Endangered and Threatened Wildlife and Plants; Listing Lepidium papilliferum, 52014-52064 [E9-24039]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 74, Number 194 (Thursday, October 8, 2009)]
[Rules and Regulations]
[Pages 52014-52064]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-24039]



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Part IV





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



Endangered and Threatened Wildlife and Plants; Listing Lepidium 
papilliferum (Slickspot Peppergrass) as a Threatened Species Throughout 
Its Range; Final Rule

Federal Register / Vol. 74, No. 194 / Thursday, October 8, 2009 / 
Rules and Regulations

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[RIN 1018-AW34]
[FWS-R1-ES-2008-0096]
[MO 922105-0008-B2]


Endangered and Threatened Wildlife and Plants; Listing Lepidium 
papilliferum (Slickspot Peppergrass) as a Threatened Species Throughout 
Its Range

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), determine 
that Lepidium papilliferum (slickspot peppergrass), a plant species 
from southwest Idaho, is a threatened species under the Endangered 
Species Act of 1973, as amended (Act). This final rule implements the 
Federal protections provided by the Act for this species. We have 
determined that critical habitat for L. papilliferum is prudent but not 
determinable at this time.

DATES: This rule becomes effective December 7, 2009. The effective date 
has been extended to 60 days after publication in the Federal Register 
to allow the U.S. Bureau of Land Management (BLM) to finish conferring 
with the Service under section 7(a)(4) of the Act on the BLM's issuance 
of grazing permits within the range of Lepidium papilliferum.

ADDRESSES: This final rule is available on the Internet at https://www.regulations.gov and also at https://www.fws.gov/idaho. Comments and 
materials received, as well as supporting documentation used in the 
preparation of this rule, will be available for public inspection, by 
appointment, during normal business hours at: U.S. Fish and Wildlife 
Service, Idaho Fish and Wildlife Office, 1387 S. Vinnell Way, Room 368, 
Boise, ID 83709; by telephone at 208-378-5243; by facsimile at 208-378-
5262.

FOR FURTHER INFORMATION CONTACT: Jeff Foss, Field Supervisor, at above 
address, telephone, and facsimile, or by electronic mail at: 
fw1srbocomment@fws.gov. Persons who use a telecommunications device for 
the deaf (TDD) may call the Federal Information Relay Service (FIRS) at 
800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

    Lepidium papilliferum is a small, flowering plant in the mustard 
family (Brassicaceae). The plant grows in unique microsite habitats 
known as slickspots, which are found within the semiarid sagebrush-
steppe ecosystem of southwestern Idaho. The species is endemic to this 
region, known only from the Snake River Plain and its adjacent northern 
foothills (an area approximately 90 by 25 miles (mi) (145 by 40 
kilometers (km)), or 2,250 square miles (mi\2\) (5,800 square 
kilometers (km\2\)), with a smaller disjunct population on the Owyhee 
Plateau (an area of approximately 11 by 12 mi (18 by 19 km), or 132 
mi\2\ (342 km\2\). The restricted distribution of L. papilliferum is 
likely due to its adaptation to the specific conditions within these 
slickspot habitats. The absence of all perennial plant species from 
these sites likewise demonstrates the specialization of L. papilliferum 
persisting in the unique conditions provided by slickspots (Fisher et 
al. 1996, p. 16). The primary threat to L. papilliferum (as described 
under The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range, below) is the present or 
threatened destruction, modification, or curtailment of its habitat and 
range due to the increased frequency and extent of wildfires under a 
wildfire regime modified and exacerbated by the spread of invasive 
nonnative plants, particularly nonnative annual grasses such as Bromus 
tectorum (cheatgrass). In addition, even under conservative projections 
of the consequences of future climate change, the threats posed by 
wildfire and the invasion of B. tectorum are expected to further 
increase within the foreseeable future. Other threats to the species 
include competition and displacement by nonnative plant species, 
development, potential seed predation by harvester ants, and habitat 
fragmentation and isolation of small populations.

Previous Federal Actions

    On July 15, 2002, we proposed to list Lepidium papilliferum as 
endangered (67 FR 46441). On January 12, 2007, we published a document 
in the Federal Register withdrawing that proposed rule (72 FR 1622). 
For a description of Federal actions concerning L. papilliferum prior 
to the 2007 withdrawal, please refer to that 2007 withdrawal document. 
The withdrawal of the proposal to list L. papilliferum was based on our 
conclusion that, while its sagebrush-steppe matrix habitat is becoming 
increasingly degraded, the best available data at the time provided no 
evidence indicating that this degradation was impacting L. papilliferum 
within its slickspot microsites. Furthermore, we concluded that, 
although we found that abundance on the Idaho Army National Guard's 
Orchard Training Area (OTA) had decreased in recent years, the observed 
rangewide fluctuations in population numbers appeared to be consistent 
with varying levels of spring rainfall, as expected. On April 6, 2007, 
Western Watersheds Project filed a lawsuit challenging our decision to 
withdraw the proposed rule to list L. papilliferum. On June 4, 2008, 
the U.S. District Court for the District of Idaho (Court) reversed the 
decision to withdraw the proposed rule, with directions that the case 
be remanded to the Service for further consideration consistent with 
the Court's opinion (Western Watersheds Project v. Kempthorne, Case No. 
CV 07-161-E-MHW (D. Idaho)).
    After issuance of the Court's remand order, we published a public 
notification of the reinstatement of our July 15, 2002, proposed rule 
to list Lepidium papilliferum as endangered and announced the reopening 
of a public comment period on September 19, 2008 (73 FR 54345). The 
initial comment period closed on October 20, 2008. After the close of 
the comment period, new information became available that was relevant 
to our evaluation. Much of this information was contained in reports 
based on several independent analyses of the available information 
regarding L. papilliferum population trends on the OTA in southwest 
Idaho, the rangewide Habitat Integrity and Population (HIP) monitoring, 
and a recent analysis of L. papilliferum data collected on the Inside 
Desert (Owyhee Plateau) from 2000 to 2002. To ensure that our review of 
the species' status was complete, we announced another reopening of the 
comment period on March 17, 2009, for a period of 30 days (74 FR 
11342). We posted several documents on https://www.regulations.gov for 
public review and comment, including the additional information and 
statistical analyses we received after the January 2007 withdrawal 
notice (72 FR 1622; January 12, 2007). A summary of the comments we 
received and our responses is provided in this document, following our 
finding.

Species Information

Description
    Lepidium papilliferum is an intricately branched, tap-rooted plant, 
averaging 2 to 8 inches (in) (5 to 20

[[Page 52015]]

centimeters (cm)) high, but occasionally reaching 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 millimeters (mm)) in diameter, white, and four petalled. Fruits 
(siliques) are 0.1 in (3 to 4 mm) across, round in outline, flattened, 
and two-seeded (Moseley 1994, pp. 3, 4; Holmgren et al. 2005, p. 260). 
The species is monocarpic (it flowers once and then dies) and displays 
two different life history strategies--an annual form and a biennial 
form. The annual form reproduces by flowering and setting seed in its 
first year, and dies within one growing season. The biennial life form 
initiates growth in the first year as a vegetative rosette, but does 
not flower and produce seed until the second growing season. Biennial 
rosettes must survive generally dry summer conditions, and consequently 
many of the biennial rosettes die before flowering and producing seed. 
The number of prior-year rosettes is positively correlated with the 
number of reproductive plants present the following year (ICDC 2008, p. 
9; Unnasch 2008, p. 14; Sullivan and Nations 2009, p. 44). The 
proportion of annuals versus biennials in a population can vary greatly 
(Meyer et al. 2005, p. 15), but in general annuals appear to outnumber 
biennials (Moseley 1994, p. 12).
Seed Production
    Depending on an individual plant's vigor, the effectiveness of its 
pollination, and whether it is functioning as an annual or a biennial, 
each Lepidium papilliferum plant produces varying numbers of seeds 
(Quinney 1998, pp. 15, 17). Biennial plants normally produce many more 
seeds than annual plants (Meyer et al. 2005, p. 15). Average seed 
output for annual plants at the OTA (an Idaho Army National Guard 
(IDARNG) training area on BLM land) was 125 seeds per plant in 1993 and 
46 seeds per plant in 1994. In contrast, seed production of biennials 
at this site in 1993 and 1994 averaged 787 and 105 seeds per plant, 
respectively (Meyer et al. 2005, p. 16). Based on data collected from a 
4-year demography study on the OTA, survivorship of the annual form of 
L. papilliferum was demonstrated to be higher than survivorship of 
biennials (Meyer et al. 2005, p. 16). For example, of the 4,065 plants 
counted in spring of 1993, a total of 2,503 survived to fruit as 
annuals, while only 85 survived to fruit as biennials in spring of 
1994. Meyer et al. (2005, p. 21) hypothesize that the reproductive 
strategy of L. papilliferum is a plastic response, meaning that larger 
plants will flower and produce seed in their first season, whereas 
smaller plants that stand less chance of successfully setting seed in 
their first season will delay reproduction until the following year. 
The biennial life form is thus maintained, despite the higher risk of 
mortality.
    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; Sullivan and Nations 2009, p. 44). Mancuso and 
Moseley (1998, p. 1) note that sites with thousands of above-ground 
plants one year may have none the next, and vice versa. 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 in many years constitutes the majority of the 
population (Mancuso and Moseley 1998, p. 1). Seed banks are adaptations 
for survival in a ``risky environment,'' because they buffer a species 
from stochastic (random) impacts, such as lack of soil moisture (Baskin 
and Baskin 2001, p. 160).
Seed Viability and Germination
    The seeds of Lepidium papilliferum are found primarily within the 
slickspot microsites where the plants are found (Meyer and Allen 2005, 
pp. 5, 6). Slickspots, also known as mini-playas or natric (high sodium 
content) sites, are visually distinct openings in the sagebrush-steppe 
created by unusual soil conditions characterized by significantly 
greater sodium and clay content relative to the surrounding area 
(Moseley 1994, p. 7). The vast majority of L. papilliferum seeds in 
slickspots have been located near the soil surface, with lower numbers 
of seeds located in deeper soils (Meyer et al. 2005, p. 19; Palazzo et 
al. 2005, p. 3). Lepidium papilliferum seeds have been found in 
slickspots even if no above-ground plants are present (Meyer et al. 
2005, p. 22; Palazzo et al. 2005, p. 10). When above-ground plants are 
present, flowering usually takes place in late April and May, fruit set 
occurs in June, and the seeds are released in late June or early July. 
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 the initially viable seeds produced in a 
given year germinate annually (Meyer et al. 2005, pp. 17, 18). When 
combined with an average annual 3 percent loss of seed viability, 
approximately 9 percent of the original seed cohort per year is lost 
after the first year. Thus, after 12 years, all seeds in a given cohort 
will likely have either died or germinated, resulting in a maximum 
estimated longevity of 12 years for seeds in the seed bank (Meyer et 
al. 2005, p. 18).
    Billinge and Robertson (2008, pp. 1005-1006) report that both small 
and large Lepidium papilliferum populations share similar spatial 
structure, and that spatial structuring within its unique microsite 
slickspot habitats suggests that both pollen dispersal and seed 
dispersal are low for this species and occur over short distances 
(Robertson et al. 2006a, p. 3; Billinge and Robertson 2008, pp. 1005-
1006). Modeling of dispersal and seed dormancy characteristics of 
desert annual plants predicts that plants with long-range dispersal 
will have few dormancy mechanisms and thus quick germination (Venable 
and Lawlor 1980, p. 272). Contrary to this prediction, however, L. 
papilliferum has delayed germination (Meyer et al. 2005, pp. 17-18), 
and, therefore, according to the model, may not disperse long 
distances. The primary seed dispersal mechanism for L. papilliferum is 
not known (Robertson and Ulappa 2004, p. 1708), although viable seeds 
have been found outside of slickspots, indicating that some seed 
dispersal is occurring beyond slickspot habitat (Palazzo et al. 2005, 
p. 10). Additionally, beginning in mid-July, entire dried-up biennial 
plants and some larger annual plants have been observed to break off at 
the base and are blown by the wind (Stillman, pers. obs., as reported 
in Robertson et al. 2006b, p. 44). This tumbleweed-like action may have 
historically resulted in occasional long-distance seed dispersal 
(Robertson et al. 2006b, p. 44). Ants are not considered to be a likely 
disperser despite harvesting an average of 32 percent of fruits across 
six sites (Robertson and White 2007, p. 11).
    Lepidium papilliferum seeds located near the soil surface show 
higher rates of germination and viability (Meyer and Allen 2005, pp. 6-
8; Palazzo et al. 2005, p. 10) and the greatest seedling emergence 
success rate (Meyer and Allen 2005, pp. 6-8). Viable seeds were more 
abundant and had greater germination rates from the upper 2 in (5 cm) 
of soil (Palazzo et al. 2005, pp. 8, 10), while Meyer and Allen (2005, 
pp. 6-8) observed the upper 0.08 in (2 mm) optimal for germination. 
Deep burial of

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L. papilliferum seeds (average depths greater than 5.5 in (14 cm)) can 
entomb viable seeds and may preserve them beyond the 12-year period 
previously assumed as the maximum period of viability for L. 
papilliferum seeds (Meyer and Allen 2005, pp. 6, 9). However, seeds 
buried at such depth, even if they remain viable, are unlikely to 
regain the surface for successful germination. The effects of 
environmental factors such as wildfire on L. papilliferum seed dormancy 
and viability are currently unknown, although L. papilliferum abundance 
is reduced in burned areas (see discussion of Wildfire under Summary of 
Factors Affecting the Species).
Pollination
    Lepidium papilliferum is primarily an outcrossing species requiring 
pollen from separate plants for more successful fruit production and 
has a low seed set in the absence of insect pollinators (Robertson 
2003a, p. 5; Robertson and Klemash 2003, p. 339; Robertson and Ulappa 
2004, p. 1707; Billinge and Robertson 2008, pp. 1005-1006). Lepidium 
papilliferum is able to self-pollinate; however, with a selfing rate 
(rate of self-pollination) of 12 to 18 percent (Billinge 2006, p. 40; 
Robertson et al. 2006a, p. 40). In pollination experiments where 
researchers moved pollen from one plant to another, fruit production 
was observed to be higher with pollen from distant sources (4 to 12.4 
mi (6.5 to 20 km) distance between patches of plants) compared to fruit 
production for plants pollinated with pollen from plants within the 
same patch (246 to 330 feet (ft) (75 to 100 meters (m)) distance within 
a plant patch) (Robertson and Ulappa 2004, p. 1705; Robertson et al. 
2006a, p. 3).
    Fruits produced from fertilized flowers reach full size 
approximately 2 weeks after pollination (Robertson and Ulappa 2004, p. 
1706). Each fruit typically bears two seeds that drop to the ground 
when the fruit dehisces (splits open) in midsummer (Billinge and 
Robertson 2008, p. 1003).
    Known Lepidium papilliferum insect pollinators include several 
families of bees (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; Robertson et al. 2006b, p. 6). Seed set was not limited by the 
number of pollinators at any study site (Robertson et al. 2004, p. 14). 
Studies have shown a strong positive correlation between insect 
diversity and the number of L. papilliferum flowering at a site 
(Robertson and Hannon 2003, p. 8). Measurement of fruit set per visit 
revealed considerable variability in the effectiveness of pollination 
by different types of insects, ranging from 0 percent in dermestid 
beetles to 85 percent in honeybees (Robertson et al. 2006b, p. 15).
Genetics
    The majority of species in the genus Lepidium have a base 
chromosome count of eight (Mummenhoff et al. 2001, p. 2051). Chromosome 
numbers for pollen mother cells in L. papilliferum ranged from 15 to 17 
(n = 15.96  0.16; Table 3; Figure 3), confirming that the 
plant is a tetraploid (has four sets of homologous chromosomes, as 
opposed to the more usual set of two) (Robertson et al. 2006b, p. 38).
    The genetics of Lepidium papilliferum have been studied using 
samples collected from areas across the entire range of the species 
(Stillman et al. 2005, pp. 6, 8, 9; Larson et al. 2006, p. 14 and Fig. 
4; Smith et al. in press, pp. 15-16). Genetic exchange can occur either 
through pollen or seed dispersal. Some researchers consider L. 
papilliferum to be closely related to L. montanum, and L. papilliferum 
was originally described as L. montanum var. papilliferum in 1900 by 
Louis Henderson. Results of 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). A more 
recent study examining the relationship between L. montanum, L. 
papilliferum, and L fremontii found that L. papilliferum is considered 
a sister taxa or closely related to L. fremontii, a native mustard of 
western North America (Smith et al. in press, pp. 15-16). Both L. 
fremontii and L. papilliferum are morphologically and ecologically 
distinct from L. montanum, and recent analyses reflect that both are 
monophyletic (organisms that share a common ancestor) with apparently 
little gene flow between them and L. montanum (Smith et al. in press, 
p. 18).
    Some genetic differences have been observed between Lepidium 
papilliferum occurring on the Snake River Plain (now separated into the 
Boise Foothills and Snake River Plain regions) and the Owyhee Plateau. 
Plants in the Snake River Plain and the Owyhee Plateau populations are 
separated by a minimum of 44 mi (70 km), which is considered beyond the 
distance that insect pollinators can travel or that seed dispersal can 
occur. Sites in the Snake River Plain with fewer numbers of plants (16 
to 746 flowering individuals) had less genetic diversity than sites 
with larger numbers of plants (more than 3,000 flowering individuals) 
(Robertson et al. 2006b, p. 42; Billinge and Robertson 2008, p. 1006), 
although this correlation between population size and genetic diversity 
was not evident in the Owyhee Plateau region (Stillman et al. 2005, p. 
9; Robertson et al. 2006b, p. 41). The lowest values for average number 
of alleles per locus were detected in two of the smallest populations 
(Seaman's Gulch in the Boise Foothills region and Orchard in the Snake 
River Plain region); in contrast, the largest number of alleles per 
locus was detected in the second largest population (Kuna Butte SW in 
the Snake River Plain) (Robertson et al. 2006b, Table 4). Larson et al. 
(2006, p. 14 and Fig. 4) also found geographically well-defined 
populations of L. 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).
    In summary, recent genetic studies thus confirm that Lepidium 
papilliferum is a full species distinct from L. montanum. 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), 2009). In addition, 
populations of L. papilliferum in the Owyhee Plateau demonstrate 
distinctive genetic differences from individuals in the Snake River 
Plain, likely a reflection of the isolation of these two populations 
due to limited seed dispersal and the limited range of pollinators, 
resulting in little current gene flow between them. Finally, there is 
some evidence that L. papilliferum has reduced genetic variability 
relative to other native species of Lepidium, such as L. montanum, and 
that smaller populations of L. papilliferum have less genetic diversity 
than larger populations.

Monitoring of Lepidium papilliferum Populations

    There are several biological programs designed to monitor 
populations of Lepidium papilliferum over time, and, in some cases, its 
habitat as well. The primary monitoring programs are

[[Page 52017]]

described here to assist in understanding subsequent references to them 
in this document.
    The Idaho Natural Heritage Program (INHP) uses element occurrences 
(EOs) to broadly describe the distribution of Lepidium papilliferum and 
assigns rankings to each EO based on measures of habitat quality and 
species abundance. EOs of L. papilliferum are defined by grouping 
occupied slickspots that occur within 1 km (0.6 mi) of each other; all 
occupied slickspots within a 1 km (0.6 mi) distance of another occupied 
slickspot are aggregated into a single EO. The definition of a single 
EO is based on the distance over which individuals of L. papilliferum 
are believed to be capable of genetic exchange through insect-mediated 
pollination (Colket and Robertson 2006). Due to the nature of their 
definition, individual EOs may differ greatly in size, based on whether 
there are many occupied slickspots distributed widely across the 
landscape relatively close to one another (which would comprise a 
single, large EO), or whether there are only a few (or even a single) 
slickspot(s) that occur close together but are relatively isolated from 
other occupied slickspots (which would comprise a single, small EO).
    Each EO is assigned a qualitative rank defined by population size 
and habitat quality; EO ranks are periodically updated when new ranking 
information becomes available. Currently, no Lepidium papilliferum EOs 
are ranked A, which is defined as an EO with greater than 1,000 
detectable above-ground plants occurring in the best habitat and 
landscape quality. The habitat quality rank diminishes from the highest 
of A to the lowest quality of D. An E ranking signifies that at least 
one plant was observed, but no abundance, habitat, or landscape data 
are available (Colket et al. 2006, p. 4). A rank of F indicates the 
most recent survey failed to find any L. papilliferum plants. A rank of 
H indicates L. papilliferum plants have not been documented at that 
location since 1970 based on old herbarium records with geographically 
vague location descriptions, such as a town name. A rank of X indicates 
L. papilliferum plants had been extirpated from that EO, based on 
agricultural conversion, commercial or residential development, or 
other documented habitat destruction where L. papilliferum plants had 
been previously recorded. An EO can also be ranked as X if it receives 
an F rank five times within a 12-year period (Colket et al. 2006, p. 
4). The current rankings for L. papilliferum are reviewed below in the 
section Element Occurrences Rangewide.
    The Habitat Integrity Index (HII) program conducted by the Idaho 
Conservation Data Center (ICDC, now the INHP) was the first rangewide 
effort aimed at monitoring Lepidium papilliferum and its habitat. The 
HII was initiated in 1998 and ran for 5 years through 2002 (Mancuso and 
Moseley 1998; Mancuso et al. 1998; Mancuso 2000, 2001, 2002, 2003). 
Although 52 transects were established over the years, a total of 17 
transects were sampled during all years of HII monitoring (Mancuso 
2003, p. 3); no rangewide monitoring of L. papilliferum was conducted 
in 2003. Monitoring was initially based on a system of transects of 
varying lengths across the range of L. papilliferum, each subjectively 
located to include 10 slickspots on sites known to contain L. 
papilliferum (summarized in Sullivan and Nations 2009, p. 33; see 
Mancuso et al. 1998 for details). The primary goal of the HII 
methodology was to assess the overall habitat condition, including 
attributes associated with the slickspots and the sagebrush-steppe 
habitat; L. papilliferum abundance was assessed categorically (assigned 
to a range of values) in this program.
    In 2004, the HII was replaced by the Habitat Integrity and 
Population (HIP) monitoring protocol, also implemented by the ICDC. HIP 
monitoring has been conducted annually since its implementation, thus 5 
years of HIP data are now available (through 2008) (ICDC 2008, p. 2; 
State of Idaho 2008). The HIP protocol was designed to provide data 
more replicable and specific to the monitoring required for the 
Candidate Conservation Agreement (CCA) developed by the State of Idaho, 
BLM, and others in 2003 (State of Idaho et al. 2003). HIP presents 
measures of habitat, disturbance, and plant community attributes at 
each transect as well as counts of L. papilliferum rosettes and 
reproductive plants observed (with the exception of 2004, which still 
utilized categorical assessments of plant abundance). Similar to the 
HII protocol, HIP is based on transects of varying lengths subjectively 
located to include 10 slickspots along their lengths (see Colket 2005 
for details on the HIP methodology); however, the HIP protocol includes 
a significantly greater number of rangewide transects, having increased 
from the original 70 established in 2004 to 80 today (ICDC 2008, p. 3).
    HIP monitoring has been annually conducted since 2004 and consists 
of the following procedures: (1) Establish and permanently mark HIP 
transects; (2) record location information; (3) take photographs; (4) 
measure population, habitat, and disturbance attributes at selected 
slickspots; (5) measure plant community attributes; and (6) analyze and 
describe the results (Colket 2008, p. 3).
    The INHP's EO records and the HII-HIP monitoring programs cover the 
entire range of Lepidium papilliferum. In addition, monitoring that has 
occurred within a subset of the species' range, on the Idaho Army 
National Guard's Orchard Training Area (OTA), provides particularly 
important information on the status of L. papilliferum due to the long-
term nature of the monitoring programs. The sagebrush-steppe on the OTA 
is considered to be some of the highest-quality habitat remaining 
within the range of L. papilliferum, and the OTA is home to one of the 
largest and most expansive EOs of the species (Sullivan and Nations 
2009, p. 22). Two of the OTA programs have been monitoring the same 
locations annually (with a few exceptions) since the early 1990s, and 
hence provide up to 18 years of population data for L. papilliferum. 
These two monitoring programs are known as rough census areas and 
special-use plots; both are conducted by staff or contractors of the 
OTA.
    The methods of the rough census monitoring areas are presented in 
Sullivan and Nations 2009 (pp. 28-29). Briefly, the program began in 
1990 by monitoring 5 areas but expanded to the current total of 15 
rough census areas by 1994; the combined extent of the rough census 
areas on the OTA is 866.1 ac (350.5 ha). Counts are conducted by 
technicians who walk across parallel transects 66 ft (20 m) apart and 
record the total number of Lepidium papilliferum individuals observed 
in any occupied slickspots that are found; reproductive status is not 
noted. The sizes of the 15 rough census areas differ, ranging from 4.1 
ac (1.7 ha) to 138.3 ac (56.0 ha), and not all areas have been 
monitored in all years; thus, analyses of the data must be standardized 
by transforming the raw count data to plant density (number of plants 
per unit area) to account for these differences (Sullivan and Nations 
2009, p. 36). Using density as the index of population abundance 
instead of total counts also allowed for the use of 18 years of rough 
census data, from 1990 through 2008 (there were no counts in 1999), 
although only a few of the rough census areas were monitored in the 
earlier years.
    The special-use plots are also located on the OTA. Although called 
``plots,'' these are actually a series of 16 belt transects, each 
containing a single

[[Page 52018]]

slickspot (see Sullivan and Nations 2009, pp. 29-33, for details). A 
stake is centered in the single slickspot, and each year the number of 
Lepidium papilliferum individuals with a 16.4-ft (5-m) radius of that 
stake (comprising a 32.8-ft (10-m) diameter circle) are counted 
(additional habitat information is collected from the remainder of the 
belt transect). Lepidium papilliferum abundance estimates for each of 
the 16 central circular plots has been collected annually each year 
from 1991 through 2008; thus, 18 years of special-use plot data are 
available. As all special-use plots were the same size and were 
surveyed in all years, estimates of abundance are based on reported 
total counts of individual plants (Sullivan and Nations 2009, p. 37). 
Beginning in 2000, the special-use plot data distinguished between 
blooming and nonblooming individuals.
    All of these programs provide information regarding the status of 
Lepidium papilliferum and its habitat, and will be referenced 
throughout this rule. In addition, we reference L. papilliferum 
Management Areas, which are units containing multiple EOs in a 
particular geographic area with similar land management issues or 
administrative boundaries as defined in the 2003 CCA (State of Idaho, 
p. 9). At a larger scale is the L. papilliferum (or ``LEPA'') 
Consideration Zone, an area also designated by the 2003 CCA and defined 
as all areas that may or do contain L. papilliferum (State of Idaho 
2003, p. 21). The LEPA Consideration Zone includes the entire range of 
the species, including all Management Areas and all EOs.

Ecology and Habitat

    The native, semiarid sagebrush-steppe habitat of southwestern Idaho 
where Lepidium papilliferum is found can be divided into two plant 
associations, each dominated by the shrub Artemisia tridentata ssp. 
wyomingensis (Wyoming big sagebrush): A. tridentata ssp. wyomingensis-
Achnatherum thurberianum (formerly Stipa thurberiana) (Thurber's 
needlegrass) and A. tridentata ssp. wyomingensis-Agropyron spicatum 
(bluebunch wheatgrass) habitat types (Moseley 1994, p. 9). The 
perennial bunchgrasses Poa secunda (Sandberg's bluegrass) and Sitanion 
hysrix (bottlebrush squirreltail) are commonly found in the understory 
of these habitats, and the species Artemisia tridentata ssp. tridentata 
(basin big sagebrush), Chrysothamnus nauseosus (grey rabbitbrush), 
Chrysothamnus viridiflorus (green rabbitbrush), Eriogonum strictum 
(strict buckwheat), Purshia tridentata (bitterbrush), and Tetradymium 
glabrata (little-leafed horsebrush) form a lesser component of the 
shrub community (Moseley 1994, p. 9; Mancuso and Moseley 1998, p. 17). 
Under relatively undisturbed conditions, the understory is populated by 
a diversity of perennial bunchgrasses and forbs, including species such 
as Achnatherum (formerly Oryzopsis) hymenoides (Indian ricegrass), 
Achillea millefolium (common yarrow), Phacelia heterophylla (varileaf 
phacelia), Astragalus purshii (Pursh's milkvetch), Phlox longifolia 
(longleaf phlox), and Aristida purpurea var. longiseta (purple 
threeawn) (Moseley 1994, p. 9; Mancuso and Moseley 1998, p. 17; Colket 
2005, pp. 2-3). Menke and Kaye (2006a, p. 1) describe high quality 
matrix habitat conditions for L. papilliferum as sagebrush-steppe 
habitat in late seral condition, and Fisher et al. (1996, p. 1) note 
that ``habitat with vigorous Lepidium populations has not been recently 
burned, is not heavily grazed, has an understory of native 
bunchgrasses, and a well developed microbiotic soil crust.'' Moseley 
(1994, p. 4) suggests that L. papilliferum serves as an indicator 
species for the health of the sagebrush-steppe ecosystem in the western 
Snake River Plain.
    The biological soil crust, also known as a microbiotic crust or 
cryptogamic crust, is one component of quality habitat for Lepidium 
papilliferum. Such crusts are commonly found in semiarid and arid 
ecosystems, and are formed by living organisms, primarily bryophytes, 
lichens, algae, and cyanobacteria, that bind together surface soil 
particles (Moseley 1994, p. 9; Johnston 1997, p. 4). Microbiotic crusts 
play an important role in stabilizing the soil and preventing erosion, 
increasing the availability of nitrogen and other nutrients in the 
soil, and regulating water infiltration and evaporation levels 
(Johnston 1997, pp. 8-10). In addition, an intact crust appears to aid 
in preventing the establishment of invasive plants (Brooks and Pyke 
2001, p. 4, and references therein; see also Serpe et al. 2006, pp. 
174, 176). These crusts are sensitive to disturbances that disrupt 
crust integrity, such as compression due to livestock trampling or off-
road-vehicle (ORV) use, and are also subject to damage by fire; 
recovery from disturbance is possible but occurs very slowly (Johnston 
1997, pp. 10-11).
    As described earlier, Lepidium papilliferum occurs in slickspot 
habitat microsites scattered within the greater semiarid sagebrush-
steppe ecosystem of southwestern Idaho. Lepidium papilliferum has 
infrequently been documented outside of slickspots, on occasion being 
found on disturbed soils, such as along graded roadsides and badger 
mounds. These are rare observations and the vast majority of plants 
documented over the past 19 years of surveys and monitoring for the 
species are documented within slickspot microsite habitats (USFWS 2006, 
p. 20). For example, in 2002, a complete census of an 11,070-ac (4,480-
ha) area recorded approximately 56,500 slickspots (U.S. Air Force, 
2003, p. 15), of which approximately 2,450 (about 4 percent) were 
occupied by L. papilliferum plants (Bashore, pers. comm. 2003, p. 1). 
Of the approximately 11,300 L. papilliferum plants documented during 
the survey effort, only 11 plants were documented outside of slickspots 
(U.S. Air Force 2002, in summary attachment of document).
    Slickspots are visually distinct openings characterized by soils 
with high sodium content and distinct clay layers; they tend to be 
highly reflective and relatively light in color, which makes them easy 
to detect on the landscape (Fisher et al. 1996, p. 3). 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), sparse native vegetation, distinct soil 
layers with a columnar or prismatic structure, higher alkalinity and 
clay content and natric properties (Fisher et al. 1996, pp. 15-16; 
Meyer and Allen 2005, pp. 3-5, 8; Palazzo et al. 2008, p. 378), 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). Fisher et al. (1996, p. 11) describe slickspots as having a 
``smooth, panlike surface'' that is structureless and slowly permeable 
when wet, moderately hard and cracked when dry. Although the low 
permeability of slickspots appears to help hold moisture (Moseley 1994, 
p. 8), once the thin crust dries, out the survival of L. papilliferum 
seedlings depends on the ability to extend the taproot into the 
argillic horizon (soil layer with high clay content), to extract 
moisture from the deeper natric zone (Fisher et al. 1996, p. 13).
    Slickspots have three primary layers: The surface silt layer, the 
restrictive layer, and an underlying moist clay layer. Although 
slickspots can appear homogeneous on the surface, the actual depth of 
the silt and restrictive layer can vary throughout the slickspot (Meyer 
and Allen 2005; Tables 9, 10, and 11). The top two layers (surface silt 
and restrictive) of slickspots are normally very thin; the surface silt 
layer varies in

[[Page 52019]]

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 rangewide mean surface silt layer depth was 0.31 in (0.78 cm) based 
on a 2005 study of 769 slickspots of unknown occupancy sampled at 79 
transects (Colket 2006, p. 38). Additionally, measurements of the depth 
of the clay layer next to L. papilliferum plants at the Juniper Butte 
Training Range were taken in 2007 and 2008 to assess if depth of the 
clay layer could be a significant factor for plant germination. The 
average depth of the clay layer next to plants measured in 2007 was 2.5 
in (6.3 cm), with a range from 1.2 to 4.7 in (3.0 to 12.0 cm) (n=18), 
and in 2008 was 2.1 in (5.4 cm) with a range from 1.6 to 3.1 in (4.0 to 
8.0 cm) (n=16) (CH2MHill 2008a, p. 13). It appears that depth to the 
clay layer is not as critical to germination at the Juniper Butte 
Training Range as other factors may be (such as depth to surface of the 
soil, the timing and amount of moisture, seed bank, and ability of the 
slickspot to capture and maintain adequate moisture).
    It is not known how long slickspots take to form, but it is 
hypothesized to take several thousands of years (Nettleton and Peterson 
1983, p. 193; Seronko 2006). Climate conditions that allowed for the 
formation of slickspots in southwestern Idaho are thought to have 
occurred during a wetter Pleistocene period. Holocene additions of 
wind-carried salts (often loess deposits) produced the natric soils 
(high in sodium) characteristic of slickspots (Nettleton and Peterson 
1983, p. 191; Seronko 2006). It may take several hundred years to alter 
or lose slickspots through natural climate change or severe natural 
erosion (Seronko 2006). Some researchers hypothesize that, given 
current climatic conditions, new slickspots are no longer being created 
(Nettleton and Peterson 1983, pp. 166, 191, 206). As slickspots appear 
to have formed during the Pleistocene and new slickspots are not being 
formed, the loss of a slickspot is apparently a permanent loss.
    Some slickspots subjected to light disturbance in the past may 
apparently be capable of re-forming (Seronko 2006). Disturbances that 
alter the physical properties of the soil layers, however, such as deep 
disturbance and the addition of organic matter, may lead to destruction 
and permanent loss of slickspots. For example, such techniques as deep 
soil tilling, the addition of organic matter, and addition of gypsum 
have been recommended for the elimination of slickspots from 
agricultural lands in Idaho (Peterson 1919, p. 11; Rasmussen et al. 
1972, p. 142). Slickspot soils are especially susceptible to mechanical 
disturbances when wet (Rengasmy et al. 1984, p. 63; Seronko 2004). Such 
disturbances disrupt the soil layers important to Lepidium papilliferum 
seed germination and seedling growth, and alter hydrological function. 
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 regain their pre-disturbance 
configuration, yet not support the species. Thus, while the slickspot 
appears to have regained its former character, some essential component 
required to sustain the life history requirements of L. papilliferum 
has apparently been lost, or the active seed bank is no longer present.
    Most slickspots are between 10 square feet (ft\2\) and 20 ft\2\ (1 
square meter (m\2\) and 2 m\2\) in size, although some are as large as 
110 ft\2\ (10 m\2\) (Mancuso et al. 1998, p. 1). 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 2002 inventory of the 
11,070 acre (ac) (4,480 hectare (ha)) Juniper Butte Range on the Owyhee 
Plateau found approximately 1 percent (109 ac (44 ha)) of the 
sagebrush-steppe area consisted of slickspot habitat, and of that 
slickspot habitat, only 4 percent (4 ac (1.6 ha)) was occupied by 
above-ground L. papilliferum plants (U.S. Air Force 2002, p. 9). It is 
not known why L. papilliferum is not found in a greater proportion of 
slickspot microsites (Fisher et al. 1996, p. 15).
    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)). Precipitation tends to 
fall as rain, primarily in winter and spring (November to May); the 
lowest rainfall occurs in July and August, with the months of June, 
September, and October receiving slightly more rainfall than July and 
August. Average annual precipitation patterns vary within the species' 
range, and are generally higher in the northern regions (e.g., 11.7 in 
(29.7 cm) near Boise, 7.4 in (18.8 cm) at the city of Bruneau, and 9.9 
in (25.1 cm) at Mountain Home).
    Several analyses have shown a positive association between above-
ground abundance of Lepidium papilliferum and spring precipitation in 
the same year. Evaluating rangewide HII monitoring data collected over 
4 years from 1998 to 2001, Palazzo et al. (2005, p. 9) found a positive 
relationship (p-value less than 0.01) between abundance of above-ground 
plants and February to June precipitation. 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 based on L. 
papilliferum census and survival data collected from 1993 to 1995. 
CH2MHill (2007a, p. 14) analyzed data from 2005 to 2007 collected at 
the Juniper Butte Range in the Owyhee Plateau region and found a 
positive correlation between spring precipitation and plant numbers. 
Utilizing HII monitoring data collected from 1998 to 2002, as well as 
2004 HIP monitoring data, Menke and Kay (2006a, b) found that March to 
May precipitation accounted for 99.4 percent of the variation in L. 
papilliferum abundance for the years 1998 to 2001 (2006a, p. 8), and 89 
percent for the years 1998 to 2002, and 2004 (2006b, pp. 10-11). These 
results appear to have been strongly influenced by the data point for 
1998, which was an unusually wet spring (Unnasch 2008, p. 16). Because 
the 1998 HII data represents an outlier with respect to both L. 
papilliferum abundance and precipitation, it largely determines the 
regression relationship by itself; thus, Menke and Kaye's 2006 
conclusion that abundance increases with spring precipitation is not 
well supported (Sullivan and Nations 2009, p. 140). More recently, 
however, Sullivan and Nations (2009, pp. 30, 41) analyzed data 
collected at the OTA over a period of 18 years between 1990 and 2008, 
and found evidence that both plant density at the rough census areas 
and plant abundance at special-use plots were positively related to 
mean monthly precipitation in late winter and spring (January through 
May). Thus, analysis of this long-term dataset again points to a strong 
relationship between L. papilliferum abundance and spring 
precipitation. This correlation of abundance with spring rainfall is 
important, as it at least partially explains annual fluctuations in L. 
papilliferum population numbers.
    In contrast, precipitation in the fall or early winter may have a 
negative effect on Lepidium papilliferum abundance the following spring 
(Meyer et al. 2005, p. 15; Sullivan and Nations 2009, p. 39). It has 
been suggested that this negative

[[Page 52020]]

relationship may be the result of prolonged flooding of the slickspot 
microsites, causing subsequent mortality of overwintering biennial 
rosettes (Meyer et al. 2005, pp. 15-16). This suggestion is supported 
by the analysis of 9 years of OTA data from the period 2000-2008 that 
shows a negative association between October to January precipitation 
and abundance of non-blooming L. papilliferum the following spring, 
although only the relationship with October to December precipitation 
is statistically significant (Sullivan and Nations 2009, p. 43). For 
blooming plants, the negative association between October to January 
precipitation and spring abundance was highly significant (Sullivan and 
Nations 2009, pp. 43-44).
    However, Unnasch (2008, p. 2) found no relationship between 
precipitation and the abundance of Lepidium papilliferum in an analysis 
of HIP data collected over a 3-year period from 2005 to 2007. Unnasch 
hypothesized that L. papilliferum may manifest threshold effects in 
germination and that there is a pulse of germination following a 
requisite amount of rainfall that could lead to a major flush of L. 
papilliferum germination during very wet years. If total rainfall is 
below that threshold, annual germination is more random (Unnasch 2008, 
p. 16). Comparing his results to those of Menke and Kaye, Unnasch 
(2008, p. 15) suggests that the relationship with spring precipitation 
reported by Menke and Kaye was strongly affected by abundance data from 
the year 1998, although in turn the relatively short 3-year study 
period may have influenced Unnasch's study results. Sullivan and 
Nations (2009, pp. 140, 142) likewise suggested that the exceptionally 
high precipitation in 1998 likely influenced the results of Menke and 
Kaye's analysis. However, as described above, Sullivan and Nation's 
more robust analysis of 18 years of data from the OTA confirmed a 
positive correlation between spring precipitation and the abundance of 
L. papilliferum (Sullivan and Nations 2009, pp. 40-44). As both annual 
precipitation and plant abundance are highly variable, the numbers of 
years included in the data set for evaluation is of great importance in 
determining the degree of confidence in the outcome of any statistical 
analysis. For this reason, the Service believes the Sullivan and 
Nations (2009, pp. 40-44) evaluation of the 18-year dataset from the 
OTA is the best available data regarding the relationship between 
precipitation and abundance of L. papilliferum.
    Recent analyses suggest that temperature also influences the annual 
abundance of Lepidium papilliferum. Although Menke and Kaye (2006b, p. 
8) found that minimum and maximum temperatures were not statistically 
correlated with L. papilliferum abundance based on a limited number of 
years of data, Sullivan and Nations (2009, p. 46-57) used more precise 
temperature data in concert with the 18-year L. papilliferum abundance 
dataset from the OTA to evaluate the potential interaction between 
precipitation, temperature, and plant abundance. Their analysis of the 
data collected between 1990 and 2008 suggests a complex relationship 
between temperature and precipitation that influences the abundance of 
L. papilliferum on an annual basis. In short, they found that 
temperature and precipitation interact during the months of October 
through January such that the lowest density or abundance of L. 
papilliferum in the spring follows a fall or early winter when both 
precipitation and temperature are low, or both are high. Spring plant 
density or abundance is greatest following a fall or early winter when 
either precipitation is high and temperature is low, or precipitation 
is low and temperature is high (Sullivan and Nations 2009, p. 56). 
During late winter and spring, analysis of one OTA dataset (the ``rough 
census'' areas) suggested that temperature had a negative impact on L. 
papilliferum density, such that density is greater when precipitation 
is high but temperatures during March through May are lower (Sullivan 
and Nations 2009, p. 47), whereas the model of the OTA special-use 
plots suggests only a positive interaction of L. papilliferum abundance 
with precipitation during this time period, with no temperature effect 
(Sullivan and Nations 2009, p. 47). Sullivan and Nations caution that 
the limited geographic area within which the interactions of 
precipitation and temperature were studied limits the ability to 
extrapolate the observed relationship beyond the bounds of the OTA 
(Sullivan and Nations 2009, p. 57).
    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 (e.g., 
Moseley 1994, p. 8, 14; Fisher et al. 1996, pp. 11, 16). Plant ecology 
literature suggests that plants tolerant of stress (e.g., plants that 
are capable of growing in harsh alkaline soils) are poor competitors 
(Grime 1977, p. 1185), making L. papilliferum a potentially poor 
competitor with other plants. In recent years, there are increasing 
observations of nonnative plants encroaching into slickspots, and 
consistent with theory, the evidence suggests that L. papilliferum is 
not able to successfully compete with these invasive exotics. Sullivan 
and Nations (2009, p. 111) report an ``apparent mutual exclusivity'' 
between nonnative plant species examined and L. papilliferum in 
slickspots. In other words, if plants such as Bassia prostrata 
(prostrate kochia or forage kochia, formerly Kochia prostrata) or 
Bromus tectorum are present in a slickspot, L. papilliferum is most 
often reduced in numbers or entirely absent.

Range and Distribution

    The range of Lepidium papilliferum is restricted to the volcanic 
plains of southwest Idaho, occurring primarily in the Snake River Plain 
and its adjacent northern foothills, with a single disjunct a 
population on the Owyhee Plateau (Figure 1). 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. 3-9). Based on differences in topography, soil, and 
relative abundance, we have further divided the extant Lepidium 
papilliferum populations into three physiographic regions: the Boise 
Foothills, the Snake River Plain, and the Owyhee Plateau. The nature 
and severity of factors affecting the species also vary between the 
three physiographic regions for the purposes of analysis. For example, 
urban and rural development, agriculture, and infrastructure 
development has been substantial in the sagebrush-steppe habitat of the 
Boise Foothills and the Snake River Plain regions, while very little of 
these types of development has occurred within the Owyhee Plateau 
region. Genetic analyses reveal some separation between the greater 
Snake River Plain and Owyhee Plateau populations of L. papilliferum 
(Larson et al. 2006, p. 14), as might be expected due to their relative 
isolation. We are not aware of any studies that may have examined the 
relative genetic differentiation, if any, of the Boise Foothills 
population from the remainder of the Snake River Plain.
    Figure 1. Range of Lepidium papilliferum in southwest Idaho, 
showing its distribution in the three physiographic provinces of the 
Snake River Plain, Boise Foothills, and Owyhee Plateau.
BILLING CODE 4310-55-S

[[Page 52021]]

[GRAPHIC] [TIFF OMITTED] TR08OC09.000

BILLING CODE 4310-55-C
    As of February 2009, there were 80 extant EOs in the three 
physiographic regions that collectively comprise approximately 15,801 
ac (6,394 ha) of total area that is broadly occupied by Lepidium 
papilliferum (Cole 2009b, Threats Table). The area actually occupied by 
L. papilliferum is a small fraction of the total acreage, since 
slickspots occupy only a small percentage of the landscape, and L. 
papilliferum then occupies only a fraction of those slickspots (see 
U.S. Air Force 2002, p. 9, for an example). Table 1 presents the 
distribution and landownership and management information for all L. 
papilliferum EOs, in total and by region.

[[Page 52022]]



 Table 1. Distribution and Land Ownership of Lepidium papilliferum Element Occurrences by Physiographic Region (Cole 2009b, Threats Table; Sullivan and
                                                                  Nations 2009, p. 77).
                                           All areas are estimates, and may not total exactly due to rounding.
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                                                       Total EO Area
                                          Number of EOs       Federal ownership in    State ownership  in   Private ownership  in   (hectares)  [percent
     Lepidium papilliferum EOs         [percent of total]       acres  (hectares)      acres  (hectares)      acres  (hectares)      of total rangewide
                                                               [percent of total]      [percent of total]     [percent of total]          EO area]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Snake River Plain                    43                      12,754 ac                55 ac                  164 ac                12,980 ac
                                     [54]..................  (5,160 ha)............   (22 ha).............   (66 ha).............  (5,250 ha)
                                                             [98]..................  [0.5]................  [1.5]................  [82]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Boise Foothills                      16                      89 ac                   0 ac                   96 ac                  185 ac
                                     [20]..................  (36 ha)...............  (0 ha)...............  (39 ha)..............  (75 ha)
                                                             [48]..................  0....................  [52].................  [1.2]
--------------------------------------------------------------------------------------------------------------------------------------------------------
Owyhee Plateau                       21                      2,636 ac                 7 ac                  0 ac                   2,643 ac
                                     [26]..................  (1,067 ha)............  (3 ha)...............  (o ha)...............  (1,070 ha)
                                                             [99.7]................  [0.3]................  [0]..................  [16. 8%]
--------------------------------------------------------------------------------------------------------------------------------------------------------
All extant                           80                      15,479 ac               62 ac                  260 ac                 15,801 ac
EOs................................  [100].................  (6,264 ha)............  (25 ha)..............  (105 ha).............  (6,394 ha)
                                                             [98.0]................  [0.4]................  [1.6]................  [100]
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The range of Lepidium papilliferum was first estimated in 1994 
(Moseley 1994, p. 6). Expanded survey efforts in recent years have 
resulted in an increase in the amount of known occupied habitat, 
particularly on the Owyhee Plateau and in the Boise Foothill regions. 
Between 2003 and 2006, 16 new EOs were documented, all within 3 mi (4.8 
km) of previously existing EOs: 2 on the Snake River Plain with a total 
area of 2.7 ac (1 ha), and 14 on the Owyhee Plateau with a total area 
of 46.6 ac (18 ha) (Colket et al. 2006, Tables and Appendix A). Since 
2006, additional surveys of previously unsurveyed lands have resulted 
in the discovery of several new occupied sites. Because most of these 
newly discovered sites were within 1 km (0.6 mi) of a documented EO, 
they typically resulted in the expansion or merging of existing EOs 
rather than the creation of a new EO. For example, in 2007, 2,560 ac 
(1,036 ha) of BLM land on the Owyhee Plateau were inventoried for L. 
papilliferum just south of the U.S. Air Force's Juniper Butte Training 
Range. Of the 2,171 slickspots surveyed, 200 (9 percent) were occupied 
by L. papilliferum with a total of 1,059 flowering plants and 214 
rosettes (ERO 2007, pp. 1, 7-8), resulting in the expansion of EO 16 
(Cole 2009a, p. 38). Surveys conducted in 2008 in the vicinity of the 
Ada County landfill in the Boise Foothills region revealed nearly 5,000 
plants in 75 slickspots (Cole 2008, p. 8), which expanded the size of 
existing EOs 38 and 65 (Cole 2009a, p. 39). Pre-development surveys 
conducted during 2007 by URS Corporation (URS) on BLM and private lands 
in the Boise Foothills region northwest of the City of Eagle detected 
43 occupied slickspots out of 187 surveyed, with approximately 17,880 
L. papilliferum plants (URS 2008, p. 10). These observations expanded 
the total area of EO 76 (Cole 2009a, p. 39). Finally, additional survey 
efforts on previously surveyed areas at the OTA resulted in the 
documentation of 365 new occupied slickspots in 2005, resulting in 
further expansion of existing EO 27 (URS 2005, pp. 6-7).
    Not all potential Lepidium papilliferum habitats in southwest Idaho 
have been surveyed, and it is possible that additional L. papilliferum 
sites may be found outside of areas that are currently known to be 
occupied. Recent modeling was completed to develop a high-quality, 
predictive-distribution model of L. papilliferum to identify potential 
habitat (Colket 2008, p. 1). Although surveys were conducted in 2008 in 
some areas identified as potential, previously unsurveyed habitat, 
these did not result in any new locations of the species (Colket 2008, 
pp. 4-6). There have also been searches for L. papilliferum in eastern 
Oregon, but the species has never been found there (Findley 2003, p. 
1). We have no historical records indicating that L. papilliferum has 
ever been found anywhere outside of its present range in southwestern 
Idaho, as described in this rule.

Abundance and Population Trend

    Forming a reliable estimate of any trend in the abundance of 
Lepidium papilliferum over time is complicated by multiple factors. For 
one, since individuals of the species may act as either an annual or a 
biennial, in any given year there will be varying numbers of plants 
acting as spring-flowering annuals versus overwintering rosettes. The 
relative proportions of these two life history forms can fluctuate 
annually depending on a variety of factors, including precipitation, 
temperature, and the abundance of rosettes produced the previous year 
(Unnasch 2008, pp. 14-15; Sullivan and Nations 2009, pp. 43-44, 134-
135). Secondly, L. papilliferum has a long-lived seed bank, likely as 
an adaptation to unpredictable conditions, in which years of good 
rainfall favorable for germination and survival may be followed by 
periods of drought; a persistent seed bank provides a population buffer 
against years of poor reproductive potential in such a highly variable 
environment (Meyer et al. 2005, p. 21). Only a small percentage of L. 
papilliferum seeds germinate annually, resulting in an estimated 
maximum longevity of 12 years for seeds in the seed bank (Meyer et al 
2005, p. 18). The presence of this persistent seed bank confounds the 
ability to determine any trend in abundance over time, as the number of 
above-ground plants that can be counted in any one year represents only 
a subset of the latent population that is present in the seed bank. In 
effect, it takes at least 12 years to trace the fate of a single year's 
cohort of seeds, resulting in a significant lag effect in detecting any 
real underlying change in total population abundance over the long 
term.
    An additional complicating factor in trying to detect any 
population trend for Lepidium papilliferum is the extreme

[[Page 52023]]

variability of annual abundance or density of the plant. As is common 
for desert annuals, the numbers of L. papilliferum can vary 
dramatically from year to year, depending on environmental conditions. 
As an example, the total number of plants on the 16 special-use plots 
at the OTA went from 624 individuals in 1997 to 3,330 plants in 1998, 
subsequently dropping back down again to 756 plants in 1999; total 
abundance over the years 1991 through 2008 ranged from a low of 249 
plants to 15,236 individuals (Weaver 2008). Some of the great variation 
in yearly plant numbers is likely due to the relationship between L. 
papilliferum and precipitation, as described above. The annual 
abundance or density of L. papilliferum shows a significant positive 
association with levels of spring rainfall, roughly from March through 
May (Meyer et al. 2005, p. 15; Palazzo et al. 2005, p. 9; Sullivan and 
Nations 2009, pp. 39-41), and survival of potential biennials is 
associated with increased summer rainfall (Meyer et al. 2005, p. 15). 
There is also some suggestion that increased winter precipitation may 
show a negative association with plant abundance, although not all 
analyses are consistently significant on this point (Meyer et al. 2005, 
pp. 15-16; Sullivan and Nations 2009, pp. 39-41). Temperature also 
appears to play a role in annual abundance of L. papilliferum in 
concert with precipitation, although the exact nature of the 
relationship is complex and not well understood (Sullivan and Nations 
2009, p. 57). Furthermore, the interaction between temperature, 
precipitation, and L. papilliferum abundance appears to vary regionally 
between the Boise Foothills, Owyhee Plateau, and Snake River Plain 
(Sullivan and Nations 2009, pp. 103-104).
    Because the population dynamics of Lepidium papilliferum are 
complicated, surrogate methods of monitoring the status of the species, 
such as monitoring the status of the ecosystem upon which it depends, 
may be preferable to counts of individual plants. For example, due to 
the extreme annual fluctuations in annual plant abundance and the 
complicating nature of the long-lived seed bank for this species, 
Mancuso and Moseley (1998, p. 1) note that ``estimating the number of 
above-ground pla