Sandsage Prairie-Clover) in the Sandsage Prairie Region of Southwestern Nebraska
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SURVEY FOR DALEA CYLINDRICEPS (SANDSAGE PRAIRIE-CLOVER) IN THE SANDSAGE PRAIRIE REGION OF SOUTHWESTERN NEBRASKA A report prepared for the Nebraska Game and Parks Commission James H. Locklear Lauritzen Gardens January 12, 2015 SUMMARY Dalea cylindriceps (sandsage prairie-clover) is a perennial herb native to the western Great Plains. It is recognized as a species of conservation concern in all but two of the eight states in which it has been documented and is recognized as a Tier I At-risk Species by the Nebraska Natural Legacy Project. Dalea cylindriceps is associated with sandsage prairie throughout most of its range in the Great Plains. In Nebraska, the most extensive occurrences of this plant community are located in southwest part of the state in Chase, Dundy, and Perkins counties. This study was undertaken to locate and document extant occurrences of D. cylindriceps in the sandsage prairie region of Nebraska. Despite four days of searching, no occurrences of D. cylindriceps were found in this region in 2014. Outside of the study area, two large and previously-unknown Nebraska occurrences of D. cylindriceps were located in Garden and Keith counties in 2014. INTRODUCTION Purpose of project Dalea cylindriceps (sandsage prairie-clover) is a perennial herb native to the western Great Plains. Occurrences are known from Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. Despite the large extent of its historical distribution, D. cylindriceps has been collected infrequently and occurrences are scattered and local (Locklear 2013b). As noted in Flora of Nebraska (Kaul et al. 2011), “This distinctive species is rare almost throughout its wide geographic range.” Dalea cylindriceps is tracked as a species of conservation concern in all but two of the states in which it has been documented, and is ranked G3G4 by NatureServe and as a Tier I At-risk Species by the Nebraska Natural Legacy Project. Dalea cylindriceps has a strong affinity for sandsage prairie and most occurrences outside of Nebraska are associated with this plant community (Locklear 2013b). There are extensive tracts of sandsage prairie in southwestern Nebraska (Farrar 1993a, 1993b; Kaul & Rolfsmeier 1993; Rolfsmeier & Steinauer 2010) which would appear to provide potential habitat for D. cylindriceps, suggesting the value of more intensive survey for this species in the region. The purpose of the project was to locate and document extant occurrences of D. cylindriceps in the sandsage prairie region of southwestern Nebraska. Plan of work The 2014 study entailed search of sandsage prairie occurrences in Chase, Dundy, and Perkins counties in southwestern Nebraska for populations of Dalea cylindriceps. The field work took place over four days, August 11-14, 2014, and was timed to coincide with the peak flowering period of the species. The search for historical occurrences was guided by locality data derived 1 from herbarium specimens held by the Bessey Herbarium of the University of the Nebraska State Museum. Search for previously unrecorded occurrences was facilitated by locating potential habitat with the aid of topographic and county soil survey maps and attempting to reach this habitat via county roads. It was also guided by locality data derived from herbarium specimens of Chenopodium cycloides and Penstemon ambiguus, two species that only occur in Nebraska in association with sandsage prairie. Previous Investigations I carried out a conservation assessment of Dalea cylindriceps for the NNLP in 2013 in which I surveyed 22 sites in Nebraska where this species has been observed or collected in the past (Locklear 2013a). The survey included three historical occurrences from Dundy County, but no D. cylindriceps plants were observed at these sites in 2013. Five small, extant occurrences were located during the survey in four northwest Nebraska counties (Box Butte, Morrill, Sheridan, and Sioux counties). Based on this survey, it appears D. cylindriceps has undergone significant population decline in Nebraska, although extensive areas of potential habitat remain to be searched for this species. Species Information Detailed species information for Dalea cylindriceps including nomenclature, history, description, distribution, and ecology are included in recent publications by Locklear (2013a, 2013b) and will not be repeated here. Study Area This survey targeted occurrences of sandsage prairie in southwestern Nebraska (Chase, Dundy, and Perkins counties). This study area is located in the northern portion of the High Plains section of the Great Plains Physiographic Province (Fenneman 1931). The surface geology of the region is influenced by Tertiary-age non-marine deposits of the Ogallala Group (Miocene to earliest Pliocene). Windblown sand and/or loess mantle the Ogallala bedrock throughout most of the study area except where it is exposed along river valleys. The study area is located in the watershed of the Republican River. Sandsage prairie is associated with two geographically distinct dune fields within the study area—the Wray Dune Field and the Imperial Dune Fields (Muhs & Holliday 1995). The Wray Dune Field is the larger and extends from Yuma and Phillips counties in northeastern Colorado (covering 4680 km2) into southwestern Nebraska (covering more than 2000 km2) where it occupies much of the western half of Dundy County and extends into the southwest portion of Chase County (Madole 1995). The sands of the Wray Dune Field were derived from South Platte River sediments (Muhs et al. 1996). The Imperial Dune Fields are located to the north and east of the Wray Dune Field in Chase and Perkins counties, with an isolated field in Hayes County. The sands of the Imperial Dune Fields were derived from both the Nebraska Sandhills (quartz-rich) and the South Platte River dune fields (K-feldspar rich) of northeastern Colorado (Muhs et al. 2000). The topography of these dune fields varies from low, rolling hills with relatively flat crests to more choppy sandhills with steep sides and local relief from a few meters to as much as 60 m (200 ft). Soils formed in this eolian sand are deep, excessively drained, and very rapidly permeable. The predominant soil association is Valent sand (Paden et al. 1982; Wilson et al. 2004). 2 Sandsage prairie is a steppe community in which the shrub sand sagebrush (Artemisia filifolia) is a dominant element. This community type is found in sandy habitat throughout a large area of the western Great Plains, from South Dakota and Wyoming south into Texas and New Mexico (Kuchler 1985). While A. filifolia is a constant in this community type, the co-dominant graminoids vary depending on topoedaphic factors, with typical associates including sand bluestem (Andropogon hallii), prairie sandreed (Calamovilfa longifolia), little bluestem (Schizachyrium scoparium), and sand dropseed (Sporobolus cryptandrus). Likewise, the forb component is influenced locally by topoedaphic factors and varies along a north-to-south gradient, with higher species diversity found in occurrences in the southwestern Great Plains. The sandsage prairie region of southwestern Nebraska shares many plant species with the Nebraska Sandhills to the north, but a few arenaceous species are limited to this part of the state, notably Chenopodium cycloides, Linum berlandieri, Penstemon ambiguus, Pomaria jamesii, and Ratibida tagetes (Kaul et al. 2011; Rolfsmeier & Steinauer 2010). These species are more common in the southern Great Plains and reach the northern limits of their distributions in southwestern Nebraska. Jon Farrar (1993a, 1993b) authored two excellent articles on the history, ecology, and conservation challenges of sandsage prairie in Nebraska for NEBRASKAland magazine. RESULTS Survey of historical occurrences of Dalea cylindriceps in southwestern Nebraska – Three historical occurrences of Dalea cylindriceps are known from the sandsage prairie region of southwestern Nebraska, all from Dundy County. Information for these is summarized below. Search was made of these sites in 2013 and 2014 but no D. cylindriceps plants were observed. Locality data for these occurrences are presented in Appendix A. Benkelman 1916 Initial record: J.H. Bates s.n. (NEB); 28 July 1916 General location: In the vicinity of Benkelman Survey dates: 23 July 2013; 11 August 2014 Haigler 1996 Initial record: S. Rolfsmeier 12963 (NEB); 10 September 1996 General location: Sandhills north of Haigler; Locklear searched this site in 2010 and found no D. cylindriceps but did locate a small population ca. 1.5 mile west and 1.5 south of this site (see Haigler 2010) Survey dates: 05 July 2010; 23 July 2013; 12 August 2014 Haigler 2010 Initial record: Small population (2 individuals counted) observed by Locklear on 05 July 2010 General location: Sandhills north of Haigler Survey dates: 23 July 2013; 12 August 2014 General survey of sandsage prairie in southwestern Nebraska – I searched approximately 25 occurrences of sandsage prairie in Dundy, Chase, and Perkins counties but found no occurrences 3 of Dalea cylindriceps. Many stands of sandsage prairie in the region appeared to be in relatively good condition but a more systematic and thorough assessment of species diversity at these sites would be needed to determine the true ecological condition of these occurrences. Some occurrences with disturbed areas were being invaded by the exotic weed kochia (Kochia scoparia), particularly sites adjacent to cultivated cropland. The primary graminoid co-dominant associates of Artemisia filifolia