Natural ecosystems, Central Asia and Uzbekistan

Ecosystems are natural (sea, lake, forest – formed without human involvement) or artificial (field, city, spacecraft – made by humans). On land the placement of ecosystems is set mainly by two abiotic factors – temperature and precipitation; the ecosystems of one climatic zone together form a biome. In the tundra the mean annual temperature is below 0 °C, the soil is permafrost, there are no trees, and lichens, mosses and low shrubs grow (reindeer, snowy owl). The taiga is conifer forest (pine, fir, spruce) with long winters and high precipitation. Temperate deciduous forests adapt to the changing seasons by leaf fall and hibernation. In steppes and meadows grasses dominate, rainfall is too low for forest and the soil is fertile, so most were ploughed. Deserts have very little rain, hot days and cold nights; xerophytes, ephemerals and nocturnal animals are numerous. Tropical forests have the most species and tiers, annual precipitation over 2000 mm, and many epiphytes and lianas. Freshwater ecosystems (lakes, rivers, marshes) occupy little space but are the source of drinking water; the limiting factor is dissolved oxygen. Seas and oceans cover about 71 % of Earth’s surface, with an average salinity of about 3.5 %.