Status and Distribution of Illinois Populations of Stenanthium gramineum (Ker-Gawl.) Morong, Grass-Leaved Lily (Liliaceae): an Endangered Plant in Illinois

Castanea, Sep 2004 by Edgin, Bob

ABSTRACT

Stenanthium gramineum (Ker-Gawl.) Morong (grass-leaved lily) is known historically from 19 populations in 13 counties in Illinois. Seven populations in the southern one-third of the state are extant and three extirpated; nine could not be located. Population size ranged from 106 plants at the Richand County site to 611 at a Pope County site. All of the populations occupied an area of 75 m^sup 2^ or less. Flower production was not observed at any of the sites in 2002. The populations occurred on acid soils in a floodplain forest, in upland forests with north- and east-facing slopes, and a gravel wash of an intermittent stream.

INTRODUCTION

Stenanthium gramineum (Ker-Gwal.) Morong (grass-leaved lily) Liliaceae is a perennial herb that occurs on rocky slopes, at the base of cliffs, in meadows, rich woods, open thickets and along streams and railroads (Steyermark 1963; Mohlenbrock 1970, 1986; Gleason and Cronquist 1991; USDA, NRCS 2002). In the United States, it occurs in Pennsylvania west to Michigan, Illinois, Missouri, Arkansas and south to Texas and Florida. In Illinois, S. gramineum is historically known from 13 western and southern counties. It was first collected in Wayne County by Schneck in 1877 and by 2000, 19 populations had been reported (Jones 1963, Mohlenbrock and Ladd 1978, Biological Conservation Database 2002).

Herkert and Ebinger (2002) reported that S. gramineum, a state endangered species, was extant in five counties in Illinois. This study was prompted by the discovery of a previously unreported Richland County population and the observation of a Fayette County population last reported in 1943.

The objectives of this project were fourfold: 1) to visit all known and historic S. gramineum. sites in Illinois to verify those populations; 2) to record the number of individuals per population, the number of individuals per population that produced flowers, fruits, and seed, and the area occupied by each population; 3) to record aspect, topographic position, natural community, forest composition, percent canopy cover, associated species, and soil type; 4) to examine seed production.

METHODS

The distribution of Stenanthium in Illinois was determined by examining specimens from herbaria (ILL, ILLS, EIU, ISU, MWI, DEK, MOR, SIU, MO), consulting the Biological Conservation Database maintained by the Illinois Department of Natural Resources, and contacting many of the State's field botanists. Field searches were conducted for known locations of Stenanthium during June and July of 2002.

Locations were determined using GPS. The total number of plants, number of flowering plants, area (m^sup 2^) occupied by population, aspect, topographic position and percent canopy cover (determined by visual observation) were recorded. Voucher specimens were collected at sites where no specimens had been reported. Specimens were deposited in the herbarium of the Illinois Natural History Survey, Champaign, Illinois (ILLS).

Species and diameter were recorded for trees > or =10.0 cm dbh that occurred within a 11.28 m radius (0.04 ha) plot centered over each Stenanthium population. Number of individuals was recorded for large saplings (> or =2.5 cm dbh and or =50 cm tall and

RESULTS AND DISCUSSION

Grass-leaved lily was reported from 19 locations in 13 counties (Figure 1). Of that number, nine had herbarium specimens. Three of the herbarium records were dated from 1877-1883 and six were dated from 1920-1953. Herbarium records and literature searches could not confirm populations in Pike County (Jones 1963) or Union County (Mohlenbrock and Ladd 1978).

Several of the S. gramineum populations have been destroyed. A Pope County population was destroyed during a highway project, another Pope County population was extirpated by stream bank erosion, and a Jackson County population was flooded following construction of Lake Kinkaid. No field searches were conducted for historic populations in Macoupin, Pike, Richland, Union, and Wayne counties due to lack of specific location data.

Field searches determined that Stenanthium exists in six counties, Fayette, Gallatin, Johnson, Pope (two locations), Pulaski, and Richland (Figure 1). Of the populations reported prior to 1955, only the Fayette County population could be located, the forests of the other sites having been converted to row crops, pasture, industrial sites, or otherwise subjected to human disturbances. Of the seven extant populations, four are on United States Forest Service land, two are privately-owned, and one is owned by a community college.

The populations consisted of one or more colonies with each occupying an area no larger than 75 m^sup 2^(Table 1). The number of plants ranged from 106 in Richland County to 611 at Pope County site #1.

No flowering Stenanthium plants were observed in 2002. At the Richland County site, one flowering stem was observed in 2000 and four were observed in 2001 (Biological Conservation Database 2002). One flowering stem was observed at the Gallatin County site in 2001 and one decaying stem, presumably from 2001, was observed at Pope County site #1 in 2002. The lack of flower production in 2002 could be attributed to the irregularity of flowering exhibited by Stenanthium and/or the unusually hot, dry conditions that persisted throughout most of the summer (Steyermark 1963).