A Site District is a polygon feature that identifies a subdivision of a Site Region based on a characteristic pattern of physiographic features which distinguish fairly large areas from one another.A Site Region is a polygon feature that identifies an area of land within which the response of vegetation to the features of landform follows a consistent pattern. Each specific type of land (defined in terms of the relief, texture and petrography of geologic materials, depth to bedrock and drainage conditions) within a specific region has its own characteristic plant succession.