Topi live primarily in grassland habitats ranging from treeless plains to savannas. In the treeless prairies homesteaders built sod houses. Alpine communities are essentially regions of Arctic tundra, or treeless tundra-like communities. It occurs rarely in heavily forested, mountainous or largely treeless habitats. There are also plant associations almost treeless&colon; grasslands, pastures, deserts. Ten percent of Soviet territory is tundra, that is, a treeless marshy plain. It is rare in Pakistan's arid treeless areas. Much of the surrounding areas are naturally treeless tundra. The limestone hills which form the almost treeless plateau are generally steep but fertile. On isolated mountains, montane forests surrounded by treeless dry regions are typical "sky island" ecosystems. Forests surround those farms, but higher up, woods give way to a treeless mountain plateau. Lewis is comparatively flat, and largely consists of treeless moors of blanket peat. However, they are rarely seen in heavy rainforests and treeless deserts. These environments were harsh, characterised by vast areas of treeless, wind-blown sand dunes. These connected peaks reach well into the treeless alpine zone.