Description

Arctic vegetation is composed of plants suchasdwarf shrubs, graminoids, herbs, lichens and mosses, which allgrowrelatively close to the ground, forming tundra. As onemovesnorthward, the amount of warmth available for plantgrowthdecreases considerably. In the northernmost areas, plants areattheir metabolic limits, and small differences in the totalamountof summer warmth make large differences in the amount ofenergyavailable for maintenance, growth and reproduction. Coldersummertemperatures cause the size, abundance, productivity andvariety ofplants to decrease. Trees cannot grow in the Arctic, butin itswarmest parts, shrubs are common and can reach 2 m (6 ft 7in) inheight; sedges, mosses and lichens can form thick layers. Inthecoldest parts of the Arctic, much of the ground isbare;non-vascular plants such as lichens and mosses predominate,alongwith a few scattered grasses and forbs (like thearcticpoppy).
Herbivores on the tundra include the Arctic hare, lemming,muskox,and caribou. They are preyed on by the Snowy owl, Arctic foxandwolf. The polar bear is also a predator, though it prefers tohuntfor marine life from the ice. There are also many birds andmarinespecies endemic to the colder regions. Other land animalsincludewolverines, ermines, and Arctic ground squirrels. Marinemammalsinclude seals, walrus, and several species ofcetacean—baleenwhales and also narwhals, killer whales andbelugas.