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Common ways to sample Populations

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Common ways to sample Populations Quadrat survey Random walk Line transect Point survey Mark and recapture Traps and passive collecting Quadrat survey Spatial ... – PowerPoint PPT presentation

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Title: Common ways to sample Populations


1
Common ways to sample Populations
  • Quadrat survey
  • Random walk
  • Line transect
  • Point survey
  • Mark and recapture
  • Traps and passive collecting

2
Quadrat survey
  • Spatial subsampling, most often used with plants
    or fixed things such as corals, nests, burrows
    etc.
  • Square area (can be any size dependent on
    organism) in which all individuals are
    documented.
  • Placement of quadrat can be random, or in area
    chosen because it is representative of larger
    community.

3
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5
Common quadrat sizes used in ecology
  • 0.1 used for quick
  • and dirty forest census
  • 5m quadrat rocky intertidal surveys, and
    seedlings.
  • 1m quadrat used for intertidal and herbaceous
    plants including seagrass

50 ha used for long-term forest demographies
1 ha forest inventory
6
Determining size of quadrat
Document species number with incremental increase
in quadrat area
Spp. No.
Where diversity levels off is ideal area for
quadrat.
Area
7
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8
Random walk/swim
  • Spatial subsampling.
  • Predetermined distance and compass bearings
    (random).
  • Document target organisms encountered.

9
Point Survey
  • Spatial subsampling
  • Randomly selected points (or could be regularly
    spaced along line transect).
  • Document all target organisms within given radius
    (varies according to organism).

10
Line transect continuous
11
Line transect discontinuous
  • Spatial subsampling.
  • Line located either randomly, or specifically to
    cross an environmental gradient (e.g. along a
    line from the shoreline straight out across a
    series of tidepools to the ocean).
  • Sample continuously or at intervals along the
    line.

12
Example sampling butterflies
  • Recorder walks along a predetermined linear path
    at a uniform pace
  • Butterflies counted within 5 m of counter
  • Types subdivided as far as possible
  • Counting conducted between 1045 and 1545.

13
  • Standardized formula for site-to-site comparisons
  • P (100 NA)/L,
  • where Ppopulation index, L length of
    transect in meters, A size of flight area in
    hectares, and N butterfly numbers per 100 m of
    transect.

14
Point-quarter survey
  • Orientation of one axis can be chosen by random
    number (0-180o). Then distance to nearest
    individual is measured in each quarter.
  • Other documentation, e.g. species, dbh, sex,
    length, etc noted.

15
Mark and recapture
  • Catch N number of a popn at time 1.
  • Mark them (paint, clipped toes, tags)
  • Return at time 2 and resample same number from
    popn and count the number (M) that are marked
    (i.e. recaptured)
  • Total population P na/r
  • Where P total population, a marked, n total
    recaptured, r marked recaptured

16
Major assumptions of mark and recapture
  • (i) marking doesn't affect animals (behaviorally,
    physiologically, or ecologically)
  • (ii) marked animals are completely mixed in
    population
  • (iii) probability of capturing a marked animal is
    the same as capturing an unmarked animal (closed
    population)
  • (iv) marked animals don't lose their marks
  • (v) marked mix naturally with unmarked.

17
Passive collectors
  • Pitfall traps for small reptiles and beetles
  • Large bucket for lizards with drift fence to
    guide critter into bucket. Must be emptied daily
  • Can half-filled with glycol and water preserves
    insects. Can be left out for a week, but may
    inadvertently catch small mammals and reptiles.

18
Cover boards
  • Sheets of plywood scattered across ground provide
    shade and resting habitat for snakes and moisture
    loving inverts.

19
Light or Black-light trap
  • UV light source shone against white sheet
    attracts a diversity of moths and night-flying
    beetles.
  • Can catch and kill everything (wasteful)
  • Or try to capture representative samples.
  • Monitor populations

20
Plankton sampling
  • Lateral or vertical tow of plankton net for known
    distance to gain planktonics. What variables need
    to be considered?
  • Scraping of known surface area of substrate to
    sample attached/settled organisms.

21
Soil fauna sampling using Berlese funnels
  • Soil fauna migrate away from light or heat.
  • Shovel leaf litter into a sieve and shine a light
    from above. Place catching tray beneath and wait
    for inverts to come tumbling out.

22
Common types of experiment
  • Exclosures
  • Reciprocals
  • Additions
  • Growth responses

23
Exclosure experiments
  • Trying to measure the effect that one organism
    has on a system. Try getting rid of the organism.
  • Hunt them out and then keep them out using
    Exclosures.
  • Then monitor changes in other populations or
    habitat.

24
Cattle exclosure What differences do you see?
No cattle
Cattle present
25
Rabbit exclosure
  • Rabbits were excluded from the grassland area on
    the left and allowed to graze the area on the
    right.

What would be the impact of a fish exclosure?
26
Fish excluded from an area
  • What might the impacts be?
  • Why might you want to do this?

Fish exclosure at Otter Lake Dr R. Newman, U.
Minn.
27
Reciprocal experiments
  • Observation The same species of plant grows in
    two locations, but the ones at location A do
    better than at B.
  • Q Is this pattern because the popn at A is
    better suited to conditions (evolutionary
    adaptation) or because location A is a better
    site?
  • Can test this by taking members of popn A and
    planting them at B, and taking some from B and
    planting at A. What happens?

28
Growth response experiments
  • Nutrient effects..does factor X enhance growth.
    Grow species A under a range of concentrations of
    X.
  • Toxicity effects..is survival (or growth)
    impaired by factor Y. Expose species A to various
    concentrations of factor Y.
  • LD 50 studies determines the dose (mg/kg) at
    which 50 of individuals die within a given
    time-frame.

29
Rank these according to their lethality, most
lethal at top
  • Nicotine - cigarettes
  • Malathion - commonly used for mosquito
    control
  • Diazinon - commonly used to kill lawn insects
  • Salt
  • Sevin - Insecticidal dust
  • Sodium hydroxide - drain cleaner
  • Household Ammonia - Bleach

30
  • Compound Oral LD50 LD50 mg/kg (g/70k
    person)
  • Nicotine 50-55 2.5 g
  • Diazinon 300 15 g
  • Ammonia 350 18 g
  • Sodium Hydroxide 500 30 g
  • Carbaryl (Sevin) 500 30 g
  • Malathion 1,375 80 g
  • Salt 3,000 (Rat) 200 g

31
Essence of good experimental design
  • Simplicity
  • Tractability
  • Controls
  • Replicates

32
Common ways to look at behavioral ecology
  • Continuous recording, e.g. satellite tracking an
    individual.
  • Time sampling, e.g. time lapse photography.
  • Must choose frequency of sampling appropriate to
    behavior.

33
Time-sampling
  • Choose a time period, e.g. one minute and record
    1 (0) if the activity occurred (did not occur)
    within that minute.
  • More open-ended. Choose a sampling interval say
    10 minutes and observe what the organism is doing
    every ten minutes. e.g. preening, swimming,
    mating, feeding, fighting, etc. After enough
    observations the proportions of activities can be
    determined. What variables might shape such
    activity, say in lizards?

34
What behavior to measure
  • Latency delay until activity occurs
  • Frequency How often activity occurs in set time.
  • Duration How long the activity was maintained.
  • Intensity The strength of the behavior (note
    this is more subjective than the others).

35
Measuring behavior is a skill
  • Like any skill it needs to be learned.
  • Surest way to fail is to start recording without
    taking the time to observe.
  • Spend at least 30 minutes (or several cycles of a
    behavior pattern) observing the range of behavior
    before starting to record field data. Garbage in
    -gt garbage out.

36
Data sheet
Location, date, observer, field observations,
e.g. weather, temp,time of day, size of group
observed, etc
Activity type
Time







37
Sampling at a larger scale
  • Data mining Use resources in existing databases.
  • Access satellite imagery and analyze using
    Geographic Information Systems (GIS)

38
National wetlands inventory
39
Layers
Vector Layers
Street Network layer lines
Land Parcels layer polygons
Raster (image) Layer Digital Ortho Photograph
Layer
Digital Ortho photo combines the visual
properties of a photograph with the positional
accuracy of a map, in computer readable form.
Projection State Plane, North Central Texas
Zone, NAD 83 Resolution 0.5 meters
Accuracy 1.0 meters Scale see scale bar
40
Overlay based on Common Geographic Location
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