Lepidium papilliferum (Slickspot peppergrass): Evaluation of Trends (1998-2004) and Analysis of 2004 Habitat Integrity and Population Monitoring Data

Lepidium papilliferum (slickspot peppergrass) is a plant species of high conservation concern in southwestern Idaho. The species is specialized to occupy “slick spots,” distinct small habitat patches with a clay subsurface soil horizon within the sagebrush steppe. In 1997, the Idaho Conservation Data Center, in collaboration with federal and state agencies, developed a Habitat Integrity Index (HII) method to assess and monitor long term trends in ecological integrity of the slickspots and their surrounding habitat. This method was used, with some modifications, from 1998-2001, and at a subset of areas in 2002. A modified version of the HII monitoring technique, using Habitat Integrity and Population monitoring (HIP) transects, was employed in 2004 to assess and monitor similar attributes of L. papilliferum element occurrences (EOs), slickspots, and surrounding habitat, using increased sample replication and a targeted approach (Colket 2005). Data from both of these monitoring efforts (from 1998 to 2002, and 2004) were analyzed to evaluate habitat and climatic factors that drive trends in L. papilliferum abundance and degrade slickspots and their surrounding habitat. The primary findings are outlined below.

•  Dynamics in L. papilliferum plant abundance appear to be more strongly linked to patterns of spring precipitation than to fire disturbance events.
•  Overall, element occurrences of L. papilliferum had negative (declining) population trends between 1998 and 2004, indicating they were decreasing in abundance region- wide.
•  Several features of slickspots, including soil crust cover and weedy species cover, were consistently more degraded in burned areas, apparently as a result of past fire events.
•  Across all transects sampled consistently for plant community since 1998, total vascular plant cover, species diversity and species richness have declined between 1998 and 2004.
•  Recent livestock use that was estimated by HIP monitoring resulted in decreased soil crust cover in slickspots, decreased vascular plant cover, and decreased plant litter cover in the surrounding plant community.
•  Previously burned habitat around slickspots had diminished soil crust cover and higher total cover of exotic species in all years sampled for plant community (1998, 2001, 2004).The HIP transects were also used in 2005, and will be used in 2006 to monitor L. papilliferum and its habitat. We recommend additional analysis of the available data to evaluate the effects of slickspot habitat quality on L. papilliferum, and to confirm or further clarify the findings presented in this report.