Enegry Value, Elemental Composition, and Productivity of Belowground Biomass of A Juncus Tidal Marsh

Belowground standing crop of a Juncus roemerianus marsh in Mississippi ranged from 9.7 to 12.4 kg dry wt/m 2 with the peak biomass occurring in April. Annual productivity estimated from expected maximum minus expected minimum biomass fitted into a periodic regression model was 1.36 kg/m 2 . Ninety—four percent of the productivity was within the top 20 cm indicating that the bulk of the materials found beyond this depth consisted of dead tissues. Energy, carbon, hydrogen, nitrogen, and phosphorus contents of belowground materials did not vary significantly during the year, but patterns of differences in samples taken from different depths were evident. The productivity of belowground materials in Juncus marshes is comparable with aboveground productions reported in the literature with respect to dry biomass. The probability that large portions of the underground production enter the aqueous system and become incorporated in estuarine energetics merits further consideration.