Importance of Scale in Ecology

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Transcript Importance of Scale in Ecology

E. O. Wilson, 2002
The totality of life, known as the biosphere
to scientists and creation to theologians, is
a membrane of organisms wrapped around
Earth so thin it cannot be seen edgewise
from a space shuttle, yet so internally
complex that most species composing it
remain undiscovered.
Selected Recommended Ecology-related Reading
Sand County Almanac, A. Leopold
The Eternal Frontier: An Ecological History of North America and Its
People, T. Flannery
Collapse: How Societies Choose to Fail or Succeed, J. Diamond
Earth Abides, G. Stewart
Song of the Dodo, D. Quammen
Wild Thoughts from Wild Places, D. Quammen
Last Chance to See, D. Adams
In Search of the Snow Leopard, P. Matthiesen
Changes in the Land: Indians, Colonists, and the Ecology of New England, W.
The Future of Life, E. Wilson
Desert Solitaire, E. Abbey
Which of these (choose one), in your opinion, poses
the greatest threat to the ecology and biological
diversity of WI?
Climate change due to increased global CO2 and
atmospheric temperatures
Land use that modifies increasing portions of the
landscape for residential and commercial uses
Spread of introduced species and the related loss of
native species (e.g. species naturally occurring during
the past 100-200 years)
Spread of infectious disease
Overarching Concept
Ecology is the study of how living
(Biotic) and non-living (Abiotic)
factors influence Living Systems
Living Systems include:
• Individual organisms
• Groups of organisms
Units of Study or Investigation
• Individual organism
• Population of a species of an organism in an area
• Community or groups of populations of several
species in an area
• Ecosystems include communities and abiotic
• Landscapes can be thought of as a geographic
region that typically includes several ecosystems
• Biosphere or global ecological systems
Expanded Definition of Ecology
Ecology is the study of how biotic and
abiotic factors influence the
distribution and relative abundance
of organisms in ecological systems.
Biological measures to describe and perceive
changes in forest communities
Density of specific populations
Distribution of specific populations
Dispersion of individuals in specific populations
Presence / Absence of key species
Relative abundance of key species
Diversity of key species
Associations of key species
Physical measurements to describe and
perceive changes in forest communities
• Soil attributes (e.g. pH, moisture, nutrients)
• Topography
• Disturbance (e.g. fire, storms, erosion, roadside, trails and
unintended trails, management)
• Weather and climate
• Light levels
Several Ways that Ecologists Study Ecology
• Observations
• Monitoring
• Experiments
• Simulations using
computer models
• Phenology
• Long-term records or
large-spatial scale
• Effects of
management on
invasive & non-invasive
• Future projections
Challenge Question
You are visiting an ecological system that you haven’t seen
before. A species that you would expect to see, based
upon its possible distribution, is not present. Which is the
more convincing explanation?
Abiotic factors, such as climate, have limited
that species distribution.
Biotic factors, such as competition with another
species or predation by another species, have
limited that species distribution.
Ways that Ecologists
Measure and Describe Populations
• Defining the population of interest
• How big is the population?
– Measure or estimate number of individuals
– Is the population growing or declining
• How are individuals in a population dispersed?
– In a particular habitat or geographic area where are the
individuals spatially and with respect to each other
• What are examples of abiotic and biotic drivers that might
affect population size and the dispersion of the individuals?
Which of the following do not depict a
random distribution or dispersion pattern?
None of the above
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Subsampling using Sample Plot Example
Scenario- 100 individuals found in 10- 1 m sq plots
What is the population density?
Density = Number in plots / Total area of plots
What is the population size if the sample plots were taken from
an area of 1000 m sq?
Population Size = Density x Total Area
Measuring or Estimating Population Density
• Population density = number of individuals of a species/area
or volume
– Complete counts of all individuals
– Extrapolation based on subsampling or counts in sample plots
(e.g. quadrats or transects)
• Density = Number of sample plots / Total area of Plots
• Population Size = Density x Total Area of Interest
– Mark and recapture estimates
• Population Size = Total Number Marked in Sample 1 x Total in
Sample 2 / Number Marked or Recaptures in Sample 2
• Density = Total Population Size / Total Area of Interest
Which forest community is more diverse?
Would you expect an invasive organism to have more
of an effect on:
Diversity within the community
Density of the populations of selected species
Distribution of individuals of selected species
Dispersion of the populations of selected species
Relative abundance of populations within the community