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

Abstract

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 stem types. In each stand, between one and nine parameters are found to give a bimodal distribution. The two stem types are ‘flowering shoots’ and ‘non-flowering shoots’. The means of nearly all 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 stem types allows investigation of the stand structure and the influence upon it by ‘rhizome-internal’ and ‘external’ factors in more detail.