Sustained enhancement of productivity of edible culms of Sasa kurilenses in response to repeated annual human harvesting in a northern forest in Japan

Abstract

ABSTRACT Sasa kurilensis is a popular wild edible bamboo in Japan. Productivity (density) of edible culms can be enhanced by human harvesting, but we know little about how long the enhanced productivity is sustained after repeated annual harvesting. Here, demography and productivity of this edible bamboo were examined in field experiments conducted following experimental harvesting of edible bamboo culms for three years. Compared to the productivity of wild edible bamboo culms in the control plots, which were maintained with no human disturbance, productivity in the harvest-treatment plots (harvest conducted annually) was always greater in years following harvesting. In addition, food quality tests for boiled, edible bamboo culms collected from both harvest-treatment and control plots showed that there was little effect of harvesting on food quality of edible bamboo culms but that harvesting might degrade the favorability of food texture of boiled edible bamboo culms. Subsequent surveys demonstrated that the enhanced productivity may occur independently of demography (density) of old culms and that the enhanced productivity effect disappeared two years after the harvest treatment was stopped. These results indicate that repeated, annual harvesting is necessary to promote productivity of edible bamboo culms. These interesting but counterintuitive results can be explained by over-compensatory growth by dwarf bamboo, which respond by producing new photosynthetic organs to compensate for tissue loss by human harvesting. Thus, effective induction of compensatory growth may be a key factor in increasing the production of wild edible plants.