In the windswept heartland of Asia, the continuous belt of coniferous forest is replaced to the south by cold grassland of mixed grasses and narrow-leaved flowering plants. At the forest edge the grasses are rooted in a rich black soil, but further south the soil is redder and drier. These grasslands are known as the steppe. Beyond the steppe a wilderness of drifting sand, hard-packed clay and shattered stone sweeps southwards to the foothills of the huge Himalayan mountain chain that partly marks the southern limit of the Palaearctic ecozone.