th
October 5 2011
Hypothesis: A proposed explanation for a fairly narrow set of phenomena usually based on prior
experience, scientific background knowledge, preliminary observations and logic.
To measure ecosystem diversity:
- To measure, we must define what organisms are sampled, the spatial area sampled, and
when/how long we sampled (time).
Species Richness: The number of species per specified collection/sample area OR specified
number of individuals.
th
October 17 2011
What are the unique properties of a community?
- Number of species (diversity)
- Trophic structure (plants, herbivores, carnivores)
- Composition (abundance, evenness, dominance)
- (Richness, trophic level and abundance) – d
What are the unique properties of a population?
- Size = number of individuals (abundance)
- Geographic distribution = area in which the individuals occur.
- Growth (increase or decrease in size)
- (Number of individuals (within species), area and growth)
What ecological factors place limits on a species’ geographic range?
- Abiotic factors
- Dispersal
- Biological interactions
- Habitat selection
What are abiotic factors?
- Climate (temperature, moisture)
- Soils (minerals, texture, acidity)
- Geology (rock type, land formations)
- Light (sun, shade)
- Nutrients (nitrogen, phosphorus, potassium)
- Habitat
- Pollutants How do abiotic factors influence the distribution of plants and animals?
- Restrict access to resources
o Food/nutrients
o Habitat
- Limit physical tolerances
o Hot/cold
o Chemistry (toxins)
- Physical barriers
o River, mountain, lake and ocean
How would you determine which abiotic factor is limiting the distribution of a species?
- Field observation of actual range of distribution.
- Determine ecological tolerances.
- Correlation between environmental gradients and a species optimum range.
- Experiments (field transplant, controlled environment)
Light Water Survival
A Low High 90%
B High High 44%
C High Low 19%
Which factor is most important? Light or water?
- Light is a critical factor in determining tree line. th
October 19 2011
The concepts of a niche
- A species has a range of tolerance to the environment
- Tolerance range defines suitable habitat (potential range)
A Niche consists of all the factors necessary for a species’ existence in terms of time, space, and
required resources.
Fundamental Niche: All the possible dimensions in which a species can survive in principle.
Realized Niche: The dimensions in which a species actually survives after the effects of biotic
interactions.
Niche differentiation (realized niche) – Natural selection for bigger and smaller beak sizes due to
competition for food.
Community Assemblage – Development of ecological niche in a forest along a gradient of time.
An ecosystem engineer is any organism that creates or significantly modifies habitats.
A functional trait of alder shrubs is nitrogen fixation via a symbiotic relationship with nitrogen
fixing bacterium.
- Increased nitrogen allows colonization of spruce.
Are old growth forests important for maintaining biodiversity?
- Yes and No
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October 12 2011
What is a woodlot?
- A forest in a city. (urban forest)
What is a forest?
-
Ecosystem: A system formed by the interaction of a community of organisms with their physical
environment.
Temperate Deciduous Forest Biome
- Seasonal variation in temperature (5-20 degree Celsius)
- Precipitation is even among the seasons (80-120 cm/year)
- Deciduous trees dominate.
Why?
- Deciduous trees outcompete conifers in summer because large leaves = greater
photosynthetic capacity.
Why do deciduous trees lose their leaves in the fall?
- Winter = drought, (water frozen in the ground),
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