Appendix b – hibernacula: forest habitat analysis 98 appendix c – literature cited 101




НазваниеAppendix b – hibernacula: forest habitat analysis 98 appendix c – literature cited 101
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Threats



Mead’s milkweed is threatened by the destruction and alteration of tallgrass prairie and glade/barren habitat or lack of active management through prescribed fire. Many locations where the species is previously known to have occurred have been destroyed by plowing and land development (Freeman 1988, Kurz and Bowles 1981). Many populations that were studied by Betz (1989) in 1965-1971, have been destroyed due to changes in management (i.e., use of herbicides instead of burning) for maintaining right-of-ways or other utility projects.


Private lands that are managed as hay meadows result in an altered population structure and reduction in genetic diversity and evolutionary potential. All but one of the Kansas milkweed populations occur on privately owned prairie hay meadows (Freeman 1988). Mowing of these prairies typically occurs in late June to early July (Brooks 1983, Freeman 1988), removing immature fruits and preventing completion of the plant’s life cycle. Hay fields in Missouri with known populations of Mead’s milkweed are managed under a similar regime. While public prairies have been acquired since the late 1970’s, mowing has continued on these sites, but in rotation with burning and occasionally grazing (Smith 1997). In Iowa, only two Mead’s milkweed sites are in public ownership and are being managed in a method compatible with the species’ life cycle. The other Iowa sites are private hay meadows, pastures, and another is a right-of-way of an abandoned railroad prairie (USFWS 2003). In Illinois, extant populations of Mead’s milkweed are protected on Forest Service land within Research Natural Areas, but suffer from lack of prescribed fire.


Reproductive isolation has occurred in many Mead’s populations due to habitat fragmentation, even in Kansas and Missouri where populations are most numerous (Freeman 1988). Many of the smaller fragments still support low numbers of plants, but fragmentation is believed to have lead to the loss of genotypes and failure of these populations to produce viable seeds. In addition, in some populations the small number of plants may not attract pollinators in large enough numbers to ensure sexual reproduction. Furthermore, it has been speculated that the loss of habitat in some portions of the species’ range have subsequently reduced pollinator populations (USFWS 2003). In addition, the Saline County, Illinois populations are threatened by encroachment of woody vegetation, trampling by hikers (Kurz and Bowles 1981 and Schwegman 1987) and theft. Other threats include predation, pathogens, herbivory (Garman and Alexander 2005), sexual incompatibility and stochastic events.


Many factors that hinder the recovery of Mead’s milkweed may be overridden by the loss of genetic diversity. This may especially be true in eastern populations where the number of genotypes appears to be very low and in some cases is limited to one genotype per population. Active management is necessary to maintain Mead’s milkweed populations. Research shows that prescribed fires are essential to successful reproduction and the long term survival of the species (Bowles et al. 1998, Tecic et al. 1998, Garman and Alexander 2005).


ENVIRONMENTAL BASELINE

Status of the Species within the Action Area



Mead’s milkweed is found on the SNF in four locations. These four populations are located in three Research Natural Areas: Stoneface, Cave Hill, and Dennison Hollow, which are remnants of a larger population that has been fragmented by the encroachment of woody vegetation resulting from decades of fire suppression (USFWS 2003). Each of these Mead’s milkweed sites can all be characterized as barrens or glade habitat along sandstone ridges and blufftops.


All Mead’s milkweed sites on the SNF are less than 0.1 hectares in size (Bowles 2001) and were last surveyed in May and June of 2005. The results of the 2005 survey are provided in Table 19. A total of 16 native plants were located, 15 of which were juveniles and one was a flowering adult (Elizabeth Shimp, SNF, pers. comm. 2005).


Table 19. Survey results for Mead’s milkweed sites on the SNF on May 27 and June 16, 2005.

Site Name

Number of Natives

Number of Reintroduced

Number of Adults

Number of Juveniles

Number of Flowering

Stoneface Upper

2

0

0

2

0

Stoneface Lower

0

0

0

0

0

Dennison Hollow

12

0

1

11

1

Cave Hill

2

0

0

2

0

Total

16

0

1

15

1


Reintroductions have been carried out at each of the four sites on the SNF by the Morton Arboretum in conjunction with the Forest Service. Reintroductions began in 1991, although a setback occurred when some of the introduced plants were stolen and two juvenile native plants were cut to ground level in 1991 (Elizabeth Shimp, USFS, pers. comm. 2005, Stone 1991). According to Bowles et al. (2001) site reintroductions average about 60 plants per site with approximately 60% being one-year-old juveniles, and the remaining 40% planted seeds. Survivorship of reintroduced juveniles was recorded at 22.5%. Germination of reintroduced seeds was 18.5% with a 14.8% survival rate (Bowles et al. 2001). An introduction was attempted at a fifth site on the SNF in 2003, but no plants were found during the last census of the area in 2004 (Elizabeth Shimp, USFS, pers. comm. 2005).


Management of the Mead’s milkweed sites began in the late 1980s at the Stoneface and Cave Hill areas. Management of these areas has included the removal of trees and shrubs and landscape scale prescribed fire. This management regime continued until 1995, after which only minor tree and shrub removal occurred at existing Mead’s milkweed locations. Upon its discovery in July 1991, management of the Dennison Hollow population was primarily tree and shrub removal, although spot burning occurred in March 1992 (Elizabeth Shimp, USFS, pers. comm. 2005).


Survey results from 1983 to 2005 are summarized in Table 20 (Elizabeth Shimp, USFS, pers. comm. 2005). Results indicate a general decline in the number of Mead’s milkweed individuals located on the SNF over the last decade. The number of individuals initially increased following the last prescribed burn in 1995. However, after almost a decade without prescribed fire, the number of individuals has been generally declining since 1999. In addition, the number of flowering individuals also initially increased after 1995, but has also been in decline for the past several years.


Table 20. Survey results of Mead’s milkweed on the SNF. Number of flowering plants is in parenthesis. A “-“ indicates the site was unknown at the time. NA = Data Not Available (site was not censused or data not accessible at the time of this report.

Year Surveyed

Stoneface Lower

Cave Hill


Stoneface Upper

Dennison Hollow

Cave Hill Fire Tower

Total

1983

8(2)

8(1)

-

-

-

16(3)

1984

7(3)

7

3

-

-

17(3)

1985

6(2)

4

1

-

-

11(2)

1986

7(2)

4

1

-

-

12(2)

1987

9

8

1

-

-

18(0)

1988

7(2)

9(1)

1

-

-

17(3)

1989

3

6(1)

0

-

-

9(1)

1990

5(1)

7(1)

2

-

-

14(2)

1991

3

5(1)

2

5(1)

-

15(1)

1992

2

3

1

14(1)

-

20(1)

1993

4

2

2

14(1)

-

22(1)

1994

1

4

1

11(4)

-

17(4)

1995

0

NA

NA

NA

-

0(0)

1996

0

1

1

22(4)

-

24(4)

1997

1

NA

1

14(6)

-

16(6)

1998

1

5

0

20(7)

-

26(7)

1999

1

5

0

20(4+)

1

26(4+)

2000

0

NA

NA

5

-

5(0)

2001

0

3

1

12(2+)

-

16(2+)

2002

NA

NA

NA

NA

-

NA

2003

0

0

0

4

-

4(0)

2004

NA

NA

1

8

-

9(0)

2005

0

2

2

12(1)

-

16(1)


Table 21. Combined population viability of Mead’s milkweed populations on the Shawnee National Forest.

Variable

Current Condition

Ranking: Definition of ranking

A. Population Size

15 Juveniles 1 Adult

0: < than 10 adults

B. Population Growth Trend

Decrease from 1995 to 2005

0: Decreased survivorship or growth

C. Effective Population Size (number of genotypes)

5 Genotypes

0: <10 Genotypes

D. Habitat Size

Each site is < 0.1 hectare, total size of all sites combined < 0.4 hectare

0: < 1 Hectare

E. Habitat condition/ successional stage

All sites in Natural Areas, lightly disturbed/late successional

3: Lightly disturbed or late successional

F. Protection status

On federal land/legal

3: Private or public ownership with legally binding protection

G. Management condition

Severe

0: Little human manipulation, but in severe need of fire to reduce woody encroachment

Total




6

PVI

(A+B+C+D+E+F+G)/21

0.285: Low viability is < 0.50


Using the Determination of Population Viability Index (PVI) as detailed in the 2003 Mead’s Milkweed Recovery Plan, the combined viability of the populations on the SNF has a PVI score of 0.29 (Table 4), which is considered low viability.


Previous Biological Opinions for Mead’s Milkweed


In Region 3, only two biological opinions have been written for the Mead’s milkweed. Both were for the Mark Twain National Forest (MTNF) and prepared by the Columbia Missouri Ecological Services Field Office. The first one was June 23, 1999 “Biological Opinion on the Impact of Forest Management and Other Activities to the Gray Bat, Bald Eagle, Indiana Bat, and Mead’s Milkweed on the Mark Twain National Forest, Missouri.” The Service concluded that the actions were not likely to jeopardize the continued existence of Mead’s milkweed. Six conservation recommendations were provided in that biological opinion, including a recommendation to obtain approval to conduct prescribed burning in the Bell Mountain Wilderness. No action on that discretionary recommendation has been taken, therefore, the viability of that population continues to decline. The MTNF has continued to monitor the Bell Mountain Wilderness population and has provided the Service with annual reports.


The second biological opinion was the September 16, 2005, “Programmatic Biological Opinion for the Mark Twain National Forest 2005 Forest Plan.” The Service concluded that the proposed Forest Plan and actions were not likely to jeopardize the continued existence of Mead’s milkweed. Five conservation recommendations were provided in that biological opinion. Additional conservation recommendations were provided for the Bell Mountain Wilderness population of Mead’s milkweed.


EFFECTS OF THE ACTION


This section includes an analysis of the direct and indirect effects of the proposed action on the species and its interrelated and interdependent activities. A Forest Plan level consultation requires two levels of analysis. The first level of the analysis will consider how the overall Forest Plan goals and objectives will affect listed species. The second level of the analysis will consider how the specific actions that implement the Forest Plan will affect the listed species.


Effects of the Implementation of the 2006 Forest Plan Goals and Objectives


As indicated in the Description of the Proposed Action, numerous goals have been established for the 2006 Forest Plan. These goals can be summarized as: 1) to promote ecosystem health and sustainability; and, 2) to provide a variety of uses, values, products and services. The only known populations of Mead’s milkweed on the SNF are in designated Research Natural Areas (RNA) in Stoneface, Cave Hill, and Dennison Hollow. These RNA’s are all managed under the Natural Areas (NA) management prescription area, which has a total acreage of 14,858 acres (USFS 2005b). Management activities that may be seen include prescribed burning, tree and shrub removal, trail construction and maintenance and non-native invasive species control.


The NA management prescription area designation protects the sites from human disturbance and directs management to the protection and management of natural communities including management to protect and improve habitat and ecological conditions for Mead’s milkweed. Actions that have been taken include trail closure to equestrian and ATV use, closures on rock climbing and rapelling in the three RNA’s, and water bar management on existing trails. These actions would continue and/or resume in the future with implementation of the 2006 Forest Plan and should have beneficial effects on the species.


In addition to the above, various administrative management activities will continue, including collection of pollen and/or seeds, introduction of seeds and plants and administrative protection of known sites. These activities are discussed in detail below. Administrative activities have had a beneficial effect on existing populations.


The overall goals and objectives of the 2006 Forest Plan for the SNF are consistent with the habitat needs of Mead’s milkweed and, in general, implementation of the plan is anticipated to have only periodic, minor, negative fitness consequences to the species. Overall the plan is expected to improve the long term viability of the populations of Mead’s milkweed on the SNF.


Effects of Implementation of the Types of Management Proposed to Accomplish Forest Plan Goals and Objectives


Direct and indirect effects to Mead’s milkweed could occur with the implementation of the 2006 Forest Plan.

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