Appendix Table 5A2 continued


Invasive Species: Climate Change: Land-Use Change:

Unmanaged (Grassland)1 Plant Species? Drought To Arable Land






and Services




















Biochemicals/ medicines


** plant compounds and microbial enzymes

** NA

1 [possible loss of native plant species]


1 [changes in microbial community]

3 [change from fungal- to bacterial-based food web, removal of native plants]

1 Lightly managed free-range grasslands (i.e., including supplemental winter livestock feed, but excluding fertilizer or pesticide inputs).

2 Considers general case of a plant species invasion.

3 Drought is defined here as a 20 percent decrease in annual precipitation, based on an average for a 10-year period.

4 Animal products are considered here.

5 Hirsch & Leisch 1998; Jacobs & Sheley 1998.

7 Refers to runoff to streams. In dryland systems, potential evapo trans pi ration generally exceeds precipitation, so these services may be less significant.

8 Branson et al. 1981.

9 Range depends upon organic matter and moisture retention. Therefore this good and/or service will be more susceptible in more xeric, low—organic matter grasslands.

10 Range depends upon whether the arable land supports winter grazing by cattle (e.g., on winter wheat fields) and if fiber crops are planted (e.g., cotton).

11 Direction of net impact will probably be negative, but could be positive if fiber production in arable land is higher (e.g., from the production of cotton) than wool or leather production of the original grassland.

12 Hikers, bicyclists, birders, hunters, etc. are often attracted to a site because they find it visually pleasing and/or because the site serves as habitat for charismatic and/or edible animal taxa (e.g., birds and deer). In part, it is the feedbacks between the soil and plant systems that result in the visually appealing structure (from a human perspective) and produces habitat and food for animals of interest to the public.

13 Some charismatic animals may increase in arable lands (e.g., some game bird species).

14 Creating a more structurally homogeneous landscape will limit the number of charismatic animals found at the site and thus will decrease public interest in using the site for recreational purposes.

15 Burke et al. 1989.

16 Habitat provision for high visibility and endangered/threatened species.

17 Direction of net impact will depend upon whether or not native taxa can utilize the invasive plant species for food or habitat. 18Assumes that the taxa important in habitat provision are adapted to the ecosystem and the ecosystem is normally subject to drought.

19 Impact could be positive or negative depending upon the response of important taxa to drought. Some taxa may be favored in drought conditions.

20 Refers to biological control of parasites and diseases of native species.

21 War die et al. 1999; Kourtev et al. 2002.

22 Rusek 1985.

23 Refers to termites and earthworms Lavelle et al. 1997.

24 Impact could be negative or positive depending on if the invasive plant species inhibits or stimulates soil biota via root exudates, above- and/or belowground litter inputs, or altering soil microclimate.

^Assumes biota are adapted to periodic drought conditions.

26A negative impact suggests that the rate of cycling of a given nutrient is slowed with the addition of an invasive plant species while a positive impact suggests an increase in the rate of cycling. Whether or not humans desire an increase or decrease in nutrient cycling rates is probably context dependent.

27 The net positive impact suggests an increase in the rate of nutrient cycling that may benefit crop plants. However, this increase can also lead to increased nitrogen and carbon losses that may contribute to greenhouse gas emissions.

28 Wardle et al. 1999.

29 Westover et al. 1997. Changes in microbial physiological traits may be suggestive of a change in microbial community structure.

30 Kourtev et al. 1999. Facilitating the persistence of nonnative invertebrates may decrease the biodiversity of native invertebrates.

3 Assumes biota are adapted to periodic drought conditions and will probably reach pre-drought biodiversity relatively quickly following the end of the drought.

32 GMOs are genetically modified organisms. There is evidence that the insecticidal toxin from the bacterium Bacillus thuringiensis, encoded into some crop plants, is released from the engineered plants into the soil environment (Saxena & Stotzky 2000).

33 Direction of net impact will be affected by any biochemical/medicinal products that could be obtained from the invasive plant species.

34 Direction of net impact will depend upon what components of the microbial community are inhibited or favored during drought conditions and whether those microbes can yield any biochemical/medicinal products.

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