Succession does not always reach its natural climax community. When human activities (or sometimes other factors) repeatedly interrupt succession and stop it progressing, this is called deflected succession.The stable community that results is called a plagioclimax. It is maintained only as long as the human activity continues.Common activities that deflect succession include:• Grazing by sheep, cattle or rabbits: animals eat the growing points of shrubs and tree seedlings, but grasses survive because they grow from near the base.
• Mowing: cutting removes woody seedlings, keeping land as grassland (for example lawns and hay meadows).
• Burning: controlled burning kills tree seedlings and shrubs; species such as heather regrow from roots and seeds.
• Trampling and ploughing, which damage or remove later seral stage plants.Examples in the UK: heather moorland on upland estates is a plagioclimax maintained by regular burning (and grazing); chalk grassland is a plagioclimax maintained by sheep grazing. Without management, both would gradually develop into scrub and then woodland.
Deflected succession is often used deliberately in conservation, because many plagioclimax habitats (such as heathland and meadows) contain rare species that would be lost if succession continued to woodland.
• Mowing: cutting removes woody seedlings, keeping land as grassland (for example lawns and hay meadows).
• Burning: controlled burning kills tree seedlings and shrubs; species such as heather regrow from roots and seeds.
• Trampling and ploughing, which damage or remove later seral stage plants.Examples in the UK: heather moorland on upland estates is a plagioclimax maintained by regular burning (and grazing); chalk grassland is a plagioclimax maintained by sheep grazing. Without management, both would gradually develop into scrub and then woodland.
Deflected succession is often used deliberately in conservation, because many plagioclimax habitats (such as heathland and meadows) contain rare species that would be lost if succession continued to woodland.