Biennial variation in production of new shoots in groves of the giant bamboo Phyllostachys pubescens in Sichuan, China

Abstract

(1) The dynamics of vegetative reproduction in the giant bamboo, Phyllostachys pubescens, at the Nature Reserve of Jinyun Mountain, Chongqing, Subtropical China, are described for a period of 20 years. (2) Production of new bamboo shoots fluctuated significantly among years. In 'good' years, the number and size of new shoots emerging and surviving in the bamboo groves significantly exceeded those in 'poor' years. Moreover, good and poor years often alternated, forming a regular biennial cycle. (3) The biennial cycle resulted from the year-to-year variation in the number of adult shoots carrying new leaves. This is based on the fact that the leaf life span of the bamboo is two years, and all leaves on a shoot have been formed simultaneously. Mean number of new shoots emerging and surviving per plot was positively correlated with the proportion of adult shoots carrying new (one year old) leaves. The annual production of new shoots of Phyllostachys pubescens was not significantly correlated with the annual values of logging intensity of bamboo poles, rainfall or temperature. The survival rate of new shoots was constant over years. (4) Severe pests (e.g., plague of locusts), extreme drought or heavy overlogging of adult shoots with new leaves can be triggers of poor production of new shoots during the following spring.