U.S. Air Force Academy Integrated Weed Management Plan

Transcription

INTEGRATED NOXIOUS WEED
MANAGEMENT PLAN
US AIR FORCE ACADEMY AND
FARISH OUTDOOR RECREATION AREA
EL PASO COUNTY, CO
October 28, 2004
PREPARED BY
Alan T. Carpenter, Ph.D., President
Steven G. Perce, Associate
Land Stewardship Consulting, Inc.
2941 – 20th Street
Boulder, CO 80304
303.443.8094 phone
[email protected]
IN COLLABORATION WITH
Mike Schmidt, Project Manger
Natalie Lovell, Task Manager
9960 Federal Drive, Suite 300
Colorado Springs, CO 80921
719.531.0001 phone
[email protected]
TABLE OF CONTENTS
LIST OF TABLES .............................................................................................................. ii
LIST OF FIGURES ............................................................................................................ ii
APPENDIX ......................................................................................................................... ii
EXECUTIVE SUMMARY ............................................................................................... iii
INTRODUCTION .............................................................................................................. 1
APPROACH ....................................................................................................................... 2
MANAGEMENT AREA .................................................................................................... 3
Climate ............................................................................................................................ 3
Physiography and Geology ............................................................................................. 5
Soils................................................................................................................................. 5
Streams, Lakes, and Ponds.............................................................................................. 5
Wetlands and Riparian Areas.......................................................................................... 7
Plant Communities .......................................................................................................... 7
Noxious Weeds ............................................................................................................... 7
Wildlife ........................................................................................................................... 9
Potential Natural Areas, Rare Plants and Plant Communities, Rare Animal Species .... 9
NOXIOUS WEED INVENTORY .................................................................................... 12
LAND MANAGEMENT GOALS AND WEED MANAGEMENT OBJECTIVES....... 14
PRIORITIES FOR WEED MANAGEMENT .................................................................. 17
WEED MANAGEMENT TECHNIQUES ....................................................................... 21
Prevention ..................................................................................................................... 21
Pulling ........................................................................................................................... 23
Mowing and cutting ...................................................................................................... 23
Livestock grazing .......................................................................................................... 24
Biological control agents .............................................................................................. 24
Herbicides ..................................................................................................................... 25
Prescribed burning ........................................................................................................ 25
Past and on-going weed management ........................................................................... 26
INTEGRATED WEED MANAGEMENT ....................................................................... 26
MONITORING AND EVALUATION ............................................................................ 32
Photo monitoring .......................................................................................................... 33
Plot monitoring ............................................................................................................. 33
REFERENCES ................................................................................................................. 39
Air Force Academy Integrated Noxious Weed Management Plan
i
LIST OF TABLES
Table 1. List of noxious weed species known to occur at the Air Force Academy or the
Farish Recreation Area.
Table 2. Factors that influence priorities for management for noxious weed species at the
Air Force Academy or Farish Recreation Area.
Table 3. Management actions applied to noxious weed species at the Air Force Academy
or Farish Recreation Area in the past three years.
Table 4. Noxious weed species for which biological control programs have been initiated
at the Air Force Academy, along with the organism(s) that has been introduced
to exert control.
Table 5. Recommended monitoring of targeted noxious weed species at the Air Force
Academy or Farish Recreation Area.
LIST OF FIGURES
Figure 1. Locator map of the Air Force Academy and Farish Recreation Area
Figure 2. Monument Creek and Named Tributaries
Figure 3. Potential Natural Areas at the Air Force Academy and Farish Recreation Area.
Figure 4. Conservation Areas at the Air Force Academy and Farish Recreation Area.
APPENDIX
Contacts list
Trade names and active ingredients of approved herbicides
Noxious weed occurrence map from 2003 – 2003 Colorado Natural Heritage Program
weed inventory
Copy of Colorado Noxious Weed Act, as amended in 2003
Copy of rules developed for Colorado Noxious Weed Act, as amended in 2003
Disclaimer: The mention of trade names does not constitute an endorsement of such
products by the United States government or any of its entities.
ii
EXECUTIVE SUMMARY
Weeds can cause a variety of problems that affect the U.S. Air Force Academy
(Academy) and the Farish Recreation Area (Farish). Weeds can alter ecosystem
processes, degrade wildlife habitat, reduce biological diversity, reduce the quality of
recreational sites, reduce the production of rangeland forage plants, and poison livestock
(Sheley and Petroff 1999). Various federal, state, and local laws, ordinances, orders, and
policies require land managers to control noxious weeds. The purpose of this plan is to
provide a guide to manage, in the most efficient and effective manner, the noxious weeds
on the Academy and Farish in accordance with their respective integrated natural
resources management plans. For clarification purposes, throughout this report, the word
“we” refers to the authors of this report (i.e., Land Stewardship Consulting, Inc.).
This plan follows the approach outlined in Creating an Integrated Noxious Weed
Management Plan: A Handbook for Owners and Managers of Lands with Natural
Values, a report prepared for the Colorado Natural Areas Program. A key part of this
approach is an inventory of the management area. A noxious weed inventory of the
Academy and Farish was conducted by the Colorado Natural Heritage Program in 2002
and 2003. The inventory documented 3,936 occurrences of fourteen noxious weed
species. (Another species, Russian knapweed, was documented by base Natural
Resources personnel after the survey was completed.)
Such a large number of occurrences necessitated a prioritization process to reduce
the number of occurrences to be controlled to a manageable number. We prioritized the
noxious weed species based on four factors (local rarity, impact on natural areas, ability
to spread, and ease of control). Based on this prioritization, the high-priority species for
control are diffuse knapweed, hoary cress, leafy spurge, Russian olive, spotted knapweed,
Scotch thistle, St. Johnswort, Russian knapweed, and tamarisk. In addition, all noxious
weed occurrences, regardless of species, that are located in high-value resource areas
were assigned a high priority. This results in a total of approximately 1200 high-priority
noxious weed occurrences, which is about 35% of the total number of mapped
occurrences.
We established weed management objectives for the fifteen most significant
noxious weed species at the Academy. Three species (Russian knapweed, Scotch thistle,
and tamarisk) are slated for eradication, eleven species are slated for suppression (bull
thistle, Canada thistle, diffuse knapweed, field bindweed, Fuller’s teasel, hoary cress,
leafy spurge, musk thistle, Russian olive, St. Johnswort, and spotted knapweed), and one
species (yellow toadflax) is slated for containment.
There are five viable broad categories of weed management techniques that could
be employed at the Academy and Farish. These include pulling, mowing and cutting,
biological control agents, herbicides, and prescribed burning. An integrated weed
management plan selects multiple techniques that ideally interact to provide effective and
feasible control for each target weed species. We have recommended specific control
measures for each of the fifteen target weed species known on the Academy and Farish.
iii
In addition, prevention measures are essential to minimize the entry of new
noxious weed species to the Academy and Farish, as well as to locate and eliminate new,
small occurrences before they can become established. We have proposed several
policies and actions that we believe will greatly reduce the entry of new weeds to the
Academy and Farish and to reduce the likelihood of inadvertently spreading weeds within
these properties. These include requiring heavy equipment used for construction, forest
management, and fire fighting to be cleaned before it enters the Academy or moves
between construction sites within the Academy, working with the base stables to improve
the condition of ranges where the government-owned horses graze, prohibiting noxious
weeds and certain other invasive plants species from being planted at the Academy and
Farish, and promptly revegetating with native plant species all disturbances created by
construction, logging, and fire fighting in the “natural” portions of the Academy and all
of Farish.
We believe that the weed management actions proposed in this plan for the
Academy and Farish will be effective. However, there is no guarantee that this will be
true, due to variations in weather, soil moisture, growth stage of the target weed species,
and genetic variation among weed populations. Thus, we have proposed a practical
monitoring program to evaluate the effectiveness of weed management actions. Broadly
speaking, monitoring will involve collecting photographs and vegetation data in
permanent plots in selected weed occurrences that are being controlled.
We recommend a list of actions that can be undertaken immediately to begin to
implement this plan. These actions include continuing to introduce and monitor
biocontrol insects, spraying rosettes and cutting and disposing of bolted stems of biennial
weed species, and spraying small, high-priority weed occurrences.
iv
INTRODUCTION
Weeds can cause a variety of problems that can affect public and private lands as
well as people who depend on these lands. Weeds can alter ecosystem processes,
degrade wildlife habitat, reduce biological diversity, reduce the quality of recreational
sites, reduce the production of crops and rangeland forage plants, and poison livestock
(Sheley and Petroff 1999).
President Clinton signed Executive Order 13112 (Invasive Species) on February
3, 1999. This Order requires all federal agencies to take certain steps to “prevent the
introduction of invasive species and provide for their control and to minimize the
economic, ecological, and human health impacts that invasive species cause..”. This
plan furthers the intent of that Executive Order.
The State of Colorado passed the Colorado Weed Management Act in 1990. The
Act requires landowners and managers to manage noxious weeds if they are likely to
damage neighboring lands. The Act requires each county and municipality to adopt a
noxious weed management plan for its jurisdiction. The Act was revised significantly in
2003. Among other things, these revisions prioritize noxious weeds listed by the State
for management.
El Paso County has adopted an ordinance that regulates the management of
undesirable plants on private and public lands within the County. The ordinance requires
certain plant species that are listed as “undesirable” to be managed within the
unincorporated portions of the County. The undesirable plants include leafy spurge,
diffuse knapweed, Russian knapweed, spotted knapweed, Canada thistle, and purple
loosestrife. In addition, musk thistle and yellow toadflax are designated as potentially
undesirable. All of these species are known to occur on the Academy, except for purple
loosestrife.
It is likely impractical to control all noxious weed species on the Air Force
Academy and the Farish Recreation Area (henceforth referred to collectively as the
“Academy” unless indicated otherwise), at least initially, due to personnel and herbicide
use restrictions imposed by the Department of Defense. Thus, it is critical to use limited
resources wisely so control efforts are focused where they do the most good. An ad hoc
approach to weed management will likely be inefficient and possibly ineffective. The
most effective and efficient way to manage weeds is to prepare and implement an
Integrated Noxious Weed Management Plan.
The purpose of this plan is to guide the management of noxious weeds at the
Academy and Farish in the most efficient and effective manner. This plan supports the
2003-2008 Integrated Natural Resources Management Plan for the Air Force Academy.
One of the objectives in that plan (page D-5) is to “Develop an integrated weed
management plan in cooperation with the U.S. Fish & Wildlife Service within one year of
completing the baseline noxious weed inventory of the base”. This plan also supports the
1
2001-2005 Integrated Natural Resources Management Plan for the Farish Recreation
Area.
This plan supports the Comprehensive Plan for the Air Force Academy. The
Land Use Plan portion of the Comprehensive Plan states that natural open space is central
to the overall planning and operation of the Academy. Proliferation of noxious weeds
threatens the quality of the Academy’s natural areas. This integrated weed management
plan seeks to prevent such proliferation and to maintain or improve the quality of the
Academy’s open space and natural landscapes.
This plan complies with Air Force Instruction 32-1053 (Pest Management
Program). The Instruction is focused primarily on animal agents that spread disease, and
the vast majority of the requirements do not pertain to noxious weed control. However,
some requirements are directly relevant, e.g., the Installation Pest Control supervisor …
“Makes sure that pest management programs and facilities comply with all applicable
Federal, state, and local laws.” (Paragraph 3.4.2.1) This plan complies with all of the
requirements contained in the Instruction that pertain to noxious weed management.
This plan also complies with draft Air Force Instruction 32-7064, Integrated
Natural Resources Management (10 March 2004), guidance on noxious weed
management.
APPROACH
This plan follows the approach outlined in Creating an Integrated Noxious Weed
Management Plan: A Handbook for Owners and Managers of Lands with Natural Values
(Carpenter et al. 2000). For the purposes of this plan, we define a “noxious weed” as a
plant species that is so designated pursuant to the Colorado Noxious Weed Act (see
Appendix for legal definition). Furthermore, we excluded from active consideration
certain noxious weeds that are so prevalent at the Academy that their management is
largely impractical (e.g., cheatgrass) or whose impact is relatively minor (e.g., common
mullein) compared to other noxious weed species that are present at the Academy. This
plan generally does not address non-native plant species that are not designated as
noxious weeds.
We initiated the planning process by meeting Dr. Brian Mihlbachler, Range and
Wildlife Biologist with the U.S. Fish & Wildlife Service, who is stationed at the
Academy. The purpose of this meeting was to obtain relevant reports, computer files and
other information that would help us understand the noxious weed situation at the
Academy and Farish. Perhaps the most important report was the noxious weed survey of
the U.S. Air Force Academy and Farish Recreation Area (Anderson et al. 2003), which
was conducted by the Colorado Natural Heritage Program in 2002-2003.
After we had an opportunity to review the available information, we attended a
field tour of the Academy and Farish to obtain an overview of the noxious weed situation.
2
We focused on weed occurrences that are being controlled as part of the biocontrol
program at the Academy (Michels et al. 2003).
We had follow-up conversations with Dave Anderson, Colorado Natural Heritage
Program; Dr. Brian Mihlbachler; Dr. Jerry Michels of the Texas Agricultural Experiment
Station about his biocontrol projects at the Academy; Mark Johnston, forestry and
noxious weed specialist with the El Paso County Environmental Services Department;
Michael Finlay, Mountain High Tree Service, Inc., the subcontractor who currently
applies herbicides to noxious weeds at the Academy; and David Kelley, J & J
Maintenance, the contractor that handles overall pest management at the Academy.
MANAGEMENT AREA
The Academy is located in El Paso County, Colorado (Figure 1) and includes
18,445 acres of land. It is a mixture of forest, woodland, shrubland, and grassland. Its
large size plus the existence of extensive areas of dense vegetation mean that it is
impossible to locate all of the noxious weed occurrences at the Academy, much less to
control them. Therefore, it is important to understand that this plan cannot cover all of
the noxious weed species and occurrences at the Academy. New species and occurrences
will be found, and this plan will need to be revised periodically to reflect new information
about noxious weeds. The Farish Recreation Area includes 655 acres of forest and
grassland, as well as three lakes.
This plan pertains to the “natural” portions of the Air Force Academy (Academy)
and excludes highly developed areas, such as around buildings, recreation fields, and
lawns. This plan covers all of the Farish Recreation Area site, including the developed
areas. The following paragraphs summarize briefly the major environmental factors,
vegetation, and wildlife of the Academy and Farish, focusing on how the factors pertain
to noxious weeds. This information has been extracted from existing documents as
noted.
Climate
The Academy is located in a semi-arid area. The Academy weather station
received an average annual precipitation of 15.4 inches from 1979 – 1991 (ESCO
Associates, Inc. 1992) and 16.4 inches from 1992 – 2003 (unpublished data from
USAFA airfield). However, wetlands and riparian areas are much wetter than the
average annual precipitation would indicate because they receive supplemental moisture
from stormwater and effluent discharges, surface flow and/or groundwater. The rather
dry climate of the Academy does not mean that noxious weeds are scarce. Most of the
noxious weed species that occur at the Academy are adapted to dry conditions (e.g.,
diffuse knapweed), while those adapted to moister conditions (e.g., Canada thistle) are
typically found in wetlands and riparian areas. Noxious weed species found at Farish are
3
Figure 1: Locator Map of the Air Force Academy and Farish Recreation Area
4
those typically found in cooler and/or moister environments or in finer-textured soils
(e.g., yellow toadflax and Canada thistle).
Physiography and Geology
The primary physical feature of the Academy is a series of east-west trending
ridges that are comprised of arkosic sandstones (Ripley 1994). The ridges create southand north-facing slopes. Generally, the south-facing slopes are relatively hot and dry,
while the north-facing slopes are cooler and moister. These environments are preferred
by different species of noxious weeds. The elevation of the Academy ranges from 6,376
feet along Monument Creek to 7,899 feet at Stanley Canyon. This wide range in
elevation interacts with changes in slope aspect, geology, and soils to create a diversity of
environments that are conducive to a variety of noxious weed species.
The Farish Recreation Area is located west of the Academy in the Rampart
Range, which consists mostly of Pikes Peak granite. The elevation of Farish ranges from
9,048 feet along Beaver Creek to 9,315 feet south of Schubarth Road.
Soils
Soils at the Academy are primarily derived from granitic parent material
(Anonymous 2003). Soils on the sides of ridges are typically coarse and thin, especially
in the natural portions of the Academy. Diffuse and spotted knapweed are well adapted
to growing in thin, coarse soils. Somewhat deeper and finer-textured soils occur at the
bases of the ridges. Yellow toadflax and Scotch thistle are noxious weeds that generally
occur on such soils. Even deeper, more productive soils are found in the floodplain of
Monument Creek. Canada thistle, hoary cress, and Fuller’s teasel are noxious weeds that
are found in these soils.
Streams, Lakes, and Ponds
The major surface water feature of the Academy is Monument Creek (Figure 2).
It rises on the eastern flanks of the Rampart Range about 6 miles northwest of the
Academy and flows northeast to the town of Palmer Lake, after which it flows south
through the Academy on its way to Fountain Creek. The area between Palmer Lake and
the Academy is rapidly developing. Monument Creek collects seeds and fragments of
noxious weeds from this developing area and transports them to the Academy. Thus,
noxious weeds that grow upstream of the Academy impact the Monument Creek
floodplain.
Within the Academy, Goat Camp Creek, Deadman’s Creek, Lehman Run,
Douglas Creek, West Monument Creek, and Stanley Creek flow from west to east and
join Monument Creek. Hay Creek joins Monument Creek immediately north of the
Academy boundary. Jackson, Smith, Monument Branch, Black Squirrel, Elkhorn, and
Pine Creek flow from east to west and joins Monument Creek. Water flowing in these
5
creeks transports noxious weeds from west to east primarily during floods. South Beaver
Creek flows through the Farish Recreation Area and can transport weed seeds.
Figure 2: Monument Creek and Named Tributaries
6
Farish contains three lakes and the Academy has five lakes that are heavily used for
recreation, mainly fishing. Trampling and erosion around the margins of the lakes
facilitates the invasion and perpetuation of Canada thistle and diffuse knapweed.
Wetlands and Riparian Areas
There are significant wetlands and riparian areas along Monument Creek, as well
as along the other creeks. Wetlands and riparian areas typically occur in floodplains,
which are nearly all classified as “natural” in the Comprehensive Plan for the Academy.
Wetlands and riparian areas typically are “high-value resource areas”, which are focal
areas for weed management. These moist areas are havens for certain noxious weed
species, including Canada thistle, Fuller’s teasel, hoary cress, Russian olive, and
tamarisk.
The Farish Recreation Area contains a small fen, which is a type of wetland
supported by ground water seepage and where peat accumulates. The fen harbors the
lowest-elevation and eastern-most occurrence in Colorado of a globally rare plant, the
Porter feathergrass (Ptilagrostis porteri). Canada thistle could invade this wetland, but
has not yet done so.
Plant Communities
The variety of elevation, slope aspect, soils, and soil moisture creates different
environments that harbor different plant communities. ESCO Associates Inc. (1992)
mapped the plant communities of the Academy. The upland forest vegetation type
includes white fir, Douglas-fir, ponderosa pine, Colorado blue spruce, and aspen
communities. The upland shrubland vegetation type includes Gambel’s oak, wax current,
skunkbrush, snowberry, and mountain mahogany. The upland grassland vegetation type
includes mountain muhly, Parry oatgrass, big and little bluestem, blue grama, western
wheatgrass, prairie sandreed, and needle-and-thread communities. The riparian
vegetation type includes the sandbar willow, sedge, rush, and wetland grass communities.
The grassland communities are commonly invaded by yellow toadflax and knapweeds.
The sandbar willow community is often colonized by Canada thistle, hoary cress, Russian
olive, and yellow toadflax. Leafy spurge and yellow toadflax frequently colonize
Gambel’s oak stands. Forested areas, particularly ponderosa pine stands, are often
colonized by yellow toadflax.
Noxious weeds
The vegetation of the Academy has been studied in some detail, primarily by
Douglas Ripley (Ripley 1994). Over 100 alien species have been recorded at the
Academy (Ripley 1994). The vast majority of these are not noxious weeds. Sixteen
species of noxious weeds have been recorded from the Academy (Table 1).
7
Table 1
Noxious weed species known to occur on the Academy. The ten species denoted with an
asterisk were the initial targets of the 2002 – 2003 Colorado Natural Heritage Program
inventory. State List refers to list A, B and C management priorities, per rules
promulgated by the Colorado Department of Agriculture and applicable as of May 6,
2004, pursuant to revisions of the Colorado Weed Management Act enacted in 2003.
Scientific names follow Weber and Wittmann (2001) with common synonyms provided.
_______________________________________________________________________
Weed Species
State List
Bull thistle (Cirsium vulgare)
B
*Canada thistle (Breea arvensis = Cirsium arvense)
B
Cheatgrass (Anisantha tectorum = Bromus tectorum)
C
Common mullein (Verbascum thapsus)
C
*Diffuse knapweed (Acosta diffusa = Centaurea diffusa)
B
*Field bindweed (Convolvulus arvensis)
C
*Fullers’ teasel (Dipsacus fullonum)
B
*Hoary cress (Cardaria draba)
B
*Leafy spurge (Tithymalus esula = Euphorbia esula)
B
*Musk thistle (Carduus nutans)
B
Russian knapweed (Acroptilon repens = Centaurea repens)
B
*Russian olive (Elaeagnus angustifolia)
B
Scotch thistle (Onopordum acanthium)
B
St. Johnswort (Hypericum perforatum)
B
*Spotted knapweed (Acosta maculosa = Centaurea maculosa)
B
*Yellow toadflax (Linaria vulgaris)
B
______________________________________________________________________
8
The Colorado Natural Heritage Program conducted an inventory of the noxious
weeds of the Academy in 2002 – 2003 (Anderson et al. 2003). This inventory was
designed to map the occurrences of selected noxious weed species. Due to the large size
of the Academy, it was not possible to map all of it. Rather, the mapping was
concentrated in areas thought to harbor the target noxious weed species. Fourteen species
of noxious weeds were mapped (see Integrated Weed Management section).
Wildlife
The wildlife of the Academy is typical of the region. The forest, woodland,
shrubland, and grassland habitats at lower and higher elevations support at wider variety
of animals. The most common large animals include mule deer, white-tailed deer,
American elk, coyote, and black bear. These animals can spread seeds of noxious weeds
in their fur and on their feet. The Academy hosts many migratory and non-migratory bird
species that may be effective dispersers of weed seeds. The presence of leafy spurge in
Gambel’s oak thickets suggests that leafy spurge seeds may be spread by birds that eat
the seeds then deposit them when perching in oak clumps.
Potential Natural Areas, Rare Plants and Plant Communities, Rare Animal Species
There have been two primary efforts to identify the significant natural areas of the
Academy. ESCO Associates Inc. (1992) identified nine Potential Natural Areas (Figure
3). Most of these harbor exemplary and/or rare plant communities. The Colorado
Natural Heritage Program (CNHP) also identified seven conservation sites that were
designed to protect rare plant and animal species and vegetation communities (Figure 4).
We classified all the natural areas and conservation sites as high-value resource
areas, meaning that they merit more noxious weed management attention than they
otherwise would. We recommend controlling Canada thistle and yellow toadflax, which
together account for 70% of the mapped weed occurrences, only in the high-value
resource areas.
The Colorado Natural Heritage Program (CNHP) also conducted a broader
inventory of the Academy, including animal species (Ellingson et al. 1996).
CNHP reported seven rare plant species at the Academy. Six of these are relatively
common globally but rare in Colorado, while one (Porter feathergrass) is rare globally.
Populations of three of the seven rare plant species are included in the Conservation
Areas identified by CNHP. In addition, the rare Parry oatgrass and xeric tall grass prairie
communities are found at the Academy and are included in Potential Natural Areas and
Conservation Sites.
The most significant rare animal is the Preble’s meadow jumping mouse, which
was listed as “threatened” in 1998 under the federal Endangered Species Act. It is
9
10
11
acceptable to USFWS to continue current weed management practices in mouse habitat,
including the use of herbicides that have been used in the past (S. Kennedy, pers. comm.).
A Conservation Agreement and Conservation and Management Plan between the
Academy and the U.S. Fish & Wildlife Service for the Preble’s meadow jumping mouse
specifically requires the control of various noxious weeds within the mouse’s habitat.
In addition, the Colorado Natural Heritage Program has found several species of
rare butterflies on the Academy, although none are listed as “threatened” or “endangered”
under the terms of the federal Endangered Species Act. It is not clear how noxious weed
management might affect these species. However, alien plant species are not part of the
evolutionary history of these rare animals, and, therefore, controlling noxious weeds
would be expected to help maintain native host plant species for the rare butterflies.
NOXIOUS WEED INVENTORY
Previous research had identified over a
hundred alien plant species, including a number of
noxious weed species, at the Academy. However,
a formal noxious weed inventory had not been
conducted until the 2002 - 2003 Colorado Natural
Heritage Program (CNHP) survey (Anderson et al.
2003).
Diffuse knapweed
At the time, the State noxious weed list
contained over 80 species, which is far too many
to adequately inventory. Therefore, CNHP
initially focused its inventory on ten target noxious
weed species, but expanded the survey to include
four other weed species (Table 1). These noxious
weeds are all known to occur on the Academy, are
highly invasive, and are capable of causing severe
natural resource damage.
The Academy and Farish were too large to census intensively with a walking
survey. Thus, the inventory focused on areas that were likely to harbor the target noxious
weed species, then walking around these areas and mapping the weeds, and assessing
plant number and canopy cover. The CNHP inventory is best described as a sampling of
the noxious weeds of the AFA and Farish and not a complete census; therefore, some
weed species and occurrences were not discovered and not mapped, e.g., the small
occurrences of Russian knapweed. The products of the inventory were primarily a
database of weed occurrences, GIS maps that depict the locations of weed occurrences,
and a narrative report (Anderson et al. 2003).
Fourteen noxious weed species were mapped by CNHP on the Academy,
including the original ten target species and four additional species that were found for
12
the first time at the Academy. One additional species (Russian knapweed) was
subsequently identified in separate locations by Academy Natural Resources personnel
and the El Paso County Noxious Weed Coordinator (Table 1).
The inventory recorded the canopy cover, plant number, and area occupied by
each target noxious weed occurrence (see Integrated Weed Management section below).
This is essential information because it helps prioritize noxious weed species and
occurrences for management. The number of occurrences of the noxious weed species
also prescribes the appropriate weed management objectives for the species and
occurrences. Several species were found in relatively few occurrences that encompassed
small total areas (hoary cress, leafy spurge, Russian knapweed, Scotch thistle, St.
Johnswort, and tamarisk). Other species were found in a moderate number of
occurrences and covered a moderate area in aggregate (bull thistle, Fuller’s teasel, musk
thistle, and spotted knapweed). Several species were wide-spread and occupied large
areas (Canada thistle, diffuse knapweed, and yellow toadflax). Field bindweed was not
mapped, although it was found in several locations during the inventory. Voucher
specimens of each noxious weed species surveyed were mounted and labeled and are
stored in a herbarium at the Academy Natural Resources office.
Yellow toadflax
13
LAND MANAGEMENT GOALS AND WEED MANAGEMENT OBJECTIVES
The 2002 – 2008 Integrated Natural Resources Management Plan for the Air Force
Academy sets forth several land management goals and objectives, some of which relate
directly to noxious weed management. These goals include the following:
·
·
Sustain healthy rangeland plant communities that promote soil conservation and
watershed protection, provide wildlife habitat, and discourage the invasion of noxious
weeds.
Prevent the establishment of new noxious weed species and implement an integrated
weed management program to control the existing noxious weed populations.
The following management objectives pertain to noxious weeds:
·
·
·
·
·
Develop an integrated weed management plan in cooperation with the U.S. Fish &
Wildlife Service within one year of completing the baseline noxious weed inventory
of the base. (This plan meets that objective.)
Chemical, biological, mechanical, and burning techniques will be used for weed
control.
Update the GIS database with newly identified noxious weed locations.
Continue to release biological control agents that have been proven effective and
host-specific for controlling noxious weeds.
Control up to 500 acres of noxious weed using approved herbicides.
The 2001 – 2005 Integrated Natural Resource Management Plan for Farish
identifies certain desired future conditions for resource management that are relevant to
noxious weed management:
·
·
The quality of the natural environment is maintained and perpetuated (noxious weed
proliferation could threaten this)
Natural vegetation diversity and vegetation patterns are maintained in the
conservation zone (noxious weed proliferation could threaten this)
The preferred alternative for the Farish plan lists “Develop noxious weed plan” as
a component of vegetation management. The plan lists various integrated pest
management options. The preferred alternative also specifies a noxious weed inventory,
which was completed by CNHP in 2002.
Weed management objectives narrow the scope even further than land
management objectives. Weed management objectives refer to the level of control that
one is attempting to attain over specific noxious weed species and/or occurrences. These
objectives are specific, measurable, achievable, relevant, and time bound. Thus, they can
serve as benchmarks, which can be used to evaluate the effectiveness of weed
management actions and to make adjustments as needed.
14
The terms eradicate, suppress, and contain have particular meanings in the context
of this plan that may not be consistent with their usage in other contexts.
Eradicate: eliminate all living plant material of a species from an area, including
stems, roots, rhizomes, and seeds in the soil.
Suppress: reduce the abundance of a noxious weed species in an area; this is best
referenced by specifying a certain degree of reduction of abundance.
Contain: prevent the expansion of a noxious weed occurrence beyond its present
boundaries; nothing is necessarily implied about the abundance of the noxious
weed within the boundaries of an existing occurrence
An underlying management objective for all weed occurrences is containment.
That is, none of the existing noxious weed occurrences should expand. For those species
slated for suppression, there is the additional objective to reduce the abundance of the
target weed species within the occurrences. Thus, successful suppression would entail
occurrences that did not increase in size (and hopefully shrank) and have fewer weeds
within the perimeters of the occurrences.
For Russian olive and the biennial weed species (bull thistle, diffuse knapweed,
Fuller’s teasel, musk thistle, Scotch thistle, and spotted knapweed ) that are relatively
uncommon, and for which suppression is the weed management objective, the objectives
are couched in terms of the density of reproductive individuals, i.e., number of
reproductive individuals per unit area. With these species, individual reproductive plants
can be easily distinguished and counted. As used here, reproductive plants are defined as
those that have “bolted” and have some flowers and/or fruits. Counts of reproductive
individuals tend to be more reproducible than ocular estimates of canopy cover,
especially by seasonal technicians. For the less abundant weed species, we recommend a
90% reduction in reproductive plant density, while we recommend a 50% reduction in
density for the more common ones. While 90% is arbitrary, the intent is to reduce the
density of reproductive plants to a small fraction of the current density. The 50%
reduction target is designed to achieve a significant diminution in weed abundance, with
the assumption that this reduction will be considerably harder to achieve for the more
common species. Note that it will be necessary to determine baseline densities as the
initial condition in order to calculate the 50% or 90% reduction target.
There are many mapped noxious weed occurrences along Monument Creek and
its tributaries, which provide habitat for the Preble’s meadow jumping mouse, a
threatened species. We do not believe that noxious weed control in these areas will
adversely affect the jumping mouse. The weed occurrences are typically small (< one
acre in size). Any effects of reducing the cover of Canada thistle (which is by far the
most common noxious weed species in jumping mouse habitat) within occurrences by
50% (or more for other less common weed species) would be localized. Research by
Schorr (2003, 2004) at the Academy has shown that the jumping mouse is able to move
up to one mile over a few days. It is reasonable to assume that the jumping mice could
15
easily move from Canada thistle (or other weed) occurrences where weed cover has been
reduced to nearby weed-free areas. Therefore, we believe that treating relatively small
weed occurrences to control 50-90% of the plants in those occurrences would not impact
a species that is capable of large-scale movements.
For the weed species that propagate from root sprouts or rhizomes, it is generally
impossible to identify individual plants. These species include Canada thistle, field
bindweed, hoary cress, leafy spurge, Russian knapweed, St. Johnswort, yellow toadflax.
For these clonal species (with the exception of field bindweed), we recommend using
canopy cover as the measure of the degree suppression. To minimize subjectivity, we
recommend using the line intercept method for estimating canopy cover (see the
Monitoring and Evaluation section below for details). We recommend 50% or 90%
reductions in reproductive plant density for more common and less common clonal
species, respectively. While both 50% and 90% are arbitrary, the intent is to achieve a
substantial yet achievable reduction in canopy cover. Note that it will be necessary to
determine baseline densities as the initial condition in order to calculate the 50% and 90%
reduction targets.
Weed management objectives for the Academy and Farish are presented in the
Integrated Weed Management section below. Note that “eradicate” is reserved for only
the least abundant noxious weeds due to the difficulty of completely eliminating a wellestablished noxious weed species from an area the size of the Academy. That said, we
believe that eradication is the appropriate weed management objective for Russian
knapweed, Scotch thistle, and tamarisk. Most of the other weed management objectives
are designed to reduce the level of the respective noxious weed species to functional
insignificance over the five-year span of this plan. A five-year time span was chosen to
correspond to the time frame of the Academy’s Integrated Natural Resources
Management Plan. For example, the weed management objective for hoary cress is
suppression, more specifically to reduce the canopy cover of hoary cress within all
occurrences by 90% over the next four years. We
Russian knapweed
recommend containment of yellow toadflax (except in the
high-value resource areas) because the cost of suppression
would likely be prohibitive due to the large number of
occurrences. Weed management funding would best be
allocated to other weed species, at least in the near term.
It should be noted that evaluating the success of achieving
the weed management objectives via the recommended
management actions will require a monitoring program, as
outlined in a subsequent section of this plan.
16
PRIORITIES FOR WEED MANAGEMENT
As noted above, the CNHP weed inventory mapped 3,936 occurrences of fourteen
noxious weed species (Anderson et al. 2003). The Academy has already updated this
database with new information on Russian knapweed occurrences and other target
species occurrences noted since the 2002 – 2003 inventory (see the Appendix for a map
that depicts the locations of CNHP weed occurrences.) Controlling this number of weed
occurrences is beyond the capacity of the Academy. Furthermore, there are surely
additional weed occurrences at the Academy and Farish because the weed inventory was
an extensive sample, but not an exhaustive census. Thus, it is imperative to prioritize
occurrences for control. We have established priorities for management in two ways.
First, we have identified high-priority species for management. Second, we have
identified high-priority weed species occurrences.
We classified the fourteen target noxious weed species as either high, medium, or
low priority for management based on four factors: local rarity, impact on natural areas,
ability to spread, and ease of control. Generally, the high-priority species are those that
are locally rare, have high impact, have high rates of spread, and are not too difficult to
control (Table 2). There is convincing evidence that the most cost-effective approach to
controlling noxious weeds is to focus management attention on small occurrences of
locally rare weed species (Moody and Mack 1988, Smith at al.
Leafy spurge
1999).
The high-priority weed species are diffuse knapweed,
hoary cress, leafy spurge, Russian olive, Scotch thistle, St.
Johnswort, Russian knapweed, and spotted knapweed (Table 2).
We have not included tamarisk as a high-priority species
because the only known individual plant has been destroyed.
These eight noxious weed species accounted for 718 of the
3,936 mapped occurrences in the CNHP weed inventory
(Anderson et al. 2003). Diffuse knapweed and Russian olive
contributed 597 (83%) of these occurrences. The large number
of Russian olive occurrences is misleading because Academy
personnel have already cut and poisoned the Russian olives in
many of the occurrences. All mapped occurrences of highpriority species are high priorities for control.
Scotch thistle
The other high-priority occurrences are those located in
the high-value resource areas, which we define as the Potential
Natural Areas and the Conservation Sites as identified by ESCO
Associates, Inc. (1992) and the Colorado Natural Heritage
Program (1996). This includes another 644 mapped
occurrences, including yellow toadflax, Canada thistle, bull
thistle, Fuller’s teasel, and musk thistle. Most of these
occurrences lie within the Monument Creek Conservation Site
17
identified by CNHP because it is large in size and encompasses riparian areas, which are
inherently weedy due to natural disturbance.
Thus, for some weed species, all of the occurrences will be the same priority, e.g.,
all leafy spurge occurrences will be high priorities for control. This reflects its relative
rarity at the Academy, its high adverse impact on native plant communities, its rapid rate
of spread, and the great potential of controlling leafy spurge with herbicides and
biocontrol insects. However, only some occurrences of Canada thistle and yellow
toadflax will be high priorities for control, i.e., those occurrences that fall within highvalue resource areas. This reflects the fact that Canada thistle and yellow toadflax are the
most abundant noxious weed species at the Academy and cannot now be controlled over
the entire area in a cost-effective manner.
Spotted knapweed
18
Table 2
Factors that influence priorities for management for noxious weed species at the Air
Force Academy or Farish Recreation Area.
_______________________________________________________________________
Weed
Species
Local
Abundance
Impact
Rate of
Spread
Ease of
Control
Priority
Bull thistle
Low
Medium
Medium
High
Medium
Canada thistle High
High
High
Low
Medium
Diffuse
knapweed
High
High
High
Medium
High
Field
bindweed
Unknown
Medium
Low
Low
Low
Fullers’ teasel Low
High
Medium
Medium
Medium
Hoary cress
High
Medium
Low
High
Leafy spurge Low
High
High
Medium
High
Musk thistle
Medium
Medium
Medium
Medium
Low
Russian
knapweed
Low
High
High
High
High
Russian olive Low
High
Medium
High
High
Scotch thistle Low
Medium
High
High
High
St. Johnswort Low
High
Medium
Medium
High
Spotted
knapweed
High
High
High
High
Medium
Medium
Yellow
High
High
High
Low
Low
toadflax
______________________________________________________________________
Other noxious weed species will undoubtedly appear at the Academy in the future
or may occur there now, having been overlooked in the previous inventory. We
encourage natural resources staff at the Academy to be alert for the following species and
19
to control them aggressively if they are discovered. All of these species could flourish at
the Academy, given their climate and soils. All occurrences of the species listed below
should be considered high-priority for management due to their (presumed) local rarity,
high impact, and high rates of spread.
·
Tamarisk (Tamarix ramosissima) – This is a B-list weed species in Colorado that has
been found at the Academy along Pine Creek. The single individual has been
destroyed, but others may be present. Tamarisk grows in wetlands and riparian areas,
and spreads rapidly once established.
·
Purple loosestrife (Lythrum salicaria) – This is an A-list weed species in Colorado
that must be eradicated if found. It grows in wetlands and riparian areas. It is a
showy species that has been widely planted in gardens. It re-sprouts readily from its
extensive root system, making it very difficult to control once it becomes established.
·
Myrtle spurge (Euphorbia myrsinites) – This is another A-list weed species that is
widely planted. It escapes from gardens into foothills environments. Fortunately, it
is easy to control by digging up plants before they set seed and disposing of them in a
dumpster. The sap of this plant irritates skin and eyes, so persons digging the plants
need to exercise caution.
·
Mediterranean sage (Salvia aethiopsis) – This is an A-list weed species in Colorado.
It is a showy species that escapes from gardens and spreads rapidly in the wild. It is a
biennial species that is readily controlled by digging and disposing of plants before
they set seed.
·
Bouncingbet (Saponaria officinalis) – This is a B-list weed species that typically
grows in moist situations such as riparian areas. It is a showy species that escapes
from gardens and spread rapidly in the wild. It is difficult to control once it is
established.
·
Houndstongue (Cynoglossum officinale) – This is another B-list weed species that
typically grows at middle elevations, such as the Farish Recreation Area. It is a
biennial weed that can be controlled by digging or cutting bolted seed stalks before
seed set or by spraying rosettes with herbicide. It spreads rapidly in the wild because
its velcro-like fruits stick to fur and clothing.
·
Tall whitetop (Lepidium latifolium = Cardaria latifolia) – This is a B-list weed
species that typically grows in moist situations such as riparian areas, ditch banks,a
and wetlands. It spreads rapidly in favorable environments and is difficult to control
once established.
In addition, there are three invasive plant species that are not currently classified
as noxious by the State of Colorado, but which could appear at the Academy in the near
future. Tartarian honeysuckle (Lonicera tartarica) and common buckthorn (Rhamnus
cathartica) are invading riparian areas along the South Platte River in the Denver
20
metropolitan area. These two species are highly invasive in the
midwestern US. Garlic mustard (Alliaria petiolata) is an
invasive plant species that is a major problem in forests and
woodlands in the upper midwest. It has been reported from the
Colorado Springs area (Weber and Wittmann 2001). These
three species could colonize riparian areas along Monument
Creek and its tributaries.
Houndstongue
The Colorado Noxious Weed Act was revised in 2003,
with the result that certain noxious weeds must be eradicated (A
list species), while others (C list species) will no longer be
mandated for control by the State (Table 1). Once management
plans are prepared by the State for the B list species (which
includes all of the worst noxious weeds mapped at the Academy
and Farish, except for field bindweed), eradication, suppression,
or containment will be required depending on location. See the
Appendix for a copy of the Colorado Noxious Weed Act and
the accompanying rules.
WEED MANAGEMENT TECHNIQUES
There are many options for controlling noxious weeds. Prevention refers to
actions that are designed to keep noxious weeds from entering an area or to eliminate
them before they become established. This section discusses prevention, as well as
techniques that can be used to control established noxious weed occurrences. These
include pulling, mowing and cutting, livestock grazing, biological control agents,
herbicides, and prescribed burning. At the end of this section, we review past and ongoing weed management actions at the Academy.
Prevention
Prevention is typically the most cost-effective way to manage noxious weeds, i.e.,
keep them from becoming established in the first place. There are a number of tactics
that can be employed to reduce the likelihood of noxious weeds from entering the
Academy or from becoming established if they arrive (Wittenberg and Cock 2001).
There is considerable anecdotal evidence that vehicles can transport weed seeds
from one location to another (Lonsdale and Lane 1994). It is obviously not practical to
inspect the vast majority of vehicles that enter the Academy for noxious weed seeds.
However, we recommend inspecting and cleaning a small subset of vehicles. We
recommend working with the appropriate officials at the Academy to develop and adopt a
policy that requires that all heavy equipment (e.g., logging trucks, bulldozers) that enters
the Academy and operates in the “natural” areas must be cleaned prior to being used and
moved around the base. This policy could be enforced through specific requirements
included in construction-type contracts.
21
Railroad and highway rights-of-way are conducive to noxious weed proliferation,
with their abundant ballast and bare ground. We recommend working cooperatively with
the Union Pacific Railroad and the Colorado Department of Transportation to identify
and control noxious weeds on the respective rights-of-way within the Academy. One of
the two known occurrences of Russian knapweed, a species slated for eradication on the
Academy, is located on the Interstate 25 right-of-way.
Protecting the soil surface from degradation is a cornerstone of natural resource
management. Soil that is covered with vigorous, desirable plant species will resist
erosion, maintain its productive capacity, and will resist noxious weed colonization.
Current Academy policy requires the use of Best Management Practices to minimize soil
disturbance and to control erosion to the extent practicable during construction and major
maintenance projects.
We strongly recommend revegetating all disturbed areas promptly with
appropriate native plant species in the “natural” portions of the Academy and Farish that
are caused by construction, logging, and fire suppression. The Academy already requires
that only certified weed-free straw and hay (in accordance with State requirements) can
be used for erosion control. After the revegetation is complete, follow-up is important to
confirm that seeding was successful, and, if not, to rectify the situation and to look for
noxious weeds that may have become established.
Certain noxious weed and invasive plant species are used in the horticultural
trade. These include Russian olive, dame’s rocket, oxeye daisy, and purple loosestrife. It
is clearly counterproductive for these species to be deliberately introduced to the
Academy. We recommend working with the appropriate officials at the Academy to
develop and adopt a policy that prohibits noxious weed and invasive plant species from
being planted at the Academy. We also recommend that an appropriate Academy natural
resources staff person review all landscaping, reclamation, and revegetation plans to
check for noxious weed species (e.g., Russian olive, purple loosestrife) or other invasive
plant species (e.g., honeysuckle) that may have be included in planting lists. The
Landscape Design Standards that are currently being drafted for the Academy address
this issue.
We recommend conducting a travel way noxious weed inventory every year
during the summer. The idea is to locate new occurrences of noxious weeds, not to revisit known occurrences. The inventory could involve driving slowly along the Academy
roads, trails, and utility easements, with an observer recording weed occurrences. It is
well known that weed occurrences often appear along travel corridors, where seeds
lodged in the undercarriages of vehicles fall to the ground. Roadsides also have disturbed
soil that is ideal for weed colonization.
Streams are also known to transport noxious weed seeds, particularly during
periods of high flows. We recommend surveying stream corridors on the Academy,
22
especially Monument Creek, for noxious weeds. Monument Creek is a high-value
resource area in addition to being a potential conduit for weed seeds.
We recommend conducting noxious weed inventories of all areas that are logged,
roller-chopped, hydroaxed, or burned within one year after the activity occurs. Logging
is a major disturbance that provides ideal conditions for weed invasion and proliferation,
especially along skid trails, staging areas, and forest roads used for logging operations.
Likewise, prescribed burning and wildfires can create suitable conditions for noxious
weed invasion. Severely burned areas, staging areas, and areas disturbed by fire line
construction are magnets for weed invasion. Brush clearing (particularly in Gambel’s
oak stands) with a hydroaxe or roller-chopper opens up shrub communities, thereby
providing increased sunlight to weeds that otherwise might not be viable.
We recommend working with the appropriate people at the Academy to improve
the grazing management of the horse pastures by implementing the existing grazing
management plan (McDermott and Lair 1990). While it is not evident that horse grazing
has created significant noxious weed problems to date, overgrazed rangelands are ideal
areas for noxious weed colonization. Well-managed, planned grazing involves moving
animals frequently in accordance with the needs of the forage plants. This would
improve range condition and help prevent noxious weed colonization. The Academy
requires that only certified weed-free hay or straw can be used for feeding or stable
bedding.
Pulling
This technique is appropriate for shallow-rooted weed species that are present in
small amounts. Bolted stems of the biennial weeds, including bull, musk, and Scotch
thistle and Fuller’s teasel, can be pulled if the soil is fairly course and/or moist. It is not
appropriate for rhizomatous weed species such as Canada thistle, hoary cress, leafy
spurge, Russian knapweed, St. Johnswort, and yellow toadflax. Pulling can always be
used to remove the current year’s seed production for most any noxious weed.
Small trees and shrubs, including Russian olive and tamarisk, can be pulled from
sandy soils, particularly if one uses a mechanical device called a Weed Wrench, heavy
construction equipment or a truck-mounted winch. However, trucks and heavy
equipment should be kept out of riparian areas and wetlands.
Small numbers of diffuse knapweed and spotted knapweed plants can be pulled
from roadsides if the soils are coarse. These species can irritate skin, so gloves and longsleeve shirts must be worn while pulling these species, followed by washing the skin
afterwards with soap and water.
Mowing and cutting
Mowing works best in relatively flat areas where large equipment can operate.
Large patches of Canada thistle can sometimes be mowed in a cost-effective manner.
23
The person conducting the mowing needs to be alert to large rocks and fallen tree limbs
that could damage the mower. It is important to remember that mowers can spread weed
seeds. Therefore, a mower should be washed prior to moving it from one location to
another if it is used to mow weeds when seeds are present.
Cutting is appropriate for small occurrences of biennial weeds, including bull,
musk, and Scotch thistle and Fuller’s teasel. Biennial plants reproduce solely from seeds.
Therefore, if their seed production can be eliminated, a weed occurrence will decline over
time. The seed stalks must be cut prior to seed dispersal, with the cut stalks being
disposed of in a dumpster. Leaving the cut stalks in the field is not appropriate because
the seeds of many weed species will ripen on cut stalks and perpetuate the weed
occurrence. The use of a roller-chopping or hydroaxe can be useful in controlling
noxious weeds that live under shrub canopies. For example, chopping Gambel’s oak
communities can expose yellow toadflax or leafy spurge plants to facilitate herbicide
application.
Livestock grazing
Certain species of domestic livestock will eat noxious weeds, and, therefore, can
potentially control them. However, it is important to use the proper species of livestock
and manage animals carefully to avoid overgrazing. Goats will eat all of the noxious
weed species known to occur at the Academy. Livestock grazing generally is a long-term
approach to weed management. Ideally, it promotes ecosystem processes such as water
infiltration and nutrient cycling, thereby promoting the establishment and growth of
desirable plant species, while harming noxious weeds. On the other hand, poorly
managed livestock grazing can promote noxious weed invasion because palatable plants
can be stressed to the point that they cannot compete with noxious weeds. It is apparent
that using livestock (including goat) grazing at the Academy is not practical due to the
lack of dense, contiguous stands of weeds and the regulatory requirements for special
protection of riparian areas and wetlands.
Biological control agents
Biological control agents include insects, other arthropods (such as mites), and
pathogens that attack noxious weeds, and, ideally, do not damage non-target plant
species. Biological control will not eradicate a noxious weed occurrence, but it can be
effective at suppressing a weed occurrence. Biological control agents are most
appropriate in situations where a weed species is so firmly established and hard to
control, that no other practical means exist to control it. In limited cases, biological
control agents have been shown to damage some non-target plant species. For example,
the weevil that has been widely introduced to control musk thistle attacks native thistles,
including at least one rare species (Louda et al. 1997).
At the Academy, yellow toadflax, field bindweed, and Canada thistle are
candidates for biological control due to their great abundance and impracticality of
control using conventional methods. Biological control agents have been shown at the
Academy to be effective at controlling diffuse knapweed, leafy spurge, and spotted
24
knapweed. In the Pacific Northwest, St. Johnswort has been controlled effectively by
beetles, and although these beetles have been released at the Academy, they have not yet
been adequately evaluated. This weed is more wide-spread than reported in the CNHP
2002 – 2003 weed survey, and is found in wetland and riparian areas where herbicide use
may not be appropriate.
Herbicides
Herbicides are widely used to control noxious weeds and are often the best
control method to eradicate weed occurrences. Herbicides are most effective in dense
stands of the target weed species where desirable plant species, especially broadleaf
species, are scarce or absent. It is against federal law to use a herbicide contrary to label
instructions. With a herbicide, the label is the law. Any person who applies herbicide for
a fee in Colorado must be certified by the State Department of Agriculture. Furthermore,
Air Force Instruction 32-1053 (Pest Management Program) requires all herbicide
applicators at Department of Defense installations to be certified as specified in DoD
Plan for Certification of Pesticide Applicators.
At the Academy, herbicides are appropriate tools for eradicating Russian
knapweed and Scotch thistle. Herbicides are also appropriate for suppressing most of the
other target noxious weed species at the Academy. There may be specific requirements
for applying herbicides to weed species that are being controlled with biological control
agents to minimize adverse effects on the agents. Dr. Jerry Michel of the Texas
Agricultural Experiment Station can provide information about applying herbicides to
weed occurrences that are being controlled with biological agents.
The Department of Defense (DoD) has adopted a policy to reduce the use of
herbicides at DoD installations. The target is to reduce pesticide use (including
herbicides) to below 50% of the level of active ingredient used by the base in 1993. At
that time, there was very little herbicide used at the Academy, so any significant increase
in the use of herbicides will negatively affect the base’s ability to meet this target.
However, the DoD policy does allow some target flexibility if herbicides are ultimately
required to achieve effective noxious weed control.
Prescribed burning
Prescribed burning is used in situations where the target weed species is more
susceptible to the effects of fire than associated desirable plant species. However, most
of the noxious weeds at the Academy are either stimulated (directly or indirectly) or are
unaffected by fire. Burning can be used to reduce biomass, particularly dead material, to
facilitate the effectiveness of follow-up herbicide application. Burning can also
invigorate plant communities that have evolved with fire, such as ponderosa pine and
prairie, thereby reducing their susceptibility to noxious weed colonization. A prescribed
burn plan must be prepared to satisfy federal, State, and local regulations. In addition, a
qualified burn boss must supervise any prescribed burn, with a crew of qualified and
25
credentialed individuals. We do not anticipate that prescribed burning will be used at the
Academy for the sole purpose of controlling noxious weeds.
Past and on-going weed management
The main noxious weed control actions used at the Academy have been herbicides
and biocontrol insects, with limited hand-pulling and cutting (Table 3). Six different
brands of herbicide have been used to control noxious weeds at the Academy from 2001
– 2003 (M. Finlay, pers. comm.). The active ingredients in these herbicides are picloram
(tradename Tordon 22K), metsulfuron (Escort), 2,4-D amine (2,4-D Amine 4),
dimethylamine + diethanolamine salts of 2,4-D (Hi-Dep), clopyralid (Transline), and
imazapic (Plateau). In addition, Russian olive trees and shrubs have been cut and the cut
stumps poisoned with glyphosate (Roundup) herbicide.
Dr. Jerry Michels, a researcher with the Texas Agricultural Experiment Station in
Bushland, Texas, is overseeing a research biocontrol project at several federal
installations in Colorado, including the Academy (Michel at al. 2003). This project
began in 2000 at the Academy and continues to the present. Table 4 summarizes the
weed species being studied, the insect species that have been introduced, and the success
to date. Biocontrol agents have shown considerable success in controlling diffuse
knapweed, leafy spurge, and spotted knapweed at the Academy. Biocontrol insects have
been introduced to control St. Johnswort (which has been very successful elsewhere) and
Canada thistle (which has not been particularly successful elsewhere). In addition, musk
thistle is probably being controlled to some degree by a weevil that has been widely
introduced in Colorado and is now essentially naturalized.
INTEGRATED WEED MANAGEMENT
The purpose of this section of the plan is to identify specific, integrated weed
management actions that are thought to be effective for each of the fourteen target
noxious weed species known to occur at the Academy. The concept is to apply multiple
management actions that ideally interact to provide maximum control for each noxious
weed species. The selection of a particular set of control methods for a particular weed
species depends on cost, environmental sensitivity, and size of the weed occurrence. In
all cases, revegetating heavily infested areas with native plant species and preventing soil
erosion and sedimentation will minimize the risk of future re-infestation.
26
Table 3
Management actions applied to noxious weed species at the Air Force Academy or Farish
Recreation Area in the past three years.
_______________________________________________________________________
Noxious Weed Species
Control Action(s)
Bull thistle
Tordon 22K (picloram), HiDep (2,4-D amine,
dimethylamine + diethanolamine salts of 2,4-D)
Canada thistle
Hi-Dep (2,4-D amine 4, dimethylamine + diethanolamine
salts of 2,4-D); biocontrol insects released at five sites
Diffuse knapweed
Tordon 22K (picloram), Hi-Dep (dimethylamine +
diethanolamine salts of 2,4-D), Transline (clopyralid);
biocontrol insects released at several sites
Field bindweed
Biocontrol mites released
Fuller’s teasel
None
Hoary cress
Hi-Dep (metsulfuron, dimethylamine + diethanolamine
salts of 2,4-D)
Leafy spurge
Plateau (imazapic), biocontrol insects released at three sites
Musk thistle
Tordon 22K( picloram), 2,4-D amine 4, Hi-Dep
(dimethylamine + diethanolamine salts of 2,4-D),
biocontrol insects, hand-pulling
Russian knapweed
diethanolamine salts of 2,4-D, Transline (clopyralid);
cutting
Russian olive
Cut and poison stumps; over 2000 individuals have been
treated
Scotch thistle
diethanolamine salts of 2,4-D
St. Johnswort
Biocontrol insects released
Spotted knapweed
Tordon 22k (picloram), Hi-Dep (dimethylamine +
diethanolamine salts of 2,4-D), Transline (clopyralid);
biocontrol insects released at several sites, hand-pulling
27
Tamarisk
Removed single individual
Yellow toadflax
Tordon 22K (picloram), Hi-Dep (2,4-D amine,
dimethylamine + diethanolamine salts of 2,4-D); biocontrol
insects released at one site
______________________________________________________________________
28
Table 4
Noxious weed species for which biological control programs have been initiated at the
Air Force Academy, along with the organism(s) that has been introduced to exert control.
No biological control organisms have been released by the Air Force at Farish Recreation
Area, but El Paso County has released biocontrol insects for leafy spurge off of the south
boundary.
_______________________________________________________________________
Noxious Weed Species
Biocontrol Agent
Success to Date
Canada thistle
Cassida rubiginosa (weevil)
Larinus planus (weevil)
Trichosirocalus horridus (beetle)
Urophora cardui (fly)
Low
Diffuse knapweed
Larinus minutus (weevil)
High
Field bindweed
Aceria malherbae (mite)
Unknown
Leafy spurge
Apthona czwalinae (beetle)
Apthona lacertosa (beetle)
Apthona nigriscutis (beetle)
High
Musk thistle
Rhinocillus conicus* (weevil)
Medium
St. Johnswort
Chrysolina sp. (beetle)
Unknown
Spotted knapweed
Larinus minutus (weevil)
Metzneria paucipunctella (weevil)
High
Yellow toadflax
Mecinus janthinus (weevil)
Unknown
* this insect is essentially naturalized and has not been introduced to AFA in recent years
______________________________________________________________________
29
In the section below, area occupied refers to the estimates from the Colorado
Natural Heritage Program 2002 – 2003 weed survey. Actual areas occupied may vary
substantially because the CNPH survey was an extensive sample and not an intensive
census of the Academy, and, therefore, undoubtedly missed some weed infested areas.
WMO means “weed management objective”.
Bull thistle
Area occupied (acres): 5.54
WMO: suppress; reduce the density of reproductive individuals within all
occurrences by 90%; prevent all seed dispersal each year
Control: apply Transline herbicide to rosettes at rate of 0.13 – 0.5 pounds active
ingredient per acre or Tordon 22K at a rate of 0.13 – 0.25 pounds active
ingredient per acre in spring or fall or 2,4-D at a rate of 1.5 – 2.0 pounds active
ingredient per acre in the spring; cut bolted stems before seed dispersal in
summer; remove cut stalks to a dumpster
Canada thistle
WMO (Academy): suppress; reduce canopy cover within high-priority
occurrences by 50%
WMO (Farish): suppress; reduce canopy cover within high-priority occurrences
by 50%
Control: cut bolted stems in summer before flowering (use weed whip or mower);
apply 2,4-D herbicide at rate of 1.5 – 2.0 pounds active ingredient per acre to resprouts in the pre-flower bud stage; continue to experiment with biocontrol
insects
Diffuse knapweed
WMO: suppress; reduce the stem density of reproductive plants within all
occurrences by 50%
Control: introduce biocontrol insects at all known occurrences; pull or dig plants
or apply herbicide to small, isolated where biocontrol insects may not be effective
Field bindweed
Area occupied (acres): unknown but substantial
WMO: suppress; reduce canopy cover by 50% within occurrences where
biocontrol mites have been introduced
Control: introduce biocontrol mites at all large occurrences
Fuller’s teasel
WMO: suppress; reduce the density of reproductive individuals within all
occurrences by 50%; prevent all seed dispersal each year
30
Control: apply Banvel herbicide to rosettes at rate of 0.25 – 0.5 pounds active
ingredient per acre in spring or fall; cut bolted stems before seed dispersal in
summer and remove cut stalks to a dumpster
Hoary cress
Area occupied (acres): 3.58 (this area was expanded in 2003)
WMO: suppress; reduce canopy cover within all occurrences by 50%
Control: apply Escort herbicide to rosettes at rate of 0.12 – 0.45 ounce active
ingredient per acre to actively growing rosettes in early summer or to regrowth in
the fall before the first killing frost
Leafy spurge
WMO (Academy): suppress; reduce canopy cover within all occurrences by 90%
WMO (Farish): eradicate; work with the adjacent private landowner to control the
infestation.
Control: introduce biocontrol insects at all known occurrences; apply Plateau
herbicide at a rate of 8 ounces product per acre to plants in late summer, using 2
pints per acres of methylated seed oil as an adjuvant
Musk thistle
WMO: suppress; reduce the density of reproductive individuals by 90%; prevent
all seed dispersal each yearControl: apply Transline herbicide to rosettes at rate of
0.13 – 0.5 pounds active ingredient per acre or Tordon 22K at a rate of 0.13 –
0.25 pounds active ingredient per acre in spring or fall or 2,4-D at a rate of 1.5 –
2.0 pounds active ingredient per acre in the spring; cut bolted stems before seed
dispersal in summer; remove cut stalks to a dumpster
Russian olive
Area occupied (acres): Not available
WMO: suppress; reduce the density of reproductive individuals by 90%; prevent
all seed dispersal each year
Control: use weed wrench, construction equipment or truck-mounted winch to
pull smaller individuals from the ground; cut stems/ trunks of larger individuals
with a chain saw and apply Roundup, Garlon 3A, or Garlon 4 herbicide within 30
seconds of cutting to the stumps with squirt bottle; cutting is most effective in the
fall; dispose of any foliage with viable seeds in a landfill
Scotch thistle
WMO: eradicate; prevent all seed dispersal each year
Control: apply Transline herbicide to rosettes at rate of 0.13 – 0.5 pounds active
ingredient per acre or Tordon 22K at a rate of 0.13 – 0.25 pounds active
ingredient per acre in spring or fall or 2,4-D at a rate of 1.5 – 2.0 pounds active
31
ingredient per acre in the spring; cut bolted stems before seed dispersal in
summer; remove cut stalks to a dumpster
St. Johnswort
Area occupied (acres): Estimated at 3-5 acres.
WMO: suppress; reduce canopy cover within all occurrences by 90%
Control: introduce biocontrol insects at all known occurrences; apply Tordon 22K
in spring to all occurrences at a rate of 0.125 – 1.5 pounds active ingredient per
acre where desirable shrubs or trees are not present; cut and remove any seed
stalks that are produced
Spotted knapweed
WMO: suppress; reduce the density of reproductive plants within all occurrences
by 90%
Control: introduce biocontrol insects at all known occurrences; pull or dig plants
or apply herbicide to small, isolated occurrences where biocontrol insects may not
be effective; apply Tordon 22K herbicide at a rate of 0.25 pounds active
ingredient per acre before seed set or apply Transline herbicide at a rate of 0.2 –
0.24 pounds active ingredient per acre during bolt or bud growth stages to small,
isolated occurrences that are too large to pull and too small for biocontrol insects
to be effective
Yellow toadflax
WMO (Academy): suppress; reduce canopy cover within high-priority
occurrences by 50%
WMO (Farish): contain, prevent new occurrences from becoming established
Control: apply Tordon 22K herbicide at rate of 4 pints product per acre to resprouts at the flowering stage; continue to experiment with biocontrol insects
MONITORING AND EVALUATION
Weed management actions recommended for the Academy are believed to be
effective. However, there is no guarantee that this will, in fact, be the case. Variations in
weather, soil moisture, growth stage of the target weed species, and genetic variation
among and within weed populations mean that weed management is not always effective.
Thus, it is important to develop a practical monitoring program to evaluate the
effectiveness of weed management actions. Potential adverse effects of herbicide
application to desirable plants will be minimized by following label instructions, using
care in applying herbicides, and visual inspection of areas sprayed.
The term “monitoring” is used in different ways by different people. As used in
this plan, monitoring refers to the structured and repeated collection and analysis of
information that enables an evaluation of the progress toward a management objective.
32
Thus, the purpose of monitoring is to provide feedback, without which, managers cannot
learn and improve their control of noxious weeds.
There are many possible ways to monitor the effects of management actions. It is
important to select methods that will provide the minimum amount of information
necessary to evaluate in an unbiased way the effectiveness of management actions in the
most cost-effective manner. Monitoring is a complex subject that cannot be adequately
summarized here. Elzinga et al. (1998) is an excellent reference that can be used to
address important details. However, we provide general recommendations for
monitoring.
Photo-monitoring
This approach involves photographing weed occurrences periodically (e.g., once a
year in the summer) and examining the photographs for evidence of weed presence or
abundance. Photopoints can either be temporary (used once) or permanent (the same
location is used for several years). The locations of temporary photopoints should be
recorded with a GPS unit. Permanent photopoints should be marked (e.g., with a length
of capped rebar driven into the ground) and their location recorded (with a GPS unit) so
they can be relocated easily. Photographs can be examined visually to evaluate the
change in abundance of the target noxious weed species. This method has the advantage
of being rapid and inexpensive. It is appropriate when one is attempting to determine if a
highly visible weed species is declining greatly in abundance, i.e., when low precision is
adequate. For example, the weed management objective for bull thistle is to eliminate all
seed dispersal each year. This could be documented by photographing a sample of bull
thistle occurrences in mid-summer. There should be no bull thistle seed stalks visible in
the photographs, because they should have already have been cut and hauled away. (Bull
thistle seed stalks are tall enough to be visible within 50 feet of the photographer.) The
number of visible bull thistle stalks visible in a photograph could be recorded as an index
of management effectiveness. At the Academy, photo-monitoring, as the sole source of
monitoring information, would be appropriate only for tall, easy-to-see species, namely
bull thistle, Russian olive, and Scotch thistle. However, photo-monitoring can be used
with plot monitoring to provide additional information that may not be evident from
quantitative data. For example, photographs can be taken along permanent transects used
for plot monitoring.
Plot monitoring
This approach involves establishing temporary or permanent plots where weed
data (and possibly data for desirable plant species) are collected. As a general rule, we
recommend establishing permanent plots because one can obtain more precise estimates
of weed abundance with fewer sampling units. It is unlikely that vandalism of permanent
plots (e.g., persons removing plot markers) will be a significant problem at the Academy,
as it can be in some areas. Permanent plots must be marked physically (e.g., lengths of
capped rebar or metal t-posts driven into the ground in the plot corners or a single length
of capped rebar driven into the ground in the center of a circular plot). The locations of
33
permanent plots must be recorded with sufficient precision (using a GPS unit) to enable
them to be relocated easily. Detailed written descriptions of the locations of permanent
plots are also very helpful. Generally speaking, we recommend long, narrow plots
(sometimes called belt transects) for estimating plant density because they tend to capture
more variation in the population of interest within each sampling unit and minimize the
variation among sampling units (Elzinga et al. 1998). Appropriate dimensions of
permanent plots depend on many factors, including the size the population of interest;
however, plots that are 25 - 50 meters long and 1 - 4 meters wide are often used. Note
that multiple plots (assuming that each plot is a sampling unit) will be necessary to obtain
an estimate of variance of a population of interest. For permanent plots, many fewer
plots are typically needed that for temporary plots. Unfortunately, estimating the number
of plots needed to achieve a target level of precision cannot be determined until after the
second year’s data have been collected. As a guide, we have generally used up to five
permanent density plots per weed occurrence. When estimating canopy cover, we
recommend arraying small, permanent microplots (e. g., 0.25 x 0.5 meters in size) along
permanent transects. Here, the microplot is the sampling unit, while transects are simply
convenient devices to organize and re-locate the microplots. We suggest keeping
microplots at least 2.5 meters apart to reduce autocorrelation between adjacent
microplots.
The types of weed data collected depend on the weed management objective, i.e.,
presence/absence or some abundance measure. We recommend using reproductive plant
or stem density where it is appropriate (for non-clonal weed species) and canopy cover
for other species. Density data are generally more precise and less subject to observer
bias that canopy cover data. Density data are obtained by counting the number of target
plants (or the number of reproductive stems of target plants) in an area of known size (a
plot) then converting the counts to density by dividing the number of plants by the area of
the plot. For example, the weed management objective for bull thistle (as well as musk
thistle and Russian olive) is to reduce the density of reproductive plants by 90%. Thus,
permanent plots can be established in bull thistle occurrences where the number of
reproductive plants of bull thistle in each plot can be counted and recorded. Relatively
large plots (e.g., 50 meters by 5 meters) could probably be used because reproductive bull
thistle plants are easy to find and count, even for inexperienced technicians.
For clonal weed species, individual plants cannot be discerned. It is possible to
estimate the density of reproductive stems, but we anticipate that many reproductive
stems will typically be present, thus counting them in plots could be tedious and timeconsuming. We recommend using canopy coverage as the measure of the effectiveness of
weed management.
Canopy cover can be estimated in several ways. Two common approaches are 1)
using a sighting devise and 2) using ocular estimates. With a sighting device, one
establishes permanent transects (depending upon the circumstances, each point or
transect can be a sampling unit) within the population of interest. Using a telescope-type
instrument, one looks vertically downward at the permanent points arrayed along the
transect (points may also be offset from the transect) and determines if the target weed
34
species is present under the cross-hairs of the instrument. The instrument is moved to the
next point and the process repeated. This approach reduces observer bias to a minimum.
Where each point is a sampling unit, the data (sometimes called point cover data) are the
number of points intercepted by the target weed species divided by the total number of
points. One – two hundred points are commonly used at each sampling location.
Another common approach is to make ocular estimates of canopy cover of the
target weed species in microplots. The microplots can be placed at permanent locations
arrayed along permanent transects. Unfortunately, ocular estimates of canopy cover are
notoriously subject to observer bias. Thus, it is best if each microplot is a sampling unit
in order to achieve a large number of samples to achieve an acceptable level of precision.
Sampling bias can be reduce somewhat by using Daubenmire cover classes (or some
similar system) to categorize plot canopy cover.
For species where the management objective is eradication (i.e., Russian
knapweed and Scotch thistle) permanent plots could be established in all mapped
occurrences (and any new occurrences that may be found). One would simply walk
through each plot and see if any living Russian knapweed or Scotch thistle plants or
reproductive plant parts are visible. The number of surviving plants or plant parts could
be counted to help evaluate control efforts. Three consecutive years with no Scotch
thistle plants or plant parts would indicate that the weed species has been eradicated in
the plots. For Russian knapweed (a clonal species), transects could be established in the
two known occurrences and canopy cover data collected to help gauge the success of
control efforts.
Recommended monitoring actions for all fourteen target noxious weed species are
listed in Table 5. They are designed to be simple yet practical measures that will provide
sufficient information to evaluate effectiveness of weed management actions in relation
to the respective weed management objectives. We recommend conducting monitoring
annually for the first three years. Thereafter, based on the initial results, the frequency of
monitoring may be lengthened.
Occurrence perimeter monitoring
As noted above, part of each weed management objective is that the size of the
weed occurrences will not increase over time. The most efficient way to estimate the size
of most weed occurrences is to walk the perimeter of the occurrence and document the
location of points on the perimeter with a global positioning system (GPS) unit. Highquality units are available commercially that are accurate to about 1 meter. The GPS data
for the weed polygons can be easily converted into areas that can be compared to
previous polygon data. By inspection, one can easily determine if a weed occurrence had
increased or decreased in size, within the error limits of the GPs data. When walking
around the perimeter of weed occurrences, it is important to be consistent in including or
not including “outlier” individuals of the target weed species.
35
Table 5
Recommended monitoring of targeted noxious weed species at the Air Force Academy or
Farish Recreation Area.
_______________________________________________________________________
Noxious Weed
Species
Monitoring Action(s)
Bull thistle
Photograph 3 randomly selected bull thistle occurrences and count
bolted plants
Canada thistle
Establish permanent plots in 3 randomly selected occurrences that
have been controlled and collect canopy cover data; continue to
collect plant and insect data at release sites
Diffuse knapweed
have been controlled and count reproductive plants; continue to
Field bindweed
Establish permanent plots in 2-3 randomly selected occurrences
where bindweed mites (Aceria malherbae) have been released and
collect canopy cover data
Fullers’ teasel
Photograph 3 randomly selected occurrences and count bolted
plants
Hoary cress
have been controlled and collect canopy cover data
Leafy spurge
have been controlled and collect canopy cover data; continue to
Musk thistle
Photograph 3 random selected musk thistle occurrences and count
bolted plants
Russian knapweed
Establish permanent plots in both occurrences and collect canopy
cover data
Russian olive
Inspect all cut and poisoned stumps for resprouts; re-treat any
resprouts found
Scotch thistle
Photograph all Scotch thistle occurrences and count bolted plants
36
St. Johnswort
Establish permanent plots in 3 randomly occurrences and collect
canopy cover data; continue to collect plant and insect data at
release sites
Spotted knapweed
have been controlled and count reproductive plants; continue to
Yellow toadflax
have been controlled in high-value resource areas and collect
canopy cover data; continue to collect plant and insect data at
release sites
______________________________________________________________________
37
Adjusting weed management actions
The point of monitoring is to provide a rational basis for determining if weed
management actions are effective in moving toward the weed management objectives.
Therefore, we recommend conducting annual weed monitoring for three consecutive
years once the monitoring program is initiated, hopefully in 2005. Even more important
is to analyze the monitoring data each year and to meet with concerned parties to discuss
the monitoring results, ideally early in the calendar year. Thereafter, weed management
actions for the forthcoming year can be changed, as needed, if indicated by the results of
the monitoring. It may also become apparent that the initial approach to monitoring for a
certain weed species is not very effective or efficient. If so, the monitoring methodology
can be adjusted, as needed. After the first three years of monitoring, the data may show
that less frequent or less intensive monitoring is acceptable for certain weed species.
38
REFERENCES
Anderson, D. G., A. Lavender, and R. Abbott. 2003. Noxious weed survey of the U.S.
Air Force Academy and Farish Recreation Area. Colorado Natural Heritage Program,
Colorado State University, Ft. Collins, CO.
Anonymous. 2003. Integrated natural resources management plan, U.S. Air Force
Academy. U.S. Air Force Academy, Colorado Springs, CO.
Anonymous. 2001. Integrated natural resources management plan, Farish Recreation
Area, United States Air Force Academy. Air Force Academy, Colorado Springs, CO.
Carpenter, A. T., T. A. Murray, and K. A. Decker. 2000. Creating an integrated weed
management plan: a handbook for owners and managers of lands with natural values.
Colorado Natural Areas Program, Department of Natural Resources, Denver, CO.
Ellingson, A. R., S. M. Kettler, S. C. Spackman, C. A. Pague, and J. G. Corn. 1996.
Significant natural heritage resources of the United States Air Force Academy and their
conservation. Colorado Natural Heritage Program, Colorado State University, Ft.
Collins, CVO.
Elzinga, C. L., D. W. Salzer, and J. W. Willoughby. 1998. Measuring and monitoring
plant populations. BLM Technical Reference 1730-1. Bureau of Land Management,
National Business Center, Denver, CO.
ESCO Associates, Inc. 1992. Natural areas inventory, U.S. Air Force Academy, El Paso
County, CO, final report. Unpublished report on file at The Nature Conservancy,
Boulder, CO.
Hiebert, R. D. and J. Stubbendieck. 1993. Handbook for ranking exotic plans for
management and control. Natural Resources Report NPS / NRMWRO / NRR-93 / 08.
U. S. Department of the Interior, National Park Service, Washington, DC.
Hiebert, R. D. 1997. Prioritizing invasive plants for planning and management. In: J. O.
Luken and J. W. Thieret (eds.) assessment and management if plant invasion. SpringerVerlag, New York. Pp. 195-212.
Kennedy, S. 2004. Personal communication between Sue Kennedy, U.S. Fish &
Wildlife Service, Lakewood, CO, and Brian Mihlbachler, USFWS, Air Force Academy.
Lonsdale, W. M and A. M. Lane. 1994. Tourist vehicles as vectors of weed seeds in
Kakadu National Park, Northern Australia. Biological Conservation 69:277-283.
Louda, S. D. Kendall, J. Connor, and D. Simberloff. 1997. Ecological effects of an
insect introduced for biological control of weeds. Science 277:1088-1090.
39
McDermott, J. and K. Lair. 1990. Grazing management plan. Unpublished report on
file at 10th Civil Engineering Squadron (CECN), U.S. Air Force Academy, Colorado
Springs, CO.
Michels, G. J., D. A. Owinds, M. Mirek, J. Bible, L. Castleberry, S, Camarata, S. Bruno,
R. Bouton, B. Villarreal, and E. McKown. 2003. Biological control of noxious weeds on
federal installations in Colorado. Texas A & M University, Texas Agricultural
Experiment Station, Bushland, TX.
Moody, M. E. and R. N. Mack. 1988. Controlling the spread of plant invasions: the
important of nascent foci. Journal of Applied Ecology 25:1009-1021.
Ripley, D. J. 1994. Vegetation of the U.S. Air Force Academy, El Paso County,
Colorado. Unpublished report on file at the U.S. Air Force Academy.
Schorr, R. A. 2004. Preble’s meadow jumping mouse population studies on the Air
Force Academy. Unpublished progress report. Colorado Natural Heritage Program,
Colorado State University, Ft. Collins, CO.
Schorr, R. A. 2003. Meadow jumping mice (Zapus hudsonius preblei) on the Air Force
Academy, El Paso County, Colorado: populations, movement and habitat from 2000 –
2002. Unpublished progress report. Colorado Natural Heritage Program, Colorado State
University, Ft. Collins, CO.
Sheley, R. L. and J. K. Petroff (eds.). 1999. Biology and management of noxious
rangeland weeds. Oregon State University Press, Corvallis, OR.
Smith, H. A., W. S. Johnson, J. S. Shonkwiler, S. R. Swanson. 1999. The implications
of variable or constant expansion rates in invasion rates in invasive weed infestations.
Weed Science 47:62-66.
Weber, W. A. and R. C. Wittmann. 2001. Colorado flora – eastern slope. Third edition.
University of Colorado Press, Boulder, CO.
Wittenberg, R. and M. J. W. Cock. 2001. Invasive alien species: a toolkit of best
prevention and management practices. CAB International, Wallingford, United
Kingdom.
40

U.S. Air Force Academy Integrated Weed Management Plan

Transcription

Similar documents

Mickey Mouse Bush / Ochna Ochna serrulata

Maderia Vine Anredera cordifolia

NEW DRUG - “CANDY WEED” JUNE 2012

Stoner Fluxx v2.1 Organizer

Volume 6 | Issue 2 - Hawthorne Management Company

www.VeryImportantPotheads.com JOSS STONE

Dutchman`s Pipe - Sydney Weeds Committees

Matt Berger, Wildlife Program Manager.

`iheal` will give students with autism better ability to

BIOCOVERS