Flowering pattern of Schizostachyum dullooa, a thin walled tropical bamboo and impact of flowering on regeneration of canopy trees in evergreen forest in North East India

Abstract

Schizostachyum dullooa is a semelparous, thin walled bamboo that grows in the moist forests of India, Bangladesh and Myanmar. The species has great potential in upliftment of socioeconomic conditions of the rural areas of North East India. The long flowering interval in S. dullooa has hindered documentation of its demography and its influence on regeneration of canopy trees. We hypothesized that mass flowering and death of S. dullooa opens a window of opportunity creating space for the regeneration of canopy tree seedlings. We studied the flowering pattern and seedling demography of this species between the years 2010 and 2015 in the Barak Valley, and evaluated if seedling abundance of canopy tree species increased after the flowering event. We followed five successive seedling cohorts to determine variation in survival of canopy tree seedlings, seedling attributes [i.e., maximum height (cm), diameter (cm) and density (individuals per 0.01 ha)]. At the local scale, mast flowering extended over 4 years in small patches of about 100 m2 where flowering and non-flowering culms were often mixed. At the landscape scale, sites with mast flowering stands were interspersed with sites that did not have flowering stands indicating spatially discontinuous flowering patterns. Mortality rate of bamboo seedlings was high during the first year. At the end of the study, 15–26% of the initial bamboo seedlings in each cohort survived and S. dullooa was able to re-colonize sites it previously occupied. Mass flowering significantly increased seedling density and growth of canopy trees compared to non-flowering sites. It is concluded that flowering and death of S. dullooa facilitates the regeneration of canopy trees, with implications for the structure and function of the forest ecosystem.