Environmental gradient

An environmental gradient, or climate gradient, is a change in abiotic (non-living) factors through space. Environmental gradients can be related to factors such as altitude, depth, temperature, soil humidity and precipitation. Often times, a multitude of biotic (living) factors are closely related to these gradients; as a result of a change in an environmental gradient, factors such as species abundance, population density, morphology, primary productivity, predation, and local adaptation may be impacted.

This keyword could refer to multiple things. Here are some suggestions: