Landscape Ecology

1
Landscape Ecology

• The interplay of spatial pattern and ecological
  processes

2
Landscape Ecology Outline

• Methods in community description
• Ordination and Classification
• The theory of island biogeography and landscape
  ecology

3
Sampling
Methods

• Sampling issues from lab also chapter 9
• BC government, Nature Conservancy, use the relevé
  method
• Quadrat or transect sampling will give a less
  subjective community description

4
Ordination
Methods

• A way to reduce complex, multivariate information
  to fewer variables fig 15.3

5
Ordination
Methods

• Many different statistical methodologies
• Usually presented as a graphical depiction of the
  distribution of sample plots across an
  environmental gradient
• Information in graph can be used to develop
  testable hypotheses
• You should be able to interpret these graphs, and
  come up with hypotheses for the patterns

6
Example
Methods

• Garry Oak Ecosystem is highly fragmented

7
Example
Methods
Road Density
Plant Density Diversity
Rockiness
Area
Habitat
Data Lisa Neame
8
Example 2
Methods
Filled circles late succession Open circles
early succession
9
Example 3
Methods

• Pollen data from 190 sites from the different BEC
  zones (compiled by S. Goring)

10
Classification
Methods

• Term used similarly to usage in evolutionary
  biology
• Concept of classification predates ordination
• Similar stands are grouped together on the basis
  of physiognomy and presence/absence

11
Classification
Methods
12
Classification
Methods

• Can be used for designating conservation areas or
  identifying indicator species
• Basically involves either visually or
  computationally forming clusters within data
• Example Pinus contorta stands in Banff and
  Jasper

13
Methods
Fig 15.7
14
Problem 3, Part 1

• According to this figure, which PCA factor is
  most important for distinguishing among the
  community types, and why?

J. of the Torrey Bot. Soc. 12744-50
15
Problem 3, Part 2

• Beech has a very low tolerance for fire, unlike
  oak and pine. Interpret the figure ecologically
  utilizing this information and the information
  from the caption.

16
The theory of island biogeography
Island biogeography

• MacArthur and Wilson, 1967
• Observation as area increases, species richness
  increases

Crawley fig 19.1 Vascular plant diversity
17
The theory of island biogeography
Island biogeography

• Theory islands will have an equilibrium number
  of species determined by immigration and local
  extinction
• Important factors
• Size of island (affects extinction)
• Distance from mainland (affects immigration)

18
The theory of island biogeography
Island biogeography
A1, A2 same distance from mainland A1, A3 same
size C is wrong! Immigration curves should be
identical
T3
T1
T
T1
T2
Fig 16.9 Size affects extinction, Distance
affects immigration
19
The theory of island biogeography
Island biogeography

• Predict higher equilibrium species number on
  large, near islands
• Predict greater species turnover on near, small
  islands
• Islands can be of many types
• Oceanic islands, sky islands, habitat islands,
  serpentine islands, bogs, lakes

20
Beyond the basics
Island biogeography

• The basic model is criticized for being too
  simple
• Several authors have suggested extensions of the
  theory two are conflated with MacArthur and
  Wilsons model in the book

21
Beyond the basics
Island biogeography

• Curves may be nonlinear
• Due to species interactions that change with
  density, differences in dispersal ability
• Fig 16.14

22
Small Island Effect
Niering 1963. Ecological Monographs 33131-160.
23
Island Biogeography Beyond the basics
Island biogeography

• Rescue effect
• Distance may also affect probability of
  extinction
• Observation probability of extinction lower for
  near (vs. far) islands
• Mechanism?
• Prediction for species turnover?

24
Rescue effect
Island biogeography
25
Island Biogeography Beyond the basics
Island biogeography

• Target effect
• Area may also effect probability of immigration
• Observation probability of immigration higher
  for large (vs. small) islands
• Mechanism?
• Prediction for species turnover?

26
Target effect
Island biogeography
27
Target Effect
J. Biogeography 13 69-70
28
Differential Immigration
Bush Whittaker 191. Journal Biogeography 18
341-356
29
Some evidence supporting MacArthur Wilson
Island biogeography
Greater turnover on near, small patches
Fig 16.15
30
Weaknesses of the theory
Island biogeography

• Does not work well for island types other than
  oceanic
• Many plants have low rates of immigration/extincti
  on over time
• Many landscapes a mosaic of patches that change
  in availability to particular species over
  successional time
• Only looks at species richness

31
Island Biogeography and Habitat fragmentation
Island biogeography

• Classic example removal of forest
• Results in species loss due to reduction of area
  of remaining fragments
• May have other impacts ease of invasion by
  weeds, loss of mutualists, abiotic effects of
  patchiness, loss of genetic diversity

32
Example fragmentation in Eastern forests
Island biogeography

• Smaller stands have reduced species richness
• Smaller Trillium populations have reduced genetic
  diversity

Closed circles primary forest Open circles
secondary forest
Vellend, 2004. Ecology 85 3043-3055
33
Example Fragmentation of the Garry Oak
Ecosystem, Bee Diversity and Pollination Services
Island biogeography
34
Island Biogeography and Reserve design
Island biogeography

• Considered important from the landscape
  perspective
• Edge to area ratio
• Corridors/connectivity
• Total area
• Distance between sources (mainland) and sinks
  (islands)

35
Island biogeography
BETTER WORSE
36
Island Biogeography and Landscape EcologySummary
Island biogeography

• Multi-community landscape studies are complex,
  and so sophisticated analytical techniques are
  needed to interpret data
• Island biogeography theory (plus extensions like
  the rescue and target effects) makes predictions
  about species richness in different fragments,
  and can also be applied to genetic diversity
  issues
• Island biogeography can inform conservation
  decisions