2004. ESTUARIES 27(2) In press.
Changes in Saltmarsh Surface Elevation Due to Variability in
Evapotranspiration and Tidal Flooding
CYNTHIA H. PAQUETTE, KAREN L.
SUNDBERG, ROELOF M.J. BOUMANS, AND GAIL L. CHMURA
Abstract -- We examine the
potential for diurnal variation in elevation of saltmarsh surfaces as a source
of error in long-term experiments; errors particularly critical in high
precision studies that employ the surface elevation table (SET) as a means to
monitor elevations. The field study was carried out along the New Brunswick
coast of the Bay of Fundy in high and low zones at three marshes with different
tidal ranges. We employed a total of 16 benchmark pipes and controlled for daily
variability in evapotranspiration (ET), as well as timing of tidal flooding, two
factors that affect soil water storage, and consequently soil volume. In six of
nine trials we detected significant elevation change over periods as short as
five days. Marsh-wide averages ranged from 1.2 to 3.0 mm, greater than the
yearly increase in relative sea level in many regions. Wood Point marsh had the
highest tidal range, but lowest soil organic matter content, thus its soils had
the lowest compressibility and showed little sensitivity to ET during two of
three trials. Despite this, the average change in elevation in Wood Point high
marsh stations was 4.0 mm during the last trial. Greater differences later in
the growing season (while temperature changes were minor) at Wood Point and
another site suggest that plant transpiration drove changes in water storage at
those sites. However, significantly greater differences in elevation with lower
plant cover in the third marsh suggests that evaporation drove changes in water
storage there. We conclude that surface elevation change due to ET should be of
greatest concern to SET users in temperate regions where there are large changes
in plant biomass and variable temperatures. Variation due to plant transpiration
could be reduced if yearly monitoring is scheduled before the start of the
growing season.
© 2003. Estuarine Research Federation.