Crossword clues for alvar
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. Most alvars occur either in northern Europe or around the Great Lakes in North America. 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. 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. The habitat also has strong competition gradients, with better competitors occupying the deeper soil and excluding other species to less productive locations. 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.
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 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.
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) and dwarf lake iris (Iris lacustris). Also associated with alvars are rare butterflies and snails.
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. 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. In the United Kingdom the exposed landform is called a limestone pavement and thinly covered limestone is known as calcareous grassland.
An alvar is a kind of biological environment poor in soil.
Alvar or Alvars may also refer to:
- Alvar Aalto (1898–1976), an architect and artist
- Alvar, Armenia, a village in Armenia
- Alvar, Iran (disambiguation), any of a number of places in Iran
- Alvars, a collection of Tamil saints
Usage examples of "alvar".
Donald instructed the household robot to waken Sheriff Alvar Kresh and suggest that he join Donald at the scene.
And when Alvar Kresh woke in a bad mood, he often flew his own aircar in order to work off his tension.
But the thought of Alvar Kresh in an evil mood, half -asleep, flying at night, was especially unpleasant.
Humans, on the other hand: These days, the sight of blood and violence scarcely bothered Alvar Kresh.
And then wait for the human, wait for Alvar Kresh, wait for the Sheriff of the city of Hades.
No doubt most people thought it was damned odd that Alvar liked to fly his own car.
Hell, Donald could probably do this job better than me, Alvar thought.
A strange chase it was, one that started with Alvar not so much as knowing who it was that he pursued.
This room was a portrait of the person who worked here, if only Alvar could learn to read it.
Alvar and Donald stood by one of the interior doors, toward what Alvar found himself thinking of as the rear of the room.
The room was a perfect forest of potential clues, jam-packed with gadgets and hardware that might have some bearing on the case, if only Alvar knew enough about experimental robotics.
At last, quite reluctantly, after working the rest of the crime scene and coming up with very little for his efforts, Alvar moved toward the center of the room, the center of the case, the scene of the attack.
Tonya Welton said with a smile that Alvar scored as being at least an attempt at courtesy.
If only it did, Alvar Kresh would have a much more peaceful time of it.
It seemed to Alvar that the furniture had been rearranged every time he came in here, in accordance with whatever sort of use to which the room was to be put--working office, meeting room, dinner reception, whatever.