Definition: Gravel is an environmental material which is composed of pieces of rock that are at least two millimeters (2mm) in its largest dimension and no more than 75 millimeters.
Definition: A desert biome is a terrestrial biome which loses more liquid water by evapotranspiration than is supplied by precipitation and includes communities adapted to these conditions.
Definition: Of plant duration, a plant whose life span ends within one year after germination, e.g. a winter annual germinating in the autumn and flowering in the spring (esp. in Mediterranean climates), approximately synonymous to therophyte, c.f. biennial, ephemeral, perennial, c.f. also of flowering with respect to architecture, hapaxanthic, monocarpic, pleonanthic.
