Ecosystems & Communities

1.  Ecosystems:  constantly change

• Dynamic
• Plants grow & die
• Animals feed on plants, other animals
• Decomposers recycle non-living organics
• Conditions within the community are the key to which organisms live there
• Climate: temperature, sun, precipitation
• Geology: mountain, flat, rocky, sandy, etc.

2.  Succession: communities proceed through a series of recognizable, predictable changes over time.

• Activities of organisms change surroundings
• Trees, shrubs, other plants drop leaves
• Earth worms process leaf litter, make soil
• Organic component of soil increases as forests, shrublands and prairies establish
• Other woody vegetation will dry and buildup as potential fuel for a fire
• Fire burns woody vegetation, organics, recycles (or remineralizes) the soil
• New plants establish in burned area
• Process starts again

3.  Climax Community

• Relatively stable, long-lasting community that is the result of succession.
• Examples:
• Forest
• Prairie
• Desert scrub
• Coral reef

4.  Fig. 6.1; Factors that determine the kind of Climax Community

5.  Types of Succession

• Primary:  begins with no life
• New lava flow
• Land exposed after retreat of glacier
• Takes a long time because soil has to accumulate, nutrients are low for plant growth

6.  Figure 6.4.  Primary succession from a pond to a wet meadow.

7.  Figure 6.3. Primary Succession on Land

8.  Types of Succession

• Secondary
• Begins with disturbance of existing ecosystem
• Examples
• Fire
• Flood
• Human development
• Faster: some soil and seeds or roots from before disturbance, begin growing immediately

9.  Fig. 6.6.  Secondary Succession on Land

10.  Fig. 6.7 -Biomes: major types of terrestrial climax communities

11.  Biomes: wide geographic distribution, specific climate

• Precipitation
• Type: rain, snow, fog
• When: seasonal distribution
• Rainy season: Florida
• Monsoons: desert SW
• Temperature patterns: tropics to arctic
• Fire
• Strong winds

12.  Figure 6.8.  Influence of precipitation and temperature on vegetation.

13.  Figure 6.9.  Relationship between height above sea level, latitude and vegetation.

14.  Biome = Desert

• Primary Climate factor = lack of water
• Desert definition:  areas that average less than 10 inches of precipitation/yr.
• Rainstorms: heavy, infrequent and most water does not sink into the ground, but runs off or evaporates.
• Temperature
• wide range from day to night
• no clouds to block sun = hot day
• No clouds to insulate, heat lost to space = cold night

15.  Biome = Desert

• Organisms
• high biodiversity, few individuals
• Adapted for low water
• Plants have reduced leaves, thorns, photosynthetic stems (cactus), some dormant between rains
• Animals hide in moist, cool burrows during heat of day, out to forage or hunt during day

16.  Biome = Desert

• Human impact
• Historical: hunter-gatherer societies, nomadic herding
• Modern:
• can bring in water or drill wells, tap aquifer
• Some limited agriculture
• Cities: Las Vegas, Phoenix --- but they are running out of water

17.  Biome = Desert Fig. 6.10.  Desert climograph, flora & fauna

18.  Biome = Grassland (Prairie, steppes)

• Climate
• Precipitation: 10 - 30 inches/yr
• Windy
• Hot summers, cold-to-mild winters
• Fire important: prevents invasion of woody vegetation (trees, shrubs)

19.  Biome = Grassland (Prairie, steppes)

• Organisms
• Grasses (60 - 90% of flora)
• Grow close together, root network binds soil
• Animals: grazers that eat grasses
• Herds of migratory mammals: bison, wildebeasts, wild horses, sheep, cattle, goats
• Small animals grazers: mice, ground squirrels
• Many insects: dung eaters, parasites, scavengers and grazers
• Recycle minerals through dung
• Eat woody species (young shoots) - keep prairie herbaceous, mostly grasses
• Predators:  snakes, lizards, coyotes, foxes, hawks

20.  Biome = Grassland (Prairie, steppes)

• Human impacts: little undisturbed left
• Land conversion to agriculture (corn, wheat)
• Grazing of cattle, sheep & goats
• Erosion
• rates high:  agricultural usage leads to water and wind removal of topsoil -->Productivity falls
• Irrigation: leads to water logging & salinization due to evaporation

21.  Biome = Grassland (Prairie, steppes) -Fig. 6.11

22.  Biome = Tropical Rainforest

• Where:  near the equator
• Climate
• Temperature
• normally warm & constant
• Precipitation:  > 80 inches/yr up to 200 inches/yr
• Soils poor - nutrients tied up in plants or washed away

23.  Biome = Tropical Rainforest

• Organisms: High biodiversity, high biomass
• Biodiversity: the measure of the kinds of organisms (number of species) in the environment
• Rainforests have many layers
• Trees are the structural base:  canopy, trunk, roots
• Many organisms live on the trees
• Epiphytes: plants, like orchids and bromeliads that attach to the branches
• Arborial animals: primates, snakes, lizards, insects
• High diversity of birds: macaws, parrots, hummingbirds, many others
• Bats important for spreading seeds of keystone species

24.  Biome = Tropical Rainforest

• Human Impacts
• Development pressure
• Mining
• Logging
• Land conversion to agriculture

25.  Biome = Tropical Rainforest (Fig. 6.15)

26.  Biome = Temperate Deciduous Forest

• Definition:  Winter-summer change of seasons, predominant vegetation is trees that loose their leaves
• Where:  E. US, S/SE Canada, S. Africa, Europe & Asia
• Climate
• Precipitation: 30 - 60 inches/yr
• Growing season: ~6 months
• Relatively mild winters

27.  Biome = temperate deciduous forest

• Organisms
• Trees:  deciduous -> maples, aspen, birch, beech, oaks, hickories
• Understory spring “ephemerals” that grow and flower before leaves are out on the canopy trees:  wildflowers like violets, trout lilys, skunk cabbage
• Animals
• Insects: beetles, moths, flies ….. Many kinds
• birds
• primarily migrants: robins, hummingbirds, chipping sparrows, N. Oriole
• Residents: woodpeckers, turkeys, finches, chickadees
• Birds of prey (raptors): hawks, eagles, osprey
• amphibians and reptiles
• Mammals:  mice to deer, foxes, coyotes, bears

28.  Biome = temperate deciduous forest

• Human Impacts
• Land conversion
• cleared for farming
• Cleared for urban development: most of major population centers in E. North America and Europe were once TDF
• Periodic logging

29.  Fig: 6.16. Temperate Deciduous Forest: climagraph, flora & fauna

30.  On your own

• How do the savannah, tropical dry forest, Mediterranean shrublands, taiga and tundra compare to the biomes discussed in class?

• Climate?
• Organisms?
• Human impacts?