Assessment of Lepidium papilliferum (Slickspot Peppergrass) Element Occurrences

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Lepidium papilliferum (slickspot peppergrass, Brassicaceae) is a small annual or biennial forb that flowers in late May and June across southwestern Idaho. It is endemic to the western Snake River Plain and Owyhee Plateau, where it inhabits slickspots—slight depressions among shrubs where clay and salts have accumulated. Lepidium papilliferum has been the subject of conservation concern for many years. In this study, we assessed and ranked all known occurrences of L. papilliferum across its range. We began by examining location data from the Idaho Natural Heritage Program database, which is part of the Idaho Fish and Wildlife Information System. From Summer 2012 through Spring 2016, we conducted field assessments at 111 of the 127 known occurrences of L. papilliferum. We did not assess sites that were extensively developed, such as irrigated fields or residential areas, or that were on private land where we were unable to get permission for access. In the field, we collected data on L. papilliferum population size, distribution of slickspots, plant community composition, landscape characteristics, and disturbances. We then used these data to rank each occurrence according to a protocol developed by NatureServe (2002), with additional information from previous ranking efforts for this species (Moseley 1994, Colket et al. 2006). According to the protocol, ranks range from A (excellent) to D (poor) based on three key factors: population size, occurrence condition, and landscape condition. For occurrences that could not be ranked, for example due to lack of recent field data, we assigned other ranks, such as ‘Historical’ or ‘Extirpated’. Of the 127 L. papilliferum occurrences that we evaluated, none were ranked A or AB, 29 were ranked B or BC, 51 were ranked C or CD, and 29 were ranked D. We also ranked two occurrences as ‘F, Failed to Find’. Five occurrences were ‘H, Historical’, because the information about their existence was older than 1980. We classified ten occurrences as ‘X, Extirpated’. One occurrence in southeast Ada County (EO 44) was determined to have been mis-mapped in the past due to ambiguous specimen label data, and so it was not ranked; the correct location corresponds to another occurrence near Orchard (EO 14). The location of EO 55, in the vicinity of the old Falk’s Store, was also revised, but remains as a valid, distinct occurrence. In comparing our 2016 results to those from 2006, we had 109 EOs ranked A through D: 26.6% B or BC, 46.8% C or CD, and 26.6% D. Colket et al. (2006) had 79 EOs ranked A through D: 20.3% as B or BC, 49.4% as C or CD, and 30.4% as D. Differences in the total numbers were due to 15 ‘new’ EOs discovered since 2006, merging of EOs that resulted in a ‘loss’ of 15 EOs since 2006, and 30 EOs that lacked sufficient information to be ranked as A through D in 2006, where we were able to collect field data for ranking. Rank changes since 2006 were minimal for the 15 EOs previously ranked H or X.

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Reference Code: U16KIN02IDUS <br>

Full Citation: Kinter, C.L., and J.J. Miller. 2016. Assessment of Lepidium papilliferum (Slickspot Peppergrass) Element Occurrences. Idaho Natural Heritage Program, Idaho Department of Fish and Game, Boise. 71 pp. plus appendices. <br>

Location: ELECTRONIC FILE - BOTANY: REVIEW SPECIES: {Lepidium papilliferum} <br>

Keywords: Lepidium papilliferum, slickspot peppergrass, Element Occurrence ranking, monitoring, habitat, rare plant conservation, sagebrush steppe, Idaho, Snake River Plain, Owyhee Plateau <br>