The Arctic and subarctic regions Compared with other biomes, the tundra biome is relatively young, having its origin in the Pleistocene (1,600,000 to 10,000 years ago). Individual plant and animal species of the tundra, however, probably first appeared in the Late Miocene (11.2 to 5.3 million years ago) or Early Pliocene (5.3 to 3.4 million years ago). Coniferous forests were present on Ellesmere Island and in northern Greenland, the northernmost land areas, in the mid-Pliocene (2.5 million years ago). Most paleoecologists believe …showed first 75 words of 3562 total…

…showed last 75 words of 3562 total…and recycling of soil nutrients through excretion. Where caribou, musk oxen, lemmings, and geese concentrate their grazing activity they may actually increase production of tundra vegetation. This results from removal of much of the annual vegetative growth, exposing the underlying new growth of plants to the rays of the sun and the soil to increased heating, and from speeding up the recycling of organic material through digestion and excretion that releases nutrients to the soil.