Impacts of Nutrient Enrichment on Native and Non-Native Plants in Serpentine Soil

Serpentine soil, derived from serpentinite, California’s state rock, is characterized by its harsh nature - due to its low levels of essential nutrients and exceptionally high levels of toxic heavy metals.In California, serpentine soils are characterized by high levels of plant endemism and rarity. Plants occurring in serpentine soil exhibit extreme tolerance of harsh soil conditions, and are typically out-competed in ‘normal’ soils due to the cost associated with physiological specialization. Atmospheric nutrient deposition is contributing to a greater invasion of non-native grass species on serpentine soils, outcompeting the native species and threatening them with local extinction. Our greenhouse study aims to explore the impact of nutrient enrichment on four species of annual grasses and herbs - Festuca microstachys and Plantago erecta as natives, and Avena fatua and Bromus hordeaceus as non-natives - growing together under a competitive environment. Our experiment monitored survival, growth, flowering time, reproductive effort and biomass of each species under the addition of nitrogen, phosphorus, nitrogen + phosphorus, and a control treatment. Each treatment was carried out in a tray containing three individuals of each species, for a total of twelve plants per tray, and six replicates of each treatment, for a total of twenty-four trays, all of which were grown within a greenhouse setting to recreate natural climate conditions. In an era where climate change and pollution are of serious concern with respect to biodiversity conservation, a study investigating native and non-native plant interactions on serpentine soils would provide useful information on how a prime aspect of climate change, atmospheric deposition of nutrients, can influence the last refuge for many of California’s rare and endemic plants. Knowledge gained from this study could be used for better management of biodiverse serpentine habitats in California