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Click on the the photo to hear John Dick introduce the
characteristics of disturbance-driven ecosystems
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Transcript of the Audio with John Dick
Disturbance-driven ecosystems are generally even-aged forest
communities in semi-dry climates that are characterized by relatively
frequent (80 to 150 year) catastrophic disturbances. They are
relatively resilient forests where maximum biodiversity occurs
at the “ecotone” (John — explain what ecotone
is) between seral communities and more mature communities.
The main characteristics of disturbance-driven forests include:
- Generally even aged stands, interspersed with mature forest
remnants resulting from extensive, often-catastrophic disturbance.
- Wildfire is a major influence, with insects (defoliators
and bark beetles) and root disease secondary initiators in
older stands. Fires are generally initiated by lightning strikes
or by accident.
- Disturbance return cycle generally 80 — 150 years.
- Biodiversity is associated with the early pioneer seral
stages of ecological succession and with mature forest remnants.
- Many species have fruits (i.e. lodgepole pine) or seeds
(i.e. Ceanothus) that require heat for dispersal and/or germination.
- Fully-stocked, regenerating coniferous stands (whether natural
or resulting from planting) are characterized by very low
biodiversity from juvenile age to maturity.
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