Edaphic factors that characterize the distribution of Lepidium papilliferum : final report

Abstract

Lepidium papilliferum, known as slick spot peppergrass, grows on visually distinct microsites within remnant communities of relatively undisturbed and moderately disturbed Wyoming big sagebrush (Artemisia tridentata ssp. wyomingensis). This species is a Federal Category 2 candidate for listing as Threatened or Endangered. Its known range is southwestern Idaho where rapid habitat alteration is occurring. Typical Lepidium microsites are variously described as "slick spots", "playettes", and "natric sites", implying a soil-chemistry explanation for the typical sparsity of vegetation and the low water permeability sometimes observed. This study examines soil factors that affect the distribution of Lep/oVu/n-microsites. It describes the soil morphology and chemistry of Lepidium-sWck spots and nearby shrub interspaces of three Lepidium populations that occur on distinct landscape units of the Lower Snake River Plain. Slick spots are best distinguished by a near-surface distribution of soluble sodium salts, thin vesicular surface crusts and shallow well-developed argillic horizons. High salinity and high sodium concentrations relative to soluble calcium and magnesium occur within 40 cm of the soil surface and the argillic horizons probably qualify as natric soil horizons. Searches for new Lepidium populations and habitat might best be focussed on remnant Pleistocene land surfaces where current soil surveys document occurrences of saline and natric soil series among the general matrix of non-saline Aridisols. This study, conducted in 1991, compares soil morphology and non-visual soil properties of Lep/d/um-bearing slick spots with those of shrub interspaces without Lepidium. The purpose is to identify what soil properties, if any, define the landscape-level distribution of Lepidium and to identify whether these properties are correlated with visual site-cues. Study Area This study examines three geographically distinct Lepidium populations, identified as Simco Road, Tenmile Ridge and Kuna Butte (Figure 1). They are documented by the Idaho Conservation Data Center as occurrences #015, #024, and #032, respectively, and are A-ranked populations, meaning that plant numbers are relatively high and that the surrounding shrubsteppe community is of high quality (Moseley, 1994). These populations occur at elevations from 2,900 to 3,300 ft (884 to 1 ,000 m) on distinct geologic units of the western Snake River Plain. The Kuna Butte population is on low, gently sloping (2 to 5%) basalt ridges. The soils formed on late-Pleistocene surfaces of loess or silty alluvium over basalt (Collette, 1980; Othberg, 1994). Lava boulders, smaller lava rocks and gravels are scattered across the terrain. The Tenmile Ridge population occurs on steeper nose and sideslopes of the oldest, early Pleistocene alluvial terrace of the Boise River. The Tenmile gravel formation is typically capped by 1 to 2 m of loess and generally has a well developed silica-cemented hardpan called a duripan (Othberg, 1994), although the loess cap appears to be significantly...

Relative contributions to seed production by floral visitors of slickspot peppergrass, Lepidium papilliferum (Brassicaceae)

“…L. papilliferum is a primarily outcrossing species that relies on insects for pollination (Robertson and Klemash 2003), although it does have a limited capacity for autogamy (*12% of self-pollinated flowers produce seed-bearing fruits, on average- Robertson and Ulappa 2004;Billinge and Robertson 2008). Within sagebrushsteppe habitat, L. papilliferum is restricted to microsites known as ''slick spots''-shallow depressions of soil characterized by high levels of clay and minerals as well as by subsurface water retention that is higher than that of surrounding areas (Fisher et al 1996). Individual plants reach 5-30 cm in height and have numerous multiflowered inflorescences that terminate at the branches (Fig.…”

Enhancement of Germination and Growth of Slickspot Peppergrass in a New Medium with Two Compost Organic Fractions

“…In 2009 L. papilliferum was federally listed as a threatened species under the Endangered Species Act (USFWS 2009). This plant is commonly known as "slickspot peppergrass" because of its association with small areas, called slickspots, which are interspersed within the large steppe habitat (Fisher, Eslick, and Seyfried 1996). These areas, known also as mini-playas or nitric sites, are characterized by a near-surface distribution of soluble sodium salts, thin vesicular (small-cavity) surface crusts, and shallow well-developed argillic horizons or layers that are impermeable when wet (Fisher, Eslick, and Seyfried 1996).…”

“…This plant is commonly known as "slickspot peppergrass" because of its association with small areas, called slickspots, which are interspersed within the large steppe habitat (Fisher, Eslick, and Seyfried 1996). These areas, known also as mini-playas or nitric sites, are characterized by a near-surface distribution of soluble sodium salts, thin vesicular (small-cavity) surface crusts, and shallow well-developed argillic horizons or layers that are impermeable when wet (Fisher, Eslick, and Seyfried 1996). Compared to surrounding habitat areas, the microsites have reduced levels of organic matter and nutrients, due to low biomass production (Fisher, Eslick, and Seyfried 1996).…”

Germination and Early Growth of Slickspot Peppergrass (Lepidium papilliferum) as Affected by Desert Soil Humic Acids

“…Because slickspots are essentially areas that accumulate water, the increased Na and electrical conductivity (EC) values may be related to the deeper depth or water-holding capacity of the slickspot. Fisher et al (1996) noted that the increase in these soil parameters may reduce growth and competition of other plants within the slickspots, but the effects of this increased soil moisture are unknown.…”

“…The name of the plant is derived from its association with slickspots, which are visually distinct small-scale depressions in the soil that collect water (Moseley, 1994;Fisher et al, 1996). The inorganic chemical composition of slickspots has been documented by the USDA-Natural Resources Conservation Service (2003).…”