Conversion of an abandoned bamboo forest to a broadleaf forest by application of herbicide and culm cutting

Abstract

Bamboo forest expansion is a well-known problem, not only in Phyllostachys pubescens but also in P. bambusoides. The conversion of abandoned bamboo groves to broadleaf forests is desirable for ecosystem function. We first investigated the effects of sodium chlorate (Chlorate S) on plant germination following disturbance by conducting a three-month sowing test. Next, we established three plots in an abandoned P. bambusoides stand in Chiba Prefecture, Japan, in May 2013 to compare the changes in vegetation over 5 years. To prepare the plots, clear-cutting of bamboo culms was carried out in all plots and chemical treatment was applied to two for examining the effects of chemical treatment on revegetation. The results of the sowing test showed the presence or absence of the chemical had no significant effect on the number of germinated species, although the response to the chemical was species-dependent. The density and average diameter of regenerated bamboo culms were lower in the chemically-treated plots than in the untreated plot. In the chemically-treated plots, bamboo culm regeneration was suppressed after September 2013, whereas other plants grew abundantly. Regenerated bamboos thrived in the non-treated plot until October 2014, after which other plants increased. By the third year, broadleaf trees were growing in all plots. The chemical treatment did not almost affect the growth of seedling-derived trees adversely and few differences in species composition emerged between treated plots and the untreated plot. Our study demonstrated that it is essential to leave as many woody species as possible when clear-cutting culms and that chemical treatment can also be an effective method for forest conversion.