The Phenology and Environmental Conditions of a Declining Population of Streptanthus Bracteatus in Eisenhower Park, Bexar County, Texas
Streptanthus bracteatus is a rare winter annual endemic to the Edward's Plateau in Central Texas. The population located in Eisenhower Park, Bexar County, Texas is at great risk of extinction due to its small population size. This study collected two years of demographic data on the Eisenhower Park population and characterized the environmental conditions impacting the success of the plant over the 2016-2017 and 2017-2018 growing seasons. The 2016-2017 growing season was significantly more productive than the 2017-2018 growing season, with plants exhibiting greater growth and reproductive capacity than the following season. Germination was correlated with mean monthly temperature and precipitation in the three days prior to the sampling date. Mortality and plant height were correlated to both temperature and precipitation. Number of flowers produced was correlated to the maximum daily temperature. Both plant size and silique production were found to be significantly greater in plants that exhibited powdery mildew growth. The demographic and environmental data collected in this study can be added to future data to produce population models, which can inform species management plans.