Discuss Succession – Sent you reading guide for Chapt 8Field Quiz today in Lab

NREM 301Forest Ecology & Soils

Day 21 – Nov 3, 2009

Golbi Desert SandstormDisturbance/Succession

How do Biological Legacies Facilitate Succession?Prepare some examples of each

• Soil Biology (micro, meso, macroorganisms)

• Dead Wood (snags, coarse woody debris (CWD)

• Soil Aggregates & Soil Organic Matter

• Soil Chemistry

• Living Trees

• Living Patches

Primary vs Secondary Succession

Describe the phase of the Shifting-mosaic & stage of the Stem Development models of this forest - describe condition of species and habitat diversity in relation to the sere.

Rest Area North Side Upland

Shifting Mosaic Steady State Model

Explain the differences in these responses

Habitat Biodiversity

Plant Species Diversity

Leaching loss

Shifting Mosaic Steady State Model

Undisturbed May Lead to Forest Decline

Gap Succession

Forbs/Shrubs/Seedlings

Even-agedSingle Species

Older Trees DieGaps – Mixed

Species

Whole Area MixOf Different AgedGaps – Uneven-agedMixed Species

Boreal Forest

Major Trees – Black & White Spruce

Less water than Eastern Deciduous Forest

Permafrost

What Can Happen Without Disturbance

Forest Decline

Bogs – absence of disturbance

Succession proceeds as a result of three major mechanisms

Site changes – changes in soil structure, pH, BD, etc., microclimate

Colonization strategies – species pool - seed or vegetativereproduction, fast or slow growing, etc.

Competition – how well can a species compete – shade vs shadeintolerant, long or short-lived, etc.

Species pool influenced by:

1. Size & severity of disturbance

2. Timing of the disturbance

Time of year

The year itself

Interval between disturbances

Explain these -

How far away are live plants – soil bank

Seed on plant mature or not

Good or bad seed year

Very long interval – no more pioneers nearby

Rate of succession is highly variable but depends on:

1. Change needed before one community is replaced by another

Very Long Time To DevelopFertile Soil

Short Time For Overstory to Create Shade for Maple

Rate of succession is highly variable but depends on:

1. Change needed before one community is replaced by another

2. The longevity of the organisms dominating each seral stage. Tolerance to sun/shade, fire, saturated soils, etc. all play a role

here.

Redwoods

Redwoods Bottomland Hardwoods

Rate of succession is highly variable but depends on:

3. Ability of a community to occupy & dominate a site & resistinvasion by subsequent communities (seral stages) (resistance)

4. Ability of a community to re-establish itself after a majordisturbance such as fire or wind (resilience)

AspenRedwood – Resistance –thick bark

Resilience –sprouts back

Disturbance Drives Succession

Scale of disturbance – massive regional ice storm or localized flood in floodplain

Sites created/changed – volcano, flood, wind

Differential disturbance effects –wind – overstory; flood - understoryfire – either; tile drainage - either

Exclusion of disturbances – excluding disturbance can bring on other disturbance

Interactive multiple disturbances – insect attack can lead to fire, windfall

Disturbance brings on succession becauseof legacies left on site

Human caused disturbance – simplify

DisturbanceWhat effects didHurricane Katrina haveon forests?

¾ of forests damaged –30-40% salvagable

DisturbanceWhat effectsdoes this dust storm haveon plant communities?

Mountain Pine Beetle

Mountain Pine Beetle Infestation Can Lead to Fire

Fire Disturbance

Flooding

Blow Down

Anthropogenic Disturbances

Anthropogenic Disturbances

A fallen log creates a local disturbance – one that leads togap succession

Original Forest Cover

Remaining Original Forest Cover (Old-growth)

Human CausedDisturbance

SystemsGenerallySimplified

Clear cut in Montana Describe what kind of successional sequence you might expect here?

What kind of species would move into this site?Consider: Site changes (soil structure, pH, BD, etc., microclimate);Colonization strategies (seed or vegetative reproduction, light seed or

heavy seed, fast or slow growing, shade vs shade intolerant)Competition (shade vs shade intolerant, long or short-lived, resistant to

disturbance or resilient (root sprouts, serotinous cones)

Site changes: mostlymore sunlight, somecompaction.

Any species can seedin if seed can get there.

All can germinate &start to grow.

Mainly shade intolerantwill capture site at the beginning

Rate of change dependson longevity of species

What would determine the rate of change from one seral stage to the next?

Pathways of Succession Following Disturbance

Summary

• Disturbance opens up relatively largespace

• Individuals of any seral species couldgrow

• Modification of early occupants has littleor no effect on later successional species

• Over time early species are replacedthrough competition with late successional species

This disturbance tolerates any availablespecies.

Tolerance Pathway

Describe what kind of successional sequence you might expect here? What kind of species would move into this site?

Consider: Site changes (soil structure, pH, BD, etc., microclimate);Colonization strategies (seed or vegetative reproduction, light seed or

heavy seed, fast or slow growing, shade vs shade intolerant)Competition (shade vs shade intolerant, long or short-lived, resistant to

disturbance or resilient (root sprouts, serotinous cones)

What would determine the rate of change from one seral stage to the next?

Site changes: loss of OMstructure but site stillfertile.

Any species can seedin if seed can get therelight seeded grasses & forbs & those carried by birds.

If well established &if fire occurred thencould keep woody plants out.

Length of grass stagedepends on fire.

Summary

• Disturbance opens up relatively largespace

• Individuals of any seral species could grow• Modification by early occupants makes it less suitable for later species • As long as these early species are maintained they will exclude later

species

This disturbance inhibits any later specie from colonizing the site.

Inhibition Pathway

Describe what kind of successional sequence you might expect here? What kind of species would move into this site?

Consider: Site changes (soil structure, pH, BD, etc., microclimate);Colonization strategies (seed or vegetative reproduction, light seed or

heavy seed, fast or slow growing, shade vs shade intolerant)Competition (shade vs shade intolerant, long or short-lived, resistant to

disturbance or resilient (root sprouts, serotinous cones)

Site changes: newmaterial, no bio-logical legacies

Only “pioneer” species can getestablished.

Next seral stage depends on rate ofmodification of site by pioneers.

Summary

• Disturbance opens up relatively large space• Only certain pioneer species can become established• Modification by pioneers makes site more suitable for later seral species• In time early species eliminated by competition of later seral species

In this disturbance early species facilitate later seral stages by preparing site.

Facilitation Pathway