Nährstoffkreisläufe und Nährstoffakkumulationen in Seeufer-Schilfröhrichten : am Beispiel des Bodensee-Untersees

Abstract

The carbon-, nitrogen- and phosphorus-budgets of the lakeshore reedbelts (Phragmitetum typicum) of Lake Constance-Untersee have been estimated using own measurements and literature data from other areas and from other fenland and littoral communities. The main objective was to estimate the deposition rates. Pool size, input, output and transfer to the 'non-available' fraction (Phragmites peat) can be taken from table 1. Nitrogen turnover in these reedbelts is of the same order of magnitude as in paddy fields but much less than in a tidal Spartina marsh. The major N sources were found to be the groundwater inflow from agricultural areas in the surrounding and the rainfall; the main P source was the detritical input by the inflow from the lake into the reeds. The N and P input from the atmosphere should be sufficient to meet 2/3 of the nutrient requirements of a Phragmites stand. The most important N sink was the denitrification; no assumptions could be made about the P sinks (except the transfer to the peat layer). The yearly deposition of organic matter amounts to 4%, of nitrogen and phosphorus to 21% and to 36%, respectively, Df the total input. The comparable high deposition rates of nitrogen are presumably due to the efficient transfer of microbially bound N to ligno-proteins in the humic fraction, and phosphorus is fixed as insoluble inositol-phosphate and in stable Fe-P-humic acidcomplexes. In terms of the actual pool size a doubling of the quantity of Phragmites peat should take approximatly 200 years.If winter cutting of the dead reed stalks is conducted as a measure for reedbelt maintenance, an additional yearly output of 10% of the organic matter pool, 2.7% of the N pool, and 1.9% of the P pool can be expected.