Limonium ramosissimum effects on native salt marsh communities in a changing environment

A recently recognized invader, Algerian sea lavender (putatively Limonium ramosissimum ssp. provinciate, LIRA) is spreading within and among marshes in the San Francisco Estuary (SFE) and appears to be doing so at the expense of native species. In this study, we considered the plant???s future distribution and potential for spread in relation to inundation and nitrogen (N), as both are expected to increase in coming years. We compared LIRA to a common native halophyte with a similar growth range, Jaumea carnosa (JACA), in their above and belowground biomass responses to two inundation levels (high and low within the current elevational range) and N enrichment (ambient and enriched) in both the field (two marshes in south SFE) and greenhouse (Romberg Tiburon\ud Center, San Francisco State University). Overall, we found that LIRA has reduced growth and reproduction at lower elevations within its current elevational range, but LIRA percent cover significantly increased with added N across elevations at one of the marshes. In contrast, JACA generally performed better at lower elevations and did not benefit from increased N supply. Our findings suggest that increased N availability will favor spread of LIRA at the expense of native JACA. In general, we expect increased inundation resulting from sea level rise to lead all marsh plant species to shift up-slope and in urban estuaries\ud bordered by development, so there will be limited space available. Our results suggest available space for LIRA will decline faster than it will for JACA due to the native's better performance at lower elevations. However, we also found that greater N supply can, in part, ameliorate negative effects of inundation on LIRA as well as promote its growth and spread at higher elevations. Further, we provide evidence that LIRA may reduce salinity and moisture in soils where it grows, suggesting that it may actively reduce these stressors at low elevations to its own benefit