tundra ecosystem An ecosystem which 1) typically has monthly average temperatures below 10 degrees Celsius 2) has a low evapotranspiration ratio 3) is dominated by treeless terrain, covered by communities of low-growing vegetation such as dwarf shrubs, sedges and grasses, mosses, and lichens, 4) contains areas of soil underlain by permafrost with a thin active layer and 5) occurs in both polar and alpine regions (i.e., both high latitudes and high altitudes), and 5) does not have permanent snow or ice cover. terrestrial ecosystem