4/7 real

ecological succession definition

directional and predictable change in community composition over time

focus of succession

temporal changes in communities at a single location

primary succession

begins with no soil and little to no life

secondary succession

occurs after disturbance with soil and seed bank remaining

primary succession examples

volcanic rock, glacial retreat, severe fires

secondary succession examples

typical fires, abandoned fields, storms

lichens role in primary succession

break down rock and contribute to soil formation

lichen composition

symbiosis between fungus and alga

seed bank

stored viable seeds in soil that enable regrowth after disturbance

disturbance effect on succession

resets community to earlier stage depending on severity

directional succession

communities move through stages in a consistent order

predictability of succession

species identities vary but functional groups are consistent

seral stages

distinct stages in succession with characteristic communities

climax community

relatively stable end-stage community for a region

example climax community (PA)

mature forest with oaks, hickories, maples, hemlocks

early succession species traits

fast-growing, many seeds, small size, shade-intolerant

late succession species traits

slow-growing, fewer seeds, large size, shade-tolerant

ruderal species

early successional species adapted for rapid colonization

early stage plants (year 1)

ragweed, crabgrass, horseweed

meadow stage plants

asters, goldenrods, Queen Anne’s lace

shrub stage plants

blackberries, sumac, greenbriar

early successional trees

tulip trees, red maple, birch, ash

late successional trees

oaks, hickories, hemlocks, maples

canopy gap effect

creates small patches of early succession within mature forest

mature forest structure

mosaic of different successional patches

early succession bird habitat

ground-nesting and insectivorous birds

examples early birds

wild turkey, ruffed grouse, American woodcock

mature forest bird habitat

high vertical structure and niche diversity

amphibian habitat preference

moist, shaded forest environments

reason amphibians avoid early stages

dry and exposed conditions

generalist mammals example

white-tailed deer

mammal habitat use

use multiple successional stages depending on season and resources

abiotic drivers of succession

temperature, precipitation, nutrients, light, soil, disturbance

topography effect

influences moisture, temperature, and sunlight exposure

disturbance regime

frequency and severity shape successional pathways

stochasticity

randomness affecting which species establish

biotic drivers of succession

competition, predation, herbivory, mutualisms, dispersal

seed dispersal methods

wind and animals

facilitation

species improve conditions for others

inhibition

species hinder establishment of others

alder facilitation example

increase soil nitrogen via nitrogen-fixing bacteria

alder inhibition example

shade reduces pine growth early on

long-term alder effect

facilitation outweighs inhibition as pines grow

taproot facilitation example

deep-rooted plants bring nutrients to surface

early species seed number

many seeds

late species seed number

few seeds

early species seed size

small

late species seed size

large

early species seed viability

often long-lived in seed bank

late species seed viability

generally shorter-lived

early species root:shoot ratio

low (more aboveground investment)

late species root:shoot ratio

high (more root investment)

early species growth rate

fast

late species growth rate

slow

early species size at maturity

small

late species size at maturity

large

early species shade tolerance

low (require full sun)

late species shade tolerance

higher (can grow under canopy)

chronosequence definition

using sites of different ages to infer temporal change

purpose of chronosequences

study succession without waiting decades

desert pipeline example

sites at different disturbance ages show slow recovery

pattern in desert succession

weeds → grasses → shrubs over decades

key insight desert

recovery can take >50 years and still be incomplete

Presque Isle State Park chronosequence example

sandbars of different ages show succession gradient

Gull Point trail concept

walking across space represents moving through time

sandbar succession pattern

bare sand → grasses → more complex vegetation

species-area eco data connection

succession and landscape patterns studied using spatial gradients

succession key takeaway

communities change predictably but are influenced by disturbance and environment