Biogeography

1
Biogeography Biodiversity

• Chapter 24

2
Ecosystems Climate

• Biogeography- study of distributions of organisms
• The shift from travel notes to surveys to
  measurements
• Vegetation structure to climatic conditions
• Using community structure for inferring climate
• The switch to using both
• Units of plant and animal life Biomes

3
Ecosystems Climate

• Classification of plant types
• Candolle (1855)
• Divided world into zones based on plant types
• Distribution along altitudinal gradient
• Merriam (1884)

4
Ecosystems Climate

• Study of animal life distribution followed
• F.E. Clements V.E. Shelford (1939)
• Combined plant / animal distribution
• Community concept
• Introduced biotic unit of Biome
• Biogeography

5
Ecosystems Climate

• Classification of climate
• Koppen (1900)
• Used Candolles plant classification
• Established link between climate and plant
  distribution

6
Classification themes

• Reflect adaptations of the dominant plant forms
  to regional climate
• Abundance of trees, shrubs, and grasses
• Leaf types
• Relative allocations of carbon above and below
  ground
• Adaptations to moisture, temperature, nutrients

7
Evidence of adaptations

• Similar climates producing similar plant forms
• Despite evolutionary relatedness of taxa
• Covergent evolution
• Charles Darwin
• Similarities in form function

8
Terrestrial ecosystems

• Classification based on plant forms
• Patterns of geographic scale
• Most prevalent equatorial diversity
• Diversity highest where productivity is highest
• Tropical production / diversity
• Altitudinal variation

9
Terrestrial ecosystems
Variations in distribution
10
Latitudinal gradients
11
Evapotranspiration gradient
AET (actual)
12
Evapotranspiration gradient
PET (potential)
13
Altitudinal gradients
14
Ecosystem biomass

• Temperature / rainfall
• Evapotranspiration rate
• Decomposition rate
• Nutrient cycling
• Biomass allocation
• trees / shrubs / grasses
• Complex physical structure ? biodiversity

Major biomes
15
Ecosystem biomass

• Standing biomass function of temperature
  precipitation

16
Aquatic ecosystems

• Linked by water cycle
• Classified by physical features
• Salt content
• Freshwater
• Marine
• Estuarine
• Flow
• Lentic
• Lotic
• Depth profile
• Light penetration
• Temperature
• Dissolved oxygen
• Productivity

17
Aquatic ecosystems

• Diversity highest equator
• Diversity/productivity inversely related
• Seasonality
• Vertical movement of nutrients
• Marine systems
• Upwellings determine productivity
• Permanent equatorial thermocline
• supports higher diversity

18
Diversity

• Alpha diversity local community
• Gamma diversity within a geographical area
  (across communities)
• Gamma diversity changes occur over geological
  time
• Alpha diversity may change with local habitat
  disturbance

19
Habitat destruction

• Leading cause of species loss
• Vegetative losses
• Patch habitat
• Global tropical rainforest loss
• 2.4 acres / second (2 football fields)
• 149 acres / minute
• 214,000 acres / day (larger than New York City)
• 78 million acres / year (larger than Poland)
• 137 species becomes extinct every day (50,000 /
  year)

20
Terrestrial ecosystems revisited

• Terrestrial ecosystem classification vegetative
  biomass production
• Vegetative heterogeneity increases species
  diversity
• Increased production ? increased diversity
• Diversity generally highest at equator

21
Aquatic ecosystem revisited

• Aquatic ecosystem classification physical
  features
• Seasonality productivity
• Increased production ? decreased diversity
• Marine vs. freshwater
• Diversity generally highest at equator

22
Edge habitats

• Edge habitats increase diversity
• Marine coastal habitats
• Estuaries, bays, lagoons
• Tidal influences
• Salinity influences
• Temperature variations
• Terrestrial edge habitats
• Increased vertical stratification
• Increased species habitat