Given the high level of precipitation in rainforest habitats, soil is inclined to erosion, which can lead to the toppling of vegetation. To increase stability, many rainforest trees have trunks that widen significantly at the base, in a wavy mass of ribbons that may stretch many metres away from the trunk and stand several metres high. This particular type of trunk base called a buttress, has a significantly larger surface area about its base increasing the stability of the plant in the soil. An alternative to this is to produce a stilled or prop root system, in which secondary roots grow obliquity from the main bole toward the ground, much like a witches’ broom. Again, this increases the amount of contact between the plant and the ground, increasing the stability of the plant and the soil.