NR 326 Lecture 5 The Regeneration Process

Some definitions Natural regeneration the renewal of a forest stand by natural seeding, sprouting, suckering, or layering seeds may be deposited by wind, birds or mammals... Vegetative

Some definitions

 Natural regeneration

the renewal of a forest stand by natural seeding, sprouting, suckering, or layering seeds may be deposited by wind, birds or mammals

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Vegetative (asexual) Regeneration

It is a process by which new organisms arise without

production of seeds

Vegetative (asexual) Regeneration

Root Suckers or Root Sprouts

Sprouts sometimes emerge from root’s buds under ground

Melia azedarach (xoan); Difterocarpus aff condorensis (dầu cát);

Stump Sprouts

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Stump sprouts can grow very

quickly and sometimes become

viable trees themselves

An intact branch develops

roots as the result of

contact with soil or other

media

Regeneration by Rhizome (bamboo)

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shoot bud of Phyllostachys edulis

in Cao Bang

Vegetative (asexual) Regeneration

Rhizome bud

Stump sprout

Stages of natural vegetative regeneration

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Advantage

Short cutting cycle

High productivity

Healthy forest stands

Low Initial costs of establishing a forest stand

Disadvantage

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Small size of products

Low quality of products

Stump & Sprouts

Regeneration from Seed

(generative regeneration)

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early growth

, mortality

Advantage

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Many size of products

High quality of products

More money

Disadvantage

Lack of healthy saplings

Difficult to establishing a forest stand

Long cutting cycle

Low productivity

Seed production influenced by…

• Mother trees: trees with well-developed crowns

exposed to sunlight  most seed

• Site quality: climate, soil,

• Weather: rainfall, sunlight, wind

• Mammals: insects, birds, small mammals

• Disease

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Viable Seed and Seed Loss

• Seed losses during production, storage, and germination:

Natural Seed Dispersal Influenced by…

• Wind: direction & speed of wind,

• Animals: numbers & movement patterns of animals

• Weight & aerodynamics

• Topographic features: slope, aspect, position

• …

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Natural Dispersal Distance

Seed Storage & Germination

• Soil seed bank

– natural storage of dormant seeds within the soil

– Most conifers, black cherry, fire cherry, yellow poplar, Rubus,

grape, Ribes > 3 years

FUN FACT: Check out this 2000-year old magnolia seed which grew into a previously unknown species

http://www.bbc.co.uk/programmes/p009c12m

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Seed Storage

contact and light covering

mo  best buried under litter and some soil

• Black spruce (sphagnum), hemlock (log, stump),

oak (buried), red pine (no ash); hardwoods can

penetrate duff layers, BUT conifers can’t

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5 radicle emergence, development of primary root

• Large seed = fast growth

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Succulent Stage, Initial Growth

and Establishment

• Young stems very vulnerable to heat & frost

• Seedling must:

– establish roots and maintain contact with favorable soil

moisture and nutrients

– Once seed reserves are depleted, must photosynthesize

more than respiration and growth

Succulent Stage, Initial Growth

and Establishment

• New seedlings more shade-tolerant than adults

– Shaded seedlings more likely to die of drought  too little light for photosynthesis that enables root growth

• Reduction of vegetative cover during early stages of

regeneration can lead to desiccation

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Initial Growth

• Factors controlling success

– soil moisture & nutrients (structure and texture)

–

–

– climate (temp and moisture)

– browse & disease

– competition

–

Seed Production

• Only large trees are effective seed producers

• Dispersal distances limited (~50 feet)

• Limited by insects and squirrels

• Germination limited by dry conditions

• Survival reduced by sod forming grass and

brush competition

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Lodgepole pine

Seed Production

• Good crops 1- to 3-year intervals

• Serotiny

– Yes or no or mixed

– Fire selects strongly for closed cone habit

• Relatively small seeds that are effective flyers

• Production not highly impacted by animals

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Germination and Survival

• In good conditions almost all seeds germinate rapidly

• Mineral soil is best for survival

• Shading and competition inhibit germination and survival

Characteristics of tropical natural forest

D1.3 N