Definition: A grassland biome is a terrestrial biome which includes, across its entire spatial extent, an unbroken layer of grasses (Gramineae), sedges (Cyperaceae) or rushes (Juncaceae).
Definition: A forest biome is a terrestrial biome which includes, across its entire spatial extent, densely packed vegetation which strongly limits light penetration to the forest floor.
Definition: A depression caused by erosion by water or ice. Low-lying land bordered by higher ground; especially elongate, relatively large gently sloping depressions of the Earth's surface, commonly situated between two mountains or between ranges of hills or mountains, and often containing a stream with an outlet.
Definition: Arenosols are sandy soils, including both soils developed in residual sands after in situ weathering of usually quartz-rich sediments or rock, and soils developed in recently deposited sands such as dunes in deserts and beach lands.
