Regeneration Mechanisms

Mechanisms of Regeneration

• Some species are capable of more than one

• Sexual

• Vegetative

Seed• All species have to have this

capability• May be uncommon• Small seed• Large seed• When dissemination?• How disseminated?

Stump Sprouts• Well established root system• Large store of carbohydrates• Young and vigorous stronger than old• Most angiosperms

– bigleaf maple– red alder

Root Suckers

• Can use root system for short period• Stored carbohydrates• Often soil temperature dependent• Some angiosperms

– aspen

Layering

• Pieces of stem form adventitious roots and shoots

• Some angiosperms and some conifers– vine maple– black and balsam popular– red cedar

USDA Forest Service

Underground stems

• Non-trees– Ferns

hay-scented fern (Dennstaedtia punctilobula )

Steve Horsley, USDA Forest Service, Bugwood.org

Buried Seed• Some seed stays alive in the duff for

many years (or decades)

– cherry– Rubus (salmonberry)

Advance Regeneration• Some species can remain alive in the

understory for long periods• May periodically die back to the root

collar• Must be quite shade tolerant• Angiosperms and conifers

– true firs– hemlock?– red cedar?– salal

1915

1930

Relationship With Disturbances

• Competitive ability is directly impacted by disturbance

• This information can be used in silvicultural planning

Intensity

• Less intense favors sprouting and advance regeneration

• Mid intensity favors layering, underground stems and perhaps buried seed

• Most intense favors seeding

Frequency

• Long intervals favor advance regeneration and sometimes seed

• Short intervals favor sprouting

Scale

• Seed may not be able to travel full distance of large scale disturbances

– “generation and a half”

Examples• Wind – advance regeneration, perhaps

seed on windthrow mounds• Cool fire – sprouting• Hot fire – root suckering, seed, buried

seed• Avalanches – advance regeneration,

sprouting

Examples• Light cutting – advance regeneration

• Heavy cutting – sprouting, seed of all types

• Machinery has effect

Site Prep

• Changes disturbance regime