Page 659 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

(a)
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PACIFIC OCEAN
ARCTIC OCEAN
ATLANTIC OCEAN
PACIFIC OCEAN
ATLANTIC OCEAN
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Hudson Bay
Gulf of Mexico
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Mallard’s Ssummer Rrange
Mallard’s Yyear-round Rrange
Mallard’s Wwinter Rrange
(b) The coast redwood is limited by the presence of fog as a moisture source; red maple tolerates a variety of environmental conditions.
110° 80° 70°
(a) The Snail Kite's small range in North America depends on a single food source; the Mallard Duck is a generalist and feeds widely.
Disturbance and succession
Over time, communities undergo natural disturbance events such as windstorms, severe flooding, a volcanic eruption, or an insect infestation. Human activities, such as the logging of a forest or the overgrazing of a range- land, also create disturbance (Figure 19.17). Such events damage or remove existing organisms, making way for new communities.
Wildfires are a natural component of many ecosys- tems and a common cause of ecosystem disturbance. The science of fire ecology examines the role of fire in eco- systems, including the adaptations of individual plants to the effects of fire and the human management of fire- adapted ecosystems. Focus Study 19.1 examines this important subject.
When a community is disturbed enough that most, or all, of its species are eliminated, a process known as ecological succession occurs, in which the cleared area undergoes a series of changes in species composition as newer communities of plants and animals replace older ones. Each successive community modifies the physical
CRITICAlthinking 19.2
Observe Ecosystem Disturbances
Over the next several days, observe the landscape as you travel between home and campus, a job, or other localities. What types of ecosystem disturbances do you see? imagine that several acres in the area you are viewing escape any disruptions for a century or more. Describe what some of these ecosystems and communities might then be like. •
(a) Damage from a debris flow in North Carolina, triggered by the rainfall associated with Hurricane Ivan in 2004.
(b) Stanley Park Storm Damage. A December 2006 storm in Vancouver with 120 km . h−1 winds resulted in almost 41 hectares of damage to the forest in Stanley Park.
▲Figure 19.17 Ecosystem disturbance, making way for new communities. [(a) nOaa. (b) gunter Marx/ST/alamy.]
Snail Kkiite’’s Yyear-round Rraannggee
▲Figure 19.16 limiting factors affecting species’ distributions.
Notebook
limiting Factors affect Plant and animal Species
Coast Rreeddwooodd
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Red mMaple
Chapter 19 ecosystem essentials 623
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