occurrence in more than 50% of alvar sites. More than one quarter of native alvar plants are restricted in there geographic occurrence in the Great Lakes region and there are several endemics. The endemics are most frequent in the alvars of the upper Lake Huron and Michigan regions, which form a distinctive group based on composition. The alvar flora appears to have originated from the south, west, and as relicts of the Picea Parkland and periglacial grasslands that existed in the area 9,000 years ago at the onset of the Wisconsin glacial retreat. Biodiversity in Great Lakes region alvars is related to regional climatic and floristic variation, as well as to 9 major recurrent vegetation types and different ecological processes operating in two major kinds of alvars. Periodic drought and fire are important in plateau alvars whereas shoreline alvars are subject to periodic flooding and sometimes ice scouring. The relict nature of alvar communities, their scarcity on the landscape and their composition including endemic and restricted species has captured widespread attention, but successful conservation has been localized and much remains to be done with regard to both conservation and research. Increasingly it has been recognized that natural history recreation and education can be very successful in alvar landscapes.
Log in to add this item to your schedule
1 - Agriculture and Agri-food Canada, National Program on Environmental Health, Central Experimental Farm, Ottawa, Ontario, K1A 0C6, Canada
Great Lakes region
Presentation Type: Symposium or Colloquium Presentation
Location: Boulevard A/Hilton
Date: Tuesday, July 10th, 2007
Time: 10:45 AM