Status of the Amargosa niterwort (Amaranthaceae) in California and Nevada

Abstract

The Amargosa niterwort is a narrow endemic restricted to alkali wetlands of the northern Mojave Desert in Inyo County, California and Nye County, Nevada. Groundwater pumping and subsequent hydrological alteration within the Amargosa groundwater basin has been identified as the most significant threat to the long-term persistence of the species. Parallel monitoring programs were established in California (2010) and Nevada (2014) to establish baseline trends in abundance, measured as ramet (stem) number, and to aid in determining management actions that are needed to ensure the long-term viability of populations. Monitoring in California shows significant variation in abundance between years; however, there are consistent trends, indicating that factors influencing increase or decrease in abundance is similar across the population. However, this pattern is not shared in Nevada, where following a sharp decline between 2014 and 2015 the population has remained relatively stable. Two of the three Nevada macroplots are downstream from Crystal Reservoir and are likely influenced by discharge from the reservoir including periodic water releases and leakage from the earthen dam. Significant increases and decreases in abundance within macroplots are not correlated with climate variables including precipitation, thus it is important to understand how groundwater flow and spring discharge impacts abundance of plants within and between populations.