A forest set to a biological clock
In the dense understory of Chile's Valdivian temperate rainforest, a species of native bamboo, Chusquea quila, follows a remarkable life cycle. This is not an annual event. Instead, vast populations of this bamboo flower in unison, an event known as gregarious or mast flowering, only once every 15 to 70 years. After this single, massive reproductive effort, the parent plants die. This synchronous bloom and subsequent death is an evolutionary strategy which floods the ecosystem with an enormous quantity of seeds—up to 50 million per hectare—overwhelming seed predators and ensuring some will survive to germinate.
The trigger for this synchronous event is not fully understood, but it appears to be controlled by a kind of internal genetic clock. Regardless of age or location, all plants derived from the same ancestral stock will flower at the same time. This creates a dramatic and widespread ecological pulse. Following the mass seeding, the dense bamboo thickets, known as quilantales, die off, creating large gaps in the forest understory and drastically altering light conditions on the forest floor for years. The next generation of Chusquea quila takes about five years to grow over two meters high, slowly re-establishing the dense undergrowth.