Succession Video Types of succession Biotic abiotic factors

Succession Video • • • Types of succession Biotic & abiotic factors Symbiosis 4 stages of primary succession How long does it take for a mature forest to establish after a primary succession?

In 1980, when volcanic activity blew up Mount St. Helens in Washington state, all the trees for hundreds of square miles of mature forest around the volcano were scorched, burned to the ground, or toppled like matchstick. More than 20 square miles were buried to an average depth of 150 feet by the largest debris avalanche in recorded history. The U. S. Congress acted quickly to protect thousands of acres of the destroyed forest from human intervention so scientists could study ecological succession in the unique living laboratory the volcano created. Soon, scientists from more than 70 universities and government agencies had started longterm research projects on Mount St. Helens. Since then, their research has made major contributions to the science of succession. The results of their research are also being applied to help restore other disturbed forests.

• How are primary and secondary succession different? • What effects do pioneer species have on an environment undergoing primary succession? • Why do communities change over time • How long does it take for young trees to grow in each case? • What is a climax community? • How have ecologists’ ideas about climax communities changed?

• How are primary and secondary succession different? In a primary succession, the environment is left with nothing but bare rock and some lichen; In a secondary succession, soil and small plants can be found. • What effects do pioneer species have on an environment undergoing primary succession? They fix atmospheric nitrogen into useful forms for other organisms, break down rock and add organic materials to form soil • Why do communities change over time? Natural or human disturbances; organisms also alter their environment and pave the way for other species/ • How long does it take for young tress to grow in each case? 35 to 80 years for primary succession, and 3 to 5 for secondary • What is a climax community? It is the community that is the end result of ecological succession. At its most developed and stable ecological state. • How have ecologists’ ideas about climax communities changed? They thought that the stages of succession were always the same and that stable climax communities were always the end results.