Our final determination concerning critical habitat for Ambrosia pumila will take into consideration all written comments and comments received during a public hearing, should one be requested, and any additional information we receive during the public comment period. These comments will be included in the public record for this rulemaking. Our final determination will also incorporate all comments requested of peer reviewers and received during the comment period. Finally, our final determination concerning critical habitat will consider all written comments and any additional information we receive during the comment period for the draft Economic Analysis (DEA). On the basis of peer reviewer and public comments, we may, during the development of our final determination, find that areas within those proposed do not meet the definition of critical habitat, that some modifications to the described boundaries are appropriate, or that areas are not appropriate for exclusion under section 4(b)(2) of the Act.

You may submit your comments and materials concerning this proposed rule by one of the methods listed in the ADDRESSES section.

We will post your entire commentincluding your personal identifying informationon http://www.regulations.gov. If you provide personal identifying information in addition to the required items specified in the previous paragraph, such as your street address, phone number, or email address, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so.

Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection at http://www.regulations.gov, or by appointment, during normal business hours, at the U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT).

You may obtain copies of the proposed rule by mail from the Carlsbad Fish and Wildlife Office (see FOR FURTHER INFORMATION CONTACT) or by visiting the Federal eRulemaking Portal at http:// www.regulations.gov.

Background

It is our intent to discuss only those topics directly relevant to the designation of critical habitat in this proposed rule. This rule incorporates new information on the biology, distribution, and abundance of Ambrosia pumila that we did not discuss in the 2002 final listing rule for this species (67 FR 44372). For more information on A. pumila, refer to that final listing rule, which was published in the Federal Register on July 2, 2002.

Previous Federal Actions

Ambrosia pumila was listed as an endangered species on July 2, 2002 (67 FR 44372). Designation of critical habitat was found to be prudent in the proposed (64 FR 72993; December 29, 1999) and final listing rules, but was deferred due to budgetary constraints and higher listing priorities. The Center for Biological Diversity filed a complaint in the U.S. District Court for the Southern District of California on December 19, 2007, challenging failure of the Service to designate critical habitat for four endangered plants, including A. pumila (Center for Biological Diversity v. United States Fish and Wildlife, et al., Case No. 07CV2378 NLS). The April 11, 2008, settlement agreement stipulates that the Service shall submit a determination as to whether it is prudent to designate critical habitat for A. pumila, and if prudent, a proposed critical habitat designation to the Federal Register for publication on or before August 20, 2009, and submit a final critical habitat designation to the Federal Register for publication on or before August 19, 2010. In this proposed critical habitat rule, we reaffirm that determination of critical habitat for A. pumila is prudent. However, we may revisit our prudency determination following additional review and consideration of information we receive during the public comment period.

Species Description

Ambrosia is a genus comprising 35 to 50 windpollinated annual and perennial plant species in the Asteraceae (sunflower) family. Members of this genus occur predominantly in the Western Hemisphere, especially North America. Species are generally found in arid or semiarid areas, while some are weeds of cultivated fields or strand species of Pacific and Caribbean beaches (Payne 1976, p. 169).

Ambrosia pumila is a clonal herbaceous perennial. Individual stems are generally 5 to 30 centimeters (cm) (2 to 12 inches (in)) tall, but may grow to 50 cm (20 in), and are densely covered with short hairs. The leaves are two to four times pinnately divided into many small segments and are covered with short, soft, graywhite, appressed (lying flat on surface) hairs. The species has separate male and female flowers on the same plant (monoecious). The male flowers have no petals, are yellow to translucent, and are borne in clusters on terminal flower stalks. The female flowers have no petals and are yellowishwhite. Female flowers are in clusters in the axils of the leaves below the male flower clusters (Nuttall 1840, pp. 344345; Gray 1882, p. 217; Munz 1935, p. 544; Keck 1959, p. 1103; Ferris 1960, p. 148; Munz 1974, p. 112; Beauchamp 1986, p. 94; Payne 1993, p. 194). Female flowers produce a dry, singleseeded fruit called an achene. References to seeds in this document refer to the singleseeded fruits.

Ambrosia pumila spreads vegetatively by means of slender, branched, underground rootlike rhizomes from which new aboveground stems (aerial stems or ramets) arise each year (Nuttall 1840, p. 344; Munz 1974, p. 112; Payne 1993, p. 194). This growth pattern results in numerous aerial stems interconnected by a system of rhizomes, called a clone. All aerial stems growing from the same root system are genetically identical and represent a single individual A. pumila plant (called a genet) (Harper 1977, p. 26). Growing rhizomes extend underground beyond the aboveground limit of the aerial stems into adjacent suitable habitat, allowing rhizomes of adjacent individuals to intermingle. The underground interconnections can break or disintegrate, resulting in aerial stems that are genetically identical but physically separate (McGlaughlin and Friar 2007, p. 319). The extent to which
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rhizomes are capable of spreading has been observed only in individuals translocated to previously unoccupied sites. For example, A. pumila individuals transplanted on the San Diego National Wildlife Refuge in January 2008 were documented to produce new stems several inches away within 10 months (by November 2008). Additionally, A. pumila individuals transplanted in 1997 to an unoccupied site at Pilgrim Creek just south of Marine Corps Base Camp Pendleton in San Diego County were documented to produce new stems up to 70 in (178 cm) from the original stems within 2 years (by 1999) (Johnson et al. 1999, p. 3).

Because of the clonal nature of Ambrosia pumila's growth, it is not possible to directly determine the number of genetically distinct plants present in an area simply by counting stems (McGlaughlin and Friar 2007, p. 320). McGlaughlin and Friar's (2007, p. 323) analysis of clonality in A. pumila determined that the aerial stemtogenet ratio is roughly 10to1 on average (about 1 genet for every 10 aerial stems counted in a patch (cluster of stems)). A patch constitutes a spatially distinct cluster of stems within an occurrence, whereas an occurrence constitutes a group of individuals separated from the next nearest group of individuals by a distance greater than or equal to 0.25 mile (mi) (0.40 kilometer (km)).

Habitat

Ambrosia pumila occurs primarily on upper terraces of rivers and drainages (Beauchamp 1986, p. 94; Johnson et al. 1999, p. 1; McGlaughlin and Friar 2007, p. 321; California Natural Diversity Database data report for A. pumila 2008 (CNDDB 2008)); however, several patches of the plant occur within the watershed of a large vernal (ephemeral) pool in the Skunk Hollow preserve in Riverside County (Dudek 2003, p. P326; CNDDB 2008). Within these areas, the species is found in open grassland of native and nonnative plant species, and openings in coastal sage scrub (Johnson et al. 1999, p. 1; Dudek 2000, p. 18; Dudek 2003, p. P330; CNDDB 2008), and primarily on sandy loam or clay soils (Johnson et al. 1999, p. 1; Dudek 2000, p. 18; CNDDB 2008; USDA 2008). The species may also be found in ruderal habitat types (disturbed communities containing a mixture of native and nonnative grasses and forbs) such as fire fuel breaks and edges of dirt roadways (Beauchamp 1986, p. 94; Payne 1993, p. 194; CNDDB 2008). Nonnative grassland and ruderal habitat types provide adequate habitat for A. pumila; however, nonnative plants can outcompete A. pumila plants for resources in some situations if not managed. Occurrences are disjunct (generally 1 or more miles (1.6 or more km) apart) and most locations have been subjected to disturbance such as nonnative plant invasion, mining activities, development, grading, and human encroachment on foot, horses, or vehicles (CNDDB 2008).

It is unclear why Ambrosia pumila consistently occurs in areas near waterways such as upper terraces of rivers or other water bodies. The areas where the species is found do not necessarily provide high levels of soil moisture, and A. pumila is adapted to dry conditions (Keck 1959, p. 1103; Munz 1974, p. 112; Dudek 2000, Appendix A; CNLM 2008, p. 18). Additionally, Service biologists have observed green (that is, not desiccated) aerial stem shoots of A. pumila after small amounts of precipitation and after other vegetation in the observed area had desiccated. Ambrosia pumila may require periodic flooding for dispersal of seeds and roots dislodged during flooding, seed germination, or some other segment of its life cycle. Further, areas subject to periodic flooding appear to be less amenable to competing nonnative and native plants.

Life History

The reproductive biology of Ambrosia pumila has not been studied to the same extent as the more common Ambrosia species, such as A. artemisiifolia (common ragweed) and A. trifida (giant ragweed) (Dudek 2000, p. 16). Thus, little is known about its pollination system, seed production, seed dispersal, and germination (Dudek 2000, p. 16; Dudek 2003, p. P331; McGlaughlin and Friars 2007, p. 320).

Aerial stems of Ambrosia pumila sprout from their underground rhizomes in early spring after winter rains, and flower between May and October (Keck 1959, p. 1103). Recently, however, Service biologists observed aerial stems sprouting under dry conditions in late fall (Folarin 2008, pers. comm.). The plants senesce after the growing season, leaving the root system in place from which new aerial stems may sprout when environmental conditions are appropriate (Keck 1959, p. 1103).

Ambrosia pumila is presumed to be windpollinated because most other species of Ambrosia are windpollinated, and because biological pollinators have not been observed visiting A. pumila flowers (Johnson et al. 1999, p. 4; Dudek 2000, p. 16; Dudek 2003, p. P331). Alternatively, pollinator(s) of A. pumila may have been extirpated (Dudek 2003, p. P331). The species is presumed to be capable of self pollination and of being selffertile (i.e., selfcompatible, where pollen from an individual plant can fertilize an ovule on the same plant, resulting in production of viable seed) because other species of Ambrosia are capable of selfpollination (Payne 1976, pp. 171172). The configuration of the male flowers in relation to the female flowers also implies opportunity for selfpollination (Dudek 2000, p. 16). However, studies are needed to determine whether viable seed is produced through selfpollination in this species (Johnson et al. 1999, p. 4; Dudek 2000, p. 16; Dudek 2003, p. P332; McGlaughlin and Friars 2007, p. 329).

Ambrosia pumila is thought to have limited sexual reproductive output due to low production of viable seed (Johnson et al. 1999, pp. 15; Dudek 2000, pp. 1617; Dudek 2003, pp. P331P332). Low seed production in this species is inferred by the lack of fertile fruits on all but a few preserved A. pumila museum specimens (Wallace 1999, pers. comm.), and field observers have found seed production in A. pumila to be low (Dudek 2000, p. 17; Dudek 2003, p. P332). Specific germination requirements of A. pumila seed are unknown. A 1998 germination study using 22 A. pumila seeds of unknown viability collected from 3 sites at Mission Trails Regional Park did not result in any germination of seedlings (Dudek 2000, Appendix B). The lack of germination could have been due to the seeds being nonviable or to inappropriate germination conditions. Regardless of what proportion of A. pumila seeds are viable, low seed production implies that little sexual reproduction is occurring in this species. Low levels of sexual reproduction is not an unusual condition in clonal plant species (Sackville et al. 1987, p. 54). This reduced sexual reproduction may negatively impact the ability of the species to adapt to rapid environmental change or environmental change over the long term, which is especially deleterious to a rare species with disjunct occurrences such as A. pumila (Dudek 2000, p. 17; Dudek 2003, p. P332).

The dispersal strategy of Ambrosia pumila is unknown. Ambrosia pumila seeds lack structures that facilitate dispersal by wind or passing animals (Nuttall 1840, p. 344; Payne 1993, p. 194). The species may depend on periodic flooding of nearby waterways for dispersal of seeds and rhizomes that can produce new aerial stems (Dudek 2003, p. P 332). The longevity of individual plants is also unknown,
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although plants with clonal growth patterns tend to be longlived (Watkinson and White 1985, pp. 4445; Tanner 2001, p. 1980). Finally, the longevity of seeds and potential for buried seed banks to develop in the soil is unknown.

Genetics

Little is known about genetic diversity or genetic distribution of Ambrosia pumila across its range. McGlaughlin and Friar (2007) conducted a genetic study of A. pumila to address conservation and management of the species. They found that each population they examined contained multiple genetically distinct individuals, but no individuals that occurred in more than one population. Therefore, they concluded that in order to maintain a level of genetic diversity capable of responding to variable ecological conditions, conservation of the species should involve the protection and maintenance of as many populations of A. pumila as possible (McGlaughlin and Friar 2007, pp. 319 and 329).

Geographic Range and Status

Ambrosia pumila is distributed in southern California from northwestern Riverside County, south through western San Diego County, to northwestern Baja California, Mexico (CNDDB 2008). It is generally found at or below elevations of 1600 feet (ft) (487 meters (m)) in Riverside County, and 600 ft (183 m) in San Diego County (CNDDB 2008). When listed as endangered under the Act in 2002, 15 occurrences of A. pumila were known in the United States: 3 in Riverside County and 12 in San Diego County (67 FR 44372; July 2, 2002). As noted previously, the term ``occurrence'' as used in this proposed critical habitat rule is defined as one or more A. pumila plants more than 0.25 mi (0.40 km) from another individual or group of individuals (Bittman 2002, in litt.). More than 80 percent of the occupied sites identified in the final listing rule were concentrated in the following 6 areas:

According to information used to develop the final listing rule (67 FR 44372; July 2, 2002), roughly 44 ac (18 ha)) of habitat in San Diego County was occupied by this species in 12 occurrences. This habitat estimate only includes areas where A. pumila stems were found in the 5 to 10 years prior to listing in 2002. Similar area estimate data were unavailable for the 3 occurrences in Riverside County.

Since this species was listed, one occurrence was identified in Riverside County about 1 mile (1.6 km) south of Skunk Hollow along San Diego aqueduct, from a survey report (AMEC 2006, pp. 1213; CNDDB 2008), and one occurrence was identified in unincorporated San Diego County on the west side of State Route 76, south of Olive Hill Road (see ``Criteria Used to Identify Critical Habitat'' below). Also since listing, we determined that one occurrence, on the west side of Interstate 15 just north of Lake Hodges and south of Via Rancho Parkway in San Diego County, previously identified as extirpated or not viable in the final listing rule is now extant and viable.

The documented range of Ambrosia pumila in Mexico at the time of listing extended from Cabo Colonet south to Lake Chapala in north central Baja California, Mexico (Burrascano and Hogan 1996, p. 8). Two of these three occurrences were confirmed by David Hogan, formerly with the Southwest Center for Biological Diversity (now Center for Biological Diversity), and Cindy Burrascano of the California Native Plant Society (CNPS), San Diego Chapter (Burrascano and Hogan 1996, p. 8). Although additional occurrences may have existed in Baja California, the species was not considered to be widespread at the time of listing due to the lack of appropriate habitat and impacts from agriculture and urban development, especially near the coast (Burrascano and Hogan1996, p. 8).

All currently known occurrences are believed to have been present at the time of listing because plants with clonal growth patterns tend to be longlived (Watkinson and White 1985, pp. 4445; Tanner 2001, p. 1980). Although stems may die and portions of the rhizome may disintegrate over time, except under extreme conditions enough of the rhizome survives from one growing season to the next to support continued growth of an individual plant. Also, because the plants produce very few if any seeds, the ability of the plant to disperse into and colonize previously unoccupied areas is diminished. Since this species was listed, no additional occurrences were documented in Mexico; the occurrences along the west coast of Baja California between Cabo Colonet and the U.S.Mexico border are rapidly disappearing due to recreational development and agriculture (Dudek 2003, p. P330). Critical Habitat

Background

Critical habitat is defined in section 3(5)(A) of the Act as: (1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the provisions of section 4 of the Act, on which are found those physical or biological features
(a) Essential to the conservation of the species, and
(b) Which may require special management considerations or protection; and
(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination by the Secretary of the Interior that such areas are essential for the conservation of the species.

Conservation, as defined under section 3 of the Act, means the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping and transplantation, and in the extraordinary case where population pressures within a given ecosystem cannot otherwise be relieved, may include regulated taking.

Critical habitat receives protection under section 7 of the Act through the prohibition against Federal agencies carrying out, funding, or authorizing activities that result in the destruction or adverse modification of critical habitat. Section 7(a)(2) requires consultation on Federal actions that may affect critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by the landowner. Where a landowner [[Page 44242]]
seeks or requests Federal agency funding or authorization for an activity that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) would apply, but even in the event of a destruction or adverse modification finding, the Federal action agency's and the applicant's obligation is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.

To be considered for inclusion in a critical habitat designation, habitat within the geographical area occupied by the species at the time of listing must contain physical and biological features that are essential to the conservation of the species, and be included only if those features may require special management considerations or protection. Critical habitat designations identify, to the extent known using the best scientific data available, habitat areas that provide essential life cycle needs of the species; that is, areas on which the physical and biological features are found laid out in the appropriate quantity and spatial arrangement essential to the conservation of the species. Under the Act and regulations at 50 CFR 424.12, we can designate as critical habitat areas outside the geographical area occupied by the species at the time it is listed only when we determine that those areas are essential for the conservation of the species and that designation limited to those areas occupied at the time of listing would be inadequate to ensure the conservation of the species.

Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the Federal Register on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106554; H.R. 5658)), and our associated Information Quality Guidelines, provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.

When we are determining which areas should be proposed as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peerreviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, or other unpublished materials and expert opinion or personal knowledge.

Habitat is dynamic, and species may move from one area to another over time. We recognize that climate change may cause changes in the arrangement of occupied habitat patches. Current climate change predictions for terrestrial areas in the Northern Hemisphere indicate warmer air temperatures, more intense precipitation events, and increased summer continental drying (Field et al. 1999, pp. 13; Hayhoe et al. 2004, p. 12422; Cayan et al. 2005, p. 6; Intergovernmental Panel on Climate Change 2007, p. 11). However, predictions of climatic conditions for smaller subregions such as California remain uncertain. It is unknown at this time if climate change in California will result in a warmer trend with localized drying, higher precipitation events, or other effects. Thus, the information currently available on the effects of global climate change and increasing temperatures does not make sufficiently precise estimates of the location and magnitude of the effects, so we are unable to determine what, if any, additional areas would be needed. However, we recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated critical habitat area is unimportant or may not be required for recovery of the species.

Areas that are important to the conservation of the species, but are outside the critical habitat designation, will continue to be subject to conservation actions implemented under section 7(a)(1) of the Act. Areas that support populations are also subject to the regulatory protections afforded by the section 7(a)(2) jeopardy standard, as determined on the basis of the best available scientific information at the time of the agency action. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if information available at the time of these planning efforts calls for a different outcome.

Physical and Biological Features

In accordance with section 3(5)(A)(i) of the Act and regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied by the species at the time of listing to propose as critical habitat, we consider the physical and biological features that are essential to the conservation of the species and that may require special management considerations or protection. Those features are the primary constituent elements (PCEs) laid out in the appropriate quantity and spatial arrangement for the conservation of the species. The PCEs include, but are not limited to:
(1) Space for individual and population growth and for normal behavior;
(2) Food, water, air, light, minerals, or other nutritional or physiological requirements;
(3) Cover or shelter;
(4) Sites for breeding, reproduction, and rearing (or development) of offspring; and
(5) Habitats that are protected from disturbance or are representative of the historical, geographical, and ecological distributions of a species.

Little is known about the habitat specificity and characteristics of this species. Therefore, the PCEs for Ambrosia pumila are based on our assessment of the ecosystem settings in which the species has most frequently been detected.
Space for Individual and Population Growth and for Normal Behavior Clonal GrowthRhizome Spread and New Aerial Stems

Individual Ambrosia pumila plants spread by underground rhizomes to produce a group of genetically identical aerial stemsa clone. Growing rhizomes extend underground beyond the extent of the aerial stems into adjacent suitable habitat, and rhizomes of adjacent plants likely intermingle to a degree. The distance rhizomes extend beyond the standing aerial stems is difficult to measure because of the difficulty in investigating an intact, underground rhizome system.

The extent and configuration of the visible portion (aerial stems) of A. pumila patches can change from one growing season to the next (Martin 2005, p. 3; City of San Diego 2008a, p.
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1). For example, see Figure 4 in Martin 2005, in which patches of A. pumila are shown to change in shape and size (up to several square meters) from 2000 to 2005, with some patches not producing any stems in 2005 (some of the patches that did not produce stems in 2005 were observed to produce stems in 2008 (Folarin 2008, pers. comm.)). These changes in patch size and shape are perhaps due to differences in available moisture or competition from other plants (Martin 2005, p. 3; City of San Diego 2008a, p. 1). Based on these and other observations, we conclude that the rhizome system of a group of A. pumila stems likely occupies a greater underground area than occupied by the stems above ground at any given time, with aerial stems produced only where conditions are appropriate. Thus, to ensure that a habitat area does not exclude unseen underground portions of A. pumila plants, the area needs to include additional surface area beyond the visible surface area covered by the aerial stems.

Germination of Seeds and Spread of Seedlings

It is unclear to what extent and with what frequency Ambrosia pumila reproduces by seed. Presuming at least low rates of sexual reproduction, space is needed for new plants to germinate, grow, and spread. However, we are not aware of any research that would provide the information needed to assess the species' germination and seedling needs.
Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements

Water

Specific water needs of the species are unknown. Ambrosia pumila is adapted to dry conditions which occur annually throughout its range (Keck 1959, p. 1103; Munz 1974, p. 112; Dudek 2000, Appendix A; CNLM 2008, p. 18). Service biologists have observed green (not desiccated) aerial stem shoots after small amounts of precipitation and after annual vegetation in the area had desiccated, implying that either A. pumila requires less water than other grassland plants, that the underground perennial rhizome system has some capacity to store enough water to sustain growth, or both (Folarin 2008, pers. comm.). Additionally, we believe that periodic flooding may be necessary to some segment of the plant's life history (such as seed germination, dispersal of seeds and rhizomes) or to maintain some essential aspect of its habitat, because of the indicator that the plant is always found on river terraces or within the watersheds of vernal pools. Light

Ambrosia pumila is limited to open or lowgrowing plant communities, which implies that the species is not shadetolerant (Dudek 2000, pp. 1819). Ambrosia pumila stems amid taller vegetation obtain adequate sunlight by growing taller (etiolation) and more slender compared to those in more open areas (Dudek 2000, p. 19), which also implies the species is not shadetolerant.

Soil

Ambrosia pumila is found primarily on sandy loam or clay soils including (but not limited to) the Placentia (sandy loam), Diablo (clay), and Ramona (sandy loam) series (Dudek 2000, Appendix A; CNDDB 2008). These soil types likely are particularly conducive to the growth and persistence of A. pumila because it is rarely found growing on other substrate types (such as gravel).

Chemical soil attributes and other abiotic and biotic characteristics have been measured and documented for Ambrosia pumila occurrences at Skunk Hollow (Riverside County), and Mission Trails Regional Park and San Diego National Wildlife Refuge (San Diego County) (Dudek 2000, Appendix A; CNLM 2008, pp. 67, 12, and 18), including pH, percent organic matter, soil moisture, and elemental composition. These measurements did not provide consistent results across the range of the species; thus, we are unable to make generalizations as to needs of the species as far as soil attributes are concerned.

Temperature

We have seen no reports of data on the tolerance of Ambrosia pumila to climatic extremes. Temperature is thought to potentially play a role in inducing (or prohibiting) seed germination (Johnson 1999, p. 5), although there is limited information at this time as to whether this species reproduces via seed.
Sites for Breeding, Reproduction, or Rearing (or Development) of Offspring

As stated above under the ``Life History'' section, little is known about sexual reproduction in Ambrosia pumila. Because occurrences are consistently found on the upper terraces of rivers and other waterways, periodic flooding of these waterways likely plays or likely has played a role in the life history of the plant. For example, Johnson (1999, p. 5) postulated that A. pumila seeds may require soaking in flood waters or scarification as they are churned about with debris in flood waters to germinate. Additionally, A. pumila may depend on floods to disperse rhizomes and seeds (Dudek 2003, p. P332) and to create space for new stems by removing or limiting the growth of competitors.

Presuming Ambrosia pumila is windpollinated, as discussed in the ``Life History'' section above, the species requires sufficient airflow through inflorescences to pick up and carry pollen (McGlaughlin and Friars 2007, p. 329). This is another reason (in addition to not being shadetolerant) that A. pumila may require habitat containing primarily lowgrowing plantslowgrowing plants do not block or dramatically reduce airflow to plants of A. pumila's stature, which is generally less than 12 in (30 cm) tall (McGlaughlin and Friars 2007, p. 329).

Ambrosia pumila is presumed to be selfcompatible (an individual can produce viable seed using its own pollen), but this aspect of the species' reproductive strategy has not been well examined. In a recent study, another Ambrosia species previously thought to be self compatible was found not to be selfcompatible (Friedman and Barrett 2008, p. 4). If A. pumila likewise is not selfcompatible, genetically distinct individuals in close proximity to one another may be crucial to maintaining sexual reproduction in the species (McGlaughlin and Friars 2007, p. 329).
Habitats Protected from Disturbance or Representative of the Historical, Geographical, and Ecological Distributions of the Species

Ambrosia pumila occurs most frequently on upper terraces of rivers (flat or gently sloping areas of 0 to 42 percent slopes are typical for terraces on which A. pumila occurrences are found, near, but not directly adjacent to, the river channel) and other drainages in western Riverside County, western San Diego County, and northwestern Baja California (Beauchamp 1986, p. 94; Johnson et al. 1999, p. 1; McGlaughlin and Friar 2007, p. 321; CNDDB 2008). These areas are or have been associated with a natural flood disturbance regime. The species is primarily associated with grassland and ruderal communities, and openings in coastal sage scrub (Johnson et al. 1999, p. 1; Dudek 2000, p. 18; Dudek 2003, p. P330; CNDDB 2008). In Riverside County, A. pumila occurs in ruderal and nonnative grassland communities adjacent to creeks and other smaller drainages (for example, Temescal (Alberhill) Creek and Santa Gertrudis Creek) (Dudek 2003, p. P326; [[Page 44244]]
CNDDB 2008). Ambrosia pumila also occurs in nonnative grassland community adjacent to and within the watershed of Skunk Hollow vernal pool in Riverside County (Dudek 2003, p. P326; CNDDB 2008). In San Diego County, A. pumila is more often found adjacent to larger waterways (for example, San Luis Rey River, San Diego River, and Sweetwater River), although the species is also often found associated with smaller drainages and washes (CNDDB 2008).

Occurrences in Riverside County are found at much higher elevation than in San Diego County. For example, the occurrence at Skunk Hollow in Riverside County is 1,350 ft (411 m) above sea level, while the occurrences at Mission Trails Regional Park and San Diego National Wildlife Refuge in San Diego County are about 315 ft and 360 ft (96 m and 110 m) above sea level, respectively (CNLM 2008, p. 7)).

The documented range of Ambrosia pumila in Mexico at the time of listing extended from Cabo Colonet south to Lake Chapala in north central Baja California. We have no information regarding additional occurrences in Mexico, or the physical and biological features essential to the conservation of the species there.

Primary Constituent Elements for Ambrosia pumila

Under the Act and its implementing regulations, we are required to identify the known physical and biological features, called primary constituent elements (PCEs), within the geographical area occupied by Ambrosia pumila at the time of listing that are essential to the conservation of the species and which may require special management considerations or protection. Again, the physical and biological features are those PCEs laid out in a specific spatial arrangement and quantity determined to be essential to the conservation of the species. Because not much is known about the specific needs and characteristics of this species, the PCEs are based on observed traits of the habitat types in which the species is most often found. All areas we are proposing as critical habitat for A. pumila were occupied at the time the species was listed, occur within the species' historical geographic range, and contain physical and biological features to support at least one lifehistory function.

Based on the above needs and our current knowledge of the life history, biology, and ecology of Ambrosia pumila, and the
characteristics of the areas where the species is known to occur, we have identified two PCEs for A. pumila:

1. Sandy loam or clay soils (regardless of disturbance status), including (but not limited to) the Placentia (sandy loam), Diablo (clay), and Ramona (sandy loam) soil series that occur on near (but not directly adjacent to) a river, creek, or other drainage, or within the watershed of a vernal pool, and that occur on an upper terrace (flat or gently sloping areas of 0 to 42 percent slopes are typical for terraces on which A. pumila occurrences are found).

2. Grassland or ruderal habitat types, or openings within coastal sage scrub, on the soil types and topography described in PCE 1, that provide adequate sunlight, and airflow for wind pollination.

Based on our current knowledge of the needs of the species, we believe the need for space for individual and population growth and normal behavior is met by PCE 2, and areas for reproduction, water, light, and soil are provided by PCEs 1 and 2. These areas provide nutrients, moisture, and proximity to water features that provide periodic flooding presumed necessary for the plant's persistence.

With this proposed designation of critical habitat, we intend to conserve the physical and biological features that are essential to support the lifehistory functions that are the basis for the proposal. All units and subunits proposed in this rule as critical habitat contain sufficient PCEs in the appropriate quantity and spatial arrangement to provide for one or more of the lifehistory functions of A. pumila.

We are soliciting public comment for information to help us more specifically identify PCEs and essential habitat for Ambrosia pumila. There is a lack of available information regarding what constitutes essential habitat for this species. Additionally, the available information does not identify a consistent pattern in specific life history requirements and habitat types where Ambrosia pumila is found. For these reasons, the PCEs in this proposed rule are broad and based on our assessment of the ecosystem settings in which the species has most frequently been detected and speculation regarding its life history. We specifically seek information that may assist us in defining those physical and biological features essential to the conservation of the species which may require special management considerations or protection, or in identifying specific areas outside the geographical area occupied by the species at the time it was listed that may be essential to the conservation of the species (see questions 2 and 3 in the Public Comments section).

Special Management Considerations or Protection

When designating critical habitat, we assess whether the physical and biological features within the geographical area occupied by the species at the time of listing contain features that are essential to the conservation of the species and that may require special management considerations or protection. All areas proposed for designation as critical habitat will require some level of management to address the current and future threats to the physical and biological features essential to the conservation of Ambrosia pumila. In all units, special management will be required to ensure that the habitat is able to provide for the growth and reproduction of the species.

Researchers estimate that Ambrosia pumila historically was known from over 50 locations in San Diego and Riverside Counties, but the number of extant occurrences has been dramatically reduced as much of its habitat has been impacted by human activities (Burrascano and Hogan 1997, p. 7; Dudek 2000, p. 17; CNDDB 2008). A detailed discussion of threats to A. pumila and its habitat can be found in the final listing rule (67 FR 44372). The primary threats impacting the physical and biological features essential to the conservation of A. pumila that may require special management considerations or protection within the proposed critical habitat include, but are not limited to, the following (67 FR 44372):

Special management considerations or protection are required within critical habitat areas to address these threats. Management activities that could ameliorate these threats include fencing Ambrosia pumila occurrences and providing signage to discourage encroachment by hikers, horses, and off road vehicle users; control of nonnative plants using methods shown to be effective (for examples, see CNLM 2008); guiding the design of development projects to avoid impacts to A. pumila habitat; and restoring and maintaining hydrology and floodplain dynamics of waterways associated with A. pumila occurrences where feasible.

The designation of critical habitat does not imply that lands outside of critical habitat do not play an important role in the conservation of Ambrosia pumila. Federal activities that may affect areas outside of critical habitat are still subject to review under section 7 of the Act if they may affect A. pumila. The prohibitions of section 9 of the Act applicable to listed plant species also continue to apply both inside and outside of designated critical habitat. Criteria Used To Identify Critical Habitat

As required by section 4(b) of the Act, we used the best scientific and commercial data available in determining areas within the geographical area occupied at the time of listing that contain the features essential to the conservation of Ambrosia pumila, and areas outside of the geographical area occupied at the time of listing that are essential to the conservation of A. pumila, or both. All essential areas were occupied at the time of listing, as discussed below. As a result, we are not currently proposing any areas outside the geographical area presently occupied by A. pumila because we have determined that including only occupied areas in critical habitat is sufficient for the conservation of the species. In San Diego County, where the pattern of extirpated occurrences reflects a loss of occurrences from each of the watersheds in which the species occurs rather than a complete loss from those watersheds, the areas occupied at the time of listing include the known historical range of the species (CNDDB 2008). In Riverside County, the loss of an occurrence near the Riverside Airport reflects a loss to the geographical extent of the range in that county (Provance and Sanders 2001, p. 47).

We also reviewed available information that pertains to the habitat requirements of this species, although A. pumila has not been well studied and little is known about its habitat specificity, characteristics, and breeding system. Additionally, data from different information sources at times conflict, further complicating the task of discerning the specific habitat requirements of the species. We used numerous sources of information, such as materials and data included in reports submitted to the Service during section 7 consultations and other project reviews, and by biologists holding section 10(a)(1)(A) recovery permits; research published in peerreviewed articles and presented in academic theses and agency reports; regional Geographic Information System (GIS) coverages for area calculations and mapping; and data collected in the field by Service biologists.

We are proposing to designate critical habitat in areas that we determined were occupied by the species at the time of listing, and that contain the PCEs in the quantity and spatial arrangement to support life history functions essential to the conservation of the species. This includes two areas occupied by occurrences detected after Ambrosia pumila was listed. We have concluded that these areas were occupied at the time the species was listed because individuals of species with a clonal growth habit like A. pumila are usually long lived (Watkinson and White 1985, pp. 4445; Tanner 2001, p. 1980). The occurrence near Santa Gertrudis Creek was found during a survey for a subtransmission line project in 2006 (AMEC 2006, p. 12). The occurrence at the intersection of State Route 76 and Olive Hill Road was found during a general survey for A. pumila in 2006 (CNDDB 2008). To our knowledge, the areas had not been surveyed for A. pumila previously, and we have no reason to believe the plant was imported or had dispersed into these areas from other areas after A. pumila was listed. The occurrences identified since listing likely were in existence for many years and were only recently detected due to increased awareness of this species.

We are also proposing to designate critical habitat in some areas where A. pumila was thought to be extirpated or where, though extant, A. pumila was not considered viable at the time of listing. We conducted surveys of historical occurrences as part of the background research for this proposed rule. We found one documented occurrence area east of Lake Hodges in San Diego County that was thought to be extirpated or nonviable because the occurrence had not been seen since 1999, and because records did not contain sufficient information to locate the occurrence site. Our survey found this site does contain a viable occurrence of A. pumila and meets the criteria set out in this rule for A. pumila critical habitat. The site was located after the species was listed and found to contain a large population of A. pumila. We are not proposing to designate any areas outside the geographical area occupied by the species at the time of listing, and all of the areas we are proposing to designate are currently occupied by the species. All units and subunits proposed contain the PCEs believed to be essential to the conservation of this species. Methods

As required by section 4(b)(1)(A) of the Act, we use the best scientific and commercial data available in trying to determine areas that contain the features that are essential to the conservation of Ambrosia pumila. We used the best scientific data available to select areas that we believe may possess those physical and biological features essential to the conservation of the species, and that may require special management considerations or protection.

After identifying the PCEs, we followed these steps to delineate critical habitat:
(1) We identified areas occupied by Ambrosia pumila at the time of listing as extant occurrences, where an occurrence is defined as an occupied habitat area separated by 0.25 mi (0.40 km) or more from the next nearest occupied habitat area.
(2) We determined that due to the lack of specific information regarding the needs of the species, we are unable to identify specific areas outside the geographical area occupied by the species at the time it was listed that may be essential to the conservation of the species. [[Page 44246]]
(3) We removed all areas where the species occurs in habitat of low quality for growth and propagation (such as pavement areas or cracks within paved areas). Although occupied, we believe these occurrences are not capable of providing for the full lifehistory requirements of this species and are not likely to contribute to its longterm conservation; therefore, we did not consider these locations as containing essential features as habitat and did not include them in critical habitat.
(4) To define an outer boundary for each patch that captures the existing underground rhizome system (which extends beyond the visible aerial stems of plants within each occurrence), we added the average distance between the visible (aerial stems) portions of each Ambrosia pumila patch and the next nearest patch to the limits of the visible portion of each patch. Using GIS data, we found the average distance between clusters of stems in adjacent patches to be approximately 1,181 ft (260 m), and we added this distance to the visible outer limit of each occurrence to delineate the presumed expanse of the occurrence that also includes the underground rhizomes.
(5) We removed any area within the outer boundary of an occurrence where habitat type was not grassland, ruderal, or coastal sage scrub.

We describe how we implemented each of the steps above in detail below.
(1) We identified all occurrences of Ambrosia pumilathose known to exist at the time of listing and those detected since listing. We compiled data from the following sources to create our database of A. pumila occurrences: (1) Data used in the 2002 listing rule for A. pumila (67 FR 44372; July 2, 2002); (2) the California Natural Diversity Database occurrence data report for A. pumila and accompanying GIS records (CNDDB 2008, pp. 149); (3) the data from the Consortium of California Herbaria and accompanying Berkeley Mapper GIS records (Consortium of California Herbaria 2008, pp. 15); (4) the Western Riverside County Multiple Species Habitat Conservation Plan (Western Riverside County MSHCP) species GIS database; and (5) the Carlsbad Fish and Wildlife Office's internal species GIS database, which includes the species data used for the San Diego Multiple Species Conservation Program (MSCP) and the San Diego Multiple Habitat Conservation Plan (MHCP), reports from section 7 consultations, and Service observations of A. pumila (CFWO internal species GIS database). As discussed in detail earlier in this section, we consider all extant occurrences to have been in existence at the time of listing. We used these data to delineate GIS polygons around Ambrosia pumila occurrences.

We reviewed the data that we compiled to ensure its accuracy. We checked each data point in our database to ensure that it represented a site documented by a herbarium voucher or observation of Ambrosia pumila and was not a duplicate voucher or observation of another occurrence in the database. Duplicates were removed from our database. Secondly, we checked each data point to ensure that it was correctly mapped. Data points that did not match the description for the original herbarium collection or observation were remapped in the correct location, if possible. We removed observations where the location could not be determined from available data or site visits.

We then determined which areas are currently occupied. For areas where we have past occupancy data for Ambrosia pumila, we assumed the area remains occupied unless: (1) Three or more surveys for the species did not find A. pumila; (2) the site was significantly disturbed (for example, converted to development) since the last observation of the species at that location; or (3) specific location information for the site was lacking, and field surveys carried out in conjunction with this proposed critical habitat determination could not locate the occurrence.
(2) We determined that there are no specific areas outside the geographical area occupied by the species at the time it was listed that are essential to the conservation of the species. Information found during the Service's research in connection with this proposed action indicated that the geographical area occupied by the species at the time it was listed provides sufficient resources for the conservation of the species. We do not have sufficient information regarding the specific needs of the species to determine if any unoccupied areas are essential for the conservation of the species. (3) We removed areas where Ambrosia pumila occurs in habitat of low quality for growth and propagation (such as pavement areas or cracks within paved areas). Although occupied, we did not consider these locations for critical habitat, as these occurrences are not likely to contribute to the longterm conservation of the species. We made this determination using site descriptions in the California Natural Diversity Database, talking to Service biologists, other researchers, and land managers familiar with the areas in question, and visiting and evaluating sites in person.
(4) We estimated the distance that the root system of an occurrence likely extends beyond the aboveground extent of the occurrence by measuring the distance of each GIS polygon representing an Ambrosia pumila patch to the nearest neighboring patch. As mentioned above, an occurrence is defined by CNDDB as an occupied habitat area separated by 0.25 mi (0.40 km) or more from next nearest occupied habitat area. A patch is defined herein as a distinct cluster of stems within an occurrence. We estimated the average distance of underground rhizome expansion beyond the aboveground aerial stems as 1,181 ft (260 m). We expanded the outer boundary of the aboveground extent of each occurrence by 1,181 ft (260 m) to account for the underground rhizome system extending beyond the area occupied by visible stems. We believe this method adequately captures the extent of individual occurrences. (5) We removed any areas within the expanded outer boundary of an occurrence where habitat type was not grassland, ruderal, or open areas within coastal sage scrub habitat, using the habitat types assigned to relevant areas in our GIS database, and personal observations of sites by Service biologists and other researchers or land managers.

Based on the results of this methodology, we are proposing to designate 7 units that include 8 subunits as critical habitat for Ambrosia pumila. After applying the above criteria and methods, we mapped the critical habitat unit boundaries at each of these seven units as GIS polygons around known occurrences. Critical habitat boundaries were delineated as polygons encompassing the extent of habitat believed to contain the physical and biological features essential to the conservation of the species that may require special management considerations or protection.

When determining the proposed critical habitat boundaries, we made every effort to avoid including developed areas such as lands occupied by buildings, paved areas, and other structures that lack PCEs for Ambrosia pumila. The scale of the maps we prepared under the parameters for publication within the Code of Federal Regulations may not reflect the exclusion of such developed areas. Any developed structures and the land under them inadvertently left inside critical habitat boundaries shown on the maps of this proposed critical habitat are excluded by text in this rule and are not proposed for critical habitat designation. Therefore, if the critical habitat is
[[Page 44247]]
finalized as proposed, Federal actions involving these lands would not trigger section 7 consultation with respect to critical habitat and the requirement

FOR FURTHER INFORMATION CONTACT

Jim Bartel, Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 6010 Hidden Valley Road, Suite 101, Carlsbad, CA 92011; telephone (760) 431 9440; facsimile (760) 4315901. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at (800) 8778339.