Effects of different nutrient levels on phenotypic characteristics and biomass allocation of the invasive plant Cenchrus pauciflorus

Cenchrus pauciflorus is an invasive agricultural species in China. Nutrient availability significantly affects plant growth and invasiveness. Understanding the responses of C. pauciflorus to different nutrients is useful for analyzing invasion mechanisms and providing a scientific basis for prevention and control. We tested the effects of five nutrient treatments, that is, 25%, 50%, 75%, 100%, and 200% standard Hoagland nutrient solution on the phenotypic characteristics, biomass accumulation, biomass allocation, and allometric growth patterns of C. pauciflorus in a pot experiment. The plant height, effective tillering number, effective spikelet number, and total spikelet number of C. pauciflorus increased with increasing nutrient content, while total tillering number first increased and then decreased with increasing nutrient content. The number of leaves was the lowest in the 25% treatment. This was significantly lower than that in the other treatments at a level of 0.05, and there were no significant differences among the other treatments. The leaf, stem, fruit, and aboveground biomasses of C. pauciflorus increased with nutrient enrichment. Under all treatments, the biomass allocation ratio of C. pauciflorus was characterized by fruit biomass allocation ratio > stem biomass allocation ratio > leaf biomass allocation ratio and fruit biomass allocation ratio. The leaf biomass, stem biomass, and fruit biomass of C. pauciflorus showed isometric growth, less than one allometric growth, and greater than one allometric growth relationships, respectively, in relation to aboveground biomass. In conclusion, nutrient-rich environments promote the growth and invasion of C. pauciflorus. Adjusting the biomass allocation and allometric growth structure may be important ecological strategies for adaptation to various nutrient habitats during the invasion and expansion processes.