Communities and Succession

community

A group of populations of deifferent species living together at the same time and place

organismic- Clements and Tansley

view of natural communities where loss of one species impacts organization of entire community and what is its author

Individualistic- Gleason

view of natural communities where communities are just whoever is in the area at the time and its author

Ehrlichs rivet hypothesis

The more species lost, the bigger the impact on the community

walker’s redundancy hypothesis

Introduces the idea of functional groups, the type of species that are missing matter in the amount of impact on community, species with more unique jobs will have larger impact if lost

functional group

species with similar jobs

structure, stability, resilience, and diversity

what characteristics define the nature of communities?

palynology

study of pollen in lake mud

biodiversity, species composition, biomass, productivity

quantifiable properties of communities

biomass

weight of living material

species richness, relative abundance, combined species diversity

components of biodiversity

productivity

rate of biomass production

Heterogeneity

degree of difference form place to place

number of connections in food web

measures complexity based on food relationships

ecotone

boundary between community types

steady state, climax commuity

in theory, there could be a ___________ or ______________ where abundances of organisms don’t change.

no

do the abundances of species typically hold steady?

disturbances

events that produce change by causing mortality to organisms or parts of organisms

no

will a community immediately return to the steady state after a disturbance?

succession

directional change in species composition over time

secondary succession

succession following a disturbance that leaves the substrate intact

primary succession

succession involving colonization of a brand new substrate

primary

which succession type takes longer?

secondary

what type of succession is a forest fire?

Clement’s facilitation model

model where species that appear early in succession make it possible for the species that appear later to live by improving the habitat

pioneer species

Species that can stand the stressful conditions
• Change the habitat, improving it
• Allow other organisms to be able to move in

Engler’s passive life history model

hypothesizes that succession is just a reflection of the life histories of organisms
• Dispersal, growth, and reproduction rates

probability

what determines who arrives first in the passive life history model?

Connell and Slatyer’s Inhibition Model

Assumes the open site is not inherently stressful
• Species appear based on LH

Instead, species depress resources and try to prevent invasion by later species.

assume only one trophic model the primary producers

What is an assumption of 3 of the 3 succession models?

differential predation model

Succession model that incorporates predation

stress tolerant, poor competitors

trade offs in the facilitation model during early succession

not stress tolerant, good competitors

trade offs in the facilitation model during late succession

good colonizers, poor competitors

trade offs in the Passive LH model during early succession

poor colonizers, good competitors

trade offs in the Passive LH model during late succession

good colonizers, poor competitors

trade offs in the Inhibition model during early succession

poor colonizers, good competitors

trade offs in the inhibition model during late succession

good colonizers and competitors, susceptible to predation

trade offs in the differential predation model during early succession

poor colonizers and competitors, resist predation

trade offs in the differential predation model during late succession

facilitation

what model connects with primary succession?

overgrowth makes it too dense and dark for pine barrens

what happens if there is no fire in the pine barrens?

glacial retreat, Mt. Saint Helens

examples of primary succession

forest fire, agricultural abandonment

examples of secondary succession