disruptions and species

Natural Disruptions

Can be due to human activities like housing, agriculture, air pollution, forest clearing, and removal of mountain tops for coal mining.

Periodic disruptions

Occurs REGULARLY (day/night or monthly cycles).

Episodic disruptions

Occur SOMEWHAT REGULARLY (cycles of high/low rain that occur every 5-10 years).

Random disruptions

NO REGULAR pattern (volcanos/hurricanes).

Resistance

Measure of how much a disruption can affect the FLOWS OF ENERGY AND MATTER.

High resistance

NO effect on overall flow of energy and matter.

Low resistance

HIGH effect on overall flow of energy and matter.

Resilience

Rate at which an ecosystem can RETURN TO IT'S ORIGINAL STATE after a disruption.

High resilience

Returns to original state RAPIDLY.

Low resilience

Returns to original state SLOWLY.

Large and rare disruptions

Cause plant adaptations such as seeds that readily germinate after fires and readily sprout new shoots from their protected underground tissues.

Intermediate disturbance hypothesis

States that ecosystems that experience INTERMEDIATE LEVELS OF DISTURBANCE will favor a HIGHER DIVERSITY of species than those with high/low disturbance levels.

Rare disturbance

Lead to intense competition between species.

Frequent disturbance

Lead to low competition due to few species being able to counter the effects of disturbance.

Migration

Often caused by SEASONAL DISRUPTIONS, usually in search of more abundant FOOD.

Short-term migration

Movement of GRAZING ANIMALS.

Long-term migration

Movement of north american BIRD SPECIES.

Community changes

Affect richness, biomass, and productivity of ecosystems.

Ecological succession

Predictable REPLACEMENT of one species by another over time.

Primary succession

Starts with BARE ROCK and NO SOIL, typically after a glacial retreat or newly cooled lava.

Pioneer species

Algae, lichens, mosses THAT CAN SURVIVE WITH LITTLE TO NO SOIL.

Mid successional plants

Grasses and wildflowers that are EASILY DISPERSED and exploit open sunny areas as well as survive in the young nutrient-poor soil.

Secondary succession

Occurs in areas that have been DISTURBED BUT NOT LOST THEIR SOIL, typically follows a forest fire or hurricane.

First plants to arrive

Grasses and wildflowers that have WIND-BORNE SEEDS, which are replaced by species that are better competitors.

First tree species to colonize

Must be able to DISPERSE EASILY AND GROW RAPIDLY, and must grow well in full sunshine.

Shade-tolerant species

Grow through the canopy created by the first tree species and eventually outcompete them.

Climax community

Historically described as the final stage of succession, but NATURAL DISTURBANCES are a REGULAR PART OF MOST COMMUNITIES.

Intertidal zones

Major storms can turn over rocks or clear their surfaces, which are later COLONIZED BY BROWN ALGAE AND SHORT-LIVED RED/GREEN ALGAE.

Barnacles and long-lived red algae

Colonize rocks soon after they are cleared by major storms.

Streams that experience major floods

Fast-moving water can displace rocks and soil, ELIMINATING ALL ALGAE AND INVERTEBRATES.

Rapid recolonization

Can occur by unaffected UPSTREAM AREAS with ALGAE AND ANIMALS TRAVELING DOWNSTREAM.

Adult flying insects

Can rapidly recolonize streams by laying their eggs in the stream.

Shallow freshwater lakes/ponds

Glaciers may have carved out a basin and scoured it of sediments and vegetation, which over time is colonized by ALGAE AND AQUATIC PLANTS.

Erosion of rock and soil

Caused by the growth of aquatic plants, which slowly fill the basin with SEDIMENT WITH ORGANIC MATTER, turning it into a TERRESTRIAL HABITAT.

Biomass increase

Can occur over time as a result of ecological succession.

Keystone species

Species that are not abundant but can have very large effects on a community, such as beavers and alligators.

Indicator species

Demonstrate a particular characteristic of an ecosystem, used to characterize when ECOSYSTEMS HAVE BEEN NEGATIVELY IMPACTED by humans.

E. coli

An indicator for water with pathogens, suggesting the presence of harmful pathogens.