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Species Interactions & Community Ecology
Chapter 6
MARSH HAWK
CROW
UPLAND SANDPIPER
GARTER SNAKE
FROG
SPIDER WEASEL BADGER COYOTE
GROUND SQUIRRELPOCKET GOPHER
PRAIRIE VOLE
CLAY-COLORED SPARROW
EARTHWORMS, INSECTS (E.G., GRASSHOPPPERS, CUTWORMS)
FIRST TROPHIC LEVEL Primary
producers
SECOND TROPHIC
LEVEL Primary consumers
(e.g., herbivores)
HIGHER TROPHIC LEVELS
Complex array of carnivores,
omnivores and other
consumers. Many feed at
more than one trophic level continually,
seasonally, or when an
opportunity presents itself
Typical Food Web
1. Maple seedling growing under an oak tree
2. Fungus (mycorrhizae) live on plant roots and facilitate water absorption
3. Frog eats a fly
4. Your dog has fleas
5. A bacteria grown in culture produces toxins that prevent others from growing near it
6. A hermit crab uses a discarded snail shell for protection
Competitive Exclusion Principle:
• When 2 species compete the more fit one will win. Two species cannot coexist in the same habitat with the same requirements for very long.
• Ex: gray squirrel vs red squirrel
It’s Squirrel versus Squirrel!
How can all these species coexist? NICHES!
• They can coexist if they utilize resources under different environmental conditions.
• Niche: the role a species plays in its habitat and under what environmental conditions.
• Fundamental Niche: conditions species can exist w/o competition.
• Realized Niche: conditions species can exist with competition. (Real world!)
Where do they belong?
• Endemic species– Native to a particular area and not elsewhere
• Exotic/non-native species– Introduced into a new geographic area
• Invasive species– Exotic that can run an endemic out of its habitat
• Cosmopolitan species– Broad distribution in suitable environments
• Ubiquitous species– They’re everywhere!
Pigeon Mouse
Lorius Lory of New GuineaRabbits of Australia
Japanese Maple in NJ
Feral Rabbits in Australia, 1963
Introduced in 1859. Diseases like myxomatosis(1991) and rabbit hemorrhagic disease (1996) were introduced in to control their numbers. Has lead to genetic resistance (esp myxomatosis)
Ecological Succession
Restoration
Previous Ideas on Restoration:• “Balance of Nature” Idea (until mid 20th century)• Equilibrium: nature left alone will achieve a
permanency of form & structure forever—the climax state.
• When there is a disturbance and then the force is removed, nature will return to its former, identical state.
• There’s a place for every creature and every creature in its place.
• Disturbance is bad…
But now…
• Nature is not constant.
• All ecosystems continually undergo change.
• Species evolve and adapt to change
• Many species require change to survive
To What Point Do We Restore?
• Pre-settlement of humans
• Restoration ecology
• Florida Everglades– Restoring wetlands– Improving water quality– Improving habitats of 60+ endangered
species
• Midwestern Prairies
How do we restore it?
• Depends on the situation.
• Redirecting water flow (adding/removing channels, dredging)
• Leave it alone/improve what goes into it
• Controlled burning
Succession:
• Natural recovery of a disturbed ecosystem. • Primary: initial establishment & development of
an ecosystem where one did not previously exist. Originally an abiotic environment. Ex: edges of lava flows, receding glaciers
• Secondary: reestablishment of an ecosystem following a disturbance. Some life will still remain. Ex: areas of fire or hurricane, abandoned farmland.
Primary Succession on a lava flow. Pioneer species had already taken hold
Secondary succession: boreal forest after a fire
Stages of Succession
• Early: plants with short life cycles, rapid seed dispersal. Stablize soil (aka 1st and 2nd stages). Often annual plants that can tolerate harsher conditions (much water, full sun, limited water, etc)– Biomass & Biodiversity both increase.
• Middle (3rd stage); larger plants, trees begin to dominate once early stage plants have made conditions more livable. Highest biodiversity
• Late (4th stage): Large, mature plants, larger animals. Slower growing, grow well in shade, have seeds that can persist.
Chemical cycling during succession:
• Organic material & other chemicals in soil increase throughout succession, but not indefinitely.
• If there is no disturbance, the ecosystem will use up stored chemicals and will no longer support late stage plants.
Biomes
• Regional complex of similar communities
• Dominant plant types & structure
http://www.globalchange.umich.edu
Precipitation, Latitude and Biomes
Temperate Deciduous Forest
Oaks, Beech, Maple; moderate temps & rain
Temperate Grasslands(steppe, prairie)
Tall grasses; less rainfall, more extreme temps between seasons
Temperate Rainforest
Hoh Rain Forest of Washington State;
Conifers such as cedars, spruce, hemlock, Douglas fir.
Heavy rainfall, moderate temps
Tropical Rain Forest
Warm temps year round; heavy rainfall; closer to equator.
Poor soils, high diversity of species
Tropical Deciduous Forest(Tropical Dry Forest)
Warm year-round w/moderate rainfall
Can have Monsoon seasons
Leaves may drop during dry seasons
Savanna
Warm year round; dry. Grasses
Deserts
Sparse rainfall
May have large daily temp fluctuations
Plants w/small-no leaves
Tundra
Very dry, cooler temps; extremely cold in winter
Permafrost
Lichens, scrubby vegetation
Taiga(Boreal Forest)
Small evergreens
Long cold winters, short cool summers, moderate rain
Chaparral
Mild wet winters, warm dry summers.
Mediterranean climate
Frequent fires
World’s Biomes