An EarthCache site is a special place that people can visit to learn about a unique geoscience feature or aspect of our Earth. Visitors to EarthCache sites can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth.
As a part of geocaching — an adventure game for Global Positioning System (GPS) users to cache and find locations with actual hidden items — an EarthCache adventure is treasure hunting for the caches that the Earth has stored. EarthCache sites do not use stored containers; their treasure is the lessons people learn about our planet when they visit the site.
(reprinted from earthcache.org)
The Reveler's Alvar Earthcache will take you to a specific point on the SNC/Reveler property and ask you to share your observations and answer some questions based on the following information.
An alvar is a biological environment based on a limestone plain with thin or no soil and, as a result, sparse grassland vegetation. Often flooded in the spring, and affected by drought in midsummer, alvars support a distinctive group of prairie-like plants.[1] Most alvars occur either in northern Europe[2] or around the Great Lakes in North America.[3] This stressed habitat supports a community of rare plants and animals, including species more commonly found on prairie grasslands. Lichen and mosses are common species. Trees and bushes are absent or severely stunted.
The primary cause of alvars is the shallow exposed bedrock. Flooding and drought, as noted, add to the stress of the site and prevent many species from growing.[1] Disturbance may also play a role. In Europe, grazing is frequent, while in North America, there is some evidence that fire may also prevent encroachment by forest.[4] The habitat also has strong competition gradients, with better competitors occupying the deeper soil and excluding other species to less productive locations.[5] Crevices in the limestone provide a distinctive habitat which is somewhat protected from grazing, and which may provide habitat for unusual ferns such as Pellaea atropurpurea. Bare rock flats provide areas with extremely low competition that serve as refugia for weak competitors such as Minuartia michauxii and Micranthes virginiensis. In a representative set of four Ontario alvars, seven habitat types were described. From deep to shallow soil these were: tall grassy meadows, tall forb-rich meadows, low grassy meadows, low forb-rich meadows, dry grassland, rock margin grassland and bare rock flats.[6]
Alvars comprise a small percentage of the Earth's ecosystems by land extent. Although some 120 exist in the Great Lakes region, in total there are only about 112 square kilometres (43 sq mi) left across the entire Great Lakes basin, and many of these have been degraded by agriculture and other human uses. More than half of all remaining alvars occur in Ontario. There are smaller areas in New York, Michigan, Ohio, Wisconsin and Quebec.[7]
In North America, alvars provide habitat for birds such as Bobolinks, Eastern Meadowlarks, Upland Sandpipers, Eastern Towhees, Brown Thrashers and Loggerhead Shrikes whose habitat is declining elsewhere. Rare plants include Kalm's lobelia (Lobelia kalmii), Pringle's aster, Juniper sedge (Carex juniperorum), Lakeside daisy (Hymenoxys acaulis), Ram's-head Lady's-slipper (Cypripedium arietinum) andDwarf Lake Iris (Iris lacustris). Also associated with alvars are rare butterflies and snails.[8]
The use of the word "alvar" to refer to this type of environment originated in Scandinavia. The largest alvar in Europe is located on the Swedish island of Öland. Here the thin soil mantle is only 0.5 to 2.0 centimeters thick in most places and in many extents consists of exposed limestone slabs.[9][10] The landscape there has been designated a UNESCO World Heritage Site. There are other more local names for similar landforms, such as a pavement barren although this term is also used for similar landforms based on sandstone.[11] In the United Kingdom the exposed landform is called a limestone pavement and thinly covered limestone is known as calcareous grassland.
(quoted from Wikipedia)
Why are alvars important?
While at first glance alvars may appear barren, at a small scale they can be among the most species-rich communities in the world. In Ontario, extensive grassland alvars provide seasonal habitat for grassland birds, Some plant, moss and lichen species are specifically adapted to alvar conditions and are found on no other habitat in the world. In fact, 54 plant species in Ontario were found mainly on alvar habitat. Alvars are an important and beautiful feature of Ontario’s landscape, and are excellent sites for greater education and research of this rare habitat.
What are the threats to alvars? 1. Quarrying: rock quarries continue to be the number one threat to alvar habitats in some regions, particularly those close to large urban markets. 2. Urban and rural development: construction of houses, cottages, incompatible agriculture or industry on alvar habitat, and construction or widening of roads.. 3.Disturbance by motorized vehicles (ATVs, dirt bikes) and cyclists: incompatible recreational use leads to trampling of vegetation, soil erosion and changes to drainage regimes. 4. Introduction of invasive and weedy species: Eurasian grasses, including Timothy and Kentucky bluegrass, and other invasive species outcompete native species and change habitat composition. 5. Overgrazing/over browsing: livestock and wildlife, including deer, can impact alvar species and composition
(quoted from Natureconservancy.ca)
Please email the C/O at my contact through Geocaching.com the answers to the following questions: Please feel free to log this cache. I will only contact you if there is a problem with your answers.
1/ According to the above information, there are 7 types of alvars described in 4 locations in Ontario. At the location that you are standing, what type of alvar do you think this is? And do you think that there is more than 1?
2/ What is the predominate colour of the rock and what do you think it's primary material is?
3/ Alvars have been noted to be a good habitat for birds. Are you experiencing birds on the Reveler property? Extra points for those of you who identify some of these birds.And of course this answer will vary by season.
4/ Alvars are most oftern found around the Great Lakes and in northern Europe. Why do you suppose that they are predominantly found in these areas?
A photo of you and your GPS at the SNC/Reveler property would be welcome, but as per the Earthcache requirements is NOT required.
This cache is placed in conjunction with SNCITO6. Please avoid searching for it before April 25, 2015. All finds on April 25, 2015 will be considered a shared First To Find.