Productivity and nutrient content of Juncus kraussii in an estuarine marsh in south-western Australia



Juncus kraussii, which is the dominant emergent macrophyte in the marshes of the Blackwood River Estuary, has an estimated net above-ground production there of 0.3 to 1.3 kg dry weight m-2 yr-1. A high standing crop of live culms is present throughout the year and dead material generally exceeds live. New culms are produced throughout the year, but especially during the warm season. Growth and senescence of culms also occurs throughout the year although there is evidence for increased growth in the warm season.

Concentrations of nitrogen and phosphorus are given on a per g dry weight and per m2 basis. Some 60% of the nitrogen and 50% of the phosphorus remain in the dead culm material, the remainder being retranslocated. Sodium and, especially, potassium are readily retranslocated during senescence, but calcium and magnesium are much less mobile.