Wolves That Changed a River Part 2

Wolves That Changed a River

Part 2

If scientists want to measure trees and shrubs to look for the impact that browsers are having on their growth, they might measure the following:

• Height

• Recruitement - growth of seedling above level of the browsers - trees are able to grow taller than the level at which elk can eat them!

• # of Rings - indicates age of tree

Trophic Cascade Affect on Plants

Examine the graphs then use them to answer questions 9 and 10

Multiple Choice

Which of the statements best describes the change in size and growth of the trees and the population of elk during the data collection period on the graphs?

• A decrease in elk population leads to a decrease in size and growth of trees

• A decrease in elk population leads to an increase in the size and growth of trees

• There is no relationship between the number of elk and the size and growth of the trees.

Relationship between beaver populations and tree growth

Examine these graphs then use the to answer questions 11 - 13

Multiple Select

Check all of the statements that describe what happened tot he beaver colonies after 1995.

• Between 1995 and 1999 there was only 1 beaver colony.

• Between 200 and 2010, the number of colonies increased to 12

• The number of willow tree rings peaked in 2010.

• Beavers didn´t eat willow trees before 2010.

Multiple Choice

After 1999 the will tree ring area started to decrease again. Based on the graphs, what might be a reason for this?

• There were more elk to eat the trees.

• Wolves started eating willow trees as elk populations decreased.

• Increase in the beaver population corresponds to a decrease in willow size - more beavers eating the willows.

• There must have been an increase in the number of elk.

Conclusion

Based on what you have learned in this lesson, about tree growth and elk population, use data from the graphs to make a statement about how the elk population impacts the beaver population. Create a google doc for this paragraph and then share it with me.