Assessment of residual herbicides applied to invasive bamboos and their effects on the vegetation of bamboo forests

Abstract

We applied select herbicides, chlorate and glyphosate, upon invasive bamboo forests and then monitored the herbicidal residue present within the fallen leaves, fine roots, soil, and stream water of the forests in question. In addition, we examined the effects of herbicides on seed germination and the understory vegetation within the bamboo forests studied. The herbicide chlorate nearly degraded completely within a one month period within the soil, whereas the herbicide glyphosate was slightly detected at low levels within the bamboo forest leaf fall, fine roots, and the soil. Simultaneously, none of the two applied herbicides were detected within nearby stream water during the assessment period. The possibility of herbicidal outflow from the application area is considered to be low. Among three tree species which are widespread within clearcutting sites, or the understory of bamboo forests, the germination rate of Zanthoxylum ailanthoides significantly decreased following the application of the herbicide chlorate. Furthermore, the understory vegetation within the bamboo forest was additionally surveyed in order to assess the effects of glyphosate application upon the vegetation. Following the application, vegetation coverage increased rapidly, reaching nearly double the amount of prior coverage before application across number of species, which included pioneer trees and herbs. It is assumed that glyphosate application caused effects akin to clearcutting via killing bamboos, since similar vegetation dynamics were reported within clearcutting sites. Taking all factors into account, the negative environmental impact of the select herbicides applied to bamboo forests should be limited in scope.