# Chapter 15. A Protocol for Prioritizing and Monitoring Invasive Exotic Plants in the Heartland Network, US National Park Service DRAFT April 23, 2007

Craig C. Young, Heartland Inventory and Monitoring Network, US National
Park Service.

## INTRODUCTION

*Note:* We judiciously use the National Park Service (NPS) definition of
"exotic" to refer to nonnative, introduced plant species. Because our
monitoring will focus only on those species that are known or expected
to negatively affect natural resources, we will use the definition of
"invasive" per Executive Order 13112 as a modifier to describe exotic
plants that will be of concern to park resource managers. The
abbreviation "IEP" is used to represent "invasive, exotic plants" in
this protocol summary.

In this chapter, we attempt to outline the decisions leading to the
development of the invasive exotic plant (IEP) monitoring protocol for
the Heartland Inventory and Monitoring network. After assessing the
needs of parks, we developed a field-based protocol that attempted to
balance early detection monitoring with monitoring of established
populations. While this protocol is undoubtedly not suited for all
networks, all networks will likely wrestle with the same types of
decisions.

Taking a holistic approach to IEP management, national park managers
work to prevent the introduction of IEPs (usually via propagules),
detect and respond rapidly to new IEP invasions, and control or, at
least contain, established invasions. The probability of successful
control decreases at each stage on this invasion continuum (Naylor 2000,
McNeely 2001). Early detection and rapid response generally require far
fewer resources than managing established IEP populations (OTA 1993).
Eradication efforts are most successful for invasions less than one
hectare and typically not successful for invasions exceeding 100
hectares (Rejmanek and Pitcairn 2002). While early detection usually
implies the establishment of plants not previously occurring on the
park, the scale should clearly be specified. For example, early
detection in previously non-infested sections of a national park may
also warrant immediate control at a more localized scale. In this
protocol summary, we term IEPs not established on a park, but that may
reasonably establish in the future as "potential" IEPs. IEP invasions of
limited magnitude will be referred to as "small", while abundant and/or
widely distributed invasions will be characterized as "large".

A three-stage approach applies to the management of IEPs regardless of
invasion status: inventory/survey, monitoring, and management (Rew et
al. 2006). Inventories document the presence and, in some instances, the
abundance and/or extent of IEPs on a national park. Monitoring, on the
other hand, provides unbiased, statistically powerful, and cost
effective approaches to detect change in IEP abundance and/or
distribution (Gibbs 1998). At the risk of oversimplification,
inventories often focus on extensive spatial scales, while monitoring
focuses only as broadly as necessary to provide a reasonably precise
variable estimate given the expected spatiotemporal variability. The
line between inventory and monitoring begins to blur if the inventory is
designed to be repeated over time and to allow detection of changes in
IEP abundance and/or distribution.

A perfect map of IEPs on a national park would fully meet most basic
inventory and monitoring needs. As an inventory product, maps
comprehensively identify and locate IEPs, allowing natural areas
managers to assess the scope of the problem, strategically plan
management strategies, and prescribe actions for exact locations. From a
monitoring standpoint, maps with reasonably small minimum mapping units
produced and reproduced accurately over time would clearly detect
changes in the abundance and spread of IEPs. Combined with information
on the controls applied to IEPs, maps could also assess management
effectiveness. Wide-spread interest in weed mapping reflects the
potential benefit of such maps and the availability of GPS technology.
Numerous weed mapping efforts have been initiated in many countries and
by local, state, federal and non-governmental agencies in the United
States. The North American Weed Management Association (NAWMA) has
issued guidelines to bring a minimum level of standardization to mapping
efforts in North America (NAWMA 2002). The Nature Conservancy, building
on a database from the Bureau of Land Management, developed a leading
mapping system known as the Weed Information Management System (WIMS)
(TNC 2005). WIMS integrates a GIS and database to manage information on
IEP locations, change over time, and management treatments (see
<http://tncweeds.ucdavis.edu/wims.html>). WIMS reports meet NAWMA
standards.

Despite numerous advantages, comprehensive mapping of IEPs on national
parks faces several challenges. In order to accurately track change
using mapped perimeters, repeatable mapping rules must be carefully
observed. For example, a minimum mapping unit must be designated and
followed. Clusters of IEPS must be clearly defined. Mapping using small
minimum units can often only be accomplished over small areas. As map
unit size increases, mapping becomes more efficient, but may increase
the difficulty of detecting change in perimeters and introduce more
error in estimates of plant abundance within the perimeter. Furthermore,
comprehensively mapping IEPs on a large landscape, even using large map
units, is generally cost-prohibitive.

Given the limitations of mapping, a few alternatives are available: 1)
develop statistically rigorous measures of IEP cover and frequency
(Elzinga et al. 2001), 2) limit mapping or sampling to suitable habitat
or likely points of invasion (Despain et al. 2001, Poon and Margules
2004, Rew et al. 2006), 3) combine sampling with a landscape modeling
approach to determine likelihood of occurrence (Chong et al. 2001,
Campell et al. 2002, Shafii et al. 2003, Rew et al. 2005, Chong et al.
2006, Barnett et al. 2007), and 4) map changes in IEP distribution and
abundance using remotely sensed imagery (Anderson et al. 1996, Everitt
et al. 1996, Lass et al. 1996, Lass et al. 2002, Lawrence et al. 2006).
The strengths and weaknesses of each approach should be evaluated
relative to the monitoring objectives.

1.  A precise measurement of IEP cover or frequency would provide a
    strong indicator of spread over time. However, the spatiotemporal
    variability in IEP populations, especially small populations, may
    preclude precise and powerful estimation. Additionally, a lack of
    spatial referencing prevents managers from determining if the plant
    may impact areas that protect particularly valuable resources.

2.  Targeting monitoring to invasion pathways or suitable habitat may
    greatly increase sampling efficiency and the precision of abundance
    and frequency estimates (see Chapters 6, 7, 8, and 12). However,
    this approach depends on the availability of an accurate habitat
    model. As with all models, sample size and methods affect model
    accuracy. Given the tendency of IEPs to expand their range, even
    accurate models may not reflect the invasion potential of a plant.
    The need to monitor multiple IEP species simultaneously can also
    diminish the practicality of this approach.

3.  Combined with spatially referenced habitat data, sampling may be
    used to map the probability of IEP occurrences on the landscape (see
    Chapters 6, 7, and 12). These maps show a generalized area where the
    species may be located and can estimate the percentage of potential
    habitat occupied. In this regard, the maps can provide a powerful
    assessment tool for management planning and for improving search or
    sampling efficiency (see #2). Once management decisions are made,
    managers must still survey high probability areas for exact IEP
    locations. Limited data can compromise the reliability of these
    habitat maps since small invasions provide little site-based habitat
    information, requiring extrapolation from other invaded sites or
    from the native range. The ability of such designs to determine
    change in IEP abundance or frequency may suffer from the same
    problems mentioned above (see #1).

4.  Successful identification of IEPs from remotely sensed imagery
    offers the potential to track changes in distribution and abundance
    over extremely large areas (see Chapter 6). This has been
    accomplished for a number of species in rangelands where
    interference from tree canopies is limited. Developing reliable
    reflectance signatures for IEPs may depend on distinct phenological
    or habitat characteristics, as well as relatively large patch sizes
    (Young and Schrader 2007). Signatures can only feasibly be developed
    for a relatively small number of species.

Given these mapping, sampling, and modeling challenges, we developed the
IEP monitoring protocol for the Heartland Inventory and Monitoring
Network with three objectives in mind. First, we decided to focus on a
large list of established and potential IEPs. Second, we sought to
maximize the amount of area covered with the time available. Third, we
opted to spatially reference IEP occurrences to the extent possible.

## MONITORING PROTOCOL

### Background 

In response to National Park Service (NPS) policies calling for a
strategic approach to invasive, exotic plant (IEP) management, the parks
in the Heartland Inventory and Monitoring Network (Heartland I&M
Network) recognized IEP management and monitoring as a network priority.
During the vital signs selection process in 2003, nine parks (CUVA,
EFMO, GWCA, HEHO, HOCU, HOME, LIBO, OZAR, PERI) identified IEPs as their
most important management issue, two parks (TAPR, WICR) identified IEPs
as their second most important management issue, and PIPE identified
IEPs as its third most important management issue (see Table 15.1 for
park codes, DeBacker et al. 2004). During this process, IEP monitoring
was recognized across all network parks as the most important shared
monitoring need. Recognizing the shared ecological characteristics of
network parks provides a basis for addressing common IEP management
issues.

The parks in the Heartland I&M Network vary with respect to size and
vegetation. Network parks include five parks less than 250 acres in
size, five parks from 750 to 5000 acres in size, and three parks greater
than 5000 acres in size (Table 15.2). The geographic range of the
network parks spans a number of physiographic provinces (Fenneman 1946),
ecoregions (Bailey 1995), and potential natural vegetation types
(Kuchler 1985). Based on these classifications, the thirteen network
park units were grouped to reflect common ecological conditions for
planning IEP monitoring (Table 15.2).

Table 15.1. Park codes for Heartland Inventory and Monitoring Network
parks.

  ----------------------------------------------------- -----------------
  **Park Units**                                        **Park Code**

  Cuyahoga Valley National Park                         CUVA

  Effigy Mounds National Monument                       EFMO

  Hopewell Culture National Historic Park               HOCU

  Lincoln Boyhood National Memorial                     LIBO

  Arkansas Post National Memorial                       ARPO

  Hot Springs National Park                             HOSP

  George Washington Carver National Monument            GWCA

  Pea Ridge National Military Park                      PERI

  Wilson's Creek National Battlefield                   WICR

  Homestead National Monument of America                HOME

  Herbert Hoover National Historic Site                 HEHO

  Pipestone National Monument                           PIPE

  Tallgrass Prairie National Preserve                   TAPR
  ----------------------------------------------------- -----------------

An overview of park species lists and planning documents highlights
three points: 1) network parks support vegetation resources of
tremendous cultural and natural resource significance; 2) these parks
contain some of the most recalcitrant IEPs found in forests (garlic
mustard, kudzu, Japanese honeysuckle, multiflora rose, privet),
grasslands (sericea lespedeza, smooth brome, leafy spurge, sweet
clover), and wetlands (reed canary grass, common reed, purple
loosestrife, Japanese knotweed); and 3) the vegetation in these parks is
susceptible to numerous plant invasions (see Tables 15.5 and 15.6 for
scientific names). The ability of IEPs to spread rapidly, displace
native plants, and in some cases, interrupt ecological processes is
amply documented. The need to detect new invasions and track existing
invasions necessitated the development of the IEP monitoring protocol
for the Heartland I&M Network.

### Monitoring Objectives

Given the need to provide early detection of potential IEPs and the size
of network parks, the Heartland I&M Network opted to allocate available
sampling effort to maximize the area searched. With this approach and
the available sampling effort in mind, we developed realistic objectives
for the IEP monitoring protocol. The monitoring objectives are:

1.  Annually update a watch list of IEP species known to occur on
    network parks and a watch list of IEP species that may invade
    network parks in the future.

2.  Provide early detection monitoring for all IEP species on the watch
    list.

3.  Determine patterns of exotic plant invasion on network parks.

4.  Estimate the abundance of IEP species on each park.

5.  To the extent possible, identify temporal changes in the
    distribution and abundance of IEP species known to occur on network
    parks.

Table 15.2. Ecological grouping of Heartland Inventory and Monitoring
Network parks.

  ------------------------ ------------------------------------ -----------
  **Ecological Group**     **Park Units**                       **Acres**

  Eastern Deciduous Forest Cuyahoga Valley National Park        32,861
  Parks                                                         

                           Effigy Mounds National Monument      2,526

                           Hopewell Culture National Historic   1,170
                           Park                                 

                           Lincoln Boyhood National Memorial    200

  Mississippi Embayment    Arkansas Post National Memorial      758
  Park                                                          

  Ouachita Mountain Park   Hot Springs National Park            5,550

  Ozark Plateau Parks      George Washington Carver National    210
                           Monument                             

                           Pea Ridge National Military Park     4,300

                           Wilson's Creek National Battlefield  1,750

  Tallgrass Prairie Parks  Herbert Hoover National Historic     187
                           Site                                 

                           Homestead National Monument of       195
                           America                              

                           Pipestone National Monument          282

                           Tallgrass Prairie National Preserve  10,894
  ------------------------ ------------------------------------ -----------

### Invasive Exotic Plant Watch Lists

A great number of exotic plant prioritization and risk assessment
protocols have been developed, often designed for particular purposes
and/or specific geographic regions (Chapter 5). The Alien Plant Ranking
System evaluates plant life-history, ecological effects, and management
feasibility to prioritize control efforts on parks (Hiebert and
Stubbendieck 1993). NatureServe's I-ranks use extensive biogeographical
information as criteria to rank plant invasiveness at local, regional,
national, and global scales (Morse et al. 2004). The California Exotic
Pest Plant Council list relies heavily on expert opinion to assess
ecosystem effects and plant invasion potential (Warner et al. 2003). The
Invasive Plants Association of Wisconsin's Working List of the Invasive
Plants of Wisconsin was developed through a systematic survey of plant
experts (IPAW 2003). Each of these systems provides a well-conceived
model for ranking invasive plants. Other less formal lists draw on
experience across a range of resource management disciplines. As an
example, state and federal noxious weed lists have historically targeted
agricultural pest plants.

We developed an exotic plant prioritization database (EPPdb) to gather
information that assisted us in prioritizing IEP monitoring on national
parks. The EPPdb provides four key pieces of information that network
staff evaluate for designating invasive plants as a high priority: 1) a
list of species that are considered exotic and/or invasive based on
numerous state and national lists (see lists below), 2) a list of exotic
plants in each state (based on USDA Plants database and state lists), 3)
a list of exotic plants in each park (based on NPSpecies database), and
4) a designation of exotic plants as high or low priority based on a
consensus of the state and regional lists. The priority ranking is an
attempt to distinguish exotic plants that are likely to be highly
invasive in natural areas from exotic plants that are naturalized and/or
highly disturbance-dependent and less likely to invade intact natural
areas. For the purposes of this protocol, high priority plants are
considered IEPs.

The following exotic plant lists were consulted:

1.  Missouri Vegetation Control Manual by the Missouri Department of
    Conservation (<http://www.mdc.mo.gov/nathis/exotic/vegman/>).

2.  Illinois Native Plant Society List
    (<http://www.inhs.uiuc.edu/inps/exotics.htm>).

3.  Invasive Plants Association of Wisconsin Working List
    (<http://www.ipaw.org/newsletters/issue4.pdf>).

4.  Invasive Plants in Arkansas\' Natural Areas, a tentative list
    obtained from Theo Witsell, Arkansas Natural Heritage Program.

5.  Nonnative Invasive Plants of Southern Forests by James H. Miller,
    United States Forest Service
    (<http://www.invasive.org/eastern/srs/>).

6.  Nebraska watch list of plants that are highly invasive and difficult
    to control by Nebraska Weed Control Association
    (<http://www.neweed.org/watchlist/wlindex.htm>).

7.  Minnesota Department of Natural Resources
    (<http://www.dnr.state.mn.us/invasives/index.htm>).

8.  Ohio\'s Top Ten Invasives
    (<http://www.dnr.state.oh.us/dnap/invasive/invasivebrochure.htm>)
    and exotic plants with fact sheets
    (<http://www.dnr.state.oh.us/dnap/invasive/>).

9.  Invasive Plants in Indiana, a joint publication of the of Indiana
    Department of Natural Resources, The Nature Conservancy, Indiana
    Native Plant Society, United States Forest Service, Indiana Academy
    of Science (<http://www.inpaws.org/InvasivePlants.pdf>).

10. Missouri Exotic Pest Plant List from the Missouri Botanical Garden
    (<http://www.mobot.org/MOBOT/research/mepp/ratings1.html>). Ranks
    A-D.

11. Plant Conservation Alliance list for plants occurring in AR, IA, IL,
    IN, KS, MO, MN, NE, OH
    (<http://www.nps.gov/plants/alien/list/all.htm>).

12. NatureServe's Data on U.S. Invasive Species: Impact Assessments with
    Invasive Ranks (I-Ranks) for 452 species
    (<http://www.natureserve.org/explorer/>).

13. [Invasive Plants of the Upper Midwest]{.underline} by E.J.
    Czarpata, 2005. Ranks: A=major concern, B=lesser concern,
    C=potential concern.

14. Invasive Plants in the Chicago Region from the Chicago Botanic
    Garden:
    (<http://www.chicagobotanic.org/research/conservation/invasive_chicago.html>).
    Ranks: E=evaluate, R=remove, P=phase-out, W=watch list.

15. New Invasive Plants in the Midwest list from the Midwest Invasive
    Plant Network ([www.mipn.org](http://www.mipn.org/)).

Within the EPPdb, the designation of an exotic plant as a high priority
(i.e., IEP) species is based on a consensus of the various lists. All
plant species with an I-rank of H and all plants on the early detection
oriented New Invasive Plants in the Midwest list were marked as a high
priority. Beyond these lists, the high priority designation was reserved
for exotic plants included on a number of lists with some caveats. The
Invasive Plants in Arkansas Natural Areas list and Nonnative Plants of
Southern Forests list were given greater consideration because only
these lists cover many of the IEPs with southern affinities. The I-rank
was also considered strongly in high priority designations. Although the
prioritization is subjective, this approach offers some advantages: 1)
the decision is based on multiple lists and does not rely on any single
listing or ranking approach and 2) the decision does not use a scoring
system in an attempt to make a subjective approach seem more objective.
Rather, this system supposes that priority ranks will be revisited and
modified over time based on new information, but assumes that a core of
the most problematic plants will continue to be designated as high
priority IEPs. Focusing on a large number of species also requires
retaining staff or contracting botanists with exceptional plant
taxonomic skills and a tolerance for difficult field conditions.

The modular structure of the EPPdb and the use of the best existing
databases are its primary advantages. The structure allows data tables
to be individually updated as needed. Metadata for state and regional
lists are documented. USDA Plants database and NPSpecies use the
Integrated Taxonomic Information System (ITIS), the national standard
for taxonomic information. NPSpecies is the standard I&M database for
species occurrence records in the National Park System. The
certification process for NPSpecies increases the accuracy of records
and maintains current nomenclature. Species occurrence data from all
park projects should eventually be included in NPSpecies. Furthermore,
the EPPdb prevents the proliferation of ad hoc exotic plant lists with
unverified source data.

Using the EPPdb, two exotic plant watch lists are generated for each
park. The first list, referred to as the "early detection watch list",
consists of high priority exotic plants that occur in the state (based
on USDA Plants), but are not known to occur on the park (based on
NPSpecies). The second list, referred to as the "park-established watch
list", is a list of high priority exotic plants documented in NPSpecies
as occurring in the park. As their names suggest, these two lists are
developed to detect new invasions and monitor established plant
invasions, respectively.

A vulnerability of the EPPdb is that the USDA Plants and NPSpecies
databases may contain mistakes or omissions. For example, USDA Plants
may not report a plant as occurring in a state where a manger knows the
plant to occur. Alternatively, a manager may identify an exotic plant on
the park that has not been documented in NPSpecies. Finally, a resource
manager may disagree with the priority designation in the EPPdb. For
this reason, a third list, referred to as the "park-based watch list",
allows park managers to request monitoring for additional IEPs. The
park-based watch list also allows managers to add IEPs known to occur on
lands adjacent to the park. Such plants are important candidates for
early detection monitoring. The three lists---the early detection watch
list, the park-established watch list, and the park-based watch
list---ensure that IEP monitoring is well prioritized on network parks.

While strong arguments can be made that monitoring should focus only on
IEPs that will be actively managed in a park, IEP management priorities
are likely to shift over time based on spread, resources threatened, and
feasibility of control. With these factors in flux, long-term monitoring
that focuses on a narrow list of species of immediate concern may fail
to provide critical information on IEP distribution and abundance. On
the other hand, while more detailed prioritization is possible, this
basic approach eliminates the need for more exhaustive, time-consuming,
and often redundant assessments of each exotic plant species. As other
organizations prioritize exotic plants based on life-history and
management feasibility, we will incorporate this information in the
EPPdb. As the lists are updated to include the most current rankings,
new species will be added to the list and some species may be removed.
Managers should be aware, however, that these lists are inevitably
imperfect, requiring managers and/or volunteers to watch for other
unlisted IEPs during routine management activities.

### Reference Frames

The reference frames directing monitoring were designed to focus on
accessible natural and restored areas (see Chapter 8). Areas requiring
special equipment for access were excluded from the reference frame. In
some cases, reference frames were much smaller than the park acreage.
For example, much of the acreage at ARPO was flooded following
downstream construction of a dam. The decision to focus on natural and
restored areas was based on the following reasons. First, because
managers are generally aware that disturbed areas support numerous
weeds, we determined that the limited resources available for monitoring
would be best allocated towards intact natural areas. Second, some IEPs
are well established on network parks, but do not show a propensity to
invade intact natural areas, particularly forests. Third, IEPs are
established (and presumably establish) throughout natural areas on
network parks, possibly due to the disturbance history and/or relatively
small size of many Heartland Network parks. Finally, as a logistical
consideration, some highly disturbed areas in the network, especially
early successional forests, are virtually impenetrable. The reference
frame for each park was created in a GIS to define the area of interest
(i.e., statistical population). Reference frames were developed
following field reconnaissance, consultation with park resource
managers, and review of vegetation maps and remotely sensed images.

### Field Methods

The sampling design was selected to balance multiple objectives,
including identifying high priority IEPs, focusing on natural and
restored areas, ensuring good spatial coverage, detecting new plant
invasions, monitoring multiple species simultaneously, tracking changes
in abundance and distribution of existing invasions, and addressing
management priorities, while working within program capacity.
Negotiating between these often competing objectives led to different
approaches for small parks (reference frame [\<]{.underline} 350 acres)
and large parks (reference frame \> 350 acres).

Two types of sampling units were developed for parks with reference
frames of different sizes (Note that this is [not]{.underline} the same
as total park size.): 1) exotic plant search units on small parks
(reference frame \<350 acres, see Figure 15.1 for example) and 2) line
transects on large parks (reference frame [\>]{.underline}350 acres, see
Figure 15.2 for example). Small parks included ARPO, GWCA, HEHO, HOCU,
HOME, LIBO, and PIPE. Large parks included CUVA, EFMO, HOSP, PERI, TAPR,
and WICR.

![](media/image1.jpeg){width="6.459722222222222in"
height="8.370833333333334in"}

Figure 15.1. Invasive exotic plant search units at Arkansas Post
National Memorial, Main Unit.

![](media/image2.jpeg){width="6.561805555555556in"
height="8.502777777777778in"}

Figure 15.2. Invasive exotic plant line transects at Pea Ridge National
Military Park.

For small parks (reference frame [\<]{.underline}350 acres), exotic
plant search units were created by dividing park management units in to
units that were generally 1 to 3 acres in size with 2 acres as the
target size (see Figure 15.1 for example at ARPO). Surveyors made three
equidistant passes through each unit, focusing on an approximately
6-meter (m) belt transect, and estimated the cover of each IEP
encountered using the following cover scale: 0=0, 1=0.1-0.9 m^2^,
2=1-9.9 m^2^, 3=10-49.9 m^2^, 4= 50-99.9 m^2^, 5=100-499.9 m^2^, 6=
499.9-999.9 m^2^, 7=1000-4999.9 m^2^, 8=5000-9999.9 m^2^. Assuming a
perfectly square 2-acre plot, surveyors assessed approximately 20% of
the park reference frame. Surveyors also had discretion to search a
larger belt if feasible, to search additional areas within the search
unit, and to target locations likely to support exotic plants (e.g.,
field edges, roads). The cover estimate assigned for each plant species
represented all observations of the plant within the search unit, not
only those within the belt. While this complicates quantitative
comparisons of plant cover over time, the benefit of more information on
invasive exotic plant location and cover are the priority. The time
required to complete monitoring depends on park size and access
logistics (Table 15.3).

Table 15.3: Number of exotic plant search units on small parks
(reference frame [\<]{.underline}350 acres).

  ---------- -------------------- ------------------- ----------------------
             **Reference Frame    **Number of Exotic  **Estimated
             Size (acres)**       Plant Search        Person-Days**
                                  Units**             

  **ARPO**   339                  169                 12

  **GWCA**   188                  97                  6

  **HEHO**   82                   50                  4.5

  **HOCU**   \*                   Not available\*     \*

  **HOME**   168                  82                  6

  **LIBO**   153                  76                  6

  **PIPE**   278                  114                 9
  ---------- -------------------- ------------------- ----------------------

\* = Due to ongoing restoration, number of exotic plant search units is
not known.

For large parks (reference frame\>350 acres), systematically located
line transects were established in a GIS using a random start (see
Figure 15.2 for example). This process created contiguous line transects
across the entire park, which increased sampling efficiency. The
distance between lines and the length of line transects was 200 m on
EFMO and WICR and 400 m on CUVA, HOSP, PERI, and TAPR. Surveyors
recorded and estimated the cover of each IEP encountered in an
approximately 6-m belt transect using the following cover scale: 0=0,
1=0.1-0.9 m^2^, 2=1-9.9 m^2^, 3=10-49.9 m^2^, 4= 50-99.9 m^2^,
5=100-499.9 m^2^, 6= 499.9-999.9 m^2^, 7=1000-4999.9 m^2^, 8=5000-9999.9
m^2^. Assuming that surveyors estimate plant cover in a 6-m belt, 3% and
6% of the park reference frame will be surveyed using 200 m and 400 m
transects, respectively. Surveyors also had discretion to search areas
away from the transect, but within a perpendicular distance of half the
transect length, targeting locations likely to support exotic plants
(e.g., field edges, roads). The cover estimate assigned for each plant
species represented all observations of the plant, not only those within
the belt. While this complicates quantitative comparisons of plant cover
over time, the benefit of more information on invasive exotic plant
location and cover are the priority. The time required to complete
monitoring depends on park size and access logistics (Table 15.4).

IEPs will be monitored at network parks on a five-year interval.
Monitoring on parks will be staggered over the five-year period. Field
work will be balanced to the extent possible among years. In general,
IEPs at a particular park will be monitored at the same time of year.
Consistency in timing should maintain consistency in detection
probabilities and cover estimates for most species. For many species,
sampling any time during June-September is not expected to drastically
alter monitoring results. However, sampling in the late summer and
autumn may prevent detection and/or identification of spring blooming
exotic plants such as dame's rocket (*Hesperis matronalis*), plants in
the families *Brassicaceae* and *Caryophyllaceae*, and exotic cool
season grasses such as Kentucky bluegrass (*Poa pratensis*), brome
grasses (*Bromus* spp), and fescues (*Lolium* spp). The semi-evergreen
nature of some species, such as *Lonicera japonica*, allows IEP
monitoring to continue through autumn. Species such as garlic mustard
(*Alliaria petiolata*) may only be effectively detected prior to
leaf-out or following leaf-fall.

Table 15.4: Number of line transects for large parks (reference frame
\>350 acres).

  --------------- --------------- --------------- ------------ -----------------
                  **Reference     **Number of     **Transect   **Estimated
                  Frame Size      Line            Miles**      Person-Days**
                  (acres)**       Transects**                  

  **CUVA (400     26,240.6        822             161.6        50
  m)**                                                         

  **EFMO (200     2,304.7         272             30.5         16
  m)**                                                         

  **HOSP (400     Not available\* \*              \*           \*
  m)**                                                         

  **PERI (400     3,123.7         102             22.5         12
  m)**                                                         

  **TAPR (400     10,734.6        301             71.5         18
  m)**                                                         

  **WICR (200     1,350.2         171             17           9
  m)**                                                         
  --------------- --------------- --------------- ------------ -----------------

\* = Reference frame development still in progress.

Because detecting new invasions is often like finding a needle in a
haystack, the protocol emphasizes the quick collection of IEP location
and abundance data. Maximizing the area searched provides the greatest
opportunity to find new invasions on parks, while also maximizing
encounter of established IEPs. For small parks, a relatively high
percentage of the ground is covered to create a map of the plant
locations on the park. Even on larger parks, the method covers a greater
portion of the park land base than is typically covered using sampling
approaches. The flexibility to observe areas at some distance from the
belt transect will allow surveyors to detect additional IEPs. At the
same time, the sampling units (search units or line transects) are
permanent, which should reduce sample variance to improve detection of
change in IEP abundance and distribution over time. By default, absence
data (i.e., negative data) are collected as IEP search routes are known.
Taken together, the map and cover and frequency estimates provide
critical information for designing IEP control strategies.

Prior to adopting this monitoring protocol, we also assessed its
weaknesses. As with any sampling or mapping approach, plants may be
overlooked due, first and foremost, to incomplete coverage of the sample
area, as well as differences in taxonomic expertise and low
detectability due to plant growth-form or surrounding vegetation.
Changes in the distribution (i.e., frequency) of IEPs must be
interpreted with this in mind. Substantial measurement and observer
error associated with visual cover class estimates applied at such a
large scale will also reduce resolution to detect change in cover over
time. The design is not necessarily suited to assess the effectiveness
of management treatments applied at small scales or to compare the
effectiveness of control treatments. For example, a replicated study
would be required to determine whether glyphosate or mowing provided
more effective treatment of smooth brome. However, as the spatial scale
of control increases with cumulative management actions, assessment of
management effectiveness becomes increasingly feasible with this design.

[]{.mark}

### Data Management

The exotic plant monitoring protocol requires two databases: 1) the
exotic plant prioritization database (EPPdb) and 2) the exotic plant
information geodatabase (EPIgdb). Microsoft Access 2003 is the primary
software environment for these databases. ESRI ArcInfo 9 is used to view
and manipulate spatial data in the EPIgdb.

#### Exotic Plant Prioritization Database

The EPPdb consists of three primary tables. One table, referred to as
the regional exotic plant list, compiles the data from national,
regional, and state exotic plant lists and designates high priority
plants. Two tables provide data from the USDA Plants database and the
NPSpecies database, respectively. The USDA Plants database provides the
exotic plant distribution data for the eight states with network parks.
The NPSpecies database provides occurrence data for exotic plants on
network parks.

#### Exotic Plant Information Geodatabase 

The EPIgdb includes the feature classes (spatial information) of the
search units and line transects. The single primary table in the EPIgdb
includes the field data: location of data collection (LocationID), time
of data collection (PeriodID), taxon, and cover class. A combination of
the LocationID and PeriodID serves as the unique identifier that allows
tables to be related to each other and to the feature classes.

### Assessment Following Protocol Implementation

The Heartland I&M Network implemented monitoring in 2006. We conducted
surveys on two parks with network staff. We also completed a contract
for surveys on seven additional parks. In the process, three points
became obvious. First, in order to monitor for the early detection of
IEPs and for established IEPs simultaneously, the field botanists must
be excellent taxonomists. As a rule, the botanist must essentially be
able to identify all vascular plants encountered. This skill allows the
botanist to quickly find established IEPs and to focus carefully on
unusual species that may be IEPs included on the early detection watch
list. Secondly, we encountered difficulty with the assignment of cover
classes. In order to accurately estimate cover, the observer should keep
in mind the scale at which they are working. For example, if an observer
focuses on an approximately 6-m wide belt along a 200 m transect, the
maximum cover for an invasive plant in that area is 1200 m^2^. We
suspect that cover was overestimated in some instances. Finally,
observers must be comfortable working in demanding field conditions. The
line transects were generally all accessible, but required working
patiently while navigating through dense vegetation in hot weather.

## An Example Report: Invasive Exotic Plant Monitoring at Wilson's Creek National Battlefield in Year 1 (2006)

### Introduction

#### Invasive Exotic Plant Management at Wilson's Creek National Battelfield 

Invasive exotic plant management is a high management priority at
Wilson's Creek National Battlefield. While a complete history of park
invasive exotic plant management issues is beyond the scope of this
report, a few important highlights are given:

1.  Invasive exotic plants, such as annual brome (*Bromus* spp.), hop
    clover (*Trifolium campestre*), and sericea lespedeza (*Lespedeza
    cuneata*) occur in glades supporting the federally endangered
    Missouri bladderpod (*Lesquerella filiformis*).

2.  Invasive plants, such as Kentucky bluegrass and sericea lespedeza,
    have invaded restored native warm season grasslands.

3.  Early successional forests at the park support numerous invasive
    exotic plant species.

### Methods

#### Watch Lists

The invasive exotic plants on three watch lists were sought during
monitoring (Table 15.5). Invasive exotic plants not known to occur on
the park based on NPSpecies (the national NPS database for plant
occurrence registration) constitute the early detection watch list.
Invasive exotic plants known to occur on the park based on NPSpecies
constitute the park-established watch list. Invasive exotic plants from
the park-based watch list included plants selected by park managers or
network staff which may not have been included on the other lists due to
incomplete information in NPSpecies (e.g., not documented) or USDA
Plants (e.g., state distribution information inaccurate) databases or
due to differing opinions regarding network designation of a plant as a
high priority. While aquatic species are listed on the watch lists,
terrestrial plants were the focus of this survey. Aquatic plants were
documented occasionally.

#### Field Methods

Invasive exotic plant species on designated watch lists (Table 15.5)
were sought in high priority areas on Wilson's Creek National
Battlefield (Figure 15.3). Dan Tenaglia, the contract botanist for this
project, used a Thales GPS unit to navigate along 200 m line transects,
identified invasive exotic plants in an approximately 6-m belt, and
attributed a coarse cover value to each species (0=0, 1=0.1-0.9 m^2^,
2=1-9.9 m^2^, 3=10-49.9 m^2^, 4= 50-99.9 m^2^, 5=100-499.9 m^2^, 6=
499.9-999.9 m^2^, 7=1000-4999.9 m^2^, 8=5000-9999.9 m^2^, and
9=10,000-14999.9 m^2^). A total of 173 transects were surveyed at
Wilson's Creek National Battlefield. Of these, 100 transects were 200 m
in length, while 40 were 0-99 m in length and 31 were 100-199 m in
length. The observer had discretion to search a larger belt if feasible,
to search additional areas up to 100 m perpendicular distance from the
transect, to target locations likely to support exotic plants (e.g.,
field edges, roads), and to circumvent extremely difficult or hazardous
terrain when needed. However, in most cases, the observer maintained the
established line transect. Cover was estimated for all plants observed
while navigating along the transect (i.e., not restricted to the 6-m
belt).

Table 15.5. Watch lists for Wilson's Creek National Battlefield.

  ---------------- ---------------- -------------------- -------------- -------------- -----------
  **Early                           **Park-Established                  **Park-Based   
  Detection Watch                   Watch List**                        Watch List**   
  List**                                                                               

  *Acer ginnala*   Amur maple       *Arctium minus*      Lesser burdock *Bromus        Bald brome
                                                                        racemosus*     

  *Ailanthus       Tree-of-heaven   *Bromus inermis*     Smooth brome   *Ligustrum     Common
  altissima*                                                            vulgare*       privet

  *Albizia         Silktree         *Bromus sterilis*    Poverty brome  *Lolium        Perennial
  julibrissin*                                                          perenne*       ryegrass

  *Alliaria        Garlic mustard   *Bromus tectorum*    Cheatgrass     *Vicia         Winter
  petiolata*                                                            villosa*       vetch

  *Alnus           European alder   *Carduus nutans*     Nodding                       
  glutinosa*                                             plumeless                     
                                                         thistle                       

  *Arundo donax*   Giant reed       *Dactylis glomerata* Orchardgrass                  

  *Azolla* spp.    Mosquitofern     *Dipsacus fullonum*  Fuller's                      
                                                         teasel                        

  *Berberis        Japanese         *Hedera helix*       English ivy                   
  thunbergii*      barberry                                                            

  *Bothriochloa    Caucasian        *Hesperis            Dames rocket                  
  bladhii*         bluestem         matronalis*                                        

  *Celastrus       Oriental         *Holcus lanatus*     Common                        
  orbiculatus*     bittersweet                           velvetgrass                   

  *Centaurea       Spotted knapweed *Humulus japonicus*  Japanese hop                  
  stoebe* ssp.                                                                         
  *micranthos*                                                                         

  *Centaurea       Yellow           *Lespedeza cuneata*  Sericea                       
  solstitialis*    star-thistle                          lespedeza                     

  *Cirsium         Canada thistle   *Lonicera japonica*  Japanese                      
  arvense*                                               honeysuckle                   

  *Cirsium         Bull thistle     *Maclura pomifera*   Osage orange                  
  vulgare*                                                                             

  *Cornus foemina* Stiff dogwood    *Melilotus           Sweetclover                   
                                    officinalis*                                       

  *Cynanchum       Black            *Morus alba*         White mulberry                
  louiseae*        swallowwort                                                         

  *Cynanchum       European         *Phalaris            Reed                          
  rossicum*        swallowwort      arundinacea*         canarygrass                   

  *Dioscorea       Chinese yam      *Plantago            Narrowleaf                    
  oppositifolia*                    lanceolata*          plantain                      

  *Dipsacus        Cutleaf teasel   *Poa compressa*      Canada                        
  laciniatus*                                            bluegrass                     

  *Egeria densa*   Brazilian        *Poa pratensis*      Kentucky                      
                   waterweed                             bluegrass                     

  *Eichhornia      Common water     *Potentilla recta*   Sulphur                       
  crassipes*       hyacinth                              cinquefoil                    

  *Elaeagnus       Russian olive    *Rhus glabra*        Smooth sumac                  
  angustifolia*                                                                        

  *Elaeagnus       Autumn olive     *Robinia             Black locust                  
  umbellata*                        pseudoacacia*                                      

  *Euonymus alata* Burningbush      *Rosa multiflora*    Multiflora                    
                                                         rose                          

  *Euonymus        Winter creeper   *Schedonorus         Tall fescue                   
  fortunei*                         phoenix*                                           

  *Euphorbia       Leafy spurge     *Schedonorus         Meadow fescue                 
  esula*                            pratensis*                                         

  *Glechoma        Ground ivy       *Sorghum halepense*  Johnsongrass                  
  hederacea*                                                                           

  *Lespedeza       Shrub lespedeza  *Torilis arvensis*   Spreading                     
  bicolor*                                               hedgeparsley                  

  *Ligustrum       Chinese privet   *Torilis japonica*   Erect                         
  sinense*                                               hedgeparsley                  
  ---------------- ---------------- -------------------- -------------- -------------- -----------

Table 15.5 (continued). Watch lists for Wilson's Creek National
Battlefield.

  --------------- ---------------- -------------------- ----------- -------------- ----------
  **Early                          **Park-Established               **Park-Based   
  Detection Watch                  Watch List**                     Watch List**   
  List**                                                                           

  *Lonicera       Amur honeysuckle *Ulmus pumila*       Siberian                   
  maackii*                                              elm                        

  *Lonicera       Morrow's         *Verbascum thapsus*  Common                     
  morrowii*       honeysuckle                           mullein                    

  *Lotus          Bird's-foot                                                      
  corniculatus*   trefoil                                                          

  *Lysimachia     Creeping jenny                                                   
  nummularia*                                                                      

  *Lythrum        Purple                                                           
  salicaria*      loosestrife                                                      

  *Melia          Chinaberrytree                                                   
  azedarach*                                                                       

  *Microstegium   Nepalese                                                         
  vimineum*       browntop                                                         

  *Miscanthus     Chinese                                                          
  sinensis*       silvergrass                                                      

  *Myriophyllum   Parrot feather                                                   
  aquaticum*      watermilfoil                                                     

  *Myriophyllum   Eurasian                                                         
  spicatum*       watermilfoil                                                     

  *Pastinaca      Wild parsnip                                                     
  sativa*                                                                          

  *Paulownia      Princesstree                                                     
  tomentosa*                                                                       

  *Phragmites     Common reed                                                      
  australis*                                                                       

  *Polygonum      Japanese                                                         
  cuspidatum*     knotweed                                                         

  *Populus alba*  White poplar                                                     

  *Populus        Quaking aspen                                                    
  tremuloides*                                                                     

  *Potamogeton    Curly pondweed                                                   
  crispus*                                                                         

  *Pueraria       Kudzu                                                            
  montana var.                                                                     
  lobata*                                                                          

  *Rhamnus        Common buckthorn                                                 
  cathartica*                                                                      

  *Securigera     Crownvetch                                                       
  varia*                                                                           

  *Sesbania       Bigpod sesbania                                                  
  herbacea*                                                                        

  *Solanum        Climbing                                                         
  dulcamara*      nightshade                                                       

  *Spiraea        Japanese                                                         
  japonica*       meadowsweet                                                      

  *Typha          Narrowleaf                                                       
  angustifolia*   cattail                                                          

  *Viburnum       European                                                         
  opulus*         cranberrybush                                                    

  *Vinca minor*   Common                                                           
                  periwinkle                                                       

  *Wisteria       Chinese wisteria                                                 
  sinensis*                                                                        
  --------------- ---------------- -------------------- ----------- -------------- ----------

![](media/image3.jpeg){width="6.323611111111111in"
height="8.183333333333334in"}

Figure 15.3. Invasive exotic plant line transects (blue) at Wilson's
Creek National Battlefield. The blue transects indicate the search
locations for invasive exotic plants in 2006.

#### Analytical Methods

Data analyses involved simple displays, as well as calculation of plant
frequency and cover. The invasive exotic plants encountered on Wilson's
Creek National Battlefield were attributed to line transects in a GIS.
Polygons surrounding occupied line transects were highlighted on maps
for each invasive exotic plant encountered (see Figures 15.4-15.6 for
examples). Note that entire polygons were not fully searched. The
park-wide frequency of invasive exotic plants was calculated as the
percentage of occupied transects. A park-wide cover range was estimated
using the high and low values of the cover classes for each invasive
exotic plant encountered, assuming that 6 % of the park was searched and
that the areas searched were representative of the entire park.

#### Invasiveness Ranks

In order to provide additional information on the ecological impact and
feasibility of control, the ecological impact and general management
difficulty sub-ranks that constitute the invasiveness rank (I-rank),
determined by NatureServe (Morse et al. 2004), were listed when
available. The ecological impact characterizes the effect of the plant
on ecosystem process, community composition and structure, native plant
and animal populations, and the conservation significance of threatened
biodiversity. General management difficulty ranks are assigned based on
the resources and time generally required to control a plant, the
non-target effects of control on native populations, and the
accessibility of invaded sites. Sub-ranks are given as high (H), medium
(M), low (L), insignificant (I), unknown (U), or a combination of ranks.

### Results and Discussion

In 2006, a total of 35 invasive exotic plant taxa were found during the
survey at Wilson's Creek National Battlefield (Table 15.6). Of these
plants, 22 taxa were known to occur on the park based on the NPSpecies
database. Bald brome (*Bromus racemosus*) was not previously included on
any watch list. Bald brome is not designated as a high priority for the
entire network, but is wide-spread at WICR. These species will be added
to the park-based watch list. The species on the early detection list
will be entered in NPSpecies and should subsequently be included on the
park-established watch list.

The distribution and abundance of the invasive exotic plant species at
Wilson's Creek National Battlefield varied widely. Four species were
widespread and very abundant (cover greater than 60 acres): bald brome,
sericea lespedeza, Japanese honeysuckle, and Osage orange. Smooth brome
was also very abundant, but restricted to a single section of the park.
Fescue, smooth sumac, multiflora rose, and hedgeparsley were moderately
abundant (cover 2 -- 25 acres) and distributed widely on the park. Amur
honeysuckle was moderately abundant, but restricted to a few locations
on the park. The remaining 26 species occurred in less than 18 % of
transects and covered less than 1 acre. The relatively low cover of
these species is encouraging and suggests that eradication or at least
successful control is likely to be a viable management option.

Based on field observations, we believe that the cover classes of
invasive exotic plant species, especially those with high cover
estimates, were systematically overestimated. Such overestimation likely
resulted from difficulty estimating high cover over the 200 m transects.
While such overestimation may complicate detection of change in the
future, the relative size of cover estimates provides a strong basis for
invasive exotic plant management planning.

Three species were noted as having unambiguously high ecological impact:
cheatgrass, crownvetch, and autumn olive (Table 15.6). Five species were
characterized as having at least a medium ecological impact. The
remaining species had ambiguous medium-low ecological impacts or less,
including three species with low or insignificant impacts. Recognizing
that the feasibility of control often strongly influences decisions
regarding invasive exotic plant management, crownvetch and autumn olive
with high ecological impacts were noted as having low management
difficulty. Controlling these species will likely provide a high benefit
for the management costs.

In summary, this report provides information on invasive exotic plant
abundance and distribution as well as ecological impacts and management
difficulty to assist park natural resource managers in planning invasive
exotic plant management. The following links may further assist
managers:
<http://www.nature.nps.gov/im/units/htln/monitoring/projects/inp.htm>
and <http://www.natureserve.org/explorer/>.

![](media/image4.jpeg){width="6.136805555555555in"
height="7.963888888888889in"}

Figure 15.4. Abundance and distribution of *Ailanthus altissima*
(tree-of- heaven) at Wilson's Creek National Battlefield, 2006. Cover
classes are as follows: 1=0.1-0.9 m^2^, 2=1-9.9 m^2^, 3=10-49.9 m^2^, 4=
50-99.9 m^2^, 5=100-499.9 m^2^, 6= 499.9-999.9 m^2^, 7=1,000-4,999.9
m^2^, 8=5,000-9,999.9 m^2^, and 9=10,000-14,999.9. See Figure 15.3 for
areas not searched.

![](media/image5.jpeg){width="6.170833333333333in"
height="7.842361111111111in"}

Figure 15.5. Abundance and distribution of *Bromus inermis* (smooth
brome) at Wilson's Creek National Battlefield, 2006. Cover classes are
as follows: 1=0.1-0.9 m^2^, 2=1-9.9 m^2^, 3=10-49.9 m^2^, 4= 50-99.9
m^2^, 5=100-499.9 m^2^, 6= 499.9-999.9 m^2^, 7=1,000-4,999.9 m^2^,
8=5,000-9,999.9 m^2^, and 9=10,000-14,999.9. See Figure 15.3 for areas
not searched.

![](media/image6.jpeg){width="5.85625in" height="7.622916666666667in"}

Figure 15.6. Abundance and distribution of *Lespedeza cuneata* (sericea
lespedeza) at Wilson's Creek National Battlefield, 2006. Cover classes
are as follows: 1=0.1-0.9 m^2^, 2=1-9.9 m^2^, 3=10-49.9 m^2^, 4= 50-99.9
m^2^, 5=100-499.9 m^2^, 6= 499.9-999.9 m^2^, 7=1,000-4,999.9 m^2^,
8=5,000-9,999.9 m^2^, and 9=10,000-14,999.9. See Figure 15.3 for areas
not searched.

> Table 15.6. Overview of invasive exotic plants found on Wilson's Creek
> National Battlefield. Ecological impact and general management
> difficulty based on NatureServe I-Rank subranks, Morse et al. 2004.
> Subranks are given as high (H), medium (M), low (L), insignificant
> (I), unknown (U), a range of ranks (indicated by /), or not available
> (\--).

  --------------- -------------- ------------------ ------------- ------------- -------------- --------------
  **Scientific    **Common       **Watch List**     **Park-wide   **Frequency   **Ecological   **Management
  Name**          Name**                            Cover         (percent)**   Impact**       Difficulty**
                                                    (acres)**                                  

  *Lespedeza      Sericea        Park-established   479 -- 851    44.7          M/L            M/L
  cuneata*        lespedeza                                                                    

  *Bromus         Bald brome     Add to park-based  257 -- 434    34.0          M/I            U
  racemosus*                                                                                   

  *Maclura        Osage orange   Park-established   120 -- 250    32.5          M/L            L
  pomifera*                                                                                    

  *Bromus         Smooth brome   Park-established   63 -- 105     4.0           M              M/L
  inermis*                                                                                     

  *Lonicera       Japanese       Park-established   48 -- 79      37.6          M              H/M
  japonica*       honeysuckle                                                                  

  *Schedonorus*   Fescue species Park-established   9 -- 25       20.8          \--            \--
  spp.                                                                                         

  *Lonicera       Amur           Early detection    5 -- 21       1.0           H/M            M
  maackii*        honeysuckle                                                                  

  *Rosa           Multiflora     Park-established   6 -- 17       48.2          L              L
  multiflora*     rose                                                                         

  *Rhus glabra*   Smooth sumac   Park-established   2 -- 6        22.8          \--            \--

  *Torilis* spp.  Hedgeparsley   Park-established   0.6 -- 2.3    25.4          \--            \--
                  species                                                                      

  *Bromus         Poverty brome  Park-established   \< 1.0        11.2          M/L            U
  sterilis*                                                                                    

  *Poa* spp.      Bluegrass      Park-established   \< 1.0        4.1           \--            \--
                  species (incl.                                                               
                  Kentucky                                                                     
                  bluegrass)                                                                   

  *Sorghum        Johnsongrass   Park-established   \< 1.0        5.1           M/L            H/M
  halepense*                                                                                   

  *Dactylis       Orchardgrass   Park-established   \< 0.75       13.2          L/I            M/L
  glomerata*                                                                                   

  *Elaeagnus      Autumn olive   Early detection    \< 0.75       3.6           H              L
  umbellata*                                                                                   

  *Verbascum      Common mullein Park-established   \< 0.75       15.7          M/L            L
  thapsus*                                                                                     

  *Ailanthus      Tree-of-       Early detection    \< 0.5        2.0           M/L            M/L
  altissima*      heaven                                                                       

  *Carduus        Nodding        Park-established   \< 0.5        2.0           M/I            H/M
  nutans*         plumeless                                                                    
                  thistle                                                                      

  *Melilotus*     Sweetclover    Park-established   \< 0.5        9.6           M              M
  *officinalis*                                                                                

  *Morus alba*    White mulberry Park-established   \< 0.5        4.6           M/L            M/L

  *Securigera     Crown vetch    Early detection    \< 0.5        2.0           H              L
  varia*                                                                                       

  *Celastrus      Oriental       Early detection    \< 0.25       2.0           M/L            M
  orbiculatus*    bittersweet                                                                  

  *Cirsium        Bull thistle   Early detection    \< 0.25       1.5           M/L            M/L
  vulgare*                                                                                     

  *Euonymus       Burningbush    Early detection    \< 0.25       3.6           L/I            L
  alata*                                                                                       

  *Euonymus       Winter creeper Early detection    \< 0.25       6.6           M              L/I
  fortunei*                                                                                    

  *Bromus         Cheatgrass     Park-established   \< 0.1        1.0           H              H/M
  tectorum*                                                                                    

  *Dipsacus       Fuller's       Park-established   \< 0.1        1.0           L              M/L
  fullonum*       teasel                                                                       
  --------------- -------------- ------------------ ------------- ------------- -------------- --------------

Table 15.6 (continued).

  ---------------- ------------- ------------------ ------------- ------------- -------------- --------------
  **Scientific     **Common      **Watch List**     **Park-wide   **Frequency   **Ecological   **Management
  Name**           Name**                           Cover         (percent)**   Impact**       Difficulty**
                                                    (acres)**                                  

  *Humulus         Japanese hop  Park-established   \< 0.1        1.5           \--            \--
  japonicus*                                                                                   

  *Ligustrum       Common privet Park-based         \< 0.1        1.5           H/L            H/M
  vulgare*                                                                                     

  *Vinca minor*    Common        Early detection    \< 0.1        1.0           I              U
                   periwinkle                                                                  

  *Arctium minus*  Lesser        Park-established   \< 0.01       0.5           L/I            M/I
                   burdock                                                                     

  *Dioscorea       Chinese yam   Early detection    \< 0.01       0.5           M/L            M/I
  oppositifolia*                                                                               

  *Miscanthus      Chinese       Early detection    \< 0.01       0.5           M/L            H/L
  sinensis*        silvergrass                                                                 

  *Poa compressa*  Canada        Park-established   \< 0.01       1.0           M/L            H/L
                   bluegrass                                                                   

  *Potentilla      Sulphur       Park-established   \< 0.01       0.5           H/L            M/L
  recta*           cinquefoil                                                                  
  ---------------- ------------- ------------------ ------------- ------------- -------------- --------------