Habitat Integrity and Population Monitoring of Lepidium papilliferum (Slickspot Peppergrass): 2011

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ABSTRACT Research premise: Lepidium papilliferum (slickspot peppergrass, Brassicaceae) is a small annual or biennial forb that flowers in late May and June across southwestern Idaho. It inhabits slickspots—slight depressions among shrubs where clay and salts have accumulated. Lepidium papilliferum was federally listed as Threatened in 2009 and has been the subject of conservation concern for many years. Our study was a continuation of intensive annual monitoring, termed ‘Habitat Integrity and Population (HIP) Monitoring’, begun in 2004 by biologists from the Idaho Natural Heritage Program (IdNHP). Less intensive monitoring, termed ‘Habitat Integrity Index’, had been conducted by IdNHP biologists from 1998 to 2002. Every year since 2004, the IdNHP has monitored L. papilliferum across its range, although in 2008, the portion of the monitoring on the Orchard Combat Training Center was conducted by the Idaho Army National Guard. Our 2011 work was conducted in cooperation with the Idaho Army National Guard, Bureau of Land Management, Fish and Wildlife Service, and others. Each year, monitoring objectives have been to assess L. papilliferum abundance, habitat, and disturbance, as well as to evaluate performance metrics described in the Candidate Conservation Agreement for Slickspot Peppergrass (Caswell et al. 2006). Methods: From 31 May to 8 July 2011, we collected data at 77 established transects, each of which included 10 permanently marked slickspots. Four types of data were collected at each transect: 1) slickspot attributes, including L. papilliferum counts, ground cover, non-native plant canopy cover, wildlife and livestock sign, and evidence of vehicles, restoration, firefighting, or fire; 2) counts of harvester ant mounds within 20 m of the first, fifth, and tenth slickspots; 3) landscape attributes; and 4) photos at the transect start, each slickspot, and each vegetation transect. We did not collect a fifth type of data that had been collected in the past—plant canopy cover on vegetation transects at three of the 10 slickspots. The vegetation transect data collection is now on a 5-year assessment cycle and was last assessed in 2009. For each type of data, we calculated descriptive statistics, with comparisons among three geographic areas and 11 management areas. Results: In 2011, mean density of L. papilliferum plants within transects ranged from 0.0 to 252.7 plants/slickspot, with a mean across all transects of 21.4 plants/slickspot. Lepidium papilliferum had a frequency of 70.1% (i.e., it was present in 54 of the 77 transects). The total count—16,462 plants—was lowest in the range of counts from 2005 to 2011. This followed the highest total count to date—58,921 plants over the 77 transects in 2010. Ground cover within slickspots was largely bare or biotic crust, though proportions of each varied widely by management area. Non-native plant canopy cover ranged from 0.5% to 82.0%, with a mean across all transects of 16.8% and frequency of 100.0%. Highest cover means by geographic areas were for Bromus tectorum (cheatgrass), Agropyron cristatum (crested wheatgrass), Vulpia spp. (fescue), Lepidium perfoliatum (claspingleaf pepperweed), Ceratocephala testiculata (bur buttercup), and Sisymbrium altissimum (tall tumblemustard). Mean active harvester ant mound density within transects ranged from 0.0 to 61.0 mounds/ha, with a mean across all transects of 12.0 mounds/ha and a frequency of 72.7%. Wildlife signs were predominantly ant mounds, badger burrows, and divots (any unclear diggings or tracks, including livestock tracks), with mean cover per slickspot of 0.4%, 0.8%, and 1.7%, respectively. Livestock sign was predominantly tracks, with low values for feces and trails. Among transects, mean track cover per slickspot ranged from 0.0% to 19.5%, with an overall mean of 1.6% and frequency of 54.5%. Mean track number ranged from 0.0 to 227.8 tracks per slickspot, with an overall mean of 16.7 tracks per slickspot and a frequency of 54.5%. Cattle feces cover had a low range (0.0% to 2.3%) and overall mean (0.4%), but a high frequency (75.3%). Vehicle tracks were found in a slickspot at one transect, and in the vicinity of eight other transects. No sign of restoration within the last year was observed on transects. Firefighting or prevention activities (bladed firebreaks) within the last year were observed at four transects. No evidence of fire within the last 12 months was recorded within 65 m of any transects at the time our data were collected, but according to BLM fire data, fire did come within 4 to 114 m of four transects, and burned transect 027E and 058 after our assessment. At the landscape scale, Chondrilla juncea (rush skeletonweed) was the noxious weed most frequently encountered—present at five transects. Comparison of our results to performance metrics described in the Candidate Conservation Agreement for Slickspot Peppergrass (Caswell et al. 2006) showed that management actions were triggered for a fire ≥40.5 ha (100 ac) in Management Areas 7, 8, and 10; wildfires in eight L. papilliferum occurrences, motorized vehicle tracks within a slickspot at one transect, >1% cover of non-native seeded species in slickspots at 23 transects, ≥5% increase in total non-native plant species cover within slickspots at 61 transects, and ≥10% penetrating livestock trampling within slickspots at three transects.

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SUGGESTED CITATION
Kinter, C.L., D.L. Clay, J.R. Fulkerson, and J.J. Miller. 2012. Habitat Integrity and Population Monitoring of Lepidium papilliferum (Slickspot Peppergrass): 2011. Idaho Natural Heritage Program, Idaho Department of Fish and Game, Boise. 58 pp. plus appendices.