Fire Effects on Canebrakes

Canebrakes are an early-succession community that are maintained by and thrive, in a large part, as a result of periodic fire.  In addition to historic lightning-induced fires, canebrakes were maintained by Native Americans through the use of prescribed fire every 7 – 10 years (Platt and Brantley 1997; Barden 1997).  Also, large canebrakes often flourished in abandoned Native American agricultural fields, which likely accounts for many of the historical canebrake descriptions (Platt and Brantley 1997; Brantley and Platt 2001).  Presently, the suppression of fire is one of several purported reasons for the decline of canebrakes (Hughes 1966; Brantley and Platt 2001).

Cane is adapted to fire disturbance in that it produces heavy rhizomes.  These underground stems serve as aerial culm support, food reserves, and asexual recruitment beyond the reach of surface fires (Hughes 1966).   Above-ground vegetation is highly flammable and quickly burned by fires, but new culm growth from these rhizomes is swift due to food stored during the summer and early fall (Hughes 1966; Platt and Brantley 1997).  This strategy is effective in out-competing other woody vegetation (Hughes 1966).  Post-fire culm regeneration is rapid (up to 1½” per 24 hrs) and stands tend to remain even-aged 2-3 years post-fire disturbance, becoming impenetrable, uneven-aged thickets after several years (Hughes 1966; Platt and Brantley 1997).  The average canebrake stand age will remain about 3-4 years however individual Arundinaria stems may reach 10 years in age (Hughes 1966).  After about 10 years of protection from fire, canebrakes reach maturity and are succeeded by other woody vegetation (Brantley and Platt 2001). 

Giant cane, like many other species of bamboo, displays mast flowering (synchronized flowering among multiple individuals at intermittent intervals) and is semelparous (flower/fruit once and then die).  This trait of bamboos is somewhat unusual in that most masting species are iteroparous (flower/fruit multiple times) (Silverton 1980).  Further, the masting cycle of bamboo is considerably delayed (up to over 50 years) compared to most other mast producing species (3-7 years) (Platt and Brantley 1997; Keeley and Bond 1999).  Therefore, once a cohort of seed has germinated and established into individual plants, canebrakes are heavily dependent upon vegetative reproduction for stand development. Without a seed crop, initial establishment of giant cane can be accomplished through planting of culms propagated from rhizomes (Zaczek et al. 2004).  Masting, in giant cane and in general, has often been considered to be a “predator satiation” mechanism, i.e. flowering irregularly so that seed predators are kept at low enough levels not to destroy a mast fruit (Janzen 1976; Keeley and Bond 1999).  However, the mast flowering, semelparity, delayed reproduction, and gregarious growing habits of bamboo have been linked to high-intensity fires (Keeley and Bond 1999; but see Saha and Rowe 2001).  Delayed reproduction and semelparity can produce high levels of fuel, and thick stands generate continuous fuel loads, both encouraging fire and consequently eliminating other woody species (Keeley and Bond 1999).  Mast flowering synchronizes seed dispersal and seedling recruitment in these canopy gaps and semelparity concentrates the breeding effort to an optimum time (Keeley and Bond 1999).  The specific factors that induce flowering however are elusive, but appear to be a combination of external (temperature, drought) and internal (genetic) controls (Janzen 1976, Platt and Brantley 1997)