Ecosystems and Communities - Ch. 6 PDF

“In wilderness I sense the miracle of life, and behind it our scientific accomplishments fade to trivia” Charles Lindbergh “All good things are wild and free” Henry David Thoreau  Ch. 6 - Communities and Ecosystems  Succession: communities proceed through a series of regular changes over...

“In wilderness I sense the miracle of life, and behind it our scientific accomplishments fade to trivia” Charles Lindbergh “All good things are wild and free” Henry David Thoreau  Ch. 6 - Communities and Ecosystems  Succession: communities proceed through a series of regular changes over time  Climax community: stable, long-lasting community resulting from succession  major disturbances renew succession→  Primary succession: begins w/total lack of organisms - rock  Very slow  ex: volcanic islands→  Secondary succession: rapid, begins w/disturbance of an ecosystem  ex: hurricane hits an island, fire, flood  Most wildlife habitat mgt mimics secondary succession→  Climax Community Characteristics:  maintain mix of species over time  E at equilibrium, increased biodiversity  What is the historical climax community?  Human settlement of N. America altered climax communities  exotic species introductions – cheat grass  Disease – Dutch elm  more plastic definition of climax community→  Biomes: terrestrial climax communities at large scales→  2 major factors that impact biomes:  1. Precipitation: total amt, form (rain/snow)  2. Temperature: tropical vs temperate regions→  Other non-human factors: fire, wind, soil type, flora/fauna  Elevation: vegetation shifts w/ elev. correspond to latitudinal shifts→  Desert  80-128” of rain/year  highest biodiversity of any biome  more than rest of biomes combined!  Under severe threat from logging, cattle grazing, urban sprawl, biofuels (cane/date palms), poverty  Mgt: difficult to restore tropical rainforest, must be preserved→  Temperate Deciduous Forest  temperate - seasonal hot/cold  deciduous trees - drop leaves in fall  30-60 in of rain/yr; Durant = 41”/yr  less diversity of tree species, but more indvls - dominant species (oak, beech)  Mgt: selective logging/thinning, prescribed burning in some cases, preservation in others→  Taiga  northern latitudes - evergreen, coniferous forests - a.k.a boreal forest  short summers, long winters, lot o’ snow  Conservation: selective logging→  10-40 in rain/yr  lakes, ponds, bogs present  Spruce-fir  wildlife often migratory→  Tundra – “arctic prairie” - lacks trees  “frozen” soil layer = permafrost  shallow H2O = nesting birds  alpine tundra - high altitude  Preservation critical: tundra plants slow growth rates (decades) → Arctic/Antarctic biomes Global warming, ozone layer issues, whaling→  Aquatic Systems  Factors affecting aquatic ecosystems:  1. Light penetration  2. H2O temp  3. Nature of bottom substrate  4. Amt of dissolved minerals  Plankton: small, drifting organisms  Phytoplankton: photosynthetic plankton (algae/ bacteria) found in the:  Euphotic zone: upper layer of water body that sunlight penetrates (~150 m)→  upwellings and river deltas - high nutrient availability for photosynthesis  = Primary Productivity!  Zooplankton: animals that feed on phytoplankton→  benthic: organisms that live on the ocean bottom  ex: kelp, coral reefs, mangroves  abyssal ecosystem: deep ocean system; rain of detritus from euphotic zone  Estuaries: marine ecosystems of shallow, partially enclosed areas w/inflow of freshwater  brackish: part saltwater, part freshwater  Nurseries: ex = flounder, shrimp - young→  Freshwater Ecosystems  Lakes/Ponds  emergent plants: plants along shore that are rooted on bottom (ex: cattail, water lily)→ submerged plants: rooted on bottom, but stay below surface (ex: coontail) Littoral zone: shallow area w/veg near the shore Limnetic zone: area of lake w/out rooted vegetation (open water)→  Oligotrophic: cold, deep, nutrient poor lakes  Eutrophic: shallow, warm, nutrient rich lakes  Streams-Rivers  attached veg = periphyton  speed of water impt; slow rivers begin to accumulate material and fill in→ swamps and marshes: both wetlands; wetland interface between aquatic/ terrestrial systems Swamps: wetlands w/trees that can tolerate permanently or semi-permanently flooded conditions→  Marshes: wetlands dominated by grasses-reeds  Shift toward terrestrial systems over time→