1. Lecture 6– Biogeography and Biomes

2. Influenced by latitude Location within a continental land mass
Vegetation Zonation:
Influenced by latitude
Location within a continental land mass
proximity to oceans, rain shadows
altitude

3. White Mountains – New Hampshire
Altitudinal Zonation
White Mountains – New Hampshire
RockMountains/ Sierra Nevada
Andes - Peru
From Smith and Smith. Ecology and Field Biology

4. Mountains: Islands in the Sky
Built by geological processes and thus concentrated in belts of geological activity.
Climate changes with elevation and latitude.
Soils are generally well-drained and thin.
Flora and fauna change with elevation.
Historically used as a source of raw materials for human settlements.

5. Mountains: Islands in the Sky

6. From Smith and Smith. Ecology and Field Biology

8. Study of distributions of organisms; past and present
Biogeography
Study of distributions of organisms; past and present
Climatic history
Past distributions and extinctions
Complex field of study drawing on multiple disciplines
Asks: Which and where – plus why (is it present) or why not?

9. Climate and Biogeography equator to poles:
mean annual temp decreases
Seasonal temp. variation increases
Decrease in available moisture (decreasing temp leads to decreasing atmos. water holding capacity)
 decreasing evapotranspiration  decreased primary productivity

10. Biomes are biotic units and are classified by predominant plant types.
Developed by E.E. Clements and V.E. Shelford (1939)
Eight major terrestrial biomes
Tropical forest
Temperate forest
Conifer forest (taiga or boreal forest)
Temperate grasslands
Tropical savanna
Chaparral (shrublands)
Tundra
Desert

11. Summarize climatic information using a standardized structure.
Climate Diagrams:
Summarize climatic information using a standardized structure.
Temperature plotted on left vertical axis.
Precipitation plotted on right vertical axis.
10o C equivalent to 20 mm precipitation.
Relative position of lines reflect water availability.
Adequate moisture for plant growth when precipitation above temperature

12. Climate diagrams – relate annual cycle of ppt and temp.
Worldwide in distribution
Convergent evolution of adaptations – ‘convergence’

13. Whittaker: system based on vegetation type and combined ppt/temp
Whittaker: system based on vegetation type and combined ppt/temp. factors
(see Fig 24.2)

14. Tropical Rainforests Most occur within 10o latitude of equator.
Little temperature variation between months.
Annual rainfall of 2, ,000 mm relatively evenly distributed.
Quickly leaches soil nutrients.
Mycorrhizae help gather nutrients.
Organisms add vertical dimension.
Harbor staple foods and medicines for world’s human populations - increasingly exploited.

15. Tropical Rainforests

16. Tropical Dry Forest Usually located between 10o - 25o latitude.
Climate more seasonal than tropical rainforest.
Soils generally richer in nutrients, but vulnerable to erosion.
Shares many animal and plant species with tropical rainforests.
Heavily settled by humans with extensive clearing for agriculture.

17. Tropical Dry Forest

18. Tropical Savanna
Most occur north and south of tropical dry forests within 10o - 20o of the equator.
Climate alternates between wet / dry seasons.
Drought associated with dry season leads to lightning-caused wildfires.
Soils have low water permeability.
Saturated soils keeps trees out.
Landscape is more two-dimensional with increasing pressure to produce livestock.

19. Tropical Savanna

20. Desert Major bands at 30o N and 30o S latitude.
Occupy about 20% of earth’s land surface.
Water loss usually exceeds precipitation.
Soil usually extremely low in organic matter.
Plant cover ranges from sparse to absent.
Animal abundance low, but biodiversity may be high.
Strong behavioral adaptations.
Human intrusion increasing.

21. Desert

22. Mediterranean Woodland and Shrubland
Occur in all continents except Antarctica.
Climate cool and moist in fall, winter, and spring, but can be hot and dry in summer.
Fragile soils with moderate fertility.
Trees and shrubs typically evergreen.
Fire-resistant plants due to fire regime.
Long history of human intrusion.
Cleared for agriculture.

23. Mediterranean Woodland and Shrubland

24. Temperate Grassland Extremely widespread distribution.
Annual rainfall ,000 mm.
Experience periodic droughts.
Soils tend extremely nutrient rich and deep.
Thoroughly dominated by herbaceous vegetation.
Large roaming ungulates.
Bison vs. cattle

25. Temperate Grassland

26. Temperate Forest (Old Growth)
Majority lie between 40o and 50o latitude.
Rainfall averages ,000 mm.
Fertile soils
Long growing seasons dominated by deciduous plants.
Short growing seasons dominated by conifers.
Biomass production can be very high.
Many major human population centers.

27. Temperate Forest (Old Growth)

28. Boreal Forest (Taiga) Confined to Northern Hemisphere.
Covers 11% of earth’s land area.
Thin, acidic soils low in fertility.
Generally dominated by evergreen conifers.
Relatively high animal density.
Historically, low levels of human intrusion.

29. Boreal Forest (Taiga)

30. Tundra Covers most of lands north of Arctic Circle.
Climate typically cool and dry with short summers.
mm precipitation.
Low decomposition rates.
Supports substantial numbers of native mammals.
Human intrusion historically low, but increasing as resources become scarce.

31. Tundra