Impact of shading and cutting on the demography and composition of mimosa pudica L., a ligneous weed species of tropical grassland

The aim of the study was to evaluate the potential impact of grazing on the control of Mimosa pudica, a ligneous weed pecies that invades grasslands in French Guiana. Three experiments were conducted in a glasshouse to test the potential impact of : (i) shading by testing different photsynthetically Active Radiation (PAR) fluxes on seedlings and (ii)cutting of juveniles, at three stages of development, on their survival flowering rate and nutritive value as leasured by the mass: length ratio of stems and by branching process. A significant mortality rate (0-20) was obtained only for seedlings at the cotyledon stage when the PAR flux was reduced proportionately by 0.83.Shading reduced both flowering rate and mass: length ratio of stems. For seedlings at the cotyledon stage, the flowering rate decreased from 0.85 for the control to zero for the low light treatment (0.13 of PAR flux of the control treatment). The mass: length ratio of stems of seedlings in the low light treatment was reduced to 0.20 of that of control seedlings, at the fifth-leaf stage. Cutting treatment had no effect on mortality of juvenile plants whatever the size of the juvenile plant. The proportion of juvenile plants flowering was high for all cutting treatments. It is suggested that regular, but no continuous grazing, could maintain a dense sward to limit recruitment by seedling establishment and seed production, and maintain branched and juvenile plants with a high-nutritive value at the seedling stage.