Transcript Biogeography & Biodiversity

Biogeography
&
Biodiversity
Chapter 24
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
Ecosystems & Climate
• Classification of
plant types
– Candolle (1855)
– Divided world
into zones based
on plant types
– Distribution
along altitudinal
gradient
• Merriam (1884)
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
Ecosystems & Climate
•Classification of
climate
–Koppen (1900)
–Used Candolle’s
plant classification
–Established link
between climate
and plant
distribution
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
Evidence of adaptations
• Similar climates producing similar plant forms
– Despite evolutionary relatedness of taxa
• Covergent evolution
• Charles Darwin
– Similarities in form & function
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
Terrestrial ecosystems
Variations in
distribution
Latitudinal gradients
Evapotranspiration gradient
AET (actual)
Evapotranspiration gradient
PET
(potential)
Altitudinal gradients
Ecosystem biomass
• Temperature / rainfall
– Evapotranspiration
rate
– Decomposition rate
– Nutrient cycling
• Biomass allocation
– trees / shrubs /
grasses
• Complex physical
structure 
biodiversity
Major biomes
Ecosystem biomass
Standing biomass
– function of
temperature &
precipitation
Aquatic ecosystems
• Linked by water cycle
• Classified by physical
features
– Salt content
• Freshwater
• Marine
• Estuarine
– Flow
• Lentic
• Lotic
– Depth profile
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Light penetration
Temperature
Dissolved oxygen
Productivity
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
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
Habitat destruction
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Leading cause of species loss
Vegetative losses
Patch habitat
Global tropical rainforest loss
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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)
Terrestrial ecosystems
revisited
• Terrestrial ecosystem classification–
vegetative biomass production
• Vegetative heterogeneity increases
species diversity
• Increased production  increased
diversity
• Diversity generally highest at equator
Aquatic ecosystem
revisited
• Aquatic ecosystem classification –
physical features
• Seasonality – productivity
• Increased production  decreased
diversity
• Marine vs. freshwater
• Diversity generally highest at equator
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