Can an Exotic Plant, Robinia pseudoacacia L., Be Removed from Riparian Ecosystems in Japan ?

Abstract

This study examined the rehabilitation of native riparian forests by removingan exotic plant, Robinia pseudoacacia L., which influences the biodiversity of riparian forests. In February 1997, allthe R. pseudoacacia canopy trees were cut down in an upstream riparian zone along the Arakawa River, while nativetrees in the sub-canopy and lower layer were left. After cutting, a mean of 49.5 sprouts, including root suckers, emerged per individual on stumps and horizontal roots. Root suckers emerged from horizontal roots located up to 11cm underground. The number of such sprouts, including root suckers, decreased yearly, and most died after five years.After cutting, the relative light intensity and mean openness increased rapidly, but returned to pre-cutting levels afterfive years with the growth of branches of the native riparian trees. These results suggest that it is possible to removeR. pseudoacacia trees from riparian ecosystems when they are mixed with native trees.