EM-A1gorithm as a too1 for structure analysis of stands of the common reed ( Phragmites australis)

27 r Ostendorp, W. and Möller, J., 1991. EM-algorithm as a tool for structure analysis of stands of the common reed (Phragmites australis). Ecol. Modelling, 53: 27-38. The frequency distributions of morphometric and mechanical properties of randomly sampled stalks of seven reed stands at Lake Constance-Untersee are analysed by the Estimation-Maximisation Algorithm. The aim was to look for composed (bimodal) distribution indicating at least two different stern types. In each stand, between one and nine parameters are found to give abimodal distribution. The two stern types are 'flowering shoots' and 'non-flowering shoots'. The means of nearly aB parameters investigated are different at the 1% level of significance. The flowerless shoots are identical with 'secondary shoots' and the flowering shoots refer to terminal (=' primary') shoots. The separation of stern types allows investigation of the stand structure and the influence upon it by 'rhizomeinternal' and 'external' factors in more detail.