STUDENT INSTRUCTIONS

In preparation for class discussion, examine Figures 1a and 1b. Begin with Figure 1a, which relates the number of medium-sized hemlock samplings found per hectare at 100 study sites with an index of deer browse intensity called the “sugar maple browse index.” The sugar maple browse index is the ratio of browsed sugar maple twigs to total sugar maple twigs counted in an area. It provides a measure of deer browsing intensity on a scale from 0 to 1. The higher the sugar maple browse index for an area, the higher we assume the intensity of deer browse to be for other species, including hemlock, that are also palatable to deer. Turn to your neighbor and first describe and then analyze Figure 1a. Take your time and make sure you understand the axes and the variables plotted. What conclusion do you draw regarding the relationship between medium-sized hemlock saplings and deer browse?

Once you understand Figure 1a, take a look at Figure 1b. Figure 1b includes additional variables, including light and ecological subsection (broad, ecologically distinct regions characterized by geomorphology, soils, and potential forest cover types), which affect hemlock trees at different stages of growth. In addition to varying in ecological characteristics, the stands also varied in ownership, which included county, state, and national forests, national lakeshore, Indian reservations, and private lands. The thickness (not length) of the arrow represents the strength of the relationship. Take time to examine the figure and understand which factors influence hemlock at different stages of growth.

With your neighbor, “talk out loud” and explain what you see in Figure 1b. Describe the relationships illustrated - what leads to what? Refer to the following questions to help guide your analysis of Figure 1b:

• What factor has the greatest influence on the number of hemlocks that progress from one size class to the next? Remember, the thicker the arrow, the stronger the relationship between two variables.


• How does light affect hemlocks - positively or negatively? Why would light availability matter? At what stage(s) of hemlock growth is light availability important?


• How does ecological subsection affect hemlocks - positively or negatively? Why would the ecological subsection matter? Remember that ecological subsections are defined by geology and soil types. At what stage(s) of hemlock growth is ecological subsection important?


• How does deer browse affect hemlocks - positively or negatively? Why would deer browse matter? For which size class is deer browse important?


• Is the pattern that you observed in Figure 1a consistent with those illustrated in Figure 1b?


• How does ownership relate to deer browse? Why would deer browse differ depending on who owns the forest? How does ownership relate to hemlock regeneration?

Once you and your neighbor are confident that you understand the relationships illustrated in Figure 1b, imagine that you are the managers of a protected forest area in northern Wisconsin. This forest has been historically dominated by hemlock, and you would like to restore hemlock in stands where it once existed but now is rare. You are responsible for developing a management plan for hemlock regeneration based on your understanding of the factors that most affect hemlock establishment (initial growth as seedlings) and recruitment (progression into subsequent size classes as saplings). Consult with your neighbor and discuss the following questions:

• In some stands with few mature hemlocks in the canopy, there are many seedlings and small saplings. What management strategy(ies) would you recommend to increase the likelihood of these saplings reaching the canopy?


• In other stands with few mature hemlocks in the canopy, there are also very few seedlings and small saplings. What management strategy(ies) would you recommend for these stands to restore hemlocks?


• What additional research would you recommend to help you improve your management of hemlock forests?