Biomes

1
Biomes

• Reviewed in Chapter 18 of GSF climate and
  physiognomy in Chapter 17
• Biomes major biogeographic regions that differ
  in vegetative structure (physiognomy) and
  dominant plant species, due to climate

2
Biomes Fig 18.1
3
Surface Air Circulation (fig 17.7)
4
How updrafts and downdrafts (Hadley Cells)
affect vegetation
5
An Idealized Continent
Band of forest in wetter area, 50-60 north
Rainforest at Equator
Deserts at 20-30 north and south
6
Biome distribution fig 18.2
7
Biomes and climate

• Latitude, altitude, topography/location in land
  mass all affect local climate
• In North America, North/South is mostly
  temperature, East/West is mostly
  precipitationbut not completely

8
The Biogeoclimatic Zones of BC
http//www.for.gov.bc.ca/hre/becweb/
9
Biogeoclimatic Ecosystem Classification
BEC zones

• Developed by V. J. Krajina of UBC in the 1960s
• 14 Biogeoclimatic zones named for BC, reflecting
  variation in topography, climate, soils, and
  resulting vegetation

10
Biogeoclimatic Ecosystem Classification
BEC zones

• BEC groups ecosystems at three levels
• Regional vegetation, soils, topography used to
  infer climate over uniform regions
• Local site units with relatively uniform
  vegetation
• Chronological based on history and seral stage
  (not really used much)

11
Biogeoclimatic Ecosystem Classification
BEC zones
12
BEC zones
BEC names

• Zones named for dominant species or vegetation
  type Coastal Western Hemlock Zone, Bunchgrass
  zone
• Subzones are based on differences in
  precipitation and relative temperature and
  continentality
• Variants given geographic names, depending on
  where they occur
• Site series based on relative soil moisture and
  nutrient availability

13
BEC zones
BEC Why?

• When site limiting factors inferred via BEC, more
  suitable planning for reforestation
• Protected area planning
• A common language for forestry, conservation,
  land managers in province

14
Species Diversity
15
Patterns and Process of Diversity

• The Niche
• Diversity Gradients
• Local diversity
• Describing diversity

16
What determines the Niche?
The Niche

• Conditions
• Resources
• Limiting Factors

17
Condition/Resource Response Curves
The Niche
Repro possible
Reproduction
Growth
Performance
Survival
Intensity of Condition or Resource
Survival not possible
Examples temperature, pH, water
18
Condition/Resource Response Curves
The Niche

• Other potential shapes

Lethal at high value Resource essential for
growth
19
A graphical representation of the niche
The Niche
20
Diversity and the Niche
The Niche

• Ultimately, diversity (species richness) depends
  on how many species can survive the limits of
  conditions for growth and reproduction, and all
  necessary resources

21
Important Niche Concepts(that you should be
familiar with already)
The Niche

• Fundamental vs. realized niche
• Niche breadth

22
Diversity gradients
Diversity Gradients

• Elevation
• Santa Catalina Mountains

Boreal Forest
Desert
Fig 19.2
23
Diversity gradients
Diversity Gradients

• Position in continental landmass
• Spruce communities in Canadian boreal forest

Bars with different capital letters indicate
statistically significant differences among
regions within community types. Bars with
different small letters indicate statistically
significant differences within regions among
community types.
Fig 19.3
24
Diversity gradients
Diversity Gradients

• Latitude

Crawley, fig 19.1 vascular plant diversity
25
Latitudinal gradient in diversity
Diversity Gradients

• Brazil 56,000 plant species
• United States 18,000 plant species
• Canada 4,200 plant species
• Many hypotheses (see table 19.2), few conclusions

26
Latitudinal gradient in diversity
Diversity Gradients

• Ecological hypotheses (mechanisms of coexistence)
• Evolutionary hypotheses (rates of
  diversification)
• Historical hypotheses (duration/extent of tropics)

Ecol Lett 10 315-331
27
Latitudinal gradient in diversity Ecological
Hypothesis 1
Diversity Gradients

• Some of the pattern may simply be due to the
  limiting factor, temperature
• Example distribution of palms (Arecaceae)

28
Latitudinal gradient in diversity Ecological
Hypothesis 1
Diversity Gradients

• Some taxonomic groups (e.g. pines in North
  America) show a different pattern of
  diversitydifferent temperature limits

29
Latitudinal gradient in diversityEcological
Hypothesis 2
Diversity Gradients

• Coexistence due to relationship between
  productivity and niche breadth?

30
Latitudinal gradient in diversity Ecological
Hypothesis 2
Diversity Gradients

• Niche breadth arguments may be related to
  dominance-diversity relationships (i.e. trees)

31
Latitudinal gradient in diversityEcological
Hypothesis 3
Diversity Gradients

• Higher productivity ? more species, larger
  population sizes, less extinction
• Some combination of the three ecological
  hypotheses accounts for a large amount of the
  gradient (but not all)

32
Latitudinal gradient in diversityEvolutionary
Hypothesis
Diversity Gradients

• In tropics, biotic interactions prevail in
  temperate areas, abiotic factors prevail
• Abiotic factors dont evolve, but are fixed
  physiological targets biotic interactions do
  evolve selection for diversification

33
Latitudinal gradient in diversityGeographic
Hypothesis
Diversity Gradients

• Combines ecological and evolutionary viewpoint
• Landmass in tropics is larger, and area somewhat
  less affected by glaciation events, so greater
  diversity due to species/area relationship
• Larger land area and longer time periods since
  glaciation allow for more speciation, more
  colonization, and adaptation of colonists (more
  time for evolution)
• Evidence? tree species richness in high latitude
  forests has been increasing over last 10,000
  yearspost glaciation northward colonization?

34
Latitudinal gradient in diversitysummary
Diversity Gradients

• Productivity is widely recognized as the most
  important mechanism
• Some support for importance of
• Habitat size and heterogeneity
• Biotic interactions (competition, herbivory)