Download Unit 4: Landscape and Ecosystem Ecology Unit 4

Biol 208 – Devito
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Lecture note taking & study methods
Prior to lecture
1) Look at the schedule provided at beginning of term
Read (with out taking notes) the pages suggested to
familiarize yourself with the topic
2) Use the outline provided at start of class as a guide
During lecture, make very cryptic / short hand notes
1) Write summaries of the discussion, not every word
2) The notes will be provided later
After class
1) That evening, read your notes, check figures in text
2) End off week, merge web notes with your lecture notes
3) Read text to fill in holes, clarify
Exam
1) 7 days before, spend 1-1.5 hr per day on one subject.
2) Arrange & organize notes.
3) Read full notes once a day
4) Day 3 start asking your self questions,
1) make a summary/ cheat sheet (outlines are provided) –
key topics, words etc – consult this and determine if you
know these, if not go back to full notes
Unit 4: Landscape and Ecosystem Ecology
ECOSYSTEMS –Biogeochemistry, energy & organisms
Ecosystem perspective Æconsequence of E & nutrient interactions
A. ORGANISMS in ecosystems p29-30, p407-408, 410-13
A.1) Trophic classification Food Chain
A.1.1)Trophic Levels or Components
a)
b)
c)
Producers (1o production)
Consumers (2o production)
Decomposers (3o production),
A.2) Controls of Trophic Level Biomass
A.2.1) Top Down Controls
a)
b)
Keystone Spp
Trophic Cascade
A.2.2) Bottom Up Controls
A.2.3) Limits to Global 1o Production
Biol 208 – Devito
Unit 4: Landscape and Ecosystem Ecology
• Until now concerned only with organism &
interaction in communities
• lets start considering surrounding
environment & landscape
Biol 208 – Devito
Unit 4: Landscape and Ecosystem Ecology
ECOSYSTEMS
-merging food webs (Ch 21), ecosystems energy (Ch 6 & 8), & nutrient (Ch 7) cycling
- concepts developed by:
C. Elton (1920-Foodweb), A.G. Tansley
- Consider community with their abiotic environment
- Hierarchical & functional relationships of communities
w geographical & functional relationship to their environment.
A.J. Lotka , R. Lindeman (1942)
- ecosystem fundamental unit of ecology= food-web & energy transfer
E.P Odum (1953)
– ecosystems as energy flow diagrams = Ecosystem Ecology
-cycling of matter & passage of energy basis for characterizing ecosystem
structure & function
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Biol 208 – Devito ECOSYSTEMS
Biol 208 – Devito ECOSYSTEMS
A. ORGANISMS in ecosystems
3 Main Components of Ecosystems
Biogeochemistry: nutrient cycling, raw materials
for ecosystem
Energy: needed to convert nutrients into life forms
Organisms: consequence of E & nutrient
interactions
A. ORGANISMS in ecosystems
A.1) Trophic classification - Food Chain –cont’d
“abstract model” to generalize ecosystem function
– systems approach
Meadow ecosystem
functions same as
Hawk Æ foxÆ rabbit Æ grass
Pond ecosystem
lg Fish Æ sm fish
Æ zooplanktonÆ algae
p29-30, p407-408, 410-13
Ecosystem perspective Æconsequence of E & nutrient interactions
A.1) Trophic classification
Food Chain
-Summary of feeding
interaction
w/in community
- basic description of
community structure,
- also transfer of energy &
masses of elements
Meadow ecosystem
Hawk Æ foxÆ rabbit Æ grass
A.1) Trophic classification - Food Webs
Food Webs more complex
than linear chains:
-complexity increases with
increase community
diversity
•2 very diff communities with diff species,
•function same manner with respect to interactions, matter & energy flows
•Replace fox, replace zooplankton?
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A.1) Trophic classification - Food Web
A.1) Trophic classification - Food Chain –cont’d
-simplify complexity, focus on important (strong) interactions,
-trophic levels or components
African Savannah
Ecosystem
-energy flow
A.1.1)Trophic Levels
or Components
a) Producers (1o production)
-they are autotrophs “self feeders”,
produce their own energy source
-basis of live on earth,
& all food chains
Photoautotrophs: derive energy via photosynthesis in
chloroplasts, reduce inorganic sources
using sun’s solar radiation.
-most ecosystems of the world
A.1) Trophic classification - Food Chain –cont’d
A.1.1)Trophic Levels or Components
A.1.1)Trophic Levels or Components
Heterotrophs: derive energy
from produced organic matter,
they consume other organisms
a) Producers (1o Production)
Chemoautotrophs:
some bacteria use energy
stored in chemical bonds
within the earth system
b)Consumers (2o production)
i) Grazers/herbivores: eat producers
ii) 1o Carnivore: eats grazer
ie bacteria Thiobacillus uses
Sulfur compounds as
energy source in deep
sea vents.
iii) 2o carnivore: carnivores that eat carnivores
Deep Sea vent ecosystem
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A.1) Trophic classification - Food Chain –cont’d
A.1.1)Trophic Levels or Components
c) Decomposers
(3o production),
- transformers, reducers
-take dead prod & consumers
break them down to elementary nutrients
-make nutrients available for re-cycling *important
A.ORGANISMS in ecosystems
A.2) Controls of Trophic Level Biomass
- unit 2 and 3, learned that predators can depress the populations of their
prey dramatically
A.2.1) Top Down Controls
a) Keystone Spp
-often major predators,
feeding activities of few:
- have dominant
influence on
community structure,
- disproportionately large
influence rel. to biomass
A.2.1) Top Down Controls
a) Trophic Cascade
example
River food webs,
-local controls on
biomass of trophic levels
Determine the number of trophic levels – 4 levels in this ecosystem
2o Carnivore
1o Carnivore
Study by Power (1990)
Eel River, California
-What is causing major
algae growth (eutrophication)
of some trout streams?
Herbivore
1o producer
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Power (1990) Eel River, California
Enclosure experiment A & B
Steelhead Æ Stickleback Æ Chironomid Æ diatoms/algae
Roach
Roach fry
Cladophora
Pred Insect
Nostoc
A. Remove Steelhead etc.
LOW# Æ algae bloom, HIGH#
due to pred
less grazing
A.2.2) Bottom Up Controls
•
the size of the trophic level
is determined by the rate
of 1O production of food
both Top-down & bottom
up occur in ecosystems
- more pronounced in aquatic
systems, less so in terrestrial
systems
a) Bottom Up Influences
Zooplankton biomass
HIGH # Æ algae #’s kept LOW
eat algae
A.2) Controls of Trophic Level Biomass
•
- Herbivory/Predation can limit
1o and 2o production
-Can use some keystone carnivore
spp to manage 1o production
B. Control (with pred fish)
High # fish Æ LOW #
Æ
Predators
due to pred
-Alternating changes in biomass
with each trophic level
A.2.2) Bottom Up Controls
•increased primary production
tends to augment all overlying
trophic levels
Algae Biomass ug/L
•global/regional scales 1o
production tends to limit 2o
production
b) Top Down Influences
Zooplankton biomass
Low # fish Æ HIGH #
Æ
No predation
Cascading Hypothesis
•Top down increases variability
in bottom-up relationship
Algae Biomass ug/L
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A.2.3) Global 1o Production
-virtually all energy originates from solar radiation
A.2) Controls of Trophic Level Biomass
A.2.3) Limits to Global 1o Production
-virtually all energy originates from solar radiation
A.2) Controls of Trophic Level Biomass
A.2.3) Limits to Global 1o
Production
a) Terrestrial 1o production:
-limited by solar input (E) and moisture (Climate)
- nutrients only control at regional & local scales
i) Latitutude, Solar Input
-Solar Energy greatest at equator,
decreases to poles
- thus, generally greater 1o production &
biomass at equator than the poles
-even though nutrients greater at the poles
ii) Moisture
- low in deserts (about 30o latitude)
b) Marine 1o Production,
- highest at mid
latitudes (40-60o )
- Ocean Currents,
nutrient regeneration
-energy/light limited at
poles
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Geographical variations
initial ecosystem
production
•Terrestrial 1o product’n
> marine
(even with less area)
•Greatest 1o Production
on Land or wetland in
humid tropics
•Lets follow how the
energy follow along
trophic levels
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