Astragalus tricarinatus

Astragalus tricarinatus is endemic to a small area of California, U.S.A., in Riverside and San Bernardino counties, that occurs in the mountains and canyons bordering the Coachella Valley. Most occurrences are in the foothills of the San Bernardino and Little San Bernardino Mountains. There are several occurrences in the Santa Rosa Mountains. Historically, the species was documented in the Orocopia Range and Chuckwalla Mountains but recent surveys could not relocate plants. The primary threats to this species are illegal off road vehicle use, fire suppression measures and fire, climate change, and invasive plant species. This species is especially vulnerable as most occurrences have less than 15 plants and high rates of mortality have been observed in some areas. There is potential suitable habitat in the vicinity of historical and extant locations that should be surveyed, focusing on areas with Precambrian gneiss.

Astragalus tricarinatus is endemic to a small area of California, U.S.A., in Riverside and San Bernardino counties. The species occurs in the mountains and canyons bordering the Coachella Valley, with most of the occurrences in the foothills of the San Bernardino and Little San Bernardino Mountains. There are three disjunct areas of occurrence in Riverside County in the Agua Alta Canyon in the Santa Rosa Mountains, and the Orocopia Range and Chuckwalla Mountains (Bell and Fraga 2021).

This species is currently known from about 53 occurrences but eight are considered historical because plants haven't been reported from those sites for over 20 years (CNDDB 2021, NatureServe 2021). Surveys in the Orocopia Range and Chuckwalla Mountains failed to relocated historical occurrences but did identify suitable habitat that should be surveyed. The same survey effort confirmed the species is extant in the Santa Rosa Mountains, where it was previously documented by historical occurrences alone (Bell and Fraga 2021).

This species is threatened by invasive species, illegal off road vehicle use, fire and fire suppression activities, and climate change (Bell and Fraga 2021, USFWS 2009). Expanding residential development near occurrences may increase illegal off road vehicle use activity, foot traffic, and exposure to exotic invasive species (Fraga et al. 2015, USFWS 2009). Sites in the Big Morongo Canyon are potentially threatened by maintenance activities for the crude oil pipeline which runs through its habitat at Big Morongo Canyon (CNPS 2001). The limited number of individuals make it especially vulnerable to unanticipated events, such as pipeline leaks, breaks, or emergency repairs (Fish and Wildlife Service 1998) but also rangewide threats like climate change. As an edaphically restricted species with small population sizes, it may not have sufficient adaptive capacity for a changing climate. Some occurrences may have been impacted by fire but the species response to fire is unknown. Fire suppression activities (bulldozer lines, use of fire retardant) may degrade habitat or create favorable conditions for the spread of non-native invasive plants (USFWS 2009).