5 Evolution and Community Ecology CHAPTER

5-4 Community Stability A 2010 report on invasive species suggests that they cost the U.S. $120 billion a year in environmental losses and damages.

Invasive kudzu

Ecological Disturbances Lesson 5.4 Community Stability A community in equilibrium is generally stable and balanced, with most populations at or around carrying capacity. Disturbances or changes in the environment can throw a community into disequilibrium. Severe disturbances can cause permanent changes to a community and initiate a predictable series of changes called succession. Forest fire

Primary Succession Lesson 5.4 Community Stability Occurs when there are no traces of the original community remaining, including vegetation and soil Pioneer species, such as lichens, are the first to colonize. The environment changes as new species move in, adding nutrients and generating habitat.

Secondary Succession Lesson 5.4 Community Stability Occurs when a disturbance dramatically alters a community but does not completely destroy it Common after disturbances such as fire, logging, or farming Occurs significantly faster than primary succession

Succession in Water Lesson 5.4 Community Stability Primary aquatic succession occurs when an area fills with water for the first time. Disturbances such as floods or excess nutrient runoff can lead to secondary aquatic succession.

Climax Communities Lesson 5.4 Community Stability Ecologists once thought succession leads to stable “climax” communities. Today, ecologists see communities as temporary, ever- changing associations of species. Communities are influenced by many factors and constant disturbances. Beech-maple forest, a classic “climax community”

Invasive Species Lesson 5.4 Community Stability Nonnative organisms that spread widely in a community A lack of limiting factors such as predators, parasites, or competitors enables their population to grow unchecked. Not all invasive species are harmful. Did You Know? Although the European honeybee is invasive to North America, it is beneficial because it pollinates our agricultural crops.