Forest Succession

What is ecological forestry

Analyzes forest resources from the standpoint of conserving native biodiversity and ecological productivity, it follows natural disturbance patterns and processes as a guide

Emulating disturbance process and their effects

Define Disturbance

Any relative discrete event in time the disrupts ecosystem, community, or population structure through changes in the physical environment (niches)

Examples of ecological forestry

Selecting silvicultural systems: even aged stands vs uneven

Selecting rotation age and desire age class

Selecting the spatial pattern of harvests

Natural Range of Variability is used to

distinguish disturbance patterns and their effects

Its an ecological guide

Selecting a time frame for estimating NRV is difficult and often limited by information and past landscape patterns

How to measure ecological forestry (5) and definitions

1. Indicator Species - status of a functional group of species, key habitat, and early warning of anticipated stressors to ecological integrity

2. Indicator Keystone Species - Effects on other ecological processes greater than predicted (woodpecker creating cavity habitat)

3. Ecological Engineer - Species alter habitat, modify availability of energy that affect others (beavers, dams)

4. Umbrella Species - Large land requirements and multiple habitats, needs overlap other species (ex. deer)

5. Link Species - Play critical roles in the transfer of matter and energy across trophic levels OR provide critical link to energy transfer in complex food webs (ex. prairie dogs in grasslands)

What is Economic Forestry

Analyze forest resources from the standpoint of maximizing their net benefit to humans

• Macroeconomics - employment and income as a measure of benefit

• Net present value as the main factor in decision making

• Estimating the cost of alternative measures to promote biodiversity

Economic VS Ecologic Forestry

What is Social Forestry

Analyze forest resources from the standpoint of sustaining the well being of people, communities, and society

What is adaptive management?

Addresses the uncertainties of sustainability: test the well designed alternatives to find “best” solutions

What is the biggest disturbance to forests in Canada

Insects

What is forest succession?

It a concept including

• Disturbance and intrinsic factors

• Forest dynamics

• Regeneration / replacement

• Functionality or desired state (ecological / economic)

In terms of long term analysis and planning, society recognizes… (3)

1. Having future forests for economic and ecological reasons is a goal

2. Today’s harvest and management affects forest outputs in the distant future

3. Long term analysis and planning is the main approach to quantitatively demonstrate how this relationship will shape future forests

Ethical practices for forest planners (4)

1. Distinguish between policy making and analysis to clearly separate and identify the facts and values

2. Document your work and recognize the accuracy and confidence of data and methods of analysis

3. Persistently try to ensure that decision makers are affected constituencies know all significant consequences of their choices

4. Pay special attention to actions and policies that are likely to permanently damage the productive capacity of soil and water resources

What is Forest Management (broad definition)

The application of a wide range of scientific, economic, and social principles to administer forest areas under best approaches that includes “succession theory”

Define Regulation

How to change or convert the existing forest over time into the target or desired forest

Define Scheduling

Conveys output schedules, cash revenues, other benefits, workloads, and costs

What is Revisiting Succession?

The changes in an ecological community following a disturbance

Impact in biomass, productivity, diversity, niche breadth, habitat

Narrowly defined: The change in species composition and canopy layer

What are pioneers in succession, what do they do?

Pioneers occupy the newly created space, available resources

Over time they create a new environment for late successional species

As pioneers die, the late successional species dominate and form an equilibrium between biotic and environment (climax)

What are the challenges to determine succession mechanisms?

• Succession is an incredibly long process

• Repeated measurements are needed to identify the mechanisms

• There may be minor, non stand replacing disturbances such as grazing animals, insect pathogens, wind and ice

• Species interaction, colonization potential

What are the known mechanisms for succession?

• Facilitation to create favorable environment (light, temp, moisture, shelter)

• Competition for resources

What are the 3 succession models and definitions?

• Facilitation (Model 1) - Assumes only certain “early successional” species are able to colonize the site immediately after a disturbance

• Tolerance (Model 2) - Successive species are more shade tolerant than the ones in the canopy

• Inhibition (Model 3) - Once earlier colonists secure the space and/or other resources, they inhibit the invasion of subsequent colonists or suppress the growth of those already present

(last two assume arriving species may be able to colonize)

Factors with Facilitation (+)

• Disturbance

• Open space, resources released (some)

• Early occupants modify environment to make it LESS suitable for early species to colonize, and MORE suitable for late succession species

• Growth of late succession species, eventually excludes early succession species

• Continues until resident species no longer facilitates invasion of new species

• Climax community

Factors with Tolerance (+, -)

• Any species that arrive can establish themselves

• Early occupants (modify environment to make it LESS suitable for the early succession species, but has LITTLE effect on late succession species

• Later successional species grow to maturity, while over time early species are eliminated

• Continues until climax community is reached

Factors with Inhibition (-)

• Any species that arrive can establish themselves

• Early occupants (modify environment to make it LESS suitable for BOTH early and late succession species

• As long as early species exist they inhibit recruitment

• When early species are displaced, recruitment of other species occurs

• Continues until climax community is reached

What are the differences between model 1-2 and model 3

Model 1 and 2

Colonists are losers when competing with later species. Latter grow up and shade or otherwise deprive the former of resources

Model 3

Early species are displaced by local disturbances caused by physical extremes or natural enemies such as herbivores, parasites, or pathogens

What are the site factors influencing fire (4)

• Landscape composition

• Site conditions )parent material, topography, soils)

• Climate

• Pre-fire stand compositions

Factors influencing post disturbance regeneration (4)

• Availability of reproductive propagules (regional species pool)

• Species reproductive traits

• Regeneration microsites

• Microenvironment

Factors influencing ongoing stand development (4)

• Species tolerance and longevity

• Ongoing regeneration

• Composition, herbivory

• Secondary disturbances

Effects of disturbances on communities (4)

• System resets

• Modifies resources available

• Modifies competition

• Influence community composition and dynamics

What factors are included in the intermediate disturbance hypothesis (3) and definitions

• Low disturbance frequency - species diversity is expected to be low because competitively dominant species exclude competitively inferior species

• High disturbance frequency - Species diversity predicted to be low because only “weedy”  species that quickly colonize and reach maturity are able to survive

• Intermediate disturbance frequency - Expected mix of colonizers and competitors co-exist

Define stand dynamics

The study of changes in forest stand structure with time, including stand behavior during and after disturbance

Includes physical and biological forces that shape forests

Define cohorts

A group of trees starting as a result of a single disturbance

How to identify age classes, what isn’t a good indicator of age alone?

Profile of the top of stands to determine age distribution

Diameter alone not a good indicator of age

What are the 4 crown classes and definitions

• Dominant - crown extends above the general level of canopy, receiving full light above and partially on sides, larger than average

• Co-dominant - crowns are generally level, full light on top, little on sides

• Intermediate - shorter than former two, crown reach general level of canopy, receive some full light on top, NONE on sides

• Overtopped - trees with crowns below canopy, no direct sunlight (suppressed)

Associations with Even Aged/ Single Cohort Stand

• Range of all ages of trees is narrow in the cohort

• Common in nature or man made

• Growth in height is most critical factor in competition. “race to the sky"

Associations with Even Aged Stratified Mixture

• Same principle as even aged stand, but more than one species is present

• Different species represented by advance regeneration, sprouts, new seedlings or combination of all three start off together

• Crown layers develop because of differential height growth of species, shade tolerance, root depth, etc

Associations with Two - Aged / Double Cohort Stand

• May arise naturally by fire

• Can be pure or mixed species

• Certain regeneration harvest cuts (leave trees) can lead to this type of stand

Associations with Uneven - Aged / Multi-cohort Stands

• Small gaps, caused by cutting or destructive events give rise to new cohorts

• Natural stands most commonly exist in places where soil moisture limits the habitat to one species

Associations of Mixed, Uneven - Aged / Multi-cohort Stands

Arise from a history of partially effective or patchy lethal disturbance

All stages of stand development likely to be going on at once

Mixtures of age classes, cohorts, fragments of stratified mixtures are all possible

Mat be the result of “high - grading”

What are the 4 stages of stand development

• Stand initiation stage

• Young stage

• Mature stage

• old growth stage for natural forests (or regeneration by clearcutting/non clearcutting for a plantation)

Info on Stand Initiation (Reorganization) Stage

• After a lethal disturbance creates vacant growing space, trees that establish do not fully occupy the growing space

• Additional plants fill in the gaps, lasting 10 or more years

• Biodiversity is very high (perhaps the highest)

Info on Stem Inclusion Phase

• After a time, growing space is occupied, crowns close, canopy is formed and elevated to do dying of lower branches

• Weaker trees die

• Rapid leaf area accumulation occurs

• Economic or financial rotation of even aged crops usually occurs

• Heavy shade, biodiversity is (probably) at its lowest

Info on Understory Re-initiation (transition) stage

• Previously successful trees are lost by pests or damage and crowns do not fully close again

• Gaps created are filled by new plants, often slow growing shade tolerant species

• Total biomass declines from its peak from former phase

• Forest floor veg reappears

• Medium shade

Info on Old Growth (steady state) phase

• Fewer than half of trees in original cohort remain, on or more new age classes compose parts of the top canopy

• May continue past the death of the last original trees, likely to be unbalanced. Production gains = losses to death/decay

• Biomass remains fairly constant

• Overstory trees die in irregular fashion

What are the (6) phases of a forest succession cycle, and when is silvicultural prescriptions?

Cohort establishment

Canopy closure phase

Stem exclusion phase

Mature phase

Old-growth phase

Gap phase- This is where silvicultural prescriptions occur, at the end of the forest’s life

What are neighborhood effects?

any process mediated by canopy trees that affect the replacement probability by the same or other species at the time of canopy mortality

What are the (3) types of neighborhood effects

1. Positive neighborhood effects - processes that promote self replacement

2. Negative Neighborhood deter self replacement

3. Neutral effects neither favor nor disfavor self replacement

Types of neighborhood effects/ disturbances (2)

Overstory - understory effects (positive or negative) - operate by influencing the species composition of seedlings and sapling underneath canopy trees. May influence the second generation tree species

Disturbance activated effects, operate mainly in forests perpetuated by intense fire where seedlings are mostly killed at the same time as the canopy trees, serotinous seed rain and sprouting as a result

(3) types of disturbance intensities and definition

Low severity disturbance - kill small parts of either the overstory and or understory

Moderate severity disturbance - Kills most of one forest layer, either the understory with its advanced regeneration and or seedbank or the overstory while leaving the other layer mostly intact

High severity disturbance - kill both the understory and overstory (ex. fires)

Why is disturbance intensity and frequency important?

Repeated disturbances of low to moderate intensity may act as a major disturbance

Case study: Kibale National park, Uganda history

Contains a wide variety of different habitats, many endangered species and fragile habitats

Two major indigenous tribes inhabit the area and depend on the natural resources. Parks are of increasing importance due to illegal logging in many African countries

Large areas that were converted to farmland are now tall grasslands, making up 1/3rd of the park

case study hypothesis, and their results (4)

1. Seed rain is higher beneath isolated trees than grasslands. This was proven true. Grass height did not have a significant effect on seed counts

2. Seed rain is higher under tall trees than short or mid size trees. This was proven true. Possibly because tall trees provide protection to seeds

3. Seed rain is negatively correlated with distance from forest edge. This was proven false. No significant differences were found with edge vs interior

4. Seed rain would increase beneath trees producing fleshy fruits. This was proved true. 4 of 5 fruited trees were found to have higher seed cohorts, possibly because they attract animals.

Case study methods

150m x 250 m tract of land with one long edge along intact forest

Seed traps placed at 13 random locations at least 1m from any nearby tree crowns

Seed rain was described in terms of density and species richness

case study result discussion

Managing anthropogenic disturbance to make natural regeneration faster/ easier

More cost effective to rely on natural processes for restoration

Establishing plantations of resilient or adapted trees can help with restoration

Case study limitations of Uganda

Does not share the same habitat as Canada

Legislation is very different

Study design could be modified for Canadian issues, but needs funding

How/where to apply this knowledge in Canada (5)

1. Mining reclamation

2. Oil and gas

3. Forest harvesting

4. account for edge effect and seed proximity when planning industrial activities

5. Agriculture

Info/Life cycles of Mountain Pine Beetle

Most of their life cycle is underneath tree bark

Adults can fly. Long distance dispersal potential

Females use pheromones to attract beetles to a certain tree

Historically, beetles have been controlled by cold winters, with global warming creating more ideal conditions

Range is west, in all of BC and most of Alberta

need to rank pictures on most shade tolerant boreal forests on exam***

know your tree species and know your sites***

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competition, which is favored (red pine)

Trees impacted by Pine Beetle

Lodgepole pine is the primary, but jack pine, ponderosa pine, whitebark pine, western white pine, and limber pine can be affected.

Trees that are larger (>20) and older (>60) are targeted

Tree dynamics post infestation

Healthy trees produce a thick resin

Infected trees will die from the beetle feeding on phloem and introducing blue stain fungi

Two years after the tree dies the needles will turn red, and after 3-6 years the needles fall off and the tree gets a grey appearance

Dead trees eventually fall and become downed coarse woody debris

MPB as a disturbance

Beetles only really target the overstory as a disturbance

Considered low to medium severity and help maintain a viable stand structure

Dead mature trees opens up the canopy and increase growth for neighboring plants and understory growth

MPB as a high severity disturbance

Recently attacks have been increasing to a high severity and frequency

They are starting to target younger trees if older is not available

Severe outbreaks can cause up to 90% mortality of tree basal area

Regeneration is primarily controlled by pre stand conditions

What is the relation to MPB and fire?

MPB creates a lot of dead trees, increasing ignition risks (especially with trees in the red needle stage) which facilitates stand replacing

Stand Development following MPB in BC even aged forests

How will climate change affect MPB

It is difficult to predict, but…

• Increase MPB populations due to warmer winters

• Encourage eastward spread into the boreal forest

• Decrease host tree resistance, due to increased stress from drought

• Likely increase frequency and severity of outbreaks

What are the management strategies of MPB

Detection through aerial surveys

• Removal of infected trees (cutting or burning)

• Restrict transportation of pine material from BC

• The mountain pine beetle program

What are the (5) results of the Mountain Pine Beetle Program

• No practical ways of using remote sensing for early detection

• Beetle infested trees must be removed quickly and properly disposed of

• Vulnerable trees should be harvested first

• pheromone baiting can control the endemic population levels

• Direct control is impractical with very large beetle populations

Spatiotemporal fire regimes

What is the fire cycle in central boreal forests

Approximately 100 years from 1921-2008

Changes spatially, longer for stands closer to water bodies, in the south, and brunisols

Intermediate to east and west boreal forests supporting climatic top down control

What is brunisols

A type of soil found in forested regions that are poorly developed. They are considered transition soils

Does a post fire stand have the same species composition as the prefire stand?

Yes, based on direct regeneration hypothesis

Direct Regeneration in Boreal Forests

Species specific post fire regeneration density is proportional to its pre fire basal area

A pure post fire aspen stand may be expected when the pre fire stand has > 20% aspen

Drivers of forest

Propagule availability and substrates —> Species specific pre-fire basal area

Competitive ability —> Fire variability within a burn

Understand competition interactions

losers and winners

Interactions among species, some collaborate

Red oak

for the first ten hears they don’t grow in height, they put energy into roots