Northern Prairie Wildlife Research Center
Alien Plant Invasion in Mixed-grass Prairie: Effects
of Vegetation Type and Anthropogenic Disturbance
Diane L. Larson, Patrick J. Anderson, and Wesley Newton
Abstract: The ability of alien plant species to invade a region
depends not only on attributes of the plant, but on characteristics of the habitat
being invaded. Here, we examine characteristics that may influence the success
of alien plant invasion in mixed-grass prairie at Theodore Roosevelt National
Park, in western North Dakota, USA. The park consists of two geographically
separate units with similar vegetation types and management history, which allowed
us to examine the effects of native vegetation type, anthropogenic disturbance,
and the separate park units on the invasion of native plant communities by alien
plant species common to counties surrounding both park units. If matters of
chance related to availability of propagules and transient establishment opportunities
determine the success of invasion, park unit and anthropogenic disturbance should
better explain the variation in alien plant frequency. If invasibility is more
strongly related to biotic or physical characteristics of the native plant communities,
models of alien plant occurrence should include vegetation type as an explanatory
variable. We examined >1300 transects across all vegetation types in both units
of the park. Akaike's Information Criterion (AIC) indicated that the fully parameterized
model, including the interaction among vegetation type, disturbance, and park
unit, best described the distribution of both total number of alien plants per
transect and frequency of alien plants on transects where they occurred. Although
all vegetation types were invaded by alien plants, mesic communities had both
greater numbers and higher frequencies of alien plants than did drier communities.
A strong element of stochasticity, reflected in differences in frequencies of
individual species between the two park units, suggests that prediction of risk
of invasion will always involve uncertainty. In addition, despite well-documented
associations between anthropogenic disturbance and alien plant invasion, five
of the six most abundant alien species at Theodore Roosevelt National Park had
distributions unrelated to disturbance. We recommend that vegetation type be
explicitly taken into account when designing monitoring plans for alien species
in natural areas.
Key words: Akaike's Information Criterion; alien plants; anthropogenic
disturbance; Great Plains; mixed-grass prairie; native vegetation type; Theodore
Roosevelt National Park, North Dakota (USA).
This resource is based on the following source (Northern Prairie Publication
1119):
Larson, Diane L., Patrick J. Anderson, and Wesley Newton. 2001. Alien
plant invasion in mixed-grass prairie: effects of vegetation type and
anthropogenic disturbance. Ecological Applications 11(1):128-141.
This resource should be cited as:
Larson, Diane L., Patrick J. Anderson, and Wesley Newton. 2001. Alien
plant invasion in mixed-grass prairie: effects of vegetation type and
anthropogenic disturbance. Ecological Applications 11(1):128-141.
Jamestown, ND: Northern Prairie Wildlife Research Center Online.
http://www.npwrc.usgs.gov/resource/plants/apinvas/index.htm
(Version 01OCT2001).
Table of Contents
Tables and Figures
- Table 1 -- Properties of vegetation
in the north and south units of Theodore Roosevelt National Park, North
Dakota, U.S.A.
- Table 2 -- Variables included in the
three best models of vegetation structure, as determined by Akaike's Information
Criterion (AIC).
- Figure 1 -- Akaike's Information Criterion
identified the fully parameterized model, including the vegetation type
× park unit × disturbance interaction, as the best model for both
(a) mean number of alien species on transects and (b) mean frequency of
alien plants on occupied transects.
- Figure 2 -- Proportion of transects
on which Salsola iberica and Tragopogon dubius were found
in 11 vegetation types at TRNP.
- Figure 3 -- Proportion of transects
on which alien species were found in 11 vegetation types, by park unit.
- Figure 4 -- Proportion of transects
occupied by species for which the best model contained park unit and/or
disturbance.
- Figure 5 -- Proportion of transects
occupied by Bromus inermis, for which the best model contained the
interaction between vegetation type and disturbance.
Diane L. Larson, USGS, Northern Prairie Wildlife Research Center,
Minnesota Project Office, 100 Ecology Building, 1987 Upper Buford Circle, University
of Minnesota, St. Paul, Minnesota 55108 USA. E-mail: dlarson@biosci.umn.edu
Patrick J. Anderson, USGS, Northern Prairie Wildlife Research
Center, 8711 37th St. SE, Jamestown, North Dakota 58401 USA. Current address:
USGS, 4512 McMurry Avenue, Fort Collins, Colorado 80525 USA.
Wesley Newton, USGS, Northern Prairie Wildlife Research Center,
8711 37th St. SE, Jamestown, North Dakota 58401 USA.
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