SEASONAL NITROGEN DYNAMICS IN REED BEDS (PHRAGMITES-AUSTRALIS (CAV) TRIN-EX-STEUDEL) IN RELATION TO PRODUCTIVITY

Shoot biomass and nitrogen, accumulated within above-ground plant biom ass in autumn, correlate with nitrogen availability indicated by nitro gen content (% DM) of several shoot parts during the height of the gro wth period. A higher nitrogen percentage of the shoots is correlated w ith a higher shoot loss and subsequent substitution by branching and t illering during and continuing toward the end of the growth period. A delayed switch from the vegetative to the generative phase reduces the translocation of reserve material to the rhizome. Increasing nitrogen load is at least one of the factors causing instability and reed-belt decline.