Succession and Climax Communities in Ecosystems

1. Chapter 6 Ecosystems and Communities • Succession • Series of regular predictable changes in community structure over time • Result in climax community

2. Chapter 6 Primary Succession • Total lack of organisms and bare rock or water • Terrestrial • Pioneer Community • First to colonize bare rocks--lichens • Successional or Seral Stage • Multiple sequence of stages/communities • Climax Community • Relatively stable, long lasting, complex community • Entire sequence of stages called a sere.

3. Chapter 6 Characteristics of Climax Communities: • 1. able to maintain mix of species for a long period of time • 2. in energy balance • 3. larger number and more kinds of organisms and interactions between organisms • è complexity and energy efficiency

4. Chapter 6 • Secondary Succession • Succession in area after destruction or major disturbance, flood, fire, agriculture • More common and rapid than primary succession • Usually some soil, seeds or root mass that can re-establish • Adjacent area can be source of seed, etc

5. Chapter 6 • Aquatic  • Except for oceans, most aquatic ecosystems are considered temporary.  • Ever increasing entrapment of soil particles and organic matter. • Less depth means establishment of submerged plants è terrestrial succession

6. Chapter 6 Types of Climax Communities • Biomes • terrestrial climax communities with a wide geographic distribution. • Variation of species exist within biomes but exhibit similar pattern and processes • Same general structure of ecosystem • Same kinds of niches present

7. Chapter 6 2 primary factors which determine biome type: • Precipitation: • total amount • form (rain, snow) • seasonal distribution—concentrated at particular time • Temperature: • temperature swings • length of seasons • Other factors: fires, winds, organisms  • Altitude and latitude can mimic these effects

8. Chapter 6 Desert: • Lack of water is primary factor • Less than 25 centimeters (10 inches) precipitation per year.  • Lack of clouds means no insulation  • Can be quite cold/hot • Many types of plants and animals, most are quite adapted to conditions. • Large space between plants, dispersed animals too

9. Chapter 6 Grassland (aka: prairies or steppes): • Between 25 and 75 centimeters precipitation per year (10-30 inches). • Windy, hot summers: cold or mild winters.  • Fire is important in maintaining biome • Prevent invasion of trees • Cycles nutrients  • Large herds of grazing mammals, many insects, many birds. • Most converted to agriculture • 0.004% of Texas Blackland Prairie remains

10. Chapter 6 Savanna: • Similar in appearance to grassland, but has more trees. • Precipitation is between 50 and 150 centimeters per year (20 - 65 inches), but it comes in a few heavy events, with drought in between. • Plants and animals behave accordingly. • Wildlife quite similar to grasslands. • Fire still important so trees fire resistant • Texas Post Oak Savanna

11. Chapter 6 Tropical Rain Forest: • Near equator • Africa, C&S America, SE Asia, some islands • More than 200 centimeters precipitation per year (80 inches). • Some over 500 centimeters (200 inches). • Warm temperatures/relatively constant. • Many species. • Soils are poor since nutrients are stored in biomass of vegetation or washed out. • Highly weathered so clayey—sun and heat make?

12. Chapter 6 Temperate Deciduous Forest: • Distinct summer/winter seasons. • Trees loose leaves in winter • 100 centimeters (or more) of precipitation (40 inches). • Mild winters, 6 month growing season  • Relatively few species of trees. • Two or three major producers  • Many flowers, insects, birds and mammals. • Texas—Eastern and Western Crosstimbers

13. Chapter 6 Taiga (aka: Northern Coniferous Forest or Boreal Forest): • Short cool summer, long hard winter. • Up to 6 months, soil freezes • Precipitation between 25 and 100 centimeters per year (10 to 40 inches), with constant high humidity. • Trees see winters as dry due to precipitation in form of snow. • Needle shaped leaves. • Flexible branches

14. Chapter 6 Tundra: • No trees, permanently frozen soil (permafrost)—north of Coniferous forests • Low precipitation (less than 25 centimeters), but comes in summer when snow melts. •  Permafrost does not allow water to soak in....many small pools. •  Damage to systems takes long time to fix. • Same conditions on high mountains (alpine tundra) but different species

15. Chapter 6 Aquatic Ecosystems: • Factors: • - sun light penetrability • - nature of bottom substrate • - water temperature • - amount of dissolved material • Marine—high dissolved salts • Freshwater—low dissolved salts

16. Chapter 6 Marine systems • Pelagic Ecosystems • Open ocean system, with free swimming organisms.  • Fish, whales, crustaceans,etc not attached to anything • phytoplankton (producer) in euphotic zone. • zooplankton • other consumers • nutrients are in short supply, except in few concentrated areas.

17. Chapter 6 Benthic Ecosystems • Systems at bottom of ocean. • Critters attached or not •  If light can penetrate, plants exist. •  Substrate determines types of organisms which can occur. •  No light: abyssal zone. •  Warm waters è coral reefs Mangrove swamps • Near shore region • Can lead to terrestrial ecosystem development

18. Chapter 6 Estuaries • Shallow partially enclosed area where freshwater enters marines systems. • Relatively few organisms capable of tolerating salt fluctuations seen in this system. • Large amount of nutrient inflow. • Typically, entire area has sunlight penetrating to bottom. • Many organisms use as nursery. • Trap sediment—salt marsh—terrestrial ecosystem

19. Chapter 6 • Freshwater Systems • Lakes and Ponds: • littoral zone (has rooted plants) • limnetic zone (no rooted plants) • Productivity: • Temperature • Depth • Nutrients in water • oligotrophic lakes—longer life • eutrophic lakes—shorter life

20. Chapter 6 • Dissolved oxygen (DO) determines what type of organisms will occur. • Free oxygen O2 • Biochemical oxygen demand (BOD) • A measure of how much decomposable organic matter is in the water. •  Enter through critter waste in lake, inflows of organic wastes, critter death, etc

21. Chapter 6 Streams and Rivers: • periphyton - organisms attached to rocks and bottom material. • Not much chance for plants, so most energy comes from material that falls in stream rather than from photosynthesis. • Many insects, fungi and bacteria use this organic matter. • Dissolved oxygen: less in slow, muddy rivers • Wetlands: transition areas