Ecology L8 Community & Species Diversity

Define Community Structure

Attributes of a community

• # of species

• Kinds of species

• Distributions

• Interactions

Define Taxonomic Affinity

Organisms grouped by classifications

Define Guild

Group of organisms that use the same resources

Define Functional Group

Species functioning similarly but not necessarily using the same resources

What is lognormal distribution?

Continuous probability of a random variable whose logarithm is normally disturbed. Each new individual in a sample can add a new species but eventually further accumulation of individuals results in few to no new species

Define Species Composition

Identity of the species present in a community

Define Species Diversity

Measure that combines the number of species and their relative abundances compared with one another

Define Species Richness

Number of species in an area

Define Species Evenness

Relative abundance of species in an area

Shannon Index

Focuses on richness

Simpson Index

Focuses on abundance

What factors influence environmental complexity?

• Nutrient distribution & quantity

• Predator distribution

• Topography

• Moisture distribution & quantity

• Competition

Which factors of environmental complexity also influence species diversity?

Nutrient distribution and competition influence

Define Direct Interactions

Occur between two species and include trophic and non-trophic interactions

Define Indirect Interactions

Occur when the relationship between two species is mediated by a third or more species

Define Trophic Cascade

A change in the rate of consumption at one trophic level that results in a series of changes in species abundance or composition at lower trophic levels

Define Trophic Facilitation

An interaction in which a consumer is indirectly facilitated by a positive interaction between its prey or food plant and another species

Define Competitive Networks

Competitive interactions among multiple species in which every species has a negative effect on every other species

Define Disturbance

Relatively discrete event that causes an abrupt change and alters resource availability, substrate availability, or physical environment

How does disturbance affect species diversity?

• Creates gaps in communities and has variosus impacts on both spatial and temporal scales; impacts may not always be negative

Define Disturbance Regime

characteristics of the disturbances occurring in that ecosystem

What are the four things used to describe Disturbance Regime?

• Intensity

• Size

• Frequency

• Timing

What are the 7 types of disturbances?

1. Wind

2. Water

3. Animals

4. Earthquakes & volcanoes

5. Disease

6. Human activity

7. Fire

How can wind impact a community?

Through windthrow - blow down of a branch, part of a tree, whole tree, or group of trees

• Important in tropical forests to open up space for new communities to grow

• May result in soil erosion

How can water disturbance impact a community?

Through drought - an extended period of months or years of a deficiency in water supply

How can animal disturbances impact a community?

Associated with herbivory; large herds and insect swarms

How can earthquakes/volcanoes impact a community?

May be massive in size, associated with landslides/mudflows/avalanches/lava flows, and can lead to primary succession

How can disease impact a community?

Through various intensities of fungi, bacteria, and viruses

How can human activity affect a community?

Can be accidental or intentional

• Domestic animals

• Logging

• Farming/ranching

• Recreation activities

How can fire disturbances impact a community?

Major source in many communities due to its great potential for destruction

What does fire require?

Fuel, proper climate conditions, and an ignition source

Describe an Underground Fire

Below the surface. Most destructive, but very infrequent

Describe a Surface Fire

In contact with the ground. Less hot than other fires, but quicker moving. Fed by lightweight fuels. Can lead to crown fires via consumption of ladder fuels

Describe a Crown Fire

Can travel faster and burn with more intensity, and is capable of creating its own weather due to two different temperatures. Highly destructive

What are the four behavior determinants of a fire?

• Ignition Pattern

• Fuel

• Weather

• Topography

How does ignition pattern determine fire behavior?

Area and definition

How does fuel determine a fire’s behavior?

• Physical properties

• Quantity

• Arrangement composition

• Moisture content

How does weather determine a fire’s behavior?

• Temperature

• Humidity

• Wind

• Atmosphere Structure

• Season

How does topography determine a fire’s behavior?

Land configuration, slope

Why is fire essential to ecosystems?

• Removal of competitors and fuel

• Recycles nutrients

• Opens serotinous cones

• Enhances wildlife habitats

What are some adaptions to surviving fire-prone ecosystems?

Thick bark, rapid growth, early maturity, evanescent branches, growth and germination stimulated by fire

Define Succession

Directional change in plant & animal communities following a disturbance or creation of a new substrate

Define Primary Succession

Colonization of ground that wasn’t previously vegetated

Define Secondary Succession

Colonization of ground previously occupied by a living organism

Which vegetation dynamics do succession responses depend on?

Pioneer Stage → Intermediate Stage → Climax Stage

Define Climax Community

Community whose populations remain stable until disrupted by disturbance

Define Stability

Persistence of a community or ecosystem; lack of or absence of change

Why is there controversy over the terms climax community and stability?

Populations may appear stable, but individuals or species aren’t. It depends on scale, measurements, and organisms of study.

What are some community changes that occur during succession?

Increases species diversity, and can increase or decrease species composition

What are some ecosystem changes that occur during succession?

• Increase in biomass

• Increase primary production

• Increase respirationn

• Increase nutrient retention

• Alterations of diversity and composition, such as soil characteristics

What is the ecosystem recovery model?

Disturbing a forest will induce a series of distinct recovery phases

• Disturbance → Ecosystem reorganizes → Biomas increases → Biomass declines during transition → Biomass steadies into a state phase

What are the three mechanisms driving succession?

• Facilitation

• Tolerance

• Inhibition

Define Facilitation

Pioneer species alter the environment and make it more suitable for the establishment of later successional species

Define Tolerance

Later successional species are able to tolerate the conditions created by earlier species

Define Inhibition

Early colonizers prevent the establishment of later species, slowing succession