Production of Coastal Louisiana Marsh Plants Calculated from Phenometric Techniques

Abstract

Production and mortality of six marsh macrophytes were measured in Louisiana, USA using phenometric methods. The Williams-Murdoch technique estimates annual production from measurements of individual culm height, mass, growth, and longevity. Annual mortality was estimated from bimonthly field measurements of culm height, mass, and death rate as a function of height, and density. Annual production estimates averaged 1.8 times higher than annual mortality estimates although in a steady-state system the rates should be about equal. A probable and correctable reason for the discrepancy is discussed. These estimates are higher than those calculated from Smalley's method but lower than those obtained from the Wiegert-Evans paired-plot technique. The validity of various techniques as applied to wetlands is discussed.

Juncus roemerianus production and decomposition along gradients of salinity and hydroperiod

“…However, all marshes have not yielded like results. Hopkinson et al (1980) estimated ANPP of J. roemerianus leaves in a Louisiana marsh as 3295 g m-2 yr-' using the Williams & Murdoch method. Gallagher et al (1980) estimated ANPP of a stand in Georgia ranging from 1500 to 2800 g m-'…”

“…They analyzed the results of changes in height of 92 tagged leaves in the context of harvested biomass to derive production and senescence rates in a North Carolina marsh. Their technique has been used by others (Hopkinson et al 1980). As the detritus food web is considered of great importance to marsh ecosystems, decomposition studies of marsh plants, especially with 'litter bags', have also been widely conducted (Brinson et al 1981, Christian 1984.…”

Salt Marsh Primary Production and Its Responses to Relative Sea Level and Nutrients in Estuaries at Plum Island, Massachusetts, and North Inlet, South Carolina, USA

“…This may be due to the low signal-to-noise ratio of the harvest method. In contrast to the census of fixed populations of S. alterniflora, the harvest method (Smalley, 1958;Wiegert and Evans, 1964) is subject to random errors of spatial variation in biomass density (Singh et al, 1984) of S. patens is 1.6 to 3 times higher than that of the more robust S. alterniflora (Hopkinson et al, 1978(Hopkinson et al, , 1980.…”

Marsh plants mediate the influence of nitrogen fertilization on degradation of oil from the Deepwater Horizon spill

“…Collected soil was cut 1:2 with carbon-free sand in order to reduce the contribution to respiration from soil organic matter while maintaining a realistic soil microbial community. The plants were allowed to establish and grow under the same conditions for 8 months, at which time stem densities approximated those in Gulf Coast marshes (Hopkinson et al 1980). Surface porewater wells were constructed from 20-ml syringes, that were perforated, covered with window screen and implanted 10 cm deep in the soil, so that porewater from 0 to 10 cm could be examined to provide information about the geochemistry of the microenvironment where the oil was deposited.…”