An Inexpensive Method to Identify the Elevation of Tidally Inundated Habitat in Coastal Wedands

Abstract

We explored the use of an inexpensive "vial" method to measure the elevations reached by a series of high tides, which included the highest tides of the year, at sites in four southern California wetlands, examined variation in the distribution and abundance of marsh, transition, and upland vegetation as a function of elevation, and assessed whether our measure of height of tidal inundation correlated with the distribution of these plants, permitting the use of vegetation <br />boundaries as a proxy for the height of tidal inundation. The potential effects of <br />factors unrelated to tidal inundation render elevational boundaries of native marsh plants unattractive as a general criterion for defining the upper edge of tidally influenced habitat. By contrast, both the upper limit of tidal inundation as measured by the vial method and the lower elevational limit of exotic grasses, such as Parapholis incurva, appears to be useful in delineating the upper edge of tidally influenced habitat. This elevation coincided with the highest spring tides and varied among sites in association with the extent of tidal muting. The vial method is a useful technique to identify sites of comparable tidal influence in restored and reference wetlands and can provide an early indication of tidal muting in restored wetlands.