Abstract: With theoretical and method ecological approach of numerical taxonomy,by selecting 8 relatively stable numerical characters in asexual propagation of Scirpus planiculmis in Songliao ecological area we have carried out the maximum synchronous branch classification for the investigation of the regularity in asexual propagation. A dendrogram of asexual propagation potency was established with maximum synchronous branch coefficients as numerical parameters and a developing level graph of asexual propagation characters in the matural propagation generations was drawn up on the basis of the total value of evolutionary steps. Thus the relativity between the ontogenesis of natural reproduction and the community competitive potency was unveiled. Based on the numerical parameters of leaped values in the asexual propagation of S. planiculmis,the key period of weed eradication was determined.

Key words: Scirpus planiculmis , Maximum synchronous branch classification, Asexual propagation potency, Community competitive potency, Evolutionary step, Dendrogram, Developing level graph