Invasion risk of clumping and running bamboo species in southeastern USA
Increasing attention has been focused on plant biomass as a potential source of fiber for industry and alternative energy. Considering biomass plantings require widespread cultivation on substantial acreage, prescreening prospective biomass species for invasion risk is necessary to balance potential economic benefits with environmental concern. There are as many as 1500 commercial applications of bamboo and currently many species are being considered as a feedstock source for paper production. Bamboo species are typically divided into running (leptomorph) and clumping (pachymorph) types based on the growth form of their rhizomes. Running bamboos in particular, share many ecological traits contributing to the establishment of non-native species, including high aboveground growth rates, low allocation to reproduction, and rapid vegetative propagation. We selected 40 bamboo species (22 clumping and 18 running) for evaluation using the predictive Australian weed risk assessment tool (WRA) modified for the U.S. We hypothesized that a higher proportion of running bamboos would score in the high-risk category than clumping species.
Results of the WRA revealed 72% of the running bamboos are a high risk for invasion and 17% are low risk. For clumping species, 5% evaluated were high risk and 82% were low risk for invasion. Results indicate that characteristics contributing to high invasion risk include climate suitability, naturalization history, and growth habit (clumping vs. running). Selection of species with the clumping growth habit for large-scale biomass production would be a precautionary approach to reducing the probability of new invaders in the US. Additionally, we recommend more research on the basic ecology (i.e. allelopathy, dispersal mechanisms, shade tolerance) of bamboo species of interest for biomass planting.