Field studies on the breakdown of Nuphar lutea (L.)SM. (Nymphaeaceae), and a comparison of three mathematical models for organic weight loss

Abstract

Aspects of the decomposition of the aquatic macrophyte Nuphar lutea (L.)Sm. were studied using the litter bag method in the field. The organic weight loss during breakdown was described by means of 1 simple and 2 composite exponential models. The nitrogen, phosphorus and potassium concentrations of the remaining detritus were analysed. The composite exponential models fitted the decay data better than the “simple exponential function”. However, it was difficult to interpret the individual estimates of the composite exponential models in terms of overall decay. The patterns of organic weight loss and nutrient dynamics of decomposing Nuphar lutea depended on which part of the plant was being studied. In general, the aboveground plant parts showed a faster organic weight loss and a faster nutrient release than the underground structures. The breakdown of Nuphar lutea leaves was considerably faster in summer than in autumn. The organic weight loss and nutrient dynamics of the decomposing leaves were influenced by the trophic status of the system. Particularly in acid moorland pool the breakdown of the leaves was relatively slow when compared to that of an eutrophicated system and an alkaline oxbow lake. The effect of the litter bag mesh size (0.27 and 0.78 mm) on the breakdown of the leaves was relatively small.