A concept is an abstract or general idea inferred or derived from specific instances. In this instance the concept is "survival."
An old moss-covered oak has so few leaves, only on the topmost branches, it is perilously close to being unable to sustain photosynthesis to the level necessary for its survival. The distinct watershed boundaries of this region determine that soils found within the High Valley area are derived only from parent material found within the basin. Brick-red volcanic cinders and pumice-like gravel and stones allow for superior drainage. The western edge and middle of High Valley are composed of gravelly loams created from eroded Franciscan shales. Perfect for viticulture. More challenging for other species.