Sunset

Graduate Take-Home Exam

Type your answers and conform to word limits. Return the completed exam by Friday, 22 February at 1:00 p.m. Please use an alias to identify your exam. The exam is open-book and open-notes.

  1. We discussed several silvicultural treatments within the context of forest management. Briefly describe a practical application of each of the following silvicultural activities within the context of livestock management: clearcut, shelterwood, thinning, pruning. [40 points; 400 words or fewer]

  2. Why does the El Nino Southern Oscillation (which typically produces cool, wet winters) typically increase the incidence of fires in the Sonoran Desert Upland and decrease the incidence of fires in the mixed-conifer forests of the southwestern United States? Hint: in this region, fire regime is controlled primarily by fuels. [10 points 150 words or fewer]

In-Class Exam

  1. Ecosystems seem to get along fine without the influence of humans, as indicated by wilderness areas. Why, then, do we manage ecosystems? [3 points]

  2. The USDA Forest Service Organic Act of 1897 mandated management for what two outputs? [4 points]

  3. Holling and Meffe (1996) described a large-scale sociological constraint on management of natural resources. What did they call this constraint? [3 points]

  4. List and give a specific example of a social or managerial constraint. [4 points]

  5. Why would a rancher in southeastern Arizona use a 3-pasture system for one herd of cattle? Give specific reasons. [4 points]

  6. Many woody plants, including mesquite, have increased in abundance in former grasslands. List four hypotheses that have been proposed to account for the increase in woody plant abundance. [4 points]

  7. Select one of the hypotheses from your list and explain the mechanism by which it would account for increased woody plant abundance in former grasslands. [4 points]

  8. List the four general classes of plant control that we discussed in class. [4 points] Circle the class that is represented by the following example: livestock are used to graze undesirable nonnative annual plants. [2 points]

  9. John Hays described the use of Tebuthiron (trade name "Spike") to kill woody plants on a ranch in central Arizona. Why, primarily, is Tebuthiron used so seldom on his family's ranch? [2 points]

  10. Which of the four general classes of plant control is associated with the greatest loss of nutrients from a site? Explain. [4 points]

  11. To a great extent, fire regime in ecosystems of the southwestern United States is controlled by the distribution and abundance of fine fuels. Explain this statement, and give a specific example. [8 points]

  12. The inverse relationship between tree abundance (i.e., cover, density) and herbaceous biomass varies as a function of site history. In other words, the shape of the overstory-understory curve is different between sites with different land-use histories. Draw a graph (or two) showing the two types of curves. [4 points] What two historical factors are different between these different sites? [2 points]

  13. Historically, vegetation at The Nature Conservancy's Lower San Pedro preserve was characterized by mesquite bosque and sacaton flats. Why, then, is The Nature Conservancy promoting cottonwood-willow riparian forest—which was uncommon at the time of Anglo settlement—at this preserve? [3 points]

  14. What are the two primary, large-scale constraints on development of cottonwood-willow forest at the Lower San Pedro preserve? [4 points]

  15. How, specifically, is The Nature Conservancy attempting to alleviate one of the two constraints you identified in the previous question? Identify the constraint in your response. [6 points]

  16. What is the primary difference between soils on loamy upland ecological sites and soils on sandy loam upland sites? [3 points]

  17. How does this difference in soils influence surface hydrology? Describe specific differences in infiltration, runoff, and erosion. [6 points]

  18. How is this difference in surface hydrology exacerbated by livestock grazing? [3 points]

    Identify the most appropriate harvest-regeneration method (coppice without standards, clearcut, seed-tree, shelterwood, single-tree selection). [2 points each]

    _______________ Very difficult to estimate growth and volume

    _______________ Uneven-aged

    _______________ Even-aged; can regenerate tolerant species

    _______________ Controversial because of aesthetics, biological diversity

    _______________ Generates relatively continuous cash flow from a stand

    _______________ Rarely used with conifers; frequently used with angiosperms

  19. According to Benjamin Disraeli, there are three kinds of lies: lies, damned lies, and statistics. Why is the following statement misleading? [4 points]

    "Less than 5% of the meat produced in the United States is raised on public lands."

  20. Sketch an ordination diagram or dendrogram with the following properties: (a) 8 sites were sampled; (b) among all sites, sites 2 and 6 are most similar; (c) sites 1, 3, 4, and 7 form a discrete group; (4) sites 5 and 8 form another discrete group. [7 points]