Distribution and Invasion Potential of Limonium ramosissimum subsp. provinciale in San Francisco Estuary Salt Marshes

Gavin Archbald,Katharyn Boyer

doi:10.15447/sfews.2014v12iss2art6

Abstract

Non-native sea lavenders (Limonium spp.) are invasive in salt marshes of southern California and were first documented in the San Francisco Estuary (the estuary) in 2007. In this study, we mapped distributions of L. ramosissimum subsp. provinciale (LIRA) and L. duriusculum within the estuary and investigated how the invasion potential of the more common species, LIRA, varies with elevation and edaphic conditions. We contacted colleagues and conducted field searches to find and then map sea lavender populations. In addition, we measured LIRA’s elevational range at three salt marshes. Across this range we measured (1) soil properties: salinity, moisture, bulk density, and texture; and (2) indicators of invasion potential: LIRA size, seed production, percent cover, spread (over 1 year), recruitment, and competition with native halophytes (over 6 months). We found LIRA in 15,144 m2 of upper salt marsh habitat in central and south San Francisco bays and L. duriusculum in 511 m2 in Richardson and San Pablo bays. LIRA was distributed from mean high water (MHW) to 0.42 m above mean higher high water (MHHW). In both spring and summer, soil moisture and salinity were lowest at higher elevations within LIRA’s range, which corresponded with greater rosette size, inflorescence and seed production (up to 17,400 seeds per plant), percent cover, and recruitment. LIRA cover increased on average by 11% in 1 year across marshes and elevations. Cover of the native halophytes Salicornia pacifica, Jaumea carnosa, and Distichlis spicata declined significantly at all elevations if LIRA were present in plots (over a 6-month, fall–winter period). Results suggest LIRA’s invasion potential is highest above MHHW where salinity and moisture are lower, but that LIRA competes with native plants from MHW to above MHHW. We recommend removal efforts with emphasis on the salt marsh-terrestrial ecotone where LIRA seed output is highest.

Highlights

Invasive plants can be harmful to native species and ecosystem functions (Vitousek et al 1997; D’Antonio et al 2004), making early identification, assessment, and response to new plant invasions important for ecosystem management (Chornesky and Randall 2003; Ielmini and Ramos 2003)
Several of these, including L. ramosissimum (Algerian sea lavender), L. duriusculum and L. binervosum have invaded estuarine wetlands on the West Coast of North America from Santa Barbara County south into Baja California (Barbour et al 2007; COCH c2007). These species were likely introduced through the horticultural trade (Hubbard and Page 1997), and L. ramosissimum and L. duriusculum are highly invasive in salt marsh habitats in central and southern California
L. ramosissimum subsp. provinciale (LIRA) was found in far greater abundance (30:1 by area) with populations ranging in size from a single plant to 4,357 m2, while LIDU populations ranged in size from a few plants to about 300 m2

Summary

Introduction

Invasive plants can be harmful to native species and ecosystem functions (Vitousek et al 1997; D’Antonio et al 2004), making early identification, assessment, and response to new plant invasions important for ecosystem management (Chornesky and Randall 2003; Ielmini and Ramos 2003). As new non-native plant species establish, it is important to understand their ecology and potential for spread so that resources may be prioritized toward controlling species that pose the greatest threat To this end, land managers and scientists recommend describing the current spatial extent of introduced species and evaluating how invasion potential is influenced by abiotic environmental factors that vary across landscapes (Grossinger et al 1998; Byers et al 2002; Robison 2009). Several of these, including L. ramosissimum (Algerian sea lavender), L. duriusculum (no common name) and L. binervosum (rock sea lavender) have invaded estuarine wetlands on the West Coast of North America from Santa Barbara County south into Baja California (Barbour et al 2007; COCH c2007) These species were likely introduced through the horticultural trade (Hubbard and Page 1997), and L. ramosissimum and L. duriusculum are highly invasive in salt marsh habitats in central and southern California

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Conclusion