Silverleaf Milkvetch Surveys Pitkin County & Town of Snowmass Village Open Space Pitkin County,

prepared for: Pitkin County Open Space & Trails 530 E. Main St. Suite 300, Aspen, CO 81611

prepared by: Western Ecological Resource, Inc. 711 Walnut Street, Boulder, CO 80302

November 2012

Table of Contents

Section / Title Page

1.0 Introduction ...... 1 2.0 Environmental Setting ...... 1 2.1 Location and Landform ...... 1 2.2 Climate ...... 1 3.0 Survey Methodology ...... 1 4.0 Species Description ...... 2 5.0 Results ...... 2 5.1 Location ...... 2 5.2 Habitat Characteristics ...... 2 5.2.1 Landform ...... 2 5.2.2 Habitat and Associated Plant Species ...... 3 5.2.3 Geology ...... 3 5.2.4 Soils ...... 3 6.0 Summary ...... 4 7.0 References ...... 5 8.0 Figures ...... 6 9.0 Tables ...... 11 10.0 Photographs ...... 16 Appendix A. 2012 CNHP Dataform for Silverleaf Milkvetch ...... 20

List of Figures

Number / Title Page

Figure 1. Vicinity Map ...... 7 Figure 2. Survey Area Tracks ...... 8 Figure 3. Result Map -Topographic ...... 9 Figure 4. Result Map -Aerial ...... 10

List of Tables

Number / Title Page

Table 1. Summer Climate Data for the Aspen 1SW Weather Station 2011-2012 ...... 12 Table 2. Known Locations of Silverleaf Milkvetch in Colorado ...... 13 Table 3. 2012 Silverleaf Milkvetch Survey Results ...... 14 Table 4. Associated Plant Species ...... 15

List of Photos

Number / Title Page

Photo 1. Silverleaf milkvetch in flower. 26-May-2011...... 17 Photo 2. Silverleaf milkvetch in fruit. 21-May-2012...... 17 Photo 3. Lamber's locoweed, which closely resembles the silverleaf milkvetch (21-May-2012). . 18 Photo 4. Silverleaf milkvetch population #5, looking northeast. 21-May-2012...... 18 Photo 5. Silverleaf milkvetch habitat on north-facing slope. 21-May-2012...... 19 Photo 6. Silverleaf milkvetch population #18, looking south. 21-May-2012...... 19

1.0 Introduction

In 2011, Biological Resource Surveys were completed on 13 open space parcels owned by Pitkin County, the City of Aspen, and the Town of Snowmass Village. During these surveys, a previously unknown population of a state sensitive plant species was found. This plant, the silverleaf milkvetch (Astragalus argophyllus var. martinii), is tracked by the Colorado Natural Heritage Program (CNHP), and is considered state critically imperiled.

In 2012, the project area was revisited to more precisely locate the occurrences of silverleaf milkvetch and take other demographic data. Specifically, the 2012 survey focused on the following parcels: Sky Mountain Park (formally Droste), Seven Star 1 & 2, Cozy Point South, as well as the adjoining Town of Snowmass Village (TOSV) open space parcels, Upper North Mesa and Hidden Valley (Figure 1). Other parcels included in the original 2011 survey (Mills, Aspen/Mass, Burlingame West, Deer Hill, Annie Mitchell, Airport Bluff, and Cozy Point) do not provide appropriate habitat for the silverleaf milkvetch.

This report includes a brief description of the target species, the survey methodology, and the results of the survey including details on the size, location, and habitat characteristics of all occurrences found, along with photographs and maps. Appendix A contains a copy of the 2012 dataform submitted to the CNHP. GIS shapefiles of the results are being submitted electronically along with this report.

2.0 Environmental Setting 2.1 Location and Landform The ±2,200 acre project area is located along the Brush Creek Valley just east of the Town of Snowmass Village. The highest elevation of the project area, 9,116 feet, occurs on the north end of Upper North Mesa, seconded by Sky Mountain Park with an elevational high of 8,693 feet along the ridgeline. The lowest elevation is 7,600 feet along Brush Creek at Cozy Point South.

2.2 Climate The climate of the project area is generally characterized by long, cold and moist winters, and short, cool, dry summers. Based on climate data from the Aspen 1 SW Weather Station (elev. 8,163 ft.), the average annual precipitation is 23.26 inches and the mean annual temperature is 40.8°F, with a mean high temperature of 77.2°F in July and a mean low of 7.4°F in January (NCDC, 2002). The growing season length, based on a 28°F air temperature, is 127 days with a 50% chance of occurring between May 24 and September 28, and the average annual snowfall is 187.3 inches (NRCS 2002).

Temperature and precipitation varied greatly between the spring of 2011 and the spring of 2012, which resulted in silverleaf milkvetch flowering and fruiting about three weeks earlier in 2012 than in 2011. As shown in Table 1, a total of 13.82 inches of precipitation fell during April through August of 2011, while only 7.83 inches fell during the same period in 2012. Both April and May of 2012 were well below the 30-year Precipitation Normal, while April and May of 2011 were above normal. Similarly, temperatures varied between the two growing seasons, with the mean April and May monthly temperatures much lower than normal in 2011 and much higher than normal in 2012.

3.0 Survey Methodology

Surveys for silverleaf milkvetch were conducted by Ms. Rea Orthner of Western Ecological Resource, Inc. and one field assistant. The surveys were conducted on May 21, 22 and 23, 2012.

1 Ms. Orthner has a M.S. degree in botany from the University of Colorado in Boulder and has completed numerous floristic inventories and rare plant surveys in Colorado over the last 15 years. During the on-site field reconnaissance, potential habitats identified from aerial photography, namely the Mancos Shale barrens, were visited. Within each habitat, the area was systematically searched for plants by walking closely spaced parallel transects. When plants were encountered, their location was recorded with a GPS device and the number of plants noted. This information was then downloaded into ESRI's ArcMap software and a GIS shapefile generated of the results. Additional data taken at each site included associated plant species, aspect, slope, and photographs. A Garmin GPSmap 60CSx unit with differential correction technology and accuracies of 10-20 feet was used to take all plant location data. Figure 2 illustrates the GPS survey tracks during the field reconnaissance.

4.0 Species Description

The silverleaf milkvetch (Astragalus argophyllus var. martinii) is ranked by the CNHP as G5T4/S1, or globally secure but state critically imperiled. This species has not been previously recorded from Pitkin County but is known from 15 other localities in Eagle, Garfield, Jackson, Mesa, Moffat, and Montrose Counties (Table 2). It's overall range includes the mountains enclosing the Colorado Basin, from the Grand River north through northwest Colorado, west along the Uinta Range, and south along the east slope of the Wasatch Range to central ; also northwest along the Bear River and adjacent hill country into southwest and southeast , and it is apparently disjunct in northern (Welsh 2007). Throughout its range, silverleaf milkvetch occurs on dry, gravelly, sandy hillsides, stony ridges, mesas, and canyon benches, in sagebrush, mountain brush, aspen, and spruce-fir communities from 5,500 to 10,000 feet (Welsh 2007). This plant is distinguished by its caespitose habit, basifixed (rather than dolabriform) hairs on its leaves, strigulose pods, and flowers that are whitish tinged with purple and a purple keel (Ackerfield 2011).

5.0 Results 5.1 Location & Number of Plants A total of 38 sub-populations or occurrences of silverleaf milkvetch were found on the Sky Mountain Park and Seven Star Ranch II Open Space parcels. Figures 3 and 4 illustrate the distribution of these occurrences and Table 3 lists them in tabular format. Photos 1 through 6 depict the plants and their representative habitat. No silverleaf milkvetch plants were found on the Cozy Point South, Hidden Valley, Upper North Mesa, or Seven Star Ranch I parcels. In total, approximately 2,500 plants were observed. Assuming a 20% missed rate (plants missed during the inventory), the population may actually be around 3,000 plants. Additional occurrences likely exist on adjacent private lands south of the project area, but these areas were not included within the survey area boundary.

5.2 Habitat Characteristics Habitat characteristics are described below with respect to landform, vegetation community, associated species, geology and soils. In addition, two specimens were collected in 2011 and have been deposited at the CU Boulder Herbarium (COLO) in Boulder, Colorado. Appendix A contains a copy of the updated 2012 survey data form which has been submitted to the CNHP.

5.2.1 Landform All silverleaf milkvetch occurrences were found on ridgetops and associated shoulders or side slopes of Mancos Shale. Plants occurred on all aspects and slopes up to 25%. In some populations, the plants were concentrated at the topographically lower edges of the Mancos Shale habitat at the transition to mountain shrubland.

2 5.2.2 Habitat and Associated Plant Species The habitat for silverleaf milkvetch is best described as shale barrens. These areas are characterized by extremely low vegetative cover of 30% or less, and they are exposed to harsh wind, desiccation and sheet erosion. The soils are typically shallow, calcareous, alkaline and clayey, and are often capped by a thin gravel layer. In addition, the shale-derived clay soils are composed of very small particles that are easily compacted which restricts water movement and oxygen exchange, both of which are required for plant growth.

The vegetation community on these shale barrens is best described by the Indian Ricegrass Shale Barrens Association, which is ranked as globally and state imperiled (G2/S2) by the CNHP. It should be noted, however, that although Indian ricegrass (Oryzopsis hymenoides) is present, it is not dominant or any more common than numerous other native plants that grow in these areas. Species commonly occurring on the shale barrens within the project area include scattered shrubs of mountain mahogany (Cercocarpus montanus), bitterbrush (Purshia tridentata), Gambel oak (Quercus gambelii), serviceberry (Amelanchier spp.), and snowberry (Symphoricarpos rotundifolius); graminoids such as Indian ricegrass, junegrass (Koeleria macrantha), and western wheatgrass (Agropyron smithii); and forbs such as tapertip onion (Allium acuminatum), largeflower hawksbeard (Psilochenia occidentalis), two-form pussytoes (Antennaria dimorpha), balsamroot, Douglas pincushion (Chaenactis douglasii), Rocky Mountain spring parsley (Cymopterus planosus), evening primrose (Oenothera caespitosa), mat penstemon (Penstemon caespitosus), Osterhout penstemon (Penstemon osterhoutii), and point-tip twinpod (Physaria floribunda).

In 2012, a list of all plant species observed to be growing within the occupied silverleaf milkvetch habitats was recorded. Table 4 lists these 30 plant species. The most common herbaceous plant associates include rock goldenrod (Petradoria pumila), phlox (Phlox multiflora), Rocky Mountain spring parsley, running fleabane ( flagellaris) and mat penstemon. The most common associated shrubs include Gambel oak, serviceberry, sagebrush (Artemisia tridentata), mountain mahogany, and bitterbrush.

Finally, there is one plant which closely resembles silverleaf milkvetch. Lambert's locoweed (Oxytropis lambertii) is of similar appearance in vegetative form, however the locoweed has more lanceolate leaflets and lacks the flowers and fruits of silverleaf milkvetch. In addition, Lambert's locoweed flowers much later in the season and has dark pink flowers on a leafless scape.

5.2.3 Geology All occurrences of silverleaf milkvetch were found on flat to moderate slopes of the upper member of the Mancos Shale Formation. The Mancos Shale is a dark-gray shale and silty shale with a few outcrops of persistent olive-gray sandstone up to 40 feet thick (Bryant 1972). The upper Mancos Shale member was laid down in the Upper Cretaceous Period 99 to 65 million years ago by mudrock that accumulated in offshore and marine environments of the Cretaceous North American Inland Sea.

5.2.4 Soils The Department of Agriculture Soil Conservation Service (USDA-SCS) completed a soil survey of the Aspen area in 1992 and mapped two soil units within the occupied silverleaf milkvetch habitat. The first, the Dollard-Rock Outcrop–Shale Complex (Map Units 29 and 30) occurs on ridges and mountain sides from 12% to 65% slopes. The Dollard soil is moderately deep and well drained and formed in residuum derived from Mancos shale, which is the underlying bedrock of the project area. Typically, the surface layer is grayish brown clay loam about 4 inches thick which is underlain by a substratum of clay loam about 29 inches thick. The soil is calcareous throughout. Also present in this mapping unit is the Rock Outcrop, which consists of slightly weathered consolidated exposures of Mancos shale. Overall, this mapping unit has a low available water capacity, high shrink-swell potential, slow permeability, rapid runoff, shallow depth and/or exposed bedrock, severe erosion hazard, and low strength. 3

The second soil mapped within occupied silverleaf milkvetch habitat is the Torriorthents-Rock Outcrop Complex (Map Units 104 and 105) which occurs on slopes from 6% to 95%. This unit is about 45% Torriorthents, 20% Camborthids, and 15% Rock Outcrop. The Torriorthents are shallow to moderately deep, well drained soils and the surface is covered with stones. The surface layer is reddish-brown to brown in color and the soil texture ranges from fine sandy loam to clay loam. The depth to the shale or sandstone bedrock is 4 to 30 inches. The Camborthids are similarly well drained and have a light colored surface layer with a clay loam or loam texture. Water runoff is rapid and the hazard of water erosion is severe for both soils of this map unit.

6.0 Summary

Surveys for silverleaf milkvetch (Astragalus argophyllus var. martinii) were conducted on six Pitkin County and Town of Snowmass Village Open Space parcels in May of 2012. Approximately 2,500 plants were observed in 38 different locations, the majority of which occur on Sky Mountain Park and a smaller number on Seven Star Ranch II. All plants occur on Mancos Shale Barrens which are characterized by low vegetative cover, shallow clayey soils, and harsh growing conditions. No plants were observed north of the Brush Creek Valley on Seven Star Ranch or Upper North Mesa despite the presence of similar habitat there. Although silverleaf milkvetch plants appear quite common on the ridgeline of the Sky Mountain Park and Seven Star II Open Space parcels, these plants have an extremely limited range and have a relatively low number of occurrences within Colorado. The populations found during this study, for example, are the first recorded occurrences in Pitkin County, Colorado. Silverleaf milkvetch and its unique shale barren habitat certainly add to Colorado's biological diversity and both are worthy of protection.

4 7.0 References

Ackerfield, J. 2011. The Flora of Colorado -DRAFT. Colorado State University. Fort Collins, Colorado.

Benedict, A.D. 1991. A Sierra Club Naturalist's Guide: The Southern Rockies. Sierra Club Books. San Francisco, CA. 578 pp.

Bryant, B. 1972. Geologic Map of the 7.5' Highland Peak Quadrangle, Pitkin County, Colorado. USGS Map GQ-932.

Colorado Natural Heritage Program (CNHP). 1999. Roaring Fork Watershed Biological Inventory. 1997-1999. Prepared for Pitkin County, the Aspen Wilderness Workshop, and the Roaring Fork Valley Audubon Society.

Colorado Natural Heritage Program (CNHP) 2012. Element Occurrence Tracking Lists, by County and Quadrangle name. Downloaded November 13, 2012 from: http://www.cnhp.colostate.edu/download/list.asp

National Climatic Data Center (NCDC) 2002. Climatography of the United States No. 81. Monthly Station Normals of Temperature, Precipitation, and Heating and Cooling Degree Days. 1971-2000.

National Resource Conservation Service. 2002. WETS Station Data available (1980-2000) obtained from http://www.wcc.nrcs.usda.gov/ftpref/support/climate/wetlands/co/08097.txt

Tweto, O., R.H. Moench, and J.C. Reed, Jr. 1978. Geologic Map of the Leadville 1° x 2° Quadrangle, Northwestern Colorado. United States Geological Survey Map I-999.

University of Colorado Herbarium (COLO). Specimen Database of Colorado Vascular Plants. http://cumuseum.colorado.edu/Research/Botany/Databases/search.php

USDA-SCS. 1992. Soil Survey of Aspen-Gypsum Area, Colorado, Parts of Eagle, Garfield, and Pitkin Counties.

Weber, W. A. and R. C. Wittmann. 2001. Colorado Flora: Western Slope (Third Edition). University Press of Colorado. Boulder, Colorado. 488 pp.

Welsh, S.L. 2007. North American Species of Astragalus Linnaeus (Leuminosae). A Taxonomic Revision. Bringham Young University.

Western Ecological Resource, Inc. and Wildlife Specialties, LLC. 2011. Biological & Historical Resource Surveys, Pitkin County, City of Aspen, and Snowmass Village Open Space. October 2011. Boulder, Colorado.

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8.0 Figures

6 106°58'0"W 106°57'0"W 106°56'0"W 106°55'0"W 106°54'0"W 106°53'0"W 106°52'0"W 106°51'0"W 106°50'0"W 106°49'0"W 39°19'0"N 39°19'0"N 39°18'0"N 39°18'0"N 39°17'0"N 39°17'0"N 39°16'0"N 39°16'0"N 39°15'0"N 39°15'0"N

Cozy Point South Upper North Mesa

Seven Star Ranch 39°14'0"N 39°14'0"N Sky Mountain Park Seven Star Ranch II

Hidden Valley 39°13'0"N 39°13'0"N Project Location 39°12'0"N 39°12'0"N 39°11'0"N 39°11'0"N

106°58'0"W 106°57'0"W 106°56'0"W 106°55'0"W 106°54'0"W 106°53'0"W 106°52'0"W 106°51'0"W 106°50'0"W 106°49'0"W Grid Lat/Long WGS 1984 Figure 1. Vicinity Map Silverleaf Milkvetch Surveys Pitkin County, Colorado Map Location Ü Scale 1:100,000 COLORADO 1 inch = 8,333 feet 7 Cozy Point Figure 2. Survey Area Tracks Mills Silverleaf Milkvetch Surveys Pitkin County, Colorado

Legend

Open Space Properties

Survey Tracks Cozy Point South Upper North Mesa

Surveys conducted on May 21, 22, & 23, 2012

Seven Star Ranch

Sky Mountain Park

Seven Star Ranch II

Airport Bluff

Hidden Valley Ü 1:18,000 1 inch = 1,500 feet

Burlingame Ranch - west parcel Date: November 2012 Grid Ticks: UTM NAD83 Z13 Background: USGS 7.5' Highland Peak Quad

8 334400 334600 334800 335000 335200 335400 335600 335800 336000 336200 336400 336600 336800 337000 337200 337400 337600 337800 338000 338200 Figure 3. Result Map -Topographic

4345200 Silverleaf Milkvetch Surveys 4345200 Pitkin County, Colorado

Cozy Point South

4345000 Legend 4345000 Upper North Mesa Open Space Properties 4344800 4344800 Seven Star Ranch Silverleaf milkvetch 4344600

4344600 Surveys conducted on May 21, 22, & 23, 2012 19 4344400 4344400

21

20 4344200 4344200

15 4344000

4344000 22 17

Sky Mountain Park 16 24 36 28

25 4343800 4343800 18 26 23 29 4343600 4343600

13 34 14 Seven Star Ranch II 12 9 8 4343400

4343400 33 7 11 32 6 10 4 5 3 31 35 4343200 4343200 38 37 1

2 4343000 4343000 Ü Hidden Valley 1:12,000

4342800 1 inch = 1,000 feet

4342800 30

Date: November 2012 Grid Ticks: UTM NAD83 Z13

4342600 Background: USGS 7.5' Highland Peak Quad 4342600 4342400 4342400

334400 334600 334800 335000 335200 335400 335600 335800 336000 336200 336400 336600 336800 337000 337200 337400 337600 337800 338000 338200 4342200 9 334400 334600 334800 335000 335200 335400 335600 335800 336000 336200 336400 336600 336800 337000 337200 337400 337600 337800 338000 338200

Figure 4. Result Map -Aerial 4345200

4345200 Silverleaf Milkvetch Surveys Pitkin County, Colorado Cozy Point South

4345000 Legend 4345000 Upper North Mesa Open Space Properties 4344800 4344800 Seven Star Ranch Silverleaf milkvetch 4344600

4344600 Surveys conducted on May 21, 22, & 23, 2012 19 4344400 4344400

21

20 4344200 4344200

15 4344000

4344000 22 17

Sky Mountain Park 16 24 36 28

25 4343800 4343800 18 26 23 29 4343600 4343600

13 34 14 Seven Star Ranch II 12 9 8 4343400

4343400 33 7 11 32 6 10 4 5 3 31 35 4343200 4343200 38 37 1

2 4343000 4343000 Ü Hidden Valley 1:12,000

4342800 1 inch = 1,000 feet

4342800 30 Date: November 2012 Grid Ticks: UTM NAD83 Z13 Background: 2010 PCOS

4342600 Aerial Photography 4342600 4342400 4342400

334400 334600 334800 335000 335200 335400 335600 335800 336000 336200 336400 336600 336800 337000 337200 337400 337600 337800 338000 338200 4342200 10

9.0 Tables

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Table 1. Summer Climate Data for the Aspen 1SW Weather Station 2011-2012 30-yr 2011 2012 Precipitation 2011 Mean 2012 Mean 30-yr Precipitation Precipitation Normal Temperature Temperature Temperature Month (inches) (inches) (inches) °F °F Normal °F April 6.45 1.75 2.56 36.3 44.0 37.9 May 2.56 1.07 2.10 43.5 50.1 47.4 June 0.80 0.35* 1.26 57.2 63.1* 56.4 July 3.16 2.38 1.76 62.5 63.7 61.7 August 0.85 2.28 1.37 63.1 62.1 60.5 Total/ 13.82 7.83 9.05 52.6 56.6 52.8 Mean * = Data for the Aspen 1SW Station not available, data from the Aspen Pitkin Co Airport used instead.

12 Table 2. Known Locations of Silverleaf Milkvetch in Colorado Specimen Location Habitat County Location ID & Date Hardscrabble Mountain Slope with scattered pinyon Eagle COLO Hartman 66811 Area, 4 air mi SE of pine and dense areas of 23 May 2000 Eagle mountain mahogany; gypsum deposits abundant, 7,250-7,700 ft. Hardscrabble Mountain Open aspen grove into Eagle RM Holt 5858 Area, along Yates spruce-Douglas fir forest 26 June 2001 Gulch Glenwood Canyon at Dry gravelly slopes Garfield CSU Wilken 12932 Grizzly Creek 26 May 1977 Hwy 14, 4.8 km SW of In sandy yellow clay with Jackson NY Spellenberg 11823 Walden horsebrush and sagebrush 08 June 1993 North slopes of Grand Mesa ? CNHP unknown Mesa Dinosaur National Gentle slope with Moffat COLO Neely 4316 Monument sagebrush and mountain 13 June 1987 mahogany Dinosaur National On sand soil of gentle Moffat COLO Needy 4309B Monument south exposure with 12 June 1987 Ponderosa pine, serviceberry and purnus Dinosaur National Rocky summit of Roundtop Moffat COLO Weber 9632 Monument Mountain, Dinosaur 2 June 1956 National Monument 3.5 mi SW of Rooted in cracks of rocks Moffat COLO MacLeod 563 Greystone 7 May 1967 Cigarette Bend, 7 mi Rocky open flat Moffat CSU MacLeod 62b SW of Greystone Drainage of Thompson -- Moffat COLO Weber 12691 Draw between 28 June 1965 Greystone and Sunbeam Near Massey Spring, Sandy soil with pinyon and Moffat RM Porter 3660 west rim of Lodors juniper 9 July 1945 Canyon of Green River Cold Spring Mountain Rare in sagebrush, dry hills Moffat RM Porter 3910 near WY and UT 23 June 1946 borders Peabody Nucla East Small remnant stands of Montrose COLO Buckner Mine, 5 mi NE of sagebrush on shallow soils, 15 May 1987 Naturita surrounded by irrigated haylands Upper Dolores River South-facing pinyon-juniper Montrose RM Moore 2004 Drainage, Wild Steer zone along canyon rim 2 June 1994 Mesa grading into open sagebrush Sky Mountain Park Mancos Shale barrens on Pitkin COLO Orthner 1164 & 1165 Open Space, near top of ridge. 26 May & 21 June 2011 Snowmass Village COLO = University of Colorado Herbarium in Boulder, CO CSU = Colorado State University Herbarium in Fort Collins, CO NY = New York Botanical Garden in New York, NY RM = Rocky Mountain Herbarium in Laramie, WY ?CNHP = Data obtained from CNHP (2012), specimen location unknown 13 Table 3. 2012 Silverleaf Milkvetch Survey Results

Number UTM UTM Id Size - ac Counted NAD83 East NAD83 North Notes 1 3.800 646 335437 4343082 2 0.676 90 335389 4342974 3 0.051 15 335618 4343186 4 0.002 20 336006 4343213 5 0.002 3 336103 4343226 6 0.002 2 336105 4343254 7 0.196 61 336237 4343328 8 0.002 1 336256 4343365 9 0.019 11 336283 4343383 10 1.109 30 336345 4343260 occur on side slopes near shrubs 11 0.980 30 336433 4343296 12 0.196 11 336353 4343417 13 0.247 8 336399 4343469 14 0.002 3 336600 4343449 15 0.107 21 337009 4343958 mainly occur along path 16 0.525 38 336639 4343805 17 0.314 30 336595 4343899 18 0.143 14 337290 4343690 19 0.870 60 337430 4344432 20 0.002 3 337280 4344166 21 2.098 481 337336 4344264 22 0.002 2 337606 4343917 23 0.599 40 337721 4343671 occur along edge of shrubline 24 0.917 74 337632 4343789 occur along edge of shrubline 25 0.002 8 337611 4343757 26 0.136 16 337604 4343670 27 0.002 1 337600 4343739 28 0.402 30 337552 4343768 29 0.159 33 337879 4343617 30 2.244 384 335370 4342740 occur next to shrubs at toe of shale outcrop 31 0.339 81 335344 4343172 occur mainly on edges of shale outcrop near shrubs 32 0.141 130 335358 4343256 33 0.103 5 335318 4343347 occur mainly on edges of shale barren 34 0.002 18 335218 4343450 35 0.002 8 335402 4343186 36 0.127 84 335345 4343785 37 0.002 6 335975 4343110 38 0.002 1 335792 4343107 SUM 16.522 2,499

14 Table 4. Associated Plant Species

Scientific Name Common Name Family Origin

Shrubs Amelanchier alnifolia Serviceberry Rosaceae N Amelanchier utahensis Utah serviceberry Rosaceae N Artemisia frigida Fringed sage N Artemisia tridentata (sensu lato) Big sagebrush Asteraceae N Cercocarpus montanus Mountain mahogany Rosaceae N Chrysothamnus viscidiflorus Green rabbitbrush Asteraceae N Mahonia repens Oregon grape Berberidaceae N Purshia tridentata Bitterbrush Rosaceae N Quercus gambelii Gambel's oak Fagaceae N Symphoricarpos rotundifolius Snowberry Caprifoliaceae N

Perennial Graminoids Carex geyeri Elk sedge Cyperaceae N Koeleria macrantha Junegrass Poaceae N Oryzopsis hymenoides Indian ricegrass Poaceae N Poa pratensis Kentucky bluegrass Poaceae I Perennial Forbs Agoseris glauca Pale agoseris Asteraceae N Balsamorhiza sagittata Balsamroot Asteraceae N Castilleja chromosa Indian paintbrush Scropulariaceae N Chaenactis douglasii Douglas pincushion Asteraceae N Cymopterus planosus Rocky mountain springparsley Apiaceae N Delphinium nuttallianum Nuttall's larkspur Helleboraceae N Erigeron flagellaris Running fleabane Asteraceae N Eriogonum umbellatum Wild buckwheat Polygonaceae N Lupinus argenteus Silvery lupine Fabaceae N Oxytropis lambertii Lambert's locoweed Fabaceae N Penstemon caespitosus Mat penstemon Scrophulariaceae N Petradoria pumila Rock goldenrod Asteraceae N Phlox multiflora Phlox Polemoniaceae N Physaria floribunda Pointtip twinpod Brassicaceae N Potentilla pulcherrima Beautiful cinquefoil Rosaceae N Senecio integerrimus Lambstongue groundsel Asteraceae N Cacti Opuntia fragilis Brittle prickly pear Cactaceae N

* N = Native; I = Introduced

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10.0 Photographs

16

Photo 1. Silverleaf milkvetch in flower. 26-May-2011.

Photo 2. Silverleaf milkvetch in fruit. 21-May-2012.

17

Photo 3. Lambert's locoweed, which closely resembles the silverleaf milkvetch (21-May-2012). Note the lack of fruits and flowers and more elongated leaflets.

Silverleaf milkvetch

Photo 4. Silverleaf milkvetch population #5, looking northeast. 21-May-2012. Note the predominance of rock goldenrod.

18

Photo 5. Silverleaf milkvetch habitat on north-facing slope. 21-May-2012.

Silverleaf milkvetch

Photo 6. Silverleaf milkvetch population #18, looking south. 21-May-2012. Plants are generally located along edge of shrubs.

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Appendix A. 2012 CNHP Dataform for Silverleaf Milkvetch

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COLORADO NATURAL HERITAGE PROGRAM PLANT ELEMENT OCCURRENCE FIELD FORM COLORADO STATE UNIVERSITY-WARNER COLLEGE OF NATURAL RESOURCES

Please submit copies of personal/agency field data forms, digital data (GIS or spreadsheet), or this field form to: CNHP, 1474 Campus Delivery, Fort Collins, CO 80523 or [email protected] (970) 491-5857 (For a list of elements tracked by CNHP, refer tohttp://www.cnhp.colostate.edu/download/list.asp)

Element Scientific Name: Astragalus argophyllus var. martinii Survey Date: 2012-May-21 (yyyy-mm-dd) Observer(s) Name & Affiliation: Rea Orthner, Western Ecological Resource Inc. Observer(s) Address & Phone Number: 711 Walnut Street, Boulder CO 80302 303-449-9009 [email protected]

Ownership Owner Type: Private USFS BLM State Military Indian BuRec NPS Other: Owner Name (or National Forest, BLM District, etc.): Pitkin County Open Space Owner Comments (special requests, permissions, circumstances): open to public with seasonal restrictions, contact Gary Tennenbaum, PCOS Steardship & Trails Manager at 970-920-5355

Locational Information (REQUIRED) (Provide a photocopy of map with location of the occurrence marked or outlined)

USGS Quadrangle Name: Highland Peak Surveysite Name (from 7.5’ quad): ridgeline SW of Cozy Point County: Pitkin Elevation (range if applicable): 8540 feet meters Legal Description: Township: Range: Section: ¼ Sec: Additional T/R/S, Sections or ¼ Secs: Coordinates: UTM Zone: 12 13 Northing: Easting: SEE TABLE 3 Datum: NAD27 NAD83 WGS84 Other: GPS accuracy (if known): GPSmap 60CSx autonomous(uncorrected) differentially corrected Other:

Directions (REQUIRED) Driving and hiking directions and prominent topographical features: Park at Snowmass Rodeo Grounds. Go east and hike the Highline, Ridge Connector and Ridge Trails to Sky Mountain Park. Some populations also easily accessible from the Airport Radar Road.

Element Occurrence Data (REQUIRED) Number of Individuals (exact count, if feasible; if plants are spreading vegetatively, indicate number of aerial stems): 2,499 Estimated Population Size: 3000 Number of Subpopulations (if applicable): 38 Size of Area Covered by Population: none (point) 16.5 acres

Phenology: Vegetative: % Flower: % Fruit: 95% Reproductive Success: (evidence of seed dispersal and establishment): yes, small plants (juveniles) visible Age Classes Present: fruiting individuals Symbiotic or Parasitic Relationships (e.g. pollinators): none observed Evidence of Disease, Predation or Injury: none present

Condition Comments (productivity, vigor/health; evidence of reproduction, health of population, degree of anthropogenic disturbance, naturalness of hydrology, and other ecological processes): Plants appear healthy and are reproductive. Very few seedlings observed.

Landscape Context Comments (biological structure, species composition, degree of fragmentation and connectivity, condition, and extent of surrounding landscape; abiotic physical/chemical factors): Population occurs on Open Space being managed by Pitkin County. Habitat (Mancos Shale Barrens) is subject to a high degree of wind and rain (sheet) erosion. Connectivity between occurrences is good.

General Habitat Description (refer to data dictionary) General Habitat Comments: Mancos Shale Barrens Dominant Plant Community (list dominant species currently present, include age structure if known): Indian Ricegrass Shale Barren Additional Associated Plant Species (be concise): Table 4 of the associated report lists the 30 plant species observed to be growing with silverleaf milkvetch. The most common herbaceous plant associates include rock goldenrod (Petradoria pumila), phlox (Phlox multiflora), Rocky Mountain spring parsley (Cymopterus planosus), running fleabane (Erigeron flagellaris) and mat penstemon (Penstemn cespitosus). The most common associated shrubs include Gambel oak (Quercus gambellii),

Rev. May 2008 1 serviceberry (Amelanchier spp.), sagebrush (Artemisia tridentata), mountain mahogany (Cercocarpus montanus), and bitterbrush (Purshia tridentata).

Topographic Position: Interfluve (ridgetop) Aspect : all degrees Slope: <25 % or degrees (circle one) Slope Shape: Concave Convex Straight Other Light Exposure: Open Shaded Partial shade Other Moisture: Dry Moist Saturated Inundated Seasonal seepage Other Soil Texture: clay or clay loam Geomorphic Land Form (e.g., glaciated mountain slopes and ridges, alpine glacial valley, rolling uplands, breaklands, alluvial-colluvial- lacsutrine, rockslides, etc.): Glaciated Mountain Slope and Ridges

Protection Comments (Comments on any legal protection or strategies needed or in place): Pitkin County will be developing protection strategies.

Management Comments Evidence of Threats and Disturbance (e.g. effects on population viability due to mining, recreation, grazing, exotic species; past/present/future recommendations): Recreation is the biggest threat Predominant Land Uses: Recreation Exotic Species: none noted

Documentation Photographs Taken: Y N Photographer: Orthner Photo Number(s): 1010988-1020027 Repository: Western Ecological Resource Specimens Taken: Y N Collector: Orthner Collection Number(s): 1164, 1165 Repository: CU Boulder Herbarium (COLO)

General Comments S1 status should be reconsidered in light of this poplation and numerous other reported occurrences at local herbaria. See Table 2 of associated report. (WER November 2012). Table 3 and Figures 3 and 4 of associated report also contains details on each subpopulation found. Also see associated GIS Shapefile.

Rev. May 2008 2