[PART 1] Population Ecology Population Characteristics, Dynamics, Growth, and Life History

POPULATION

A group of individuals belonging to the same species occupying the same space at the same time

POPULATION ECOLOGY

Answers the following questions:

• Why do populations grow and decline?

• What regulates population size?

Size

• How large is the population?

• How fast is the population growing?

____________ - total number of individuals in a population and can indicate the health of a population

Density

How dense is the population?

___________________ – size of a population in relation to a definite unit of space; number of individuals of the same species per unit area

Crowding affects the health of a population

relative abundance; Species abundance; relative abundance

Two communities may be equally rich in species but differ in relative abundance. For example, each community may contain 5 species and 300 individuals, but in one community all species are equally common (e.g., 60 individuals of each species), while in the second community one species significantly outnumbers the other four.

Species diversity is determined not only by the number of species within a biological community—i.e., species richness—but also by the _____________ of individuals in that community. ______________ is the number of individuals per species, and _________________ refers to the evenness of distribution of individuals among species in a community.

Basal area

_______________ - total cross-section area of tree trunks; used by forest ecologists

Also provide the formula.

Biomass

____________ - the mass or weight of living tissue

Frequency

_______________ – the number of times a plant species occurs in a given number of quadrats; usually expressed as a percentage

Cover

_– percentage of ground surface covered as determined by the projection of areal parts

Transect-Quadrat sampling

Plotless methods (point quarter method)

Importance percentage value

Lincoln-Petersen Index (Capture Mark Recapture)

What are all the Methods for Estimating Population Densities?

Transect-Quadrat sampling

What does it mean by “appropriate”?

• Body size (range) of target groups

• Behavior (obvious or cryptic etc.)

• Mobile, sessile; weak-/strong-flying etc.

Methods of Estimating Population Densities

Involves counting of organisms of a single species in plots or transects of appropriate size and number

Transect-Quadrat sampling

Methods of Estimating Population Densities

Objective: to get an estimate of the density of the area sampled

Transect-Quadrat sampling

Methods of Estimating Population Densities

Applicable to a wide variety of terrestrial and aquatic species in environments ranging from forests to the bottom of the sea

• bird & butterfly transect – 2 km

• Ant transect – 180-250 m

• Weed sampling – 1 sq m quadrat

• Forest – 1 sq km plot

Methods of Estimating Population Densities

Transect-Quadrat sampling

• ___________________ – 2 km

• ______________ – 180-250 m

• ______________ – 1 sq m quadrat

• ________ – 1 sq km plot

Plotless methods

Methods of Estimating Population Densities

Based on random points (0 dimensional method)

• Applicable to sessile organisms (trees)

Plotless methods

Methods of Estimating Population Densities

advantages over quadrat-based techniques:

• Usually faster (especially in sparse communities)

• Does not require selection or adjustment in quadrat size

Plotless methods

Methods of Estimating Population Densities

advantages over quadrat-based techniques:

• Requires less equipment - just need a way to measure distance (e.g., meter stick, tape measure, or laser range finder)

Point center quarter method

Methods of Estimating Population Densities - Plotless methods

• based on a series of random points

• Distance to nearest individual is measured in each of 4 quarters at each point along this series of random points

Point center quarter method

Methods of Estimating Population Densities - Plotless methods

Methods of Estimating Population Densities - Plotless methods - Point center quarter method

What is the formula for point center quarter method?

Methods of Estimating Population Densities - Plotless methods - Point center quarter method

For example:

Distance of point to shrub with 1 m² area

Quarter 1= 0.5 meters

Quarter 2 = 0.35 meters

Quarter 3 = 0.4 meter

Quarter 4 = 1.2 meters

Solve for Density or # of individual/specified area.

Nearest neighbor

Methods of Estimating Population Densities - Plotless methods

The distance from a selected plant to its nearest plant (neighbor) is measured.

Nearest neighbor

Methods of Estimating Population Densities - Plotless methods

• Choose a referent plant - (usually the closest individual to a selected point.)

• Identify the plant closest to the referent plant and measure the distance between these two plants

Methods of Estimating Population Densities - Plotless methods - Nearest neighbor

What is the formula for Nearest neighbor?

Methods of Estimating Population Densities - Plotless methods - Nearest neighbor

For example: The nearest neighbor is 2.0 m in an area of 1 ha.

Solve for the Density or # of individual/ specified area.

Closest individual

Methods of Estimating Population Densities - Plotless methods

The distance from a sample point to the closest individual is measured.

• Choose a series of points in the sample area

• Measure the distance to the closest plant of interest

Methods of Estimating Population Densities - Plotless methods - Closest individual

What is the formula for Closest individual?

Methods of Estimating Population Densities - Plotless methods - Closest individual

For example: The nearest neighbor is 3.6 m in an area of 1 ha.

Solve for the Density or # of individual/ specified area.

Importance percentage value = sum of relative density (RDen), relative dominance (RDom) and relative frequency (RF) of a species in a community = RDen + RDom + RF

• Rden = density of a species / total density for all species x 100

• Rdom = basal area for a species / total basal area for all species x 100

• RF = frequency for a species in a plot / total frequency for all species x 100

Methods of Estimating Population Densities - Importance values

What is the formula for Importance values and their respective variables (how to solve for them)?

Lincoln-Petersen Index (capture mark recapture)

Methods of Estimating Population Densities

random samples of the population are captured and these individuals are marked and then released to mingle with the general population

• the population is resampled after enough time has passed to allow complete remixing of the marked individuals

Lincoln-Petersen Index (capture mark recapture)

Methods of Estimating Population Densities

Assumes that the proportion of marked animals in the second sample is the same as the proportion of marked animals to non-marked within the whole population

Assumptions:

• the population is closed (births, deaths, emigration, and immigration are negligible)

• all individuals have the same probability of capture and recapture

• marked animals are randomly distributed in the population at the time of recapture

Methods of Estimating Population Densities - Lincoln-Petersen Index (capture mark recapture)

What are the assumptions of Lincoln-Petersen Index (capture mark recapture)?

Methods of Estimating Population Densities - Lincoln-Petersen Index (capture mark recapture)

What is the formula for Lincoln-Petersen Index (capture mark recapture)?