Endangered and Threatened Wildlife and Plants; Withdrawal of Proposed Rule To List Lepidium papilliferum (Slickspot Peppergrass), 1622-1644 [07-60]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 72, Number 8 (Friday, January 12, 2007)]
[Proposed Rules]
[Pages 1622-1644]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 07-60]



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Part III





 Fish and Wildlife Service





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50 CFR Parts 17



 Endangered and Threatened Wildlife and Plants; Withdrawal of Proposed 
Rule To List Lepidium papilliferum (Slickspot Peppergrass); Proposed 
Rule

Federal Register / Vol. 72, No. 8 / Friday, January 12, 2007 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AU99


Endangered and Threatened Wildlife and Plants; Withdrawal of 
Proposed Rule To List Lepidium papilliferum (Slickspot Peppergrass)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule; withdrawal.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), again 
withdraw our July 15, 2002, proposal (67 FR 46441) to list Lepidium 
papilliferum (slickspot peppergrass) as an endangered species under the 
Endangered Species Act of 1973, as amended (Act). The best available 
data for L. papilliferum indicates that, while its sagebrush-steppe 
matrix habitat is degraded, there is little evidence of negative 
impacts on the abundance of L. papilliferum, which inhabits slickspot 
microsites within this system. Annual abundance of the plant is 
strongly correlated with spring precipitation, therefore a high degree 
of variability in annual abundance is to be expected. Data on overall 
population trends are inconsistent; although recent declines that do 
not correlate with spring rainfall are noted in one portion of the 
species' range, range-wide data demonstrate increases in abundance that 
continue to track consistently with rainfall during those same years. 
The best available range-wide data indicate that abundance of the 
population range-wide is strongly correlated with precipitation and has 
increased in recent years in association with increased rainfall, as 
expected.

ADDRESSES: Supporting documentation for this action is available for 
public inspection, by appointment, during normal business hours at the 
Snake River Fish and Wildlife Office, 1387 S. Vinnell Way, Boise, ID 
83709.

FOR FURTHER INFORMATION CONTACT: Jeffery Foss, Field Supervisor, Snake 
River Fish and Wildlife Office at the above address; by telephone at 
208/378-5243; by facsimile at 208/378-5262; or by electronic mail at: 
fw1srbocomment@fws.gov.

SUPPLEMENTARY INFORMATION:

Species Information

    Lepidium papilliferum was originally described as L. montanum var. 
papilliferum in 1900 by Louis Henderson. It was renamed L. papilliferum 
by Aven Nelson and J. Francis Macbride in 1913, based on its 
distinctive growth habit, short lifespan, and unusual pubescence 
(Nelson and Macbride 1913, p. 474). Hitchcock regarded L. papilliferum 
as L. montanum var. papilliferum (Hitchcock et al. 1964, p. 516; 
Hitchcock and Cronquist 1973). In a review of taxa in the mustard 
family (Brassicaceae), Rollins (1993) maintained the species based on 
differences in the physical features between L. papilliferum and L. 
montanum. More recently, a taxonomic review concluded that L. 
papilliferum warrants species recognition based on distinct 
morphological features (Lichvar 2002), and a contrasting life history 
when compared to L. montanum regarding seed dormancy and its seed bank 
(Meyer et al. 2005, p. 21). The preliminary results of recent genetic 
studies comparing L. papilliferum with L. montanum indicate that L. 
papilliferum forms a monophyletic group or subgroup that is genetically 
distinct from L. montanum (Larson et al. 2006, p. 13 and Figs. 4, 8; 
Smith 2006, pp. 5-7, Fig. 1). The currently accepted taxonomy 
recognizes Lepidium papilliferum (Henderson) A. Nels and J.F. Macbr as 
a full species (Taxonomic Serial No. 53383, Integrated Taxonomic 
Information System (ITIS), 2006).

Biology

    Lepidium papilliferum is a taprooted, intricately branched plant. 
The plant flowers once and then dies (it is monocarpic), and displays 
two different life cycles, an annual and a biennial form. The plant 
averages 2 to 8 inches (in) (5 to 20 centimeters (cm)), but can reach 
up to 16 in (40 cm) in height. Leaves and stems are covered with fine, 
soft hairs, and the leaves are divided into linear segments. Flowers 
are numerous, 0.1 in (3 to 4 millimeter (mm)) diameter, white, and 4-
petalled. Fruits (siliques) are 0.1 in (3 mm), round in outline, 
flattened, and 2-seeded (Moseley 1994, pp. 3 and 4; Holmgren et al. 
2005, p. 260).
    The annual form of the Lepidium papilliferum matures, reproduces by 
setting seed, and dies in one growing season. The biennial life form 
initiates growth in the first year as a rosette, but does not produce 
seed and die until the second year. Biennial rosettes must survive dry 
summers on the Snake River Plain and Owyhee Plateau, and consequently 
many of these rosettes die before flowering and producing seed. The 
proportion of annuals versus biennials in a population can vary greatly 
(Meyer et al. 2005, p. 15). Depending on individual plant vigor and the 
effectiveness of pollination, dozens, if not thousands, of seeds can be 
produced by a single L. papilliferum plant (Quinney 1998, pp. 15 and 
17), with individual biennial plants producing a much greater number of 
seeds than annual plants (Meyer et al. 2005, p. 15). Average seed 
output for annual plants at the Orchard Training Area (OTA) (an Idaho 
Army National Guard training area on BLM land) in 1993, was 125 seeds 
per plant, and in 1994, was 46 seeds per plant. Biennial seed 
production in 1993 and 1994 averaged 787 and 105 seeds per plant, 
respectively (Meyer et al. 2005, p. 16).
    Lepidium papilliferum seeds produced in a given year are dormant 
for at least a year before any germination takes place. Following this 
year of dormancy, approximately 6 percent of seeds produced in a given 
year germinate annually and approximately 3 percent die annually (Meyer 
et al. 2005, pp. 17, 18). After 12 years, all seeds in a given cohort 
will likely have either died or germinated (Meyer et al. 2005, p. 18). 
Seeds are released in late June or early July.
    Like many short-lived plants growing in arid environments, above-
ground numbers of Lepidium papilliferum individuals can fluctuate 
widely from one year to the next, depending on seasonal precipitation 
patterns (Mancuso and Moseley 1998, p. 1; Meyer et al. 2005, pp. 4, 12, 
15; Palazzo et al. 2005, p. 9; Menke and Kaye 2006a, p. 8; Menke and 
Kaye 2006b, pp. 10, 11). In an analysis of monitoring data, minimum and 
maximum temperatures were not statistically correlated with L. 
papilliferum abundance (Menke and Kaye 2006b, p. 8). Above-ground 
plants represent only a portion of the population; the seed bank (a 
reserve of dormant seeds, generally found in the soil) contributes the 
other portion, and apparently in many years constitutes the majority of 
the population (Mancuso and Moseley 1998, p. 1). According to Meyer et 
al. (2005, p. 21), ``Without a persistent seedbank, L. papilliferum 
could probably not succeed as an annual in its stochastically varying 
habitat.'' Seed banks are adaptations for survival in a ``risky 
environment,'' because they buffer a species from stochastic impacts 
such as lack of soil moisture (Baskin and Baskin 2001, p. 160).
    Lepidium papilliferum seeds have an extremely patchy distribution, 
making it difficult to estimate seed density without taking a large 
number of samples (Meyer and Allen 2005, pp. 5, 6). The vast majority 
of L. papilliferum seeds in slickspots (see Ecology and Habitat 
section) have been located near the soil surface, with lower numbers of 
seeds located in deeper soils (Meyer et

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al. 2005, p. 19; Palazzo et al. 2005, p. 3). L. papilliferum seeds have 
been found in slickspots with no above-ground plants (Meyer et al. in 
press, p. 18; Palazzo et al. 2005, p. 10). Viable seeds have also been 
located outside of slickspots, indicating that some seed dispersal is 
occurring beyond slickspot habitat (Palazzo et al. 2005, p. 10). The 
primary seed dispersal mechanism for L. papilliferum has not been 
identified and is not known (Robertson and Ullappa 2004, p. 1708).
    Lepidium papilliferum seeds located near the soil surface show 
higher rates of germination and viability (Meyer and Allen 2005, pp. 6 
to 8; Palazzo et al. 2005, p. 10), and the greatest seedling emergence 
success rate (Meyer and Allen 2005, pp. 6 to 8). Seeds were more 
abundant, more viable, and had greater germination percentages and 
rates from the upper 2 in (5 cm) of soil (Palazzo et al. 2005, pp. 8, 
10). In another study, the highest level (60 percent) of seedling 
emergence was observed at a seed depth of 0.1 in (approximately 2 mm), 
with a marked decrease in seedling emergence at 0.2 in (approximately 5 
mm) (Meyer and Allen 2005, pp. 6, 7).
    Deep burial of slickspot peppergrass seeds (average depths greater 
than 5.5 in (14 cm)) entombs seeds that are still viable and preserves 
them beyond the 12-year period previously assumed as the maximum period 
of viability for Lepidium papilliferum seeds (Meyer and Allen 2005, pp. 
6, 9). While there may be processes such as badger (Taxidea taxus) 
burrow-digging that could return these buried viable seeds to the near-
surface, the successful establishment of seedlings may be reduced due 
to modification of soil layers following previous disturbance events 
(Meyer and Allen 2005, pp. 6, 8). The effects of environmental threats 
such as wildfire on L. papilliferum seed dormancy and viability are 
currently unknown.
    Lepidium papilliferum has low seed set in the absence of 
pollinators, and is primarily an outcrossing species requiring pollen 
from separate plants for more successful fruit production (Robertson 
2003a, p. 5; Robertson and Klemash 2003, p. 339; Robertson and Ulappa 
2004, p. 1707). In pollination experiments where researchers moved 
pollen from one plant to another, fruit production was observed to be 
higher with pollen from distant sources 246 to 330 feet (ft) (75 to 100 
meters (m)) away within a plant patch, and 4 to 12.4 miles (mi) (6.5 to 
20 kilometers (km)) away from another patch of plants (Robertson and 
Ulappa 2004, p. 1705). Genetic exchange can occur either thorough 
pollen or seed dispersal.
    Lepidium papilliferum has been observed to be visited by at least 
25 families of insects, although only some of these insects serve as 
effective pollinators (Robertson 2003b, pp. 10, 11; Robertson and 
Klemash 2003, p. 336). Scarcity of pollinators were not found to limit 
seed set at any site (Robertson et al. 2004, p. 14). Pollinators 
include insects from several families of bees and ants (Hymenoptera), 
including Apidae, Halictidae, Sphecidae, and Vespidae; beetles 
(Coleoptera), including Dermestidae, Meloidae, and Melyridae; flies 
(Diptera), including Bombyliidae, Syrphidae, and Tachinidae; and others 
(Robertson and Klemash 2003, p. 336). The pollen transfer efficiency 
for L. papilliferum varies among these insects. Pollinators of L. 
papilliferum with high pollen transfer efficiencies and visitation 
rates include sphecid and vespid wasps, bombyliid and tachnid flies, 
and honeybees, with lesser contributions from halictid bees.
    The genetics of Lepidium papilliferum were studied using samples 
collected from areas across the entire range of the species, including 
both the Snake River Plain and a disjunct range on the Owyhee Plateau 
(Stillman et al. 2005, pp. 6, 8, 9). The largest amounts of genetic 
difference occurred between the Snake River Plain and the Owyhee 
Plateau populations. The Snake River Plain and the Owyhee Plateau 
populations are separated by 44 mi (70 km), which is considered beyond 
the distance that insect pollinators can travel or that seed dispersal 
can occur. Despite the distance that separates the Snake River Plain 
and the Owyhee Plateau populations, plants from these two areas share a 
94-percent similarity in allelic diversity. This high degree of 
similarity suggests that they were either part of one continuous 
distribution or they originated from similar ancestral material 
(Stillman et al. 2005, pp. 6, 8, 9). Sites in the Snake River Plain 
with fewer numbers of plants had less genetic diversity than sites with 
larger numbers of plants. Interestingly, a correlation between 
population size and genetic diversity did not exist in the Owyhee 
Plateau region. The authors suggested that this may be because the 
Owyhee Plateau region is less fragmented than the Snake River Plain, 
but suggested further genetic research is needed. Larson (2006, p. 14 
and Fig. 4) also found geographically well-defined populations of 
Lepidium papilliferum between the Snake River Plain and Owyhee Plateau 
based on genetics. In contrast to the Stillman et al. (2005) study, 
Larson's findings indicate the possibility of depressed genetic 
diversity in L. papilliferum based on significantly greater average 
similarity coefficients within collection sites of L. papilliferum 
compared to those of L. montanum, (Larson et al. 2006, p. 13).

Ecology and Habitat

    The habitat of Lepidium papilliferum is found within semiarid 
sagebrush-steppe habitats in southern Idaho. This plant is known from 
the extensive volcanic plains of the Snake River Plain (and foothills) 
and the Owyhee Plateau, with most element occurrences (EOs) occurring 
on flat to gently sloping terrain (see Figure 1 below). Element 
occurrences are defined as ``an area of land in which a species is or 
was present'' (NatureServe 2002). L. papilliferum is associated with 
basalt ridges and plains, stable piedmont, and older alluvial 
floodplains and deposits (Fisher et al. 1996, pp. 14, 16).

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BILLING CODE 4310-55-P
    Range-wide, Lepidium papilliferum is associated with visually 
distinct microsites known as slickspots (mini-playas or natric sites) 
(Moseley 1994, p. 7). Slickspots are distinguished from the surrounding 
sagebrush matrix as having the following characteristics--microsites 
where water pools when rain falls (Fisher et al. 1996, pp. 2, 4); 
little vegetation; more distinct soil layers with a more columnar or 
prismatic structure; higher alkalinity and clay content and natric 
(higher sodium) properties (Fisher et al. 1996, pp. 15, 16; Meyer and 
Allen 2005, pp. 3 to 5, 8); and reduced levels of organic matter and 
nutrients due to lower biomass production (Meyer and Quinney 1993, pp. 
3, 6; Fisher et al. 1996, p. 4). The slickspots range in size from less 
than 10 square feet (ft \2\) (1 square meter (m \2\)) to about 110 ft 
\2\ (10 m \2\) (Mancuso et al. 1998, p. 1), but most are between 10 ft 
\2\ and 20 ft \2\ (1 m \2\ and 2 m \2\).
    Slickspots cover a relatively small cumulative area within the 
larger sagebrush-steppe matrix, and only a small percentage of 
slickspots are known to be occupied by Lepidium papilliferum. For 
example, a thorough field inventory within the Juniper Butte Range in 
2002 found that of the 11,070

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acres (ac) (4,480 hectares (ha)) surveyed, approximately 1 percent (109 
ac (44 ha)) consisted of slickspot habitat, and only 4 percent of the 
slickspot habitat was occupied by above-ground L. papilliferum plants 
(U.S. Air Force 2002, p. 9). The total amount of occupied slickspot 
habitat (above-ground plants and known occurrences of seed in the soil) 
within this large occurrence was approximately 4 ac (1.6 ha) at the 
time it was surveyed (0.1 percent of the acreage).
    Based on studies in 2004 on the Orchard Training Area (OTA), a 
training area of the Idaho Army Reserve National Guard (IARNG) on the 
Snake River Plain, slickspots have three primary layers: the surface 
silt layer, the restrictive layer, and the moist clay layer beneath. 
The top two layers (surface silt and restrictive) of slickspots are 
very thin; the surface silt layer varies in thickness from 0.1 to 1.2 
in (a few mm to 3 cm) in slickspots known to support Lepidium 
papilliferum, and the restrictive layer varies in thickness from 0.4 to 
1.2 in (1 to 3 cm) (Meyer and Allen 2005, p. 3). The moist clay basal 
layer, which continues down to bedrock, is consistently below the 
restrictive layer (Meyer and Allen 2005, p. 3). All slickspots have 
variations in surface silt thickness.
    As part of the Lepidium papilliferum Habitat Integrity and 
Population (HIP) monitoring conducted range-wide in 2005, the depth of 
the surface silt layer was measured 3 times in every slickspot along 79 
transects across the range of L. papilliferum; a total of 769 
slickspots were sampled. Measurements were taken directly adjacent to 
live L. papilliferum plants; the range-wide mean surface silt layer 
depth was 0.31 in (0.78 cm) (Colket 2006a).
    The surrounding sagebrush matrix soils are distinguished from 
slickspot soils by a deeper silt layer with a clay layer beneath, and 
usually the restrictive layer is lacking (Meyer and Allen 2005, pp. 3 
to 5). Non-slickspot soils at the OTA had thick silt layers with a mean 
depth of 4.7 in (12 cm); the silt layer typically transitioned directly 
into the clay layer beneath, although some samples had restrictive 
layers which were abnormally thickened (over 3.9 in (10 cm)) (Meyer and 
Allen 2005, pp. 3 to 5, 8).
    It is unknown how long slickspots take to form, but it is 
hypothesized to take several thousands of years (Nettleton and Petersen 
1983, p. 193; Seronko 2006, p. 1). The conditions that allowed for the 
formation of slickspots in southwestern Idaho are thought to have 
occurred during a wetter Pleistocene climate. Holocene additions of 
wind-carried salts (often loess deposits) produced soils high in sodium 
(natric) (Nettleton and Petersen 1983, p. 191; Seronko 2006, p. 1). It 
may take several hundred years to alter or lose slickspots through 
natural climate change or severe natural erosion (Seronko 2006, p. 1). 
Some researchers hypothesize that, given current climatic conditions, 
new slickspots are no longer being created (Nettleton and Petersen 
1983, pp. 166, 191, 206), but that some slickspots subjected to light 
disturbance in the past may re-form (Seronko 2006, p. 1). Slickspots 
may be destroyed and lost to disturbances that alter the physical 
properties of the soil layers.
    The forces that hold clay particles together are greatly weakened 
when sodium-clay and water come into contact. In this condition, clay 
particles are easily detached or dispersed from larger aggregates, 
i.e., slickspot soils are especially susceptible to mechanical 
disturbances when wet (Rengasmy et al. 1984, p. 63; Seronko 2004, pp. 
1, 2). Such disturbances disrupt the soil layers important to Lepidium 
papilliferum's seed germination and seedling growth. Meyer and Allen 
(2005, p. 9) suggest that if sufficient time passes following the 
disturbance of slickspot soil layers, it is possible that the slickspot 
soil layers may reform similar to their pre-disturbance configuration. 
Slickspots that no longer support L. papilliferum, but still retain the 
thin silt and restrictive layer structure, are the most likely sites to 
support reintroductions. Restoration and species reintroduction 
potential for L. papilliferum habitat have not been studied.
    The highest monthly temperatures within the range of Lepidium 
papilliferum normally occur in July (approximately in the low 90 
degrees Fahrenheit (approximately 33 degrees Celsius)), and lowest 
monthly temperatures occur in January (approximately in the low 20 
degrees Fahrenheit (minus 7 degrees Celsius)). Average precipitation 
within the species' range is 11.7 in (29.7 cm) for Boise, 7.4 in (18.8 
cm) for Bruneau, and 9.9 in (25.1 cm) for Mountain Home. Precipitation 
tends to fall as rain, primarily in winter and spring (November to 
May); the lowest rainfall occurs in July and August, and June, 
September, and October receive slightly more. Freeze-free days average 
about 120 days in Boise, 146 days in Bruneau, and 138 days in Mountain 
Home (WRCC 2006).
    Spring precipitation has been correlated with above-ground numbers 
of Lepidium papilliferum in several analyses. Palazzo et al. (2005, p. 
9) and Menke and Kaye (2006a, p. 8) utilized Habitat Integrity Index 
(HII) range-wide data collected from 1998 to 2001. Menke and Kaye 
(2006b, pp. 10, 11) utilized HII data collected from 1998 to 2002, as 
well as 2004 Habitat Integrity and Population (HIP) data. Meyer et al. 
(2005, p. 15) utilized demographic data from the OTA collected from 
1993 to 1995. Palazzo et al. (2005, p. 9) found a positive relationship 
(p-value of less than 0.01) between above-ground plants and February to 
June precipitation. Menke and Kaye (2006a, p. 8) found March to May 
precipitation accounted for 99.4 percent (2006a, p. 8) and 89 percent 
(2006b, pp. 10, 11) of the variation in L. papilliferum numbers. Meyer 
et al. (2005, p. 15) found that an increase in February through May 
precipitation increased the number of L. papilliferum seedlings at the 
OTA. This correlation of abundance with spring rainfall is important, 
as it at least partially explains past fluctuations in population 
numbers, and suggests that perceived declines were largely a result of 
years with low precipitation levels. Menke and Kaye (2006b, p. 8) also 
found that minimum and maximum temperatures were not statistically 
correlated with L. papilliferum abundance.
    The sparse native vegetation naturally present at slickspots 
suggests that Lepidium papilliferum is more tolerant than surrounding 
vegetation at surviving in alkaline soils and spring inundation. Plant 
ecology literature suggests that plants tolerant of stress (e.g., 
alkaline soils) are poor competitors (Grime 1977, p. 1185).

Range and Distribution

    Lepidium papilliferum is known only from the Snake River Plain and 
its adjacent northern foothills (an area 90 by 25 mi (145 by 40 km)) in 
southwest Idaho, and a disjunct population on the Owyhee Plateau in 
Idaho (see Figure 1 above). The plant occurs at elevations ranging from 
approximately 2,200 ft (670 m) to 5,400 ft (1,645 m) in Ada, Canyon, 
Gem, Elmore, Payette, and Owyhee Counties (Moseley 1994, pp. 3 to 9). 
The separation of population centers into two physiographic regions is 
important for the conservation of L. papilliferum. We regard the two 
physiographic regions as two distinct metapopulations, the Snake River 
Plain metapopulation and the Owyhee Plateau metapopulation. 
Metapopulation concepts are useful when considering fragmented 
habitats, such as those within L. papilliferum's range, because they 
include discussion of when extinction events exceed colonization 
events, which can cause

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the species to not persist (Husband and Barrett 1996, pp. 461 to 462).
    In 2003, a ``Candidate Conservation Agreement for Slickspot 
Peppergrass (Lepidium papilliferum)'' (CCA) was developed by several 
State, Federal, and private entities in Idaho (State of Idaho et al. 
2003) (see Previous Federal Actions section). The CCA is based on two 
geographical management areas that include known EOs, one on the Snake 
River Plain and a second on the Owyhee Plateau, called ``consideration 
zones.'' Although somewhat arbitrary in nature, this designation is 
useful for management purposes. There are 1,595,205 ac (645,597 ha) 
within the Snake River Plain consideration zone, and 126,946 ac (51,373 
ha) within the Owyhee Plateau consideration zone. Factors affecting the 
species vary between the two physiographic regions. For example, urban 
and rural development, agriculture, and infrastructure development of 
sagebrush-steppe habitat has been substantial within the Snake River 
Plain, but little development has occurred within the Owyhee Plateau 
portion of L. papilliferum's range.
    Element occurrences have been used to describe distribution of 
Lepidium papilliferum by assuming that slickspots within 1 kilometer 
(0.6 mi) of each other are capable of genetic exchange through 
pollination (Colket and Robertson, pers. comm. 2006). As of February 
2006, there were 85 delineated EOs that occupied 13,359 ac (5,406 ha) 
(Colket et al. 2006). We estimate that the actual acreage occupied by 
L. papilliferum is only a fraction of a percent of this total acreage 
number because the majority of slickspots are not occupied by L. 
papilliferum and slickspots occupy a small percentage of the landscape 
(see U.S. Air Force 2002, p. 9, for an example). Of these EOs, 60 
(11,025.3 ac (4,461.8 ha)) occur on the Snake River Plain, and 25 
(2,333.8 ac (944.5 ha)) occur on the Owyhee Plateau (Colket et al. 
2006, Table 14). Of the total EO acreage, 521 ac (211 ha) (3.9 percent) 
occur on private lands, 1,254 ac (507 ha) (9.4 percent) occur on lands 
managed by the State of Idaho, and 11,582 ac (4,687 ha) (86.7 percent) 
occur on Federal lands (USFWS 2006c). On the Snake River Plain, 85 
percent of the EO acreage occurs on federally managed lands, 10.3 
percent of the EO acreage occurs on State-managed lands, and 4.7 
percent of the EO acreage occurs on private lands. On the Owyhee 
Plateau, 94.7 percent of the EO acreage occurs on Federally managed 
lands, with the remaining 5.3 percent occurring on State managed lands; 
no EOs on the Owyhee Plateau occur on private lands.
    The approximate extant range of the plant was first described in 
1994 (Moseley 1994, p. 6), and has not changed substantially since, 
although the amount of known occupied habitat, particularly on the 
Owyhee Plateau, has expanded in recent years. Since 2003, sixteen new 
occurrences, all within 3 mi (4.8 km) of previously existing 
occurrences, have been documented: 2 on the Snake River Plain with an 
area of 2.7 ac (1 ha) and approximately 2,500 individuals, and 14 on 
the Owyhee Plateau with an area of 46.6 ac (18 ha) and approximately 
650 individuals (Colket et al. 2006, Tables and Appendix A). It should 
be noted that not all potential L. papilliferum habitat in southwest 
Idaho has been surveyed, and it is likely that additional occupied L. 
papilliferum sites will be found.
    Estimating the number of individuals (abundance) of Lepidium 
papilliferum is confounded by its annual or biennial life cycle, 
because the number of individuals of each life form can fluctuate 
widely depending on precipitation. To assess abundance, we utilized 
four available data sets: range-wide EO records maintained by the Idaho 
Conservation Data Center (CDC), range-wide data associated with the 
HII/HIP monitoring, transect monitoring data collected on the OTA, and 
special use plot data from the OTA.
    As of February 2006, the Idaho CDC had ranked 101 EO records for 
Lepidium papilliferum (Colket et al. 2006a, pp. 15 to 41); 9 are ranked 
as extirpated (lost) or probably extirpated, and 7 are considered 
historical (information for most is too vague for relocation). All 9 
extirpations were verified locations from old herbarium collections, 
the most recent from 1955, where the habitat has been completely 
converted to urban or agricultural lands (Colket et al. 2006, Table 
13). The remaining 85 records (as of February 2006) are for EOs 
considered extant (existing). In the review of EO specifications and 
ranks conducted in February 2006, observed abundance was categorized as 
being greater than 1,000 plants, 400 to 999 plants, 50 to 399 plants, 
less than 50 plants, 0 plants, or an unknown number of plants. This 
classification was based on the number of plants present at the last 
survey, regardless of year and associated precipitation patterns. 
Existing data provide an estimated abundance for extant EOs: 15 (18 
percent) have over 1,000 plants, 11 (13 percent) have between 400 and 
999 plants, 1 (1 percent) has about 400 plants, 18 (21 percent) have 
between 50 and 399 plants, 22 (26 percent) have fewer than 50 plants, 9 
(11 percent) had no plants at the last visit, and 9 (11 percent) have 
an unknown number of individuals.
    Two monitoring methods, HII and HIP, have been used range-wide for 
Lepidium papilliferum. Each included different methodologies, but are 
still useful for tracking abundance at transects across the two 
efforts. HII monitoring was developed to assess the overall habitat 
condition that includes attributes associated with the slickspots and 
the sagebrush-steppe habitat, occurred for 4 years (1998 to 2001), and 
is presented in various reports (Mancuso and Moseley 1998; Mancuso et 
al. 1998; Mancuso 2000, 2001, 2002; Menke and Kaye 2006a, b). HIP 
monitoring was developed to assess the overall habitat condition that 
includes those attributes associated with the slickspots and the 
sagebrush-steppe habitat, and also the effectiveness of the CCA. HIP 
monitoring was conducted in 2004 and 2005 (State of Idaho et al. 2006, 
p. 18), and is expected to continue. HIP monitoring results in 2004 are 
reported in Menke and Kaye 2006b, and results through 2005 are included 
in our report ``Best Available Biological Information for Slickspot 
Peppergrass (Lepidium papilliferum)'' (USFWS 2006f, Figures 8, 9). 
Although neither the HII nor HIP methodologies have been peer reviewed, 
they represent the best available survey and monitoring techniques for 
L. papilliferum.
    Abundance data for Lepidium papilliferum have been collected range-
wide since 1998, and collected at the OTA since the early 1990s. The 
range-wide HII and HIP transect data illustrate that plant abundance is 
positively correlated with spring precipitation, and specifically that 
rainfall in the months of March through May accounts for 89 percent of 
the variability in plant numbers (Menke and Kaye 2006b, p. 10). Plant 
abundance therefore fluctuates widely between years in association with 
precipitation. In the areas monitored by HII and HIP, Menke and Kaye 
(2006b, p. 10) report that L. papilliferum abundance decreased range-
wide between 1998 and 1999, remained low through 2002, and began to 
increase again beginning in 2002. This pattern closely tracks that of 
rainfall during those same years. Abundance data from transects at the 
OTA illustrate declines in abundance first noted in 1996, with a 
declining trend in recent years that is not correlated with spring 
precipitation (Weaver 2006, pp. 1-6). Abundance data from the range-
wide HII and HIP transects showed increasing trends in L. papilliferum 
between the years 2002 and 2005 (no data were collected in 2003) (USFWS 
2006f, Figures 8, 9).

[[Page 1627]]

Thus range-wide abundance data from the HII and HIP transects continue 
to show a consistently positive correlation with spring precipitation. 
We consider this range-wide data to be the best available at this time.
    We conducted a review of the abundance data and study methodology 
following the reopened comment period on the proposal to list L. 
papilliferum as endangered (October 23, 2006, to November 13, 2006; 71 
FR 62078). A review of the special use plot counts at the OTA (USFWS 
2006e, Figure 7) shows a decline in plant numbers during the drought 
years of 1992 (249 plants), 1997 (624 plants), and 2002 (270 plants) 
followed by a positive response in plant numbers as spring 
precipitation increased in subsequent years 1993 (6,369 plants), 1998 
(3,330 plants), and 2003 (4,080 plants). Reviewing the special use plot 
data at OTA for 2004-2006 illustrates a relatively stable or declining 
number of plants despite increases in spring precipitation.
    We reviewed the OTA population monitoring transect study and 
updated the description of the study methods from our BAI based upon 
clarification of new information provided by IARNG staff during the 
reopened comment period on the proposal to list L. papilliferum as 
endangered (October 23, 2006, to November 13, 2006; 71 FR 62078). The 
BAI cited study methods as described by IARNG staff and stated that the 
census effort occurred annually at the OTA and that observers cover 98 
percent of the plants' habitat at OTA. New information obtained since 
the BAI was written suggests that 90 percent may be a more accurate 
estimate of the amount of habitat surveyed at OTA. Since 2003, 
additional plant inventories have increased the size of the known 
population of L. papilliferum at OTA, including the documentation of 
365 new occupied slickspots in 2005 (URS Corporation 2005, pp. 6-7). 
The OTA population monitoring transects for 2005 reported 18,599 plants 
in the transect areas; the survey inventory by URS corporation reported 
43,925 plants (365 new slickspots with L. papilliferum, 125 historic 
slickspots with L. papilliferum, 66 historic slickspots without L. 
papilliferum) in the areas surveyed at OTA (URS Corporation 2005, p. 
7).
    We reviewed the results of range-wide HII and HIP monitoring, 
including reported plant abundance since these studies were initiated 
in 1998, and new information available to us since the time we last 
issued a listing finding on this species. These data illustrate a 
general pattern of plant numbers correlating with spring precipitation 
(USFWS 2006f, Figures 8, 9). Data are incomplete for 2002 and 2003. 
Menke and Kaye (2006b, p. 19) report that ``populations generally 
decreased during 1998-2004 and these trends appear to be strongly 
influenced by spring precipitation.'' In contrast to the results 
reported from the OTA, range-wide abundance of Lepidium papilliferum as 
measured by the HII and HIP increased as spring precipitation increased 
in the years 2002 through 2005 (USFWS 2006f, Figures 8, 9). Comparing 
years 1998 and 2005, which are relatively comparable in terms of range-
wide spring precipitation (6.6 inches and 6.3 inches, respectively), 
plant numbers are also similar (17,611 and 15,226 respectively), 
indicating little change in overall abundance of L. papilliferum range-
wide over this time interval, despite the intervening fluctuations in 
yearly abundance that are to be expected for an ephemeral annual plant. 
In general, the HII and HIP data from 1998-2005 indicate that the 
abundance of L. papilliferum range-wide remained relatively stable over 
this time interval (USFWS 2006f, Figure 8). We consider this range-wide 
data to be the best available at this time.

Habitat Quality

    Vegetation community data are collected as one component of 
Lepidium papilliferum HIP monitoring. One of the attributes documented 
in HIP monitoring is the fire history pattern. Observations are 
recorded to document if there is evidence of fires at four landscape 
scales; in the HIP transects, and in the surrounding habitat at 65 
meters, 250 meters, and 500 meters from the transect. Given the mosaic 
pattern of wildfire burns, often the surrounding habitat may be burned 
while an individual HIP transect is unburned or predominately unburned. 
In 2004, vegetation communities were sampled at 71 HIP transects, and 
41 (58 percent) of the transects were classified as unburned, with 
predominantly big sagebrush cover and less than 33 percent introduced 
annual cover; 7 (10 percent) were classified as unburned, with moderate 
big sagebrush cover and at least 33 percent introduced annual cover; 6 
(8 percent) were classified as burned, with predominantly native 
vegetation, although introduced annual cover sometimes comprised up to 
50 percent of the total plant cover; 2 (3 percent) were classified as 
burned, with predominantly introduced annual cover (Salsola kali 
(Russian thistle or tumbleweed) and Ceratocephala testiculata (bur 
buttercup, formerly Ranunculus testiculatus)), with low cheatgrass 
(Bromus tectorum) and some crested wheatgrass (Agropyron cristatum); 11 
(14 percent) were classified as burned and dominated by cheatgrass; and 
4 (6 percent) were classified as burned and seeded with crested 
wheatgrass (Colket 2005a, p. 8). In summary, over 42 percent of the HIP 
vegetation plots along HIP transects were in habitats with over 33 
percent nonnative, invasive plant cover.
    Menke and Kaye (2006b) evaluated the association between measures 
of habitat quality measured by HIP and abundance of L. papilliferum. 
For the one year for which data were available (2004), they report that 
L. papilliferum abundance was not significantly correlated with soil 
crust cover or weedy species cover in slickspots, and that the 
proportion of flowering plants had a positive correlation with soil 
crust cover, but was not significantly correlated with livestock print 
cover or weedy species cover (Menke and Kaye 2006b, p. 15). In their 
overall evaluation of habitat condition, they report that total 
vascular plant cover, species richness, and species diversity had 
declined between 1998 and 2004, and suggest that past fires have been a 
factor in degrading slickspot condition (Menke and Kaye 2006b, p. 19). 
Several features of slickspots, including soil crust cover and weedy 
species cover, were consistently more degraded in burned areas. 
Although slickspots in burned areas had more dense weedy annual species 
cover (Menke and Kaye 2006b, p. 19), Menke and Kaye state that 
``Competition from weedy annual species (which may be promoted by 
fire), does not appear to influence abundance of L. papilliferum plants 
in a given year, but may influence reproductive output, other plant 
traits, and other life history stages' (Menke and Kaye 2006b, p. 17). 
Soil crust cover was significantly lower in 2004 transects with 
evidence of livestock grazing, but there was no direct relationship 
between abundance of L. papilliferum and total livestock print cover or 
cover of print penetrating to the slickspot clay layer (Menke and Kaye 
2006b, p. 15).
    Another measure of habitat quality within Lepidium papilliferum's 
range is the EO ranking by the Idaho CDC. The first EO ranks for L. 
papilliferum were assigned in 1993 (Colket et al. 2006, Tables 1-13). 
In 2006, EO specifications and ranking were revised by the Idaho CDC 
(Colket et al. 2006, pp. 15 to 44). Due to the change in methodology, 
it is difficult to draw conclusions about changes in EO rankings over 
time. EO ranks are designed as an assessment of estimated viability or 
probability of persistence and help prioritize

[[Page 1628]]

conservation planning or actions (NatureServe 2002, p. 36). We consider 
EO rankings to be part of the best available data on the species at 
this time.
    Table 1 summarizes the rankings for 85 EOs based on the 2006 
revised methodology. A-ranked EOs have one or more of the following 
conditions that are summarized through a formula: (1) Over 1,000 
detectable above-ground plants; (2) intact native plant communities 
with trace nonnative species cover; (3) slickspots with zero or trace 
nonnative cover or livestock disturbance; (4) zero or few minor 
anthropogenic disturbances; (5) a lack of burning; and (6) a 
surrounding landscape within 0.6 mi (1 km) that is not fragmented by 
agricultural lands, residential or commercial development, introduced 
annual grasslands, or drill seeding projects (Colket et al. 2006, p. 
3). By contrast, D-ranked EOs exist in the most highly degraded 
habitats, with the fewest plants, and with the most degraded 
surrounding landscape (Colket et al. 2006, p. 3).

                                    Table 1.--Number of Element Occurrences in 2006 by CDC Ranking (Percent of Total)
                                                   [Colket et al. 2006, Tables 1 to 13 and Appendix C]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                 A                        B            BC           C          pC \1\         D          pD \1\       E \2\          F          Total
--------------------------------------------------------------------------------------------------------------------------------------------------------
0..................................     15 (18)        1 (1)      26 (31)        4 (5)      19 (22)        1 (1)      10 (12)       9 (11)           85
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Probable ranks assigned when incomplete information available.
\2\ Not enough habitat information available to make a ranking.

    Of the 66 EOs with B through D rankings (13,123 ac (5,310 ha)), 51 
occur on the Snake River Plain (10,804 ac (4,372 ha)), and 15 on the 
Owyhee Plateau (2,318 ac (938 ha)). Of these 66 middle-ranked EOs, 50 
are ranked as a C or D (averaging fewer than 399 plants, partial to 
nonexistent native plant communities that are partially to 
predominately burned, and partially to predominantly fragmented 
landscapes). The 40 EOs on the Snake River Plain cover 3,170 ac (1,283 
ha), and the 10 EOs on the Owyhee Plateau cover 73 ac (30 ha).
    Habitat data (HII, HIP) have been collected annually for 
approximately one-half of the extant EOs since 1998. Given that 
monitoring methodologies and the specifications for determining EO rank 
changed in 2004/2005, and not every EO is monitored annually, it is not 
possible to draw definitive conclusions about the change in habitat 
quality over time. It is possible, however, to gain an understanding of 
the current condition of habitat quality from the available data. Based 
on the most recent EO ranks, at least 75 percent (n = 49) were ranked 
as C, D, or F, indicating that most EOs occurred in partially or 
predominantly fragmented landscapes with partial to nonexistent native 
plant communities. As discussed below we don't have any data that 
correlate L. papilliferum population numbers with effects to habitat.

Previous Federal Actions

    For a description of Federal actions concerning Lepidium 
papilliferum that occurred prior to January 22, 2004, please refer to 
the document to withdraw our July 15, 2002, proposal published in the 
Federal Register on January 22, 2004 (69 FR 3094).
    On January 22, 2004, we published a document withdrawing our 
proposed rule to list Lepidium papilliferum as endangered (69 FR 3094). 
That action was based on our conclusion that there was ``a lack of 
strong evidence of a negative population trend, and the formalized 
conservation plans (e.g., the CCA and INRMPs) had sufficient certainty 
that they would be implemented and effective such that the risk to the 
species was reduced to a level below the statutory definition of 
endangered or threatened.''
    On April 5, 2004, Western Watersheds Project filed a lawsuit 
challenging our decision to withdraw the proposed rule to list Lepidium 
papilliferum as threatened or endangered (Western Watersheds Project v. 
Jeffery Foss, et al., Case No. CV 04-168-S-EJL). On August 19, 2005, 
the U.S. District Court for the District of Idaho reversed the decision 
to withdraw the proposed rule, with directions that the case be 
remanded to the Secretary of the Department of Interior for 
reconsideration of ``whether a proposed rule listing the slickspot 
peppergrass as either threatened or endangered should be adopted.''
    After issuance of the District Court's remand order, we notified 
Federal, State and local agencies, county governments, elected 
officials, and other interested parties of the Court's decision in a 
letter dated October 13, 2005. We requested new scientific data and 
comments about Lepidium papilliferum. We also stated that scientific 
data received from the public would be included in an updated ``Draft 
Best Available Biological Information for Slickspot Peppergrass 
(Lepidium papilliferum)'' (BAI) document. In response to our request, 
we received a total of 13 comment letters. The updated BAI combined all 
existing and new information about the species and its habitat, and we 
utilized it in making this final listing determination.
    On February 27, 2006, we opened a 30-day public comment and peer 
review period, through an electronic process referred to as VOCUS, for 
our comprehensive document entitled ``Draft Best Available Biological 
Information for Slickspot Peppergrass (Lepidium papilliferum)'' (USFWS 
2006f). Following public and peer review, we used new data and 
technical corrections, along with existing data, for our analysis 
described below as the best available scientific and commercial data.
    After an order by the district Court on October 4, 2006, which 
requires ``a final listing determination on the slickspot peppergrass 
by January 4, 2007,'' we opened a 22-day public comment period that 
closed on November 13, 2006 (71 FR 62078). A variety of documents were 
posted on the FWS Web site for public comment, including peer review 
comments on the draft BAI and results of the expert panel.

Summary of Comments and Responses

    We received a total of 13 comment letters in response to our 
October 13, 2005, request for additional information to assist with the 
listing determination for Lepidium papilliferum; 17 public comment 
letters and 19 peer review responses on the Draft BAI released on 
February 27, 2006; and 20 public comment letters in response to our 
October 23, 2006, reopening of the public comment period. The majority 
of comments were specific to the draft BAI and associated data as well 
as issues surrounding the 2003 CCA developed to conserve L. 
papilliferum. Comments that were substantive or that provided new 
information were incorporated into the final determination where 
appropriate, or are addressed below. We consolidated the comments into 
categories by issue.

[[Page 1629]]

    Issue 1: Several commenters provided new data and information 
regarding the biology, ecology, life history, genetics, and factors 
affecting Lepidium papilliferum, and requested that it be incorporated 
into the body of existing knowledge concerning the species and 
considered by us in making any future management determinations.
    Our response: In making this final listing determination, we have 
considered scientific and commercial data contained in over 75 
technical reports, published journal articles, and other general 
literature documents, including nearly 30 reports received since the 
January 23, 2004. The body of available information specific to this 
species has greatly expanded since 2004, with new information regarding 
species locations, known condition of its habitat, slickspot soil 
characteristics and disturbance, Lepidium papilliferum's pollinators, 
seed viability and germination, ongoing conservation efforts, genetics, 
and factors affecting the species. This information was contained in 
various State agency reports (Colket 2005a; Colket 2006; Colket et al. 
2006; IDARNG 2005; State of Idaho et al. 2006) and other scientific 
reports and peer reviewed articles (Menke and Kaye 2006a, b; Meyer and 
Allen 2005; Meyer et al. 2005; Meyer et al. 2006; Palazzo et al. 2005; 
Robertson 2003a; Robertson and Klemesh 2003; Robertson and Ulappa 2004; 
Robertson et al. 2005; Stillman et al. 2005). Additionally, we reviewed 
and considered data from ongoing L. papilliferum conservation efforts 
(Binder 2006; Boise Airport 2003; Hoffman 2005; IDARNG 2005; State of 
Idaho et al. 2006; U.S. Air Force 2004). Further research and continued 
monitoring would provide a more thorough understanding of the species; 
however, we have a legal obligation to make a final listing 
determination based on the best available scientific and commercial 
data.
    Issue 2: Some commenters stated that an urgent need to list 
Lepidium papilliferum exists due to ongoing and current threats. One 
commenter suggested that there is evidence for widespread and rapid 
population decline. Another commenter stated that the species is at 
such risk of extinction that it should be listed to ensure that the BLM 
and other Federal land management agencies implement management actions 
that result in substantive conservation. Other commenters stated that 
existing regulations are insufficient in providing for the long-term 
persistence of the species. Conversely, some commenters stated that 
existing regulatory mechanisms, primarily through the CCA and its 
associated conservation measures, are sufficient or more than 
sufficient to preclude the need to list L. papilliferum under the Act.
    Our response: The Act requires us to make listing decisions based 
solely on the best scientific and commercial data available at the time 
the decision is made (section 4(b)(1)(A) of the Act). We thoroughly 
reviewed all available scientific and commercial data for Lepidium 
papilliferum in preparing this final determination. We reviewed 
historical and recent publications, and unpublished reports concerning 
L. papilliferum and the sagebrush-steppe habitat of southwestern Idaho. 
From this information, we produced the document ``Draft Best Available 
Biological Information for Slickspot Peppergrass (Lepidium 
papilliferum)'' (BAI); we solicited public comment and peer review on 
the BAI in February 2006. We also convened a panel of seven scientific 
experts to review the scientific information available to us pertaining 
to L. papilliferum. Additionally, we reopened the public comment period 
on the proposed rule in October 2006 (71 FR 62078) to solicit 
additional review and comment on new data that we have considered in 
this final determination.
    We followed our Policy on Information Standards Under the 
Endangered Species Act, published in the Federal Register on July 1, 
1994 (59 FR 34272), and our associated Information Quality Guidelines 
in preparing this final determination. Our evaluation of the 
significance of these numerous ongoing threats across the range of 
Lepidium papilliferum is presented in the Summary of Factors Affecting 
the Species section of this final determination. This analysis includes 
the adequacy of existing regulatory mechanisms, including public land 
management practices. During the listing process, we provided 6 public 
comment periods that were open for a total of 262 days, and held 2 
public hearings. We received new information since the proposed rule 
specific to L. papilliferum that ranged from additional Idaho CDC 
survey data to slickspot soils information. While the body of available 
information specific to this species is limited, our legal obligation 
is to make a final listing determination based on the best available 
data.
    Issue 3: Several comments regarded the effectiveness of the CCA 
(first approved in 2003 and subsequently revised in 2006) in conserving 
Lepidium papilliferum. Some commenters stated that the voluntary 
commitment of non-governmental cooperators developed during the CCA 
process is equal to or better for conservation of L. papilliferum than 
mandated actions that would be associated with listing the species. One 
commenter suggested that the commitment to better livestock grazing 
management by the L. papilliferum Conservation Committee and permittees 
continues, and is still strong after 2 years of implementation, and 
that the follow-through on implementing CCA conservation measures, such 
as responding to grazing triggers and off-highway vehicle (OHV) events 
during 2005, was good. The State of Idaho reported that, of the 203 
conservation measures identified in the CCA, 193 were accomplished in 
either 2004 or 2005, and 7 measures were not implemented due to 
wildfire or ongoing litigation. One commenter stated that the inclusion 
of an adaptive management process within the CCA will ensure that the 
identified conservation measures, if initially ineffective, would 
become effective well before the probable extinction of L. papilliferum 
given existing threats. The U.S. Air Force provided comments on our 
October 23, 2006 draft description and analysis of conservation 
measures (71 FR 62078). The U.S. Air Force believed that several more 
conservation measures have been implemented and are effective in 
conserving L. papilliferum at the Juniper Butte Range than what we had 
determined.
    Conversely, some comments suggested that there is little certainty 
that implementation of Lepidium papilliferum conservation measures 
identified in the CCA will occur. One commenter stated that the 
adaptive management approach used in the CCA provides no certainty of 
protection for L. papilliferum. Another commenter suggested that any 
cooperator can drop out of the CCA at any time without repercussion. 
Another comment asserted that the adaptive management approach as 
currently described in the CCA allows for a one-time disturbance event 
that could result in irreversible harm to L. papilliferum habitat. 
Comments indicated that the CCA provides vast opportunity for a one-
time livestock penetrating trampling event to occur, and is therefore 
insufficient. Other comments suggested that the CCA does not protect L. 
papilliferum and its habitat from soil disturbance, and did not include 
active restoration measures for the vast majority of the species' 
habitats. Commenters stated that, due to the downward trend in L. 
papilliferum abundance, reintroduction of the species should be 
considered. One commenter stated that management

[[Page 1630]]

under an Instruction Memorandum (IM) is uncertain, and that because the 
IM is not a legal requirement, interpretation will be inconsistent 
among field staff.
    Our response: We support utilizing a collaborative conservation 
approach to address factors affecting species being considered for 
listing under the Act. Prior to July 18, 2003, we worked with various 
agencies and individuals to assess the status of Lepidium papilliferum, 
and also to identify and implement conservation actions. Since February 
2000, we have been an active technical advisor in an interagency group 
of biologists and stakeholders to share data and coordinate 
conservation actions for L. papilliferum.
    Using our Policy for Evaluation of Conservation Efforts When Making 
Listing Decisions (PECE) (68 FR 15100), we reviewed the conservation 
measures in five plans, or conservation strategies, for L. 
papilliferum: (1) The Candidate Conservation Agreement for Slickspot 
Peppergrass (CCA), which was initially approved in 2003 and revised in 
2006; (2) the Idaho Army National Guard Integrated Natural Resource 
Management Plan for Gowen Field/Orchard Training Area; (3) the U.S. Air 
Force Integrated Natural Resource Management Plan for Mountain Home Air 
Force Base, which was modified in 2004 and contains more measures that 
promote the conservation of L. papilliferum than the 2000 version; (4) 
the Conservation Agreement (Hull's Gulch Agreement) by and between 
Boise City and the U.S. Fish and Wildlife Service for Allium aasea 
(Aase's onion), Astragalus mulfordiae (Mulford's milkvetch), and 
Lepidium papilliferum (slickspot peppergrass), which was in place until 
it expired on October 22, 2006, and (5) the Conservation Agreement for 
slickspot peppergrass (Lepidium papilliferum) at the Boise Airport, Ada 
County, Idaho. These five agreements and plans include a wide array of 
conservation measures to address the need to maintain and enhance 
slickspot peppergrass, and to potentially avoid or reduce adverse 
effects that might occur in relation to various types of activities. We 
recognize that many of the conservation efforts identified in the plans 
are having conservation benefits for the species, particularly as they 
relate to limiting the effects of wildfire and livestock use. We 
believe conservation efforts are important for this species because, 
while we do not have sufficient information to determine that potential 
threats are having a population level impact on the species, further 
research is necessary. To the extent that there are effects from 
activities, these conservation efforts should offset them.
    We evaluated conservation efforts within each plan under PECE (60 
FR 15100). PECE is relevant in situations where it is necessary to 
determine whether individual conservation efforts that have not been 
implemented, or that have been implemented but have not yet 
demonstrated whether they are effective, are sufficiently certain to be 
implemented and effective so as to have contributed to the elimination 
or adequate reduction of one or more threats to the species identified 
through our threats analysis conducted pursuant to section 4(a)(1) of 
the Act. In this case, the efforts that met the standard in PECE for 
sufficient certainty of implementation and effectiveness were not used 
as a basis for our conclusion, because our analysis did not show that 
the species met the definition of threatened or endangered. However, 
this does not mean that conservation efforts which have yet to be 
implemented, or which have yet to be demonstrated to be effective, are 
unimportant. In fact we strongly encourage continued implementation of 
all on-going and planned conservation efforts, as they can contribute 
to maintaining or improving the status of L. papilliferum.
    Issue 4: There were several comments regarding the use of available 
monitoring and survey data in determining the historical and existing 
distribution, population size, and trend information for Lepidium 
papilliferum. One commenter suggested there have been no comprehensive 
systematic surveys for L. papilliferum, and therefore, we do not fully 
understand the distribution or status of the species. Numerous 
commenters stated that monitoring protocols and methods used to gather 
data regarding L. papilliferum trends and distribution were biased 
toward documenting declines, were insufficient, or were poorly timed, 
and therefore conclusions are poor. Several commenters stated that 
there is no clear relationship between L. papilliferum trends and 
threat factors affecting the species. Some commenters suggested that 
the data demonstrate a negative population trend for L. papilliferum; 
other commenters suggested the data are inconclusive, and no trend can 
be determined. One commenter thought the trend from 2004 to 2005 was 
positive or stable due to implementation of the CCA, a wet spring, and 
a minimal wildfire season. Another commenter identified that the number 
of extant EOs have increased from 45 in 1998 to 85 in 2006, and there 
has been only 1 EO that has been extirpated since 1955. Several 
commenters cited information relating L. papilliferum annual abundance 
to precipitation, while other commenters disputed the claim that annual 
abundance is related to precipitation. Several commenters stated that 
the number of element occurrences has increased from 1998 (45 extant 
EOs) to 2006 (85 extant EOs).
    Several commenters thought that the soil type (slickspots) used by 
Lepidium papilliferum is a limited resource that is not reforming, 
because the processes that originally created it no longer occur. 
Slickspots being modified, altered, or developed are lost to the 
ecosystem forever.
    Our response: In this determination, we have reviewed and 
considered scientific and commercial data contained in over 75 
technical reports, published journal articles, and other documents, 
including nearly 30 reports received since January 22, 2004. We must 
base our listing determination for Lepidium papilliferum on the best 
available data regarding the plant's current known population status, 
the known condition of its habitat, and the current factors affecting 
the species, along with ongoing conservation efforts, as described in 
the Summary of Factors Affecting the Species section of this final 
determination. We also acknowledge that uncertainties exist.
    While a systematic survey, utilizing similar techniques, has not 
been conducted for Lepidium papilliferum range-wide, at least 30 
separate survey efforts for L. papilliferum have occurred (Baczkowski 
2006; USFWS 2006d). Some of these surveys were within the known range 
of L. papilliferum habitat, and others were outside of the known 
distribution, for example, in the State of Oregon, in the Saylor Creek 
area between the Snake River Plain and the Owyhee Plateau, and the City 
of Hagerman. In 2003, for example, 2,350 acres were surveyed in the 
Saylor Creek area between the Snake River Plain metapopulations and the 
Owyhee Plateau metapopulations. During these surveys, 1,727 slickspots 
were documented, but no L. papilliferum individuals were found (U.S. 
Air Force 2003, p. 16). We agree that undiscovered sites occupied by L. 
papilliferum likely exist. Inventories for L. papilliferum have not 
been completed on the majority of private lands within its range due to 
restricted access. Recent discoveries of new occupied slickspot sites 
and new EOs since 1998 have not added substantially to our knowledge of 
where the species exists. For example, an inventory survey at the OTA 
in 2005 found 365 new slickspots with L. papilliferum all within the 
range of known habitat on the OTA (URS

[[Page 1631]]

Corporation 2005, p. 6). Since 2003, 16 new EOs on approximately 50 ac 
(28 ha) (0.4 percent of the total acreage) have been documented, all 
within 3 mi (4.8 km) of previously existing EOs (Colket et al. 2006, 
Tables 1 to 14). Although there has been only one documented 
extirpation since 1955, up to 9 small and isolated EOs had no plants 
detected during one or more recent monitoring surveys.
    Numerous monitoring efforts have been conducted for Lepidium 
papilliferum, including population trend monitoring transects at the 
OTA (IDARNG 2005) completed since 1991, demographic monitoring at the 
OTA from 1993 to 1996 (Meyer et al. 2005), Habitat Integrity Index 
(HII) monitoring done by the Idaho CDC at L. papilliferum EOs range-
wide conducted from 1998 to 2002 (Mancuso and Moseley 1998; Mancuso et 
al. 1998; Mancuso 2000; Mancuso 2001; Mancuso 2002), Habitat Integrity 
Population (HIP) monitoring built on HII monitoring at L. papilliferum 
EOs range-wide conducted by the Idaho CDC in 2004 and 2005 (Colket 
2005a, Colket 2005b), and monitoring done at the Juniper Butte Range in 
2003 and 2005 (U.S. Air Force 2003). HIP monitoring, the most extensive 
range-wide effort to date, was developed by the Idaho CDC in 
conjunction with the L. papilliferum Technical Team to statistically 
analyze and detect trends in L. papilliferum and its habitat (the 
technical team includes IDARNG, BLM, Air Force, the Service, Idaho 
Department of Agriculture, and other interested parties) (Colket 2005a, 
p. 3). Both the HII and HIP monitoring, because of the difficulties 
associated with tracking numbers of L. papilliferum individuals across 
years, utilize habitat information as a metric of L. papilliferum 
health (Mancuso et al. 1998, pp. 1 to 7).
    Because of the fluctuations in Lepidium papilliferum numbers 
associated with precipitation (Meyer et al. 2005, pp. 4, 12, 15; 
Palazzo et al. 2005, p. 9; Menke and Kaye 2006b, p. 10), determining 
trends requires long-term monitoring data sets. Two long-term 
monitoring data sets in which we see a downward trend in recent years 
in numbers of individuals that do not mimic precipitation are the 
population trend monitoring transect data and special use plot data at 
the OTA. In contrast, an analysis by Palazzo et al. (2005, p. 9) for 
all 4 years of HII data found a relationship (p-value less than 0.01) 
between February to June precipitation and numbers of L. papilliferum. 
In their analysis of range-wide HII and HIP data collected from 1998-
2002 and 2004 (no data was collected in 2003), Menke and Kaye (2006b, 
p. 10) further refined this relationship and found a strong positive 
relationship between precipitation from March through May and L. 
papilliferum abundance. In contrast to the monitoring data from OTA, 
the range-wide data shows that L. papilliferum continues to track 
consistently with precipitation throughout all years of the data set 
(Menke and Kaye 2006b, p. 10 and Figs. 1, 2). We consider this range-
wide data to be the best available at this time.
    The conditions that allowed for the formation of slickspots in 
southwestern Idaho are thought to have occurred during a wetter 
Pleistocene climate (Nettleton and Petersen 1983, p. 191; Seronko 
2006). Under natural conditions, several hundred years may be necessary 
to alter or lose slickspots, generally through climate change or severe 
natural erosion (Seronko 2006). Meyer and Allen (2005, p. 9) suggest 
that if sufficient time passes following the disturbance of slickspot 
soil layers, it is possible that slickspots can reform similar to their 
pre-disturbance configuration.
    Issue 5: Numerous commenters provided information or opinions 
regarding how various threats may or may not affect Lepidium 
papilliferum, its habitat, and its p