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Chapter 9

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  1. Chapter 9 Global Biogeography

  2. Review and Introduction • Chapter 8 review • Looked at processes involved in ecological and historical biogeography • Food web, photosynthesis, respiration, factors influencing biogeography (climate, geomorphic, soil), succession, spatial and temporal distribution patterns • Now, turning to general patterns of vegetation cover over Earth and their relation to climate

  3. Natural Vegetation • What is natural vegetation? • Plant cover that develops or grows in a region without (or with very little) influence of humans, or what grows somewhere with no or little interruption by humans • Opposite of human-influenced vegetation – plant cover that results from human interference, introduction, or modification – might be “invasive species”

  4. Human Influences on Vegetation • Intensive agriculture • Domestication • Grazing by domesticated animals • Urbanization – expansion and new development • Fighting fires – why? • Introducing new/non-native plant species • Careless/reckless recreational activities • Greenhouse gas emissions • Genetic engineering (gene splicing, selective cross-breeding)

  5. Natural Vegetation of North America From http://www.uwsp.edu/geo/faculty/ritter/geog101/modules/natural_vegetation_of_north_america_map.html

  6. Natural Vegetation of the World

  7. What Environmental Factors Influence Vegetation? • Climatic, geomorphic, and edaphic factors • More specifically amount of soil water, type and amount of nutrients in soil, and temperature • Each factor affects plant cover structure and outward appearance • Therefore, we see different vegetation in different regions (compare SE AZ with over areas of U.S.)

  8. Structure and Life-form of Plants • Botanists focus more on species where biogeographers tend to focus on overall plant cover and life-form • Life-form – physical structure, size, and shape of plants • Looking at size and shape: trees (large woody plants with branching usually farther away from ground, ex. Ponderosa pine), shrubs (woody plants with branching near ground, ex. creosote), lianas (woody vines supported by trees and shrubs, ex. poison ivy), herbs (small tender plants, ex. grasses), lichens (structure formed by combination of algae and/or fungi, ex. moss)

  9. Life-forms by Size and Shape Shrubs and Lianas Tree Herb Lichens

  10. Structure and Life-form of Plants (cont’d) • Types of life-form by life span • Annuals – live only for one season or year, many grasses and flowers • Perennials – survive for many seasons or years, trees and shrubs • Types by overall structure • Forest – trees grow close together with crowns in contact, ex. NE US (Fig. 9.14), Amazon (background of figure on p. 321) • Woodland – trees farther apart (crowns not in contact), ex. southern India (Fig. 9.9), Tanzania (Fig. 7.15), portions of California (bottom figure on p. 252)

  11. Forest vs. Woodland Forest Woodland

  12. Ecosystems • Definition (from Ch. 8): group of organisms and the environment with which they interact • Two major groups • Aquatic – marine (saltwater) and freshwater environments • Terrestrial – land environments; solid part of continents • Even though these are considered separate ecosystems, there is actually some interaction.

  13. Terrestrial Ecosystems • Subdivisions • Biome – largest recognizable subdivision; total of plant cover and animal species • Formation – subdivision of biome based on vegetation structure, size, and shape • Example: Jungle (rainforest) in Brazil and forests in Catalina Mountains are in same biome (forest), but are in different formations • Five main biomes: forest, savanna, grassland, desert, and tundra

  14. Forest Biome • Overall structure is forest (trees grow close together with crowns in contact) • Canopy closed or nearly closed at least part of year • Abundant soil moisture, and therefore precip, is necessary (lose leaves in dry season) • Requires either warm temps year-round or at least a warm season (lose leaves in cold season) • Range from low to high latitudes (0° - 35°S, 0° - 70°N)

  15. Forest Biomes Tropical deciduous forest ↑ ↑ Coniferous forest Temperate deciduous forest 

  16. Savanna Biome • Overall structure is woodland (tree widely spaced and crowns not in contact) • Combination of trees, grasses, and herbs • Transition zone between forest and grassland biomes • Occurs in regions with distinct wet and dry seasons • Temps tend to be warm much of year • Mainly in low latitudes (between 30°S and 30°N)

  17. Savanna Biomes Africa Australia

  18. Grassland Biome • Mainly grasses; few, if any, trees • Occurs in regions with fairly lengthy dry season (semi-arid) • Distinct warm and cool/cold seasons; temps must be warm enough for portion of year to support a growing season • Mainly in middle latitudes (30° - 40°S, 30° - 50°N)

  19. Grassland Biome

  20. Desert Biome • Combination of some trees, shrubs, and grasses • Transition from savanna and grassland to little/no vegetation • Precipitation is rare (moderate to severe drought conditions), maybe a short wet season • Large temp range: cool to very hot • Range from low to middle latitudes (0° - 50°S, 0° - 50°N)

  21. Desert Biome

  22. Tundra Biome • Combination of some trees, some shrubs, grasses, and lichens • Precipitation is mainly snow • Temps cold most of year, maybe short periods warmer than 0°C (32°F) • Mainly in high latitudes (60° - 80°N) and high elevations

  23. Tundra Biome

  24. Elevation and Vegetation • Can see changes in vegetation with elevation • Think of driving up Mt. Lemmon Highway Due to changes in temp and precip with elevation • Change in climate factors with elevation results in systematic changes in vegetation cover – vegetation (or altitude) zonation • Life zones – series of vegetation zones describing vegetation type seen with increasing elevation (Fig. 9.25) • May also hear term sky island, which refers to forest areas in locations where type of vegetation is not expected or common (e.g., mountains in southeastern AZ)

  25. Natural Vegetation, Altitude Zonation, and Life Zones in Arizona From http://southwest.library.arizona.edu/azso/body.1_div.4.html

  26. Climate and Vegetation • Already saw different biomes associated with Köppen climate types • Climate changes by latitude and longitude, so it follows that vegetation changes as well • Experience vegetation zonation over long transects (i.e., long lines drawn from north to south, east to west, or on diagonal over land masses) • See Fig. 9.26

  27. A Final Word on Changes in Vegetation • Are changes in climate or vegetation abrupt or gradational/gradual? • Same is true for vegetation zones and life zones • Do we see this on maps? Why or why not? • Show abrupt boundaries out of necessity... would be difficult to analyze spatial patterns if map colors representing different vegetation regions were gradual (Fig. 9.3 or figures for formations in each biome)