Biogeography Biodiversity Chapter 24 Ecosystems Climate Biogeography study

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 • • 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 • • 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)

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