Field Assessment of Lepidium papilliferum (Slickspot Peppergrass) Element Occurrences: Jarbidge Geographic Area

Publication Type:

Unpublished

Authors:

Jennifer J. Miller; C. Lynn Kinter

Source:

Idaho Natural Heritage Program, Idaho Department of Fish and Game, Boise, Idaho, p.63 pp. plus appendices (2019)

Call Number:

U19MIL05IDUS

Keywords:

eastern Owyhee Plateau, Element Occurrence, habitat, Idaho, Inside Desert, Lepidium papilliferum, monitoring, rare plant conservation, sagebrush steppe, slickspot peppergrass

Abstract:

Lepidium papilliferum (slickspot peppergrass, Brassicaceae) is a small annual or biennial forb that flowers in May and June across southwestern Idaho. It is endemic to the western Snake River Plain, adjacent foothills, and Owyhee Plateau, where it inhabits slickspots—slight depressions among shrubs where clay and salts have accumulated. Lepidium papilliferum is federally listed as a threatened species and has been the subject of conservation concern for many years. In 2016, we published the status ranks of all 127 occurrences of L. papilliferum known across its range (Kinter and Miller 2016). This report includes the details of our field research used to develop the ranks within the Jarbidge Geographic Area (GA). Our field results for the Foothills and Snake River Plain Geographic Areas were published in 2018 (Miller and Kinter 2018). We began by examining location data from the Idaho Natural Heritage Program database, which is part of the Idaho Fish and Wildlife Information System (IFWIS). From Summer 2014 through Fall 2015, we conducted field assessments at 41 occurrences known in the Jarbidge GA. We did not assess sites located within the Mountain Home Air Force Base— Juniper Butte Range. In the field, we walked across the occurrences in a systematic manner recording waypoints for each slickspot observed using a hand-held Garmin GPS unit. When L. papilliferum was present, we counted individual plants by category—rosettes or flowering/fruiting. We also collected data on plant community composition, landscape characteristics, and disturbances. An estimated total of 11,670 L. papilliferum plants were observed—8408 (72%) rosettes and 3262 (28%) flowering/fruiting. The presence of invasive and seeded non-native species, harvester ant mounds, and livestock sign constitute the most widespread disturbances to L. papilliferum throughout the study area. Incidental to our inventories in mapped areas, we found L. papilliferum outside of 16 previously mapped known occurrences. These data will expand those known occurrences, and be added to the IFWIS database. These incidental discoveries indicate the need for future surveys. At 16 occurrences, we did not find L. papilliferum during our field assessments. We recommend re-evaluating these 16 occurrences at least once in the near future. If assessments are possible in five of the next 12 years, and no plants are found, the rank would be changed to ‘Extirpated’ (NatureServe 2002, Kinter and Miller 2016).