Basic
Ecology
Ecology – the basics
Study of the interactions among ecosystem
residents and their environment
Residents…
…individuals
…populations
…communities
Niche…
…the role or function of a population within
its ecosystem
Ecology – the basics
Study of the interactions among ecosystem
residents and their environment
Abiotic components…
…air
…water
…soil
…temperature
Habitat…
…the local environment of a population,
biotic and abiotic
Ecology – the basics
Fundamental concerns:
…
…flows through ecosystems; not recycled
Fixed by producers, harvested by
consumers & detritivores
Used for respiration, tissue
maintenance & reproduction
Transformed, stored and transferred
Some is lost with each transformation
The trophic pyramid of a terrestrial ecosystem
1-10% energy
transformation
efficiencies
Ecology – the basics
Fundamental concerns:
…
…cycles within ecosystems.
Assembled by producers, harvested by
consumers, reused by producers
Cycle: Carbon enters ecosystems
from an atmospheric reservoir
Reservoirs: GT
Transfers: GT/yr
Cycle: Nitrogen enters ecosystems
from an atmospheric reservoir via biological fixation
Compartments: MT
Transfers: MT/yr
Compartments: GT
Transfers: GT/yr
enters ecosystems from the soil and is
stored in geochemical reservoirs
Compartments: MT
Transfers: MT/yr
A Food Web (Trophic Web) illustrates energy and
nutrient transactions in an ecosystem
Ecosystems are dependent on their primary producers
Limits to Primary Production
Light
Water
Nutrients
Temperature
On land, the most favorable
combination of these assets is
found in tropical rainforests
soil
nutrients
!!Tropical rainforest litter
residence time is very low!!
The effect of climate on organic decomposition
temperate forest floor
tropical rainforest floor
over comparable time periods
GPP – R = NPP
Gross Primary Production – Respiration
= Net Primary Production
NPP is higher in
tropical
rainforests than
other forest
ecosystems
Energy Budget
Energy available for consumer trophic levels
depends on…
…NPP*efficiency of transfer(s) (5-20%)*
assimilation efficiency(ies)
= assimilated/ingested
…depends on type of ingested material
e.g. wood: 15%; seeds/animal tissues: 90%
Energy Budget
Consumer production…
=assimilated energy – respiration – excretion
Net Production Efficiency =
production/assimilation
…depends on the animal
bird: 1%; sedentary cold-blooded: 75%
Soils develop from above and below
Soils
provide primary
producers with…
…water
O (organic) Horizon
organic
A Horizon
Zone of Leaching
…mineral nutrients
…anchorage
B Horizon
Zone of Accumulation
C Horizon
Partially decomposed
parent material
mineral
Soil Texture Classification
Soil particle size classes
<0.002 mm
clay
0.002-0.05 mm silt
0.05-2 mm
sand
% sand
Some Soil Properties Influenced by Soil Texture
Texture Class
Soil Property
Sand
Silt Loam
Clay
Aeration
excellent
good
poor
Drainage
excellent
good
poor
Tillage
easy
moderate
difficult
Spring Warming
rapid
moderate
slow
Water holding
low
moderate
high
Cation Exchange
low
moderate
high
Soil Weathering in Tropical Rainforests
Laterization
– wet warm climates
– clay particles broken down
– silica leached downward
– iron & aluminum oxides retained
– low nutrient holding capacity
– low organic content