Vegetative phenology and growth of a facultatively deciduous bamboo in a monsoonal climate

Canopy closure, leaf flush, and ramet recruitment in Bambusa arnhemica, a semelparous, clumping bamboo from the Australian monsoonal tropics, were monitored monthly for 2.5 years at three sites along a flood gradient. Bambusa arnhemica was facultatively deciduous, remaining evergreen at a downslope riparian site but suffering total loss of canopy on a hillside for up to 4 mo during the dry season. Leaf flush was flexible, occurring after as little as 25 mm of rain at the onset of wet season, in response to unusual dry season storms, and apparently also in response to fire independent of rainfall. New culms emerged soon after leaf flush early in the wet season. Culm growth took place during the middle and late wet season, with peak elongation rates of 15-30 cm/day. Some growth continued into the dry season, mostly on branches and leaves of new culms at riparian sites. Not all culms completed elongation before the onset of the dry season, and those that did not were permanently stunted. The demands of culm elongation may limit the occurrence of bamboo in wet-dry climates to areas with predictable and sustained wet season rainfall, but the flexibility of branching and leaf processes facilitates coping with, and permits exploitation of less predictable pre- and postmonsoonal rains. The bamboo growth form and phenological patterns differ markedly from those of dicotyledonous trees and shrubs.