+5.2+Limits+to+Growth+Density+Independent+Factors

Density-Independent Limiting Factors  By Emily Bourke, Priya Thorat and Nikki Wrin **The following events, listed below, are all examples of Density-Independent Limiting Factors. A Density-Independent Limiting Factor is a factor that affects the size of a population regardless of the population size/density.** **These factors greatly endanger populations because of the overall harsh affect it creates.** Natural Disasters: (EPB!) factors in nature that tend to destroy communities, etc., all due to nature. examples: Why do natural disasters affect populations?
 * tornadoes[[image:http://z.about.com/i/ga/0/NYT_katrina_womanrubble-resized.jpg align="right" caption="After Hurricane Katrina Hit"]]
 * hurricanes
 * earthquakes
 * floods
 * typhoons
 * if one of the previously mentioned disasters strike, then it would affect a whole habitat of a type of species or population
 * ex: humans in New Orleans, Hurricane Katrina hit and left thousands homeless
 * ex2: a city filled with humans, an earthquake or tornado strikes and their lives are forever changed. Their property is often damaged, people they know are seriously injured/dead, and they are left homeless

Seasonal Cycles:  (PT!) Seasonal Cycles are weather related time periods that often damage property and destroy environments.
 * Heavy Rainstorm
 * insects, such as thrips or aphids, that feed on plant buds and leaves might be washed out by a heavy rainstorm


 * Extremes of Hot or Cold
 * extreme hot or cold may affect a population regardless of the population density.


 * Severe Winter Frost
 * severe winter frost can kill giant cacti in deserts--including the Amazon Desert

  Human Events: (NW!)
 * Droughts
 * periodic droughts can affect entire regions of vegetation
 * these events affect the populations of consumers within the food web
 * River damming - fish cannout move through damns and populations are reduced
 * fish ladders allow fish to move up and down stream around damns in controlled pools
 * [[image:http://www.lakeoroville.water.ca.gov/about/stats/images/fish-ladder.jpg width="246" height="246" caption="Fish Ladder"]]media type="youtube" key="gJkwsiEpfIw" height="364" width="445"
 * Clear cutting forests
 * Silvicultural Clearcut- Removes every stem so the forest will be regenerated with no overstory.
 * Commercial Clearcut- Also known as high grading, removes only commercially valuable trees, leaving the other trees standing.


 * Pros Of Clearcutting**
 * Simplest method to implement
 * Most cost-effective method to use for forest regeneration after harvesting[[image:http://upload.wikimedia.org/wikipedia/en/8/86/Rouge_clearcut.jpg width="483" height="309" align="right" caption="File:Rouge clearcut.jpg" link="http://upload.wikimedia.org/wikipedia/en/8/86/Rouge_clearcut.jpg"]]
 * Provides an opportunity to plant seedlings of a specific species or stock type
 * Best method for planting shade-intolerant species


 * Cons of Clearcutting**
 * Leads to soil erosion, especially from stands harvested on steep slopes or inclines
 * Results in the displacement and loss of wildlife, fish, and bird species
 * Also results in a loss of carbon in the atmosphere
 * Contributes to global warming
 * Leads to a loss of biodiversity such as the removal of animals, insects, fungi, bacteria, and plant species that live in the under story part of a forest.
 * Poses an increased risk of insect infestation
 * Can lead to poor forest regeneration and often demands follow-upregeneration treatment