Trophic Levels and Food Webs

Primary producer

Ecological succession that occurs on newly exposed or formed land where no soil exists (e.g., volcanic rock, glacial till)

Secondary succession

• Ecological succession that occurs on land that has been previously vegetated but has been disturbed, leaving the soil intact (e.g., after a fire, flood, or agricultural abandonment).

Inhibition model of succession

• Early colonizing species inhibit the establishment of later successional species.

Facilitation model of succession

• Early colonizers modify the environment in ways that benefit later successional species.

Tolerance model of succession

• Later successional species are those that can tolerate the environmental conditions created by earlier colonizers, without necessarily being helped or hindered by them.