Population biology and disturbance ecology of a native north American bamboo (Arundinaria gigantea)

This dissertation explores effects of windstorm and fire disturbances on the clonal and reproductive biology of cane (Arundinaria gigantea Muhl., Poaceae). In this collection of studies, multiple disturbances interact in complex ways, and some interactions appear only after a substantial lag. One implication of this research is that multiple, interacting disturbances might strongly influence the boundary between monodominant and species-rich plant communities. Cane is the only bamboo native to the United States, and once covered vast areas of bottomlands in the southeastern U.S. in monodominant stands called “canebrakes.” The study took place on the Buckhorn Wildlife Management Area in Tensas Parish of northeastern Louisiana, in the Mississippi alluvial valley. Here in 2000 a tornado blew down a large swath of bottomland hardwood forest. The four-year experimental study focused on the effects of windstorm and prescribed fire on cane ramet dynamics, reproduction and regeneration from seed. The effect on cane of a large windstorm-generated gap is accelerated new ramet production and increased ramet density. Cane spreads continually, albeit irregularly. This suggests that cane stands might shift location over time as small forest gaps open and close. The effects of fire on cane are complex, and some may be lasting. In the large wind-generated forest gap, populations of cane ramets grow faster for having been burned. Forest-grown ramet populations decline in the year of fires, but growth rates rebound the next year. Unburned populations decline during the study’s final year, but previously burned populations do not, suggesting that fire one year might impart resistance to shocks one or more years later. The dissertation proposes how a sequence of windstorm and fire disturbances might promote natural canebrake formation. The counterpoint is that without periodic disturbances, cane ramet populations decline. The dissertation explores cane reproductive ecology and regeneration, and discusses three critical stages: seed production, germination and seedling establishment. Cane seeds and seedlings appear to germinate and survive most frequently on sites receiving partial sunlight with a layer of leaf litter. The final chapter describes how these experimental results inform cane restoration, and suggests three pathways by which cane restoration might be achieved