Abstract

The flowering periods of woody bamboos, seed set, natural regeneration and death after flowering have been rarely observed and evaluated in the field. Dendrocalamus membranaceus Munro, a tropical woody bamboo mainly distributed in the Yunnan, displayed both sporadic as well as gregarious (mass) flowering and fruited from 2006 to 2013 following severe droughts. The aim of this study is to examine potential differences in seed set and natural regeneration between the two flowering patterns in natural D. membranaceus forests. We investigated and analyzed seed set, seed germination, seedling growth and mortality in both mass and sporadic flowering populations. Observations were made over a period of three years to record changes in bamboo seedling density, height and culm diameter. We observed a low natural seed set ranging from 1.76% to 7.49%, and a relatively high seed germination rate in the nursery from 59.6% to 71.0% for both types of flowering populations. Seeds germinated in 5–7 days after sowing and the germination period lasted 10–15 days. Seed set and germination rates in mass-flowering populations were significantly higher than those of sporadically flowering stands. The seedlings within sporadically flowering populations died within two years. In comparison, seedling mortality in the mass flowering population increased over two periods of observation from 64.92% to 98.89%, yet there was good seedling establishment left over, which showed mean height and mean culm diameter increasing by 1053.25% and 410.71%, respectively, in the second year of observations, and 137.10%, and 217.48%, respectively, in the third year. There are significant differences in seed set, natural regeneration ability and sustainability of bamboo populations between the mass flowering and sporadically flowering populations of D. membranaceus. Sporadic flowering populations failed to produce effective regeneration, while mass flowering populations were able to regenerate successfully. This study provides useful insights for conservation and natural forest management of D. membranaceus. We consider the merits of introducing other genetic provenances towards long-term maintenance of the stand features at sporadically flowering sites; meanwhile, the most economic option for mass flowering stands is to allow natural regeneration to take place through protecting such sites from further disturbance.

Highlights

  • Dendrocalamus membranaceus Munro is a species of giant woody sympodial bamboo in tropical Asia

  • The seed set in natural populations of D. membranaceus was low, ranging from 1.76% to 7.49% (Table 2)

  • The seed set in quadrat A of the mass flowering population (7.49% ± 0.40) was significantly higher (4.26 and 3.67 times) than those in quadrats B and C of the sporadically

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Summary

Introduction

Dendrocalamus membranaceus Munro is a species of giant woody sympodial bamboo in tropical Asia. The culms of this species have a height of 10–20 m and a diameter of 7–15 cm. D. membranaceus forest is the largest and most representative natural stands of tropical large-sized sympodial bamboo found in China [5]. D. membranaceus is not a threatened plant on the present Red List of the International Union for Conservation of Nature (IUCN), its main distribution in southern Yunnan includes the Xiaomengyang National Nature Reserve (XNNR) [6], one of the habitats of the wild Asian elephant [7], an endangered species on the IUCN Red List (www.iucnredlist.org). D. membranaceus is a multi-purpose bamboo species important for industrial ulitization and for ecological conservation [1,8]

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