BOT 330 Final

Timeframe for succession

- >1 season - Not long-term (climate change)

The Fire Triangle

- Combustion

Abiotic

- Fire - Hurricanes - Windstorms - Ice events - Ice push on shores - Frost damage (at edge of tropics) - Fluctuating water levels in basins - Droughts - Floods - Landslides - Lava flows - Lightning - Wind - River meandering (cut bank erosion) - Avalanches

Sprout (endurer)

- Grow fast in full sun - Outgrow competitors

Pre-Columbian fire uses

- Heat - Light - Cooking - Hunting - Communication - Cultivate plants for food, medicine, & basketry - Modify landscape for game management & travel

• In mid-1980s, wildfire activity increased through

- Higher frequency - Longer durations

Biotic

- Insects and other herbivores - Diseases (mainly fungal) - Burrowing animals

Seedlings (endurer)

- Less competitive - Delayed establishment - Slow early growth

Era of No (little) Fire included

- Logging - Overgrazing - Fire Suppression - Removal of Native American Burning

Ignition limitation

- PNW & northeastern forests: dry-season lightning rare - Hard to explain frequency of historic burns - Humans likely major ignition source

Even resistors can incur damage, what does it depends on

1) Fuel loading 2) Climate (how dry are things?) 3) Intensity 4) Residence time

What influences invasion success?

1) Species Characteristics 2) Generalizations Regarding Habitat Invasibility

Effects of fire suppression

1. Higher fuel loads • Longer residence time • More intense 2. Higher mortality • Stem breakage • Dead cambium 3. Species composition

Fire Effects on Ecosystems

1. Increase structural diversity 2. Increase resource availability 3. Influence nutrient cycling 4. Influence pathogens 5. Influence species composition

the great discovery of the 1970s and 1980s was the ubiquity of natural disturbance. disturbance has two crucial effects.

1. It kills plants. 2. It frees up resources (especially light) and thus encourages regeneration. In short, the two fundamental process in population dynamics -- birth and death-- revolve around disturbances

Plant Fire Strategies

1. Resistors 2. Evaders 3. Endurers 4. Colonizers

Diversity Measures

1. Richness (S) 2. Dominance (d & 1/d) 3. Shannon Diversity Index (H') 4. Evenness (E) • Rank Abundance Graphs

Four things matter in the ecological effects of disturbance:

1. Size (how big) 2. frequency (how often) 3. severity (which strata-- and what % of each stratum-- are killed. . .) 4. Specificity—which species are killed (not shown on graph)

Since ___________, reduced fires due to reduced human ignitions & fire suppression

1930

Estimated ____ million indigenous people inhabited NA at time of initial European settlement

21

Series:

A vegetation type based on the dominant plant - e.g., Jeffrey pine series, white fir series, native dunegrass series.

N.A. species don't impact Centaurea, but Eurasian decrease Centaurea biomass (white bars) Mechanism:

Added carbon = one N.A. species decreases Centaurea biomass, but Eurasian no longer impact Centaurea (black and "no competitor" white)

Evaders

Adult plants have no resistance to fire • Seeds quickly germinate after fire • Often seed dispersal and/or germination rely on external trigger (heat, smoke, charrate) (Knobcone pine, Baker cypress

• Hydrology:

Alterations of water regimes

Shannon Diversity Index (H') assumes

Assumes individuals were sampled from very large population and all species are represented

Burning and grazing led to what action

Bison prefer C4 grasses---> Increased diversity (forbs)

80-90% of ______________ grasslands cover area is non-native

California's

Mechanisms of Succession

Clements, 1916 - Facilitation • Connell and Slayter, 1977 - Facilitation - Tolerance - Inhibition

Structuring plant populations

Distribution of individuals among different ages/sizes/stages B/D/I/E will not be the same for all ages/stages

Ecosystem Level Impacts from invasive species

Disturbance regimes Hydrology • Geomorphological processes (erosion, sedimentation) • Nutrient cycling

2002 Biscuit Fire

Diverse burn pattern -> variable canopy mortality ->variable forest structure • Compare diversity on either side of serpentine soil

1/d =

Dominance Diversity Index

ASSOCIATION EXAMPLES:

Douglas fir - tanoak/huckleberry-oceanspray association Douglas fir - bigleaf maple/swordfern association

Evenness (E)

E = H'/ ln S E = 1 means completely even

Clements organism view of communities

Each community is a "node"

Inhibition

Early occupants of an area modify the environment in a way that makes it less suitable for later successional species. - Early arrivals inhibit colonization by later arrivals. - Succession eventually occurs when later species outcompete earlier species

Fire was and is

Effectively suppressed for a century • Recently increasing: bigger & more frequent

Ants importance to plants

Endemic plant Mimetes cucullatus • Ant dispersed seeds - Elaiosome at both ends - Suite of native ants bring seeds to nests, eat elaiosomes, & bury in refuse piles • Fire kills seeds in surface soils, but buried seeds survive!

Centaurea competition impacts N.A. species more than ____________(hatch and white) Mechanism:

Eurasian Added carbon = helps N.A., hurts Eurasian

Slope Affects __________ Behavior

Fire

Fire Effects Increased structural diversity

Fire burns in uneven patterns • Even-aged stand uneven-aged, more diverse • Create canopy gaps, openings for different species to establish increase species diversity • e.g. 2002 Biscuit Fire

Fire Effects Reduce pathogens

Fire can negatively affect pathogens in a # of ways 1. Directly impact pathogen 2. Directly impact a symbiotic organism 3. Alter stand dynamics to reduce pathogen spread - i.e. Thinning sugar pine stands slows white pine blister rust progress 4. Alter environment so less hospitable to pathogens

How can fire help pathogens

Fire can potentially create an entry point for pathogen • A heart rot fungus might have hard time getting into a healthy tree but a fire scar provides access

Does the density of the single species being considered change the impact of the factor?

Fire: trees vs. herbs in a forest - Drought: could depend on level of competition for H2O

Secondary succession examples

Floods • Fires

Fire History in West

Forest fires' spatial & temporal patterns vary • Region historically fire prone • Increased fire return interval after European settlement in West

Most ecologists support ______________'s view

Gleasons

"community"

Group of populations that coexist in space and time, and interact with one another (directly or indirectly)

Shannon Diversity Index (H')

H' = - Σpi ln pi

PEST

Has Negative Impact

BENEFICIAL

Has Positive Impact

Why define communities?

Identifying communities with specific management needs • Looking for particular interactions that are common within one community • Ecosystems functions differ between communities • Changes over time (within a community and within a location) • Learning about one community type can inform understanding of other community types • Landscape level frequency of community types - are they rare? Are they in need of conservation/protection

Fire

Important Disturbance • Most common disturbance in North America, especially in western US • Two ignition sources? • Study fire scars to rebuild regional fire history

Era of Bad Fire

Increased in Fire Severity in Sierra Nevada and Southern Cascades Increased temperatures, fire season, and fire size

How does fire exclusion effect the ecosystem

Increases shade-tolerant, fire-sensitive species - Reduces species that benefit from disturbance & exposed bare soil Closed canopy & litter accumulation -> reduced under-story cover & diversity Reduced herbaceous species -> reduced butterfly, avian, reptile, amphibain & mammalian diversity Increased tree density -> homogenous landscape Alters wildlife habitat

Plant communities support Gleasonian view why

Independent distributions and each species occurs outside the forest type bearing its name

Tolerance

Initial stages of colonization are not limited to pioneer species. - Early successional species do not facilitate later successional species, but do change the environment. - Species remain, leave, or establish based on tolerance to environment. - Long lived species are most broadly tolerant to a range of environmental change.

Bison in Tallgrass Prairie had __________________ interaction

Interspecific interaction between bison, grasses, & forbs

Fire intensity is derived from

It is derived from: - Energy content of the fuel - Mass of fuel consumed - Rate of spread of fire

Type 3

Large Doug-fir and cohort of smaller hemlock with sparse understory

McGraw and Furedi 2005

Minimum Viable Population (MVP) MVP = 800 in normal conditions Median population was 93, and largest found (400) has 43% survival probability

Bison in Tallgrass Prairie

Native tallgrass prairie • Historically, fire & grazing were main disturbances • Cessation of these disturbances decreased diversity • Tried different treatments to restore diversity - Grazing & burning

INTRODUCED, NON-NATIVE EXOTIC, ALIEN

Not "Originally" "Here"

Conifer Encroachment on

Oaks

Endurers

Part of plant dies, but some part survives • Frequently, roots survive • e.g. Madrone, huckleberry, most oaks, beargrass, SESE, rhodi, tanok

Facilitation

Proposes many species may attempt to colonize newly available space. - Only certain species will establish. • Colonizers "Pioneer Species" modify environment so it becomes less suitable for themselves and more suitable for species of later successional stages

What happens given same initial conditions? Different end results:

Randomness (stochasticity) - Species happens to go extinct • Species that survive and occupy their niche are different - Disturbances that have different impacts on islands - New species might show up (plants or animals) • Could be deterministic (distance from mainland) • Could be invasive, aggressive colonizer - Genetic drift - Did we start with the same genetic diversity?

NATURALIZED

Self-sustaining non-native

What happens given same initial conditions? Same end result:

Similar environment (and same initial species) • Disturbances that have similar impact for all islands • Initial species will change environment and interact with each other in the same way

INVASIVE

Spreading non-native

Stand Development

Stand Initiation • Stem Exclusion • Understory Reinitiation • Old-growth

Knobcone pine

Strictly serotinous cones • Persist on tree in annual rings until a fire • At ~200°F, resin melts, cones open, seeds disperse into fertile, noncompetitive environment

Apomixis

The asexual production of seeds.

What are the four main ecologically important characteristics of a disturbance regime? Provide examples to demonstrate your understanding of each one.

The four main ecologically important characteristics of a disturbance regime are size, frequency, severity, and specificity. Size of a disturbance can influence how a community recovers after the disturbance. It is harder for seeds of some species to disperse into an area after a very large forest fire, compared to a small fire. Frequency of disturbances can influence what species can survive in a community. Grasslands that see frequent fires are dominated by species well-adapted to the effects of fire. The severity of a disturbance (ie how much of the plant life is killed) can vary between a weak windstorm that kills a few trees and a hurricane that flattens a whole forest. Specificity accounts for which particular species the disturbance impacts. For example, a pathogen that only infects species in a certain genus is highly specific compared to a landslide that kills any vegetation in its path.

The figure below shows the results of mapping tree species distributions in the Great Smoky Mountains over the gradients of elevation and moisture, and then comparing them to defined community boundaries (upper left quadrant). Do these results support the Gleasonian or Clementsian view of communities and why? Be specific!

These results support the Gleasonian view, as the figures showing the tree species' distribution imply that they exist outside of their designated community boundaries. Considering this, there must be some other factor (other than interactions with other species in their primary community) that determines their distributions. For example, red oak is present in several community types beyond just the red oak-chestnut forest. If red oak had tight interrelationships with species in the red oak-chestnut forest, we wouldn't expect to see it established much outside that community. Instead it appears that species distribution is determined by environmental factors, as the Gleasonian view argues.

Primary succession examples

Volcanic eruptions • Glaciers

Type 1

Wide range of ages for shade-tolerant trees

Association:

a vegetation type that has something and it has the connection to it

Warm/wet ecosystems: (fuel limitation)

accumulate fuel quickly but fine fuels too wet to burn

The view 100 years ago- _______________caused great majority of disturbances. Natural fires, hurricanes, etc were rare.

agriculturalists

Crown

burns through the canopies of forests

Clausen, Keck, & Hiesey geographic transect

coast, over Sierras, to Great Basin

- Cold/dry ecosystems: (fire limitations)

combustible biomass accumulates slowly

Gleasonian idea(s).

communities have arbitrary boundaries species respond idiosyncratically to environmental gradients

How to measure dominance

d = Berger-Parker Index = Nmax/N

From burning, C4 grasses dominate lads to

decreased diversity

Succession

directional change in community composition and structure over time Orderly and predicatable

Gleason's continuum view of communities

each community is 'A, B, C' is an arbitrary section

• Fire intensity =

energy released (kW) per unit length (m) of fireline.

Rate of succession • Secondary

faster - fraction of the time to reach same stage - Disturbance characteristics influence succession

Bormann and Likens found

felling trees in Hubbard Brook substantially increased nutrient losses Herbicide used to suppress regrowth. • When application stopped, succession proceeded, nutrient losses decreased,and primary production increased.

Serotinous conifer cones only open after _________, why

fire, Typically coated in thick resin that melts with intense heat (Fire most common trigger, but can be other things, • Parent death • Wetting • Warming • Drying • Post-fire wetting)

Secondary succession

following disturbance that does not destroy soil

genet

genetically distinct individuals

Burning ---> decreased diversity Burning + ______________ --->increased diversity

grazing

What explains this increase in atmospheric CH4 5,000 years ago?

human use and expansion etc

• Ground -

largely flameless fires that burn slowly in the duff and in organic matter below the soil surface

There are ~30,000 established ___________ species in the U.S.

non-native

Primary succession

on newly exposed geological substrates.

Ordination is most often used for

pattern detection and hypothesis generation

ramet

physiologically independent but not genetically distinct individuals

Deterministic

process with a fixed outcome

Surface -

rapidly moving fires that burn in the litter, downed dead fuel, and surface living vegetation

pi =

relative cover of each species

Rate of succession • Primary

slow - may take 100s - 1000s of years

The graphical results from most techniques often lead to intuitive interpretations of _________________-________ relationships.

species-environment

Serotiny is on a _______________

spectrum

Fire severity =

the effect of fire on plants.

Reducing multiple dimensions

the goal is to arrange sites or species in one-, two-, or three dimensional space so that the distance between any pair is proportional to their degree of similarity

N =

total mean cover % of all species

- Nmax =

total mean cover % of most abundant species

Facilitation and inhibition can operate simultaneously. (t or f)

true

Humans migrated to Western Hemisphere at least 14K years ago (t or f)

true

More than land-use history, strongly associated with increased spring & summer temperatures coupled with earlier spring snowmelt increasing wildfire season length (in Northern Rockies, maybe not Northern CA) (t or f)

true

• Some species (pitch pine, P. rigida) produce serotinous & non-serotinous cones on one plant (t or f)

true

What is a plant community

vegetative subset of the community, simply all of the plants occupying an area which an ecologist has circumcised for study an abstraction

Fish affecting flowers

• A number of interactions link different ecosystems • Direct evidence for many steps in the cascade • Seminal paper: Knight et al. 2005, Nature

Fire Effects Increased resource availability

• Big fire clears canopy, new slew of resources available (space, light, snags, woody debris, etc.) • Surface fires open up new understory space

Problems With Richness Experiments

• Disentangling interactions in natural systems is difficult • Measuring productivity (below ground) • Scale (too short and too small) • 'Sampling effect' problem in constructed communities (or 'Portfolio Effect') - Sampling effect may be an important biological property or an experimental artefact if natural community assembly rules are broken

Colonizers

• Evade (far dispersal) & endure (low flammability, sprout) • Fire stimulates growth & reproduction

Acorn weevils after a fire

• Female bores hole in immature nut & lays eggs • Eggs hatch into grubs which consume cotyledons • Fall, grub emerges into soil where it overwinters • Light burns kill grubs in soil

Fire Effects Nutrient cycling

• Fire can increase or decrease nutrient availability • Depends on fire characteristics (frequency, intensity, & magnitude) & ecosystem conditions

Community or Population Level Impacts from invasives

• Habitat structure • Community composition • Resource competition • Population reductions, eliminations

Species Richness and Ecosystem Function:

• If niches are complementary, adding species could increase process rates linearly • As niches overlap the response should saturate

Prescribed Fires

• Increase mineral soil • Increase SEGI regeneration (serotinous cones) • Reduce fuel loads

What nutrients increase post fire

• Increase nutrients - Deposit N-rich ash - Rapid ammonification & nitrification - Promotes quick vegetation recovery

Why is diversity an interesting/useful property of communities to study?

• Knowing number of species • Resilience (ability to bounce back) • Genetic diversity • More interactions between species to study

How does fire influence species composition

• Open habitat for fire-dependent species • Some species can't establish w/o fire • Some species stimulated by fire (beargrass, chamise) • Fire strategies

Bond & Slingsby, second study

• Put out seeds in areas w/ & w/o AA • Burned study sites 3 weeks later • Areas w/o AA: 35% emergence, 53 seedlings • Areas w/ AA: 0.67% emergence, 1 seedling

Future of Good Fire

• Pyrodiversity = Biodiversity • Pay It Forward - apply good solutions across larger landscapes - treat around communities • Wildfires Are Complex - some are good, some are bad, most are mixed

Shannon Diversity Index (H') is sensitive to

• Sensitive to changes in proportion of rare species

Resistors

• Thick bark • Survive low- to med-intensity burns • Tolerate significant charring (Ponderosa pine, Coast Redwood, Giant sequoia, Mature oaks)

What nutrients decrease post fire

• Volatilization of vegetation & litter via pyrodenitrification (available N nitrate -> unavailable N2) • Ash lost to wind • Newly available N lost to system due to increased erosion & runoff

Shade Tolerant Encroachment

• White fir not fire adapted (when it burns, burns hot) • No fire, white fir thrives • White fir thicket supports crown fires fatal to mature, fireadapted SEGIs • Prescribed fire to restore historical conditions

1) Species Characteristics

• high fecundity • small body size • vegetative or asexual reproduction • high genetic diversity • high phenotypic plasticity • broad native range • abundant in native range • physiological tolerance • habitat generalist • human commensal • *loss of natural enemies* • invasional meltdown • polyphagy