Environmental Science: Chapter 4 Ecosystems: How they change

Biotic Potential Vs. Environmental Resistance

Predator-prey Balance:Wolves and Moose

Steps in predation Encounter Attack Capture Ingestion

Encounter Ambush: Wait for prey to come to you. Burst speed. Pike, muskie, barracuda, gar Lepisosteus osseus http://fcn.state.fl.us/fwc/fishing/Fishes/gar.html Rover: Actively search for food. Constant motion. Bass, yellow perch

 forward (most fish) or sideways (gar) lunge Attack:  forward (most fish) or sideways (gar) lunge  special grasping organs http://insects.ummz.lsa.umich.edu/michodo/test/index.htm Odonate larvae mentum extends to grasp prey Capture:  prey have adaptation to avoid capture  piscivores have lots of teeth

predator – prey sizes ~ 1mm Blue Whale 100 ft, up to 220 tons http://bio-images.bgsu.edu ~ 1mm Blue Whale 100 ft, up to 220 tons http://www.calpoly.edu/~jiturrir/ED480/whales/baleen.html

Other factors effect population levels; ex. parasitism, weather predation parasitism Time population size Time population size

Mechanisms of Population Equilibrium: Plant-Herbivore

Livestock grazing in western US -Livestock grazing occurs on more federal public lands than any other commercial use -Affects more than 260 million acres – an area the size of Texas and California combined -Water diversions, predator control, vegetation manipulation and fencing -In the US, livestock grazing has contributed to the listing of 22 percent of federal threatened and endangered species (almost equal to logging (12 percent) and mining (11 percent) combined)

= Selective feeders Migratory Non-selective Non-migratory

Interactions between species: competition vs predation resource consumer + predation - + - competition - - +

intraspecific competition: between members of same spp  density dependent population regulation  evolutionary change resources scarce, competition K= # that resources can support population size Time

interspecific competition: occurs between members of different species  negative effect on both populations  depends on adaptations of each population spp 1 niche spp 2 niche realized niche competition

Dry habitat, trees can’t compete w/ grass Expect to find different kinds of vegetation types at different places in the landscape Different types will affect the passage of water and its chemical composition differently Chemical composition of water entering lake affect the biota (living things) in the lake

Territoriality: defense of a resource against individuals of the same species -Examples: wolves, songbirds, bluegill -Means habitat supports fewer individuals and less competition is result

Tipping the Balance: Introduced Species http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/A/AustralianRabbits.jpg http://www.gdaywa.com/g5.php

Chestnut Blight -Fungus which entered US on Asian nursery stock imported to New York ~ 1900 -Spread by wind, rain, birds etc…, enters through cracks or wounds, multiplies rapidly, making sunken cankers which expand and kill everything above the canker -American chestnut was devastated throughout the natural range, the Appalachian hills and highlands from Maine to Georgia -By 1940, three and a half billion American chestnuts had perished. -American chestnut stock advertised as "blight free", means it was grown in an area where no blight is present, outside the natural range or inside a greenhouse.

Introduced Species Why have these introductions resulted in a degradation of the ecosystems? (Think in terms of environmental resistance and biotic potential.)

Disturbance and Succession Equilibrium = No change

Ecological succession: transition between biotic communities Primary- no previous biotic community Secondary- previously occupied by a community Aquatic- transition from pond or lake to terrestrial community

Primary Succession Mosses invade an area and provide a place for soil to accumulate. Larger plants germinate in the new soil layer resulting in additional soil formation. Eventually shrubs and trees will invade the area.

Dramatic examples: HI lava flows Relies on adjacent ecosystems Rain of organic material, seeds, and spores accumulates in cracks Some pockets moist enough to support scattered `ohi`a seedlings and a few hardy ferns and shrubs Accumulation leaves, bark… converted by soil organisms into a thin but rich organic soil A forest can develop in wet regions in less than 150 years

Aquatic Succession

Ecosystems can show resilience during a disturbance Fire

Disturbance Removes organisms, favors tolerant spp. Reduces populations Creates opportunities for other species to colonize

Fire and Succession Fire climax ecosystems: maintained by fire; e.g., grasslands, pine and redwood forests What significance does this have for humans and where they live?

Resilience Mechanisms After A Forest Fire Nutrient release to soil Re-growth by remnant roots and seeds Invasions from neighboring ecosystems Rapid restoration of energy flow and nutrient cycling

Ecosystem management: thinking about the entire system rather than trying to maximize harvest of few populations Adaptive management: 1) be prepared to chance policy 2) bring in stakeholders 3) do experiments