1. Biomes and Changes in Ecosystems: Stability and Succession

2. Biome defined
Biome- a regional ecosystem characterized by distinct types of vegetation, animals, and microbes that have developed under specific soil and climatic conditions
Rule of climatic similarity – similar environments provide similar opportunities for life and similar constraints, so they lead to the evolution of organisms similar in form and function

3. Joshua tree, Arizona
Euphorbia, E. Africa
Saguaro cactus, N. America

5. Temperate Deciduous Forest
Avg. temp: moderate, 4 seasons (-30 – 30 °C) Avg. rainfall: 75 – 150 cm/year Where?: E. half of N. America and middle of Europe, Japan and E. China (23 °N to 38 °S) Biotic life: tall deciduous trees such as maples, beeches, oaks, hickories, chestnuts, small mammals, birds and insects, fire is natural

7. Tropical Rainforest
Avg. temp: high and rel. constant throughout year (~20 – 34 °C) Avg. rainfall: high and relatively frequent (160 – 660 cm/year) Where?: northern S. Amer., Central America, w. Africa, NE Australia, Indonesia, Phillippines, Borneo, Hawaii, parts of Malaysia (latitude b/w 10 °N and 10 elevations lower than 3000 feet) Biota: large diversity of vegation: trees, plants, ferns, mammals live in trees, some ground dwellers, abundant insects and invertebrates, soils low in nutrients- most nutrients in living vegetation (why would soils be low in nutrients?)

9. Tundra
Avg. temp: coldest of all (-34 °C avg. winter, 3-12 °C summer) Avg. rainfall: 15 to 25 cm/year, mostly snow, low rainfall Where?: around the North Pole in Arctic circle, arctic tundra is high latitudes, alpine is high elevations Biota: grasses, mosses, lichens, mat-forming plants, some large mammals such as caribou, small rodents and insects

11. Desert (Hot and Dry type)
Avg. temp: mean annual range is 20-25° C (with highs of ~44 C and lows of -18 C) Avg. rainfall: less than 50 cm/year (some areas like the Acatama in Peru receive less than 1.5 cm/year) Where?: Chihuahuan, Sonoran, Mojave and Great Basin Deserts in N. America, Southern Asian realm, Neotropical (South and Central America), Ethiopian (Africa) and Australian (15-28° N and S of equator) Biota: snakes and reptiles, small mammals like kangaroo mice, ground-hugging shrubs, short woody trees, yucca, cactus

13. http://www. globalchange. umich

14. List the four biomes in order of increasing net primary productivity
Use the data on the previous slide as a reference. What are the two most likely limiting factors for primary productivity?

15. Ecosystems and Equilibrium
Steady-state “equilibrium,” also called climax state The energy entering the system exactly balances the output true for open systems, all ecosystems are open systems Versus “static equilibrium” theoretical concept involving no change at all

16. Succession!
An example of long-term changes to an ecosystem’s steady state -can be a response to a natural (or human-induced) disturbance, but ecological succession can take time!

17. Primary Succession
The initial establishment and development of an ecosystem where there previously was none.

18. Human examples of disturbances leading to primary succession

19. General Patterns of Succession
Larger plants (intermediate species), including shrubs then trees begin to dominate (5-150 years!)
Mature forest develops (climax community) 150+ years
Small stature plants, rapidly growing with seeds that spread quickly- perennials (3-4 yrs)
Initial vegetation is specifically adapted to unstable conditions- typically small in stature, annuals(1-2 yrs)

20. Although the types of species will vary depending on ecosystem…
Main stages of secondary succession:
Early successional (two stages combined into one)
Middle successional
Late successional

21. Secondary Succession- far more common!
Series of community changes which take place on previously colonized, but disturbed or damaged habitat
Why faster than prim.:
-already existing seed bank in soil
-undisturbed root systems can regenerate
-fertility substantially favorably modified by previous organisms

22. Climax community and the idea of steady-state
Ecosystems will generally change towards a climax community
- a long-term change to a steady-state
Examples of secondary succession:
(early, late middle)

23. Ecosystem Stability
Species loss past a certain point (↓ in biodiversity) is likely to have a detrimental effect on the stability of the ecosystem Ecosystem stability – its ability to resist change

24. Components of Ecosystem Stability
Inertia –ability to resist disturbance Resilience- ability to recover from external disturbances Stability is closely linked to biodiversity Uncertainty, however, over what level of biodiversity provides an insurance against catastrophe

25. Biodiversity, biomass (productivity), and succession oh my!
In the early stages (pioneer communities) biomass and biological diversity increase

26. In the middle stages (intermediate communities) there are trees of many species and sizes
In general as succession occurs, GP increases and NP decreases. Why?

28. Chemical Cycling and Succession
Storage of chemical elements increases (in general) from the earliest stages of succession to middle succession.
Soils store more elements than does live tissue but they cycle them at a slower rate.

29. Why the pattern in chemical cycling?
OM stores elements, so increase in OM means increase in chemical storage Root nodules of legumes help assimilate atmospheric nitrogen Increasing vegetation helps prevent erosion of the soils

30. Eventually…
An ecosystem that persists for a very long time without disturbance will a slow loss of chemical elements

31. Interactions Among Species during Succession
Facilitation
Early-successional species help guide the establishment of later-successional species
Example: A pine tree will provide shade that will help oaks to grow

32. Interactions Among Species during Succession
Interference
Certain early-successional species can interfere with the establishment of other species
Ex: In parts of Asia bamboo can grow so dense that seeds of other, later-succ. Species cannot reach the ground, germinate, or obtain enough light, H2O, nutrients to survive.

33. Interactions Among Species during Succession
Life history differences:
Differences in the life cycles of different species that results in the species having minimal effects on each other
Ex: seeds of early-succ. species are readily transported by wind or animals (red cedar) vs. late-succ. species whose seeds take longer to travel (sugar maple)

34. Absence of Interaction
Shipleygroup.com
Chronic patchiness
Species grow in patches and do not interact with each other, and succession as we know it does not take place
Ex: desert patchiness in CA, AZ, and highly polluted environments

35. Connections Biotic factors Biodiversity Biological indicators
Succession (primary, secondary)