Gregarious flowering of bamboo opens a red:far red window of opportunity for forest regeneration

GIORDANO C. V.; SÁNCHEZ R. A.; AUSTIN A. T.

Memphis, USA

Congreso; 91st Annual Meeting of the Ecological Society of America; 2006

Gregarious flowering of understorey bamboo species, which flowers a single time and then dies, occurs in temperate, subtropical and tropical forests around the world. Explosions of granviore populations and threats to key specialist herbivores have been linked to these events, but long intervals between flowering events, which range from 12 to 120 years, make it difficult to evaluate the importance of these events for ecosystem processes.  We examined the consequences of a massive flowering event of over 200,000 hectares of bamboo (Chusquea culeou) in native temperate forests of Patagonia, Argentina, on the germination and growth of overstorey forest trees. The age structure of this forest correlates with registered flowering events of bamboo, and germination of native southern beech (Nothofagus obliqua) was significantly positively correlated with increased red:far red ratios (P<0.001) generated by the massive death of the understorey. Manipulative experiments with filters to alter red:far red ratios reversed the germination response (P<0.05). Secondarily, the combination of increased PAR and red:far red ratios in microsites of bamboo dieback affected the growth and mortality response of emerged seedlings. Through changes in light quality and quantity, the gregarious flowering of the understorey bamboo opened a window of opportunity for germination and survival of overstorey species, demonstrating that this infrequent ecological phenomenon of massive flowering and senescence is a primary control for regeneration of this native forest ecosystem.