Ecology of the Endangered Species Solidago shortii. I. Geography, Populations, and Physical Habitat

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Abstract
Solidago shortii T. and G. (Asteraceae) is endemic to a 12.2-km2 area in the Eden Shale Belt in Fleming, Nicholas, the Robertson counties, Kentucky [USA]. It was extirpated from the type locality on Rock Island at the Falls of the Ohio River in Louisville, Jefferson County, Kentucky, apparently over 100 years ago. Approximately 73,000 stems occur at 13 population sites, which are in various stages of succession from open glades and glade-like areas to fairly dense redcedar and hardwood thickets or woodlands. Some of the sites have remained relatively stable for at least 50 years, while others have undergone marked successional changes. Solidago shortii grows in a range of light environments from full sun to fairly dense shade, and on several geologic formation and soil series. The soils are not atypical in amounts of major nutrients and organic matter, pH, or texture. Sixty-two percent of 934 soil depth measurements taken at the 13 sites were 25 cm or less, but 17% were greater than 50 cm. Although moisture content at the 5-10-cm soil depth zone, where most of the roots of S. shortii occur, frequently drops below the permanent wilting percentage in summer, established plants do not wilt because some roots extend 50 cm or more into cracks in the rocky soil. A conceptual model of the successional relationships of S. shortii was developed based on extensive field observations and on examinations of USDA aerial photographs taken in 1937, 1949, 1973 and 1985.