Harvesting Aerial Shoots of Zizania latifolia at Different Growth Stages: Effects on Belowground Biomass, Regrowth, and Rhizome Morphology

ABSTRACT

Zizania latifolia Turcz., wild rice, is a very productive and invasive plant, and its growth sometimes needs to be controlled. We conducted cutting experiments to elucidate the effects of cutting when it was done at different growth stages of Z. latifolia. The aerial organs were cut 10 cm above the water on 15 May, 15 July, and 15 September 2004, with and without covering of the re-growing shoots. Compared with the control, cutting treatments decreased leaf production, shoot height, and shoot density. The aboveground net primary production was reduced 14% and 16% by May and September cutting, respectively, whereas the stand cut in July did not differ from the control. On the other hand, belowground biomasses at the end of the growth season were decreased 28%, 17%, and 23% by the May, July, and September cuttings, respectively. Early cutting sufficiently suppressed the belowground biomass, while cutting in September drastically reduced the number of basal buds. Our study identified two weak seasons of Z. latifolia—one when substantial self-thinning of shoots occurs and the other when the plant is mature (before senescence), the time of significant growth of rhizomes.