Horizontal distribution of stolons of a temperate lianaWisteria floribunda DC. and its ecological significance

The spatial distribution of stolons ofWisteria floribunda DC. was investigated, and the ecological significance of clonal growth of this temperate liana is discussed. The study plot (0.15 ha) was located in a secondary deciduous broad-leaved forest dominated byQuercus serrata in central Japan. The tree canopy was almost closed with a mean openness of 4.2%.W. floribunda was dominant among lianas accounting for 86% of their total basal area.W. floribunda stolons of three individuals branched numerous times and intersected among individuals, and showed a large horizontal “web-like” extension on the ground. The total length of stolons was 66.0, 260.2, and 310.6 m, respectively, for each individual. A mean of 25 ramets were established on stolons per individual, and one-third of the ramets obtained a host tree. These results suggested that the expansion of stolons was effective in obtaining host trees forW. floribunda individuals. On the other hand, clonal growth ofW. floribunda did not always contribute to vertical growth of ramets in the study forest, since few ramets reached the forest canopy. Lack of sub-canopy trees in this forest appeared to constrain the vertical growth ofW. floribunda ramets, since sub-canopy trees are thought to bridge lianas from smaller trees to canopy trees.