Lecture 12 (chapter 10)

Question 2

Isostasy

Answer 2

Isostasy: isostic rebound (many thousand year prosse)
earths crust rebounding from the weight of the ice
increasing amounts of sandy soil being projected up through isostasy rebound (makes dunes)

Question 3

Pinery

Answer 3

Because of isostacy there is a new environment by the water: Begins with bear exposed sand

A Thousand years (little further away): growth (more mature) no big trees yet

Thousands of years old (middle): Mature Oak savanna ecosystem

Plant millions of pine trees and suppress fires
- This ecosystem depends on fire
- every 20 to 30 years, we used to have fires because of building up debris
- They started to have controlled fires
- The oak sevan is a fire dependent ecosystem.
- It started to look like what an oak sevana forest is supposed to look like
We have fires there every 2 to 3 years now
- burns planted pines because they are not adapted to fire. The oak trees are well adapted to fire.
-Oaks reproduce with acorns. They move deeper down into soil because they are heavier. They are one of the 1st seeds to germinate after fire
- After prescribed burns, old organisms started to come back
ex. red-headed woodpecker
ex. blue lupine grows after fire
ex. Mottled Duskywing and Karner blue butterfly

Question 4

What are Disturbances?

Answer 4

An event that causes destruction of
some part of a community or ecosystem
ex. fire

Question 5

What is succession?

Answer 5

Is the community-level recovery
that follows a disturbance
ex. The introduction of species that thrive in environments after fires

Question 6

Resilience and resistance

Answer 6

Resilience: If succession restores the original community, (how fast can they bounce back)

Resistance: If the system can avoid disturbance, (how long can it wistand the disturbance)
ex. Jack pine forests come back fast after fires
ex. chestnut experiences invasive chestnut blight. In spit of the blight the forest communities still exist.

ex.
x-axis how much environmental stress?
y axis = community stress
- Low intensity disturbance ecosystem is fine
- When it’s more intense, the ecosystem is more stressed

Question 7

Small-scale disturbances

Answer 7

Small-scale disturbances
often occur in an
otherwise intact
community

ex. death of a single tree
ex. small landslide
ex. grazing by cattle

Question 8

Large scale disturbance

Answer 8

Large-scale disturbances affect entire community

ex.
– Wildfire
– Wind storms
– Glaciation
– Biological agents

Question 9

Frequency of disturbance

Answer 9

Frequency of disturbance can be regular or
unpredictable
* Tides , cold or dry
seasons, spring floods are
regular and predictable

• Wildfires can be regular but unpredictable
• regular because of accumulation of biomass
• Volcanic explosions are irregular and
  unpredictable
  Tidal communities experience a twice-a-day
  inundation with salt water

Question 10

Patterns of succession

Answer 10

• Community-level recovery often follows a
  sequence of community types, called seral stages
• Seral stages: Stages that a community undergo after experiencing a disturbance together form a sere (how ecosytem changes)
• A stable community
  develops, depending on
  environmental factors,
  species present, and
  stochastic factors

Question 11

Climax comunuities

Answer 11

• Final seral stage (end of succession)
  ex. oak forest at pinery
  (clements community unit concept)
• Gleasen says there’s no predictable stable end point

Question 12

A forest sere

Answer 12

A forest sere
* Initial seral stages: r-strategist plants and survivors (fast-growing, can live in direct sun)
* Pioneer trees are fast-growing, shade-intolerant, with strong dispersal
- Shade tolerating trees dominate over time

Question 13

Hydrosere

Answer 13

• Open lake isnt much vegetation there
• Initial stage: a young
  lake or pond after glacial
  melting
• Oligotrophic at first,
  sediment accumulates
  slowly
• Nutrients increase over
  time
• Eventually the entire
  lake may turn into a
  wetland, even a forest
  (bog)

Question 14

Lithosere

Answer 14

• Serel stages that you see on bare rock
• Common after glacial retreat or
  volcanic activity
• Begins with algae, lichens, mosses
• Followed by grasses and later
  by shrubs

Question 15

Psammosere

Answer 15

• Seral stage that occurs on a sandy soil
• Difficult for initial plants to take off
• Succession on sandy
  substrates, such as
  shores of lakes and
  oceans
• Moving substrate is a
  special stress for plants:
  this instability favours
  vegetative reproduction
  ex. Pinery’s dune

Question 16

What are alternative stable states?

Answer 16

In some cases, end point of succession may be dissimilar to the original community.
ex. costal communities in bc
kelp forests sea urchins thrive and eat the kelp creates barren ground (sea urchins= keystone species)
- Dominance of kelp depends on how many sea urchin, which depends on otters

Question 17

Facilitation model of succession

Answer 17

A predictable sequence of species occurs because earlier seral stages facilitate
conditions for later stages
ex. Lichens and mosses create a substrate
for grasses, which create substrate for trees
* Nitrogen-fixing organisms
help Nitrogen-requiring
organisms to follow
- foccus on ways eaerly seral stages alow older stages to take place

Question 18

Tolerance model of succession

Answer 18

• A predictable sequence
  of species occurs
  because species vary in
  their ability to utilize
  resources and tolerate
  certain conditions
• Example: colonizing
  species are displaced at
  later seral stages as they
  cease to be able to
  tolerate new conditions

Question 19

Inhibition model

Answer 19

Different stages stop other stages from occurring
A predictable sequence of
species occurs because
early species prevent or
delay the establishment
of later species
* Example: tall and dense
stands of pioneers
prevent growth of other
species (dense grasses
preventing establishment
of trees)

Question 20

Life history and succession

Answer 20

Early successional stages are
dominated by organisms
adapted to disturbance
* Spatially unpredictable
disturbance: species with
good dispersal have an
advantage
* Temporally unpredictable
disturbance: species with
long-lived seeds (seed bank)
have an advantage
ex.
Dandelions have far-
dispersing seeds
ex.
birds (navigate the glob dropping seeds in poop)
r strategist are common members of early sere stages

Question 21

Seed bank

Answer 21

Enduring pop of seeds that sit in the surface of the soil
Naturally occurring seeds that sit in the soil waiting for disturbance to occur
following disturbances increase in light or nutrients stimulate germination

Question 22

Means of regeneration

Answer 22

Plants reproduce either
Vegetative or by seed
* Reproduction by seed has the advantage of
large numbers, good dispersal, and durability
during cold or dry periods, long periods of durability.
* Vegetative reproduction is more dependable
Limitations: cant get far away

Question 23

Advanced regeneration

Answer 23

Many trees survive over years as small plants
under a canopy of mature trees
* They start to grow when the canopy opens
* This enables rapid response to disturbance

Question 24

Serotiny

Answer 24

• seeds that stay for many years on the plant
• release is triggered by environmental factors
  ex. cones of jack pine, pine cone need fire to open up

Question 25

Primary vs secondary sucession

Answer 25

Primary: newly exposed rock is colonized for the first time. (volcanic erruption)
Secondary: recolinization after disturbance (forest fire)