Characterization and quantitative assessment of interspecific and intraspecific penetration of below‐ground vegetation by cogongrass ( Imperata cylindrica (L.) Beauv.) rhizomes

Cogongrass ( Imperata cylindrica (L.) Beauv.), an invasive C4 perennial grass, negatively influences native plant communities by forming dense monotypic stands that alter ecosystem properties and lower local species diversity. A hypothesized mechanism by which cogongrass achieves competitive dominance is a novel use of below‐ground vegetative disturbance of neighboring vegetation (i.e. puncturing). However, very little empirical evidence is found in the peer‐reviewed literature to quantify this phenomenon, much less establish it as a true form of competitive interaction. The present field study was conducted to quantify the occurrence of rhizome‐mediated, below‐ground vegetative penetration, both interspecifically and intraspecifically, document how this phenomenon is influenced by spatial location relative to the cogongrass stand, and determine the role that above‐ground and below‐ground biomass might have in the process. Analyses of 100 sod samples indicated that rhizome‐mediated, below‐ground vegetative penetration is a much larger intraspecific phenomenon than an interspecific one. The data also strongly suggested spatial location as a significant factor, with most penetrations occurring in the interior of a cogongrass stand as opposed to the advancing border. Significant correlations between rhizome‐mediated, below‐ground vegetative penetration and above‐ground cogongrass biomass were found in the overall plot analysis and most strongly in the advancing border of the cogongrass stands.