Name:
NRES 441/641 – Spring 2007
Ecology and Management of Invasive Plants
Second Mid-term Exam – Place your name at the top of this page in the space provided and on
any other sheets of paper that you use.
I. Multiple Choice. Circle the most correct answer for each question below (one answer only).
(1 pt each)
1. The majority of plant invaders that have altered fire regimes in ecosystems usually:
a. Sequester large amounts of carbon.
b. Are trees.
c. Represent new life forms.
d. Decrease fire regimes.
2. Which of the following is true about mechanical control methods?
a. Tilling should be implemented to control the riparian invader tall white top.
b. Mowing is often successful when used on rhizomatous plants.
c. Grazing at the proper time is an effective way to reduce seed production.
d. Weeding is feasible over a large area.
3. Controlling invasive plants:
a. Usually requires only one application of a specified treatment.
b. Always costs more money than the benefits that will accrue.
c. Needs to consider economic constraints only.
d. Usually requires more than one type of treatment.
4. What are the steps in eradicating an invasive plant?
a. Containment, mechanical control, delimitation
b. Delimitation, containment, extirpation
c. Chemical control, mechanical control, biological control
d. Prevention, detection, cooperation
5. Which of the following statements is true?
a. The micro-evolutionary hypothesis is scientifically well-documented.
b. Humans are the cause for plant invasions according to the anthropogenic
hypothesis.
c. If an area is biologically diverse, then the area is well protected against plant
invasions.
d. Allelopathy has been shown to be a common mechanism used by invasive plants.
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NRES 441/641 – Spring 2005
Second Mid-term Exam
6. The assigned reading by Denslow and D’Antonio 2005 discusses the indirect effects of
biological control. Which of the following statements is a common theme across the biocontrol projects reviewed in this paper?
a. Impacts on the target weed are uniform across the plant’s invasive range
b. Community response to reduction of the target weed is well documented
c. Combining biological control with other weed management strategies is most
successful
d. Biological control is rarely successful because of land mis-management
7. Which of the following is true about the economic impacts due to invasive plants?
a. The economic benefits associated with tamarisk removal are greater than the
costs of eradication.
b. The United States incurs the highest costs due to invasive plants in the world.
c. Indirect-use values are easy to quantify.
d. The least cost method used in a cost-effectiveness approach is often more beneficial
than the costs of control.
8. Which of the following is true about plant introductions?
a. Invasive plants usually arrive through natural long-distance dispersal.
b. Rates of plant invasions were highest during colonial times.
c. Invasive plants are usually accidentally transported.
d. Repeated introductions are associated with higher invasion success.
9. If you were the manager of a national park using the weed control priority scoring system,
which sort of invasive weed would be your priority for control?
a. Narrow distribution, large impact, easy to control, high risk of spread
b. Wide distribution, small impact, easy to control, low risk of spread
c. Wide distribution, large impact, hard to control, low risk of spread
d. Patchy distribution, small impact, hard to control, moderate risk of spread
10. In a cost-benefit analysis, the amount that an individual pays to see the coastal redwoods
during their vacation is considered a:
a. Non-consumptive value.
b. Indirect-use value.
c. Opportunity cost.
d. Consumptive value.
11. In Nevada:
a. APHIS is in charge of creating and administering the noxious weed law.
b. The noxious weed list is very similar to the US federal list.
c. The state can put a lien on a property to pay for the cost of control if a
landowner does not control a noxious weed.
d. All of the above.
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NRES 441/641 – Spring 2005
Second Mid-term Exam
12. With respect to species replacement by invasive plants, which statement is true?
a. Few extinctions have been attributed to invasive plants.
b. Cape Ivy appears to suppress other plants in the San Francisco Bay area.
c. Presence of cheatgrass can inhibit recruitment of seeded native perennial grasses.
d. All of the above.
13. The “Tens Rule” states that:
a. About 10% of imported species become invasive pests.
b. About 10% of naturalized species become invasive pests.
c. Concentrations of herbicides need to be increased by 10 times for invasive plants.
d. One in every 10 biological control agents attacks a non-target plant species.
14. Guest speaker Lisa Ellsworth discussed some ecological aspects of fire and invasion in the
great basin. Which of the following statements is NOT true?
a. Big sagebrush is fire intolerant and frequent fire reduces sagebrush populations.
b. After 80 years, shrubland invaded by pinyon and juniper crosses an ecological
threshold that makes it difficult to restore the original community by prescribed fire.
c. Fire can be an effective restoration tool if the conditions are appropriate (fuel loads,
species composition, seed sources, e.g.)
d. Fire was not part of the disturbance regime in sagebrush ecosystems prior to
European settlement and invasion by cheatgrass
15. Because tamarisk invades riparian areas in western North America,
a. Populations of the red cockaded woodpecker have increased.
b. The key to evaluating the economic damage from tamarisk invasions is water.
c. We can conservatively estimate its water use at about 1 acre-feet of water per year
less than native species.
d. We can conservatively estimate its water use at about 3 acre-feet of water per year
more than native species.
16. Which of the following statements is true about biological control?
a. It is hard to find biological control agents because it is not evolutionary
advantageous to kill your host.
b. Biological control has high public opposition.
c. The underlying concepts for biological control are based on the biological diversity
hypothesis.
d. The likelihood of a biocontrol agent moving to a non-target host is high, even without
the presence of related species.
17. A key issue to be resolved in determining which herbicide to use in a chemical control
program for an invasive plant includes:
a. Carefully examining the adjuvants for mitotic mimics.
b. Matching the mode of action with the characteristics of the target species.
c. Which public relations strategy should be used to garner public support.
d. Whether to use only those herbicides with an EPA Human Toxicity rating of
Category I or both Category I and II.
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NRES 441/641 – Spring 2005
Second Mid-term Exam
18. Which of the following is true of the invasion process and associated barriers according to
Richardson et al. (2000)?
a. Casual aliens consistently reproduce.
b. A species is invasive once it begins to compete with the native vegetation.
c. Naturalized species can create self-replacing populations without human
intervention.
d. Transformers are robots in disguise.
19. Invasive plants impact ecosystem structure and function by:
a. Replacing primary production with secondary production.
b. Detrending the dynamics of communities.
c. Altering the cycling of water and nutrients within the ecosystem.
d. All of the above.
20. Which of the following statements about the 2007 paper by Keller et al. entitled, ‘risk
assessment for invasive species produces net bioeconomic benefits’ is NOT true?
a. The authors use low estimates for the value of introduced species and high
estimates for their potential costs, inflating the estimated benefit of quarantine
programs.
b. It is important to include the effect of ‘discounting’ for potential future benefits
compared to short term benefits.
c. At the current level of risk assessment and plant screening accuracy, economic
benefits outweigh costs within 15 years.
d. If one adopts a 50-100 year planning horizon it is beneficial to screen plant imports as
long as the accuracy of the risk assessment procedure is 70% or higher.
II. Matching. Below is a list of words and phrases. For each of the numbered statements, write
on the line at the end of that statement the word or phrase from this list that best matches the
statement. Each word or phrase is used only one. (1 pt each)
exotic engineers
naturalized
introgressant
discount rate
mutualism
restoration
auxin mimics
adjuvants
facilitation
immobilization
maintenance management
eradication
1. An important component of plans to control invasive species: restoration. (eradication OK)
2. Controlling an invasive species at a tolerably low level maintenance management
3. What is sometimes more toxic than the herbicide chemical? Adjuvants.
4. What decreases the amount of active chemical that is available to attack the target plant?
Immobilization.
5. In the study of Myrica faya by Vitousek and Walker (1989), nitrogen-fixation by this invasive
plant on new lava flows in Hawaii is an example of which process? Exotic engineer, facilitation.
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NRES 441/641 – Spring 2005
Second Mid-term Exam
IV. Short answer. On the attached pieces of lined paper, answer TWO of the following
questions. Be sure to clearly number each question. (10 pts each)
1. You are a land manager faced with two different invasive species under your jurisdiction, but
you only have the resources to control one species. Summarize how you would prioritize which
species to control. Discuss the types of information that you would need to know to make this
decision and how you would weigh that information for your decision.
Answer: I was specifically looking for information from our lecture on ‘prioritizing control’ and
in particular from the prioritization questionnaire used by the National Park Service. You would
get 1 point each for mentioning things like the damage caused by each species, ease of control,
risk of spread, the relationship between the plant and the disturbance regime, and the
consequences of control. You would also get a point for mentioning how each of these things
would affect your decision – e.g. easy to control puts plant at higher priority, as does being more
ecologically damaging (invading undisturbed habitats for instance). Additional points for
considering methods of control, public opinion, and restoration plans.
2. Pick 1 of the 9 different mechanical control methods that were presented in class. Elaborate on
your chosen method, making sure that you discuss what types of species are susceptible to the
method, advantages and disadvantages of the method, and the appropriate situations to
implement the method or special considerations for using the method.
Answer: the nine methods are weeding, mowing, grazing, burning, tilling, solarization,
mulching, girdling, and flooding. I gave two points for choosing one and defining it, three points
each for types of species and situations and advantages and disadvantages, two more points for
special considerations. For example: girdling = removing a ring of bark, including cambium
layer, to ‘starve’ tree. Best for use in places where leaving plant in place is advantageous (soil
stabilization, habitat) and works for woody perennial shrubs/trees with one or few stems.
Advantages – very specific, little collateral damage, effective on single-stemmed plants;
disadvantages labor intensive and doesn’t work on plants that re-sprout, death can be slow, and
t. Special considerations: time consuming and labor intensive; can be facilitated by using special
equipment (tool to assist in girdling) and can be augmented by application of herbicide to cut.
Dead trees can be advantageous wildlife habitat or have a negative impact on esthetics.
3. Briefly describe each of the three major components of valuation that are associated with
economic analyses of invasive species. For each of the 3 components, provide an example of
something with monetary value that illustrates that component.
Answer: the three types of values are direct use (consumptive and non-consumptive), indirect
use, and non-use (existence value). Direct use is value obtained by using resource either by
consuming it (e.g. cutting forest for timber), enjoying it (recreation value). Indirect use value is
value of an ecosystem service – e.g. the value of a wetland for purifying water; cost of replacing
the wetland with a purification plant. Non-use value is the value placed on a resource just for its
existence – e.g. willingess to pay to preserve wilderness, possible future value of a yetundiscovered resource in a wilderness area, like a medicinal plant. 3 points for defining and
providing an example of each component, plus one ‘discretionary’ point.
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NRES 441/641 – Spring 2005
Second Mid-term Exam
V. Essay. On the paper provided, answer the following question in essay format. 15 points.
Invasive species can have profound effects on ecosystem processes, as illustrated in the
following diagram from Luken and Theiret 2000. Discuss the ecosystem level effects of invasive
species as outlined in this diagram, providing examples from your readings and our lectures to
illustrate.
Answer: Up to 4 points per section for discussing possible effects of invasive species on each
component of the diagram, including +ve and –ve effects on ecosystem aspects (refer to table
from handout – walker and Smith in Luken and Thieret 1997). Examples could include
cheatgrass changing frequency and severity of fire (disturbance regime); Myrica facilitating
invasion of other species on lava flows (community dynamics); cape ivy overgrowing other
species and changing diversity and composition of vegetation (primary productivity); and
tamarisk transpiring substantially more water than native vegetation and creating much more
stable banks altering flooding regimes (nutrients/water).
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