Dryas and Alders in Glacier Bay, and Dwarf Lupines on the Pumice

question 193

Multiple Choice

Dryas and alders in Glacier Bay, and dwarf lupines on the Pumice Plain of Mount St.Helens, all have root nodules containing nitrogen-fixing bacteria.Why were these plants important to the development of communities on these two primary succession sites?

• A) The nitrogen they produced added to nitrogen already available on the sites.
• B) They could remove excess nitrogen from the site so they would not be poisoned.
• C) They shared their nitrogen with other plants already colonizing the sites.
• D) The nitrogen provided strong roots that allowed them to colonize in soil-free areas.
• E) They could colonize first and leave nutrients and habitat for subsequent colonizers.

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