Accessing the impacts of bamboo expansion on NPP and N cycling in evergreen broadleaved forest in subtropical China

Qing-Ni Song,Guang-Yao Yang,Jun Yang,Hui Lu,Jun Liu,Qing-Pei Yang

doi:10.1038/srep40383

Abstract

Bamboo (Phyllostachys pubescens) expansion into adjacent forests is a widespread phenomenon in subtropical regions, and it has greatly changed the dominance hierarchy from trees to bamboos. This process may be accompanied by changes in productivity, nutrients accumulation and biogeochemical cycles. We compared the net primary production (NPP) and major pools and fluxes of nitrogen (N) in bamboo-dominant forest (BDF) and neighboring secondary evergreen broadleaved forest (EBF) in South China using the space-for-time substitution method. We found that the mean NPP of the BDF was 30.0 t ha−1 yr−1, which was 51.5% greater than that of the EBF (19.8 t ha−1 yr−1). The plant N pool for the BDF was 37.5% larger than that of the EBF, whereas the soil inorganic N pool significantly decreased by 31.2% with conversion of the EBF to BDF. Additionally, the ratio of N return to N uptake was 0.69 in the BDF and 0.88 in the EBF because of the lower litter N return of the BDF compared with that of the EBF. These results indicated that the expansion of P. pubescens significantly increased the NPP and plant N accumulation but reduced the soil N available pool and slowed the N cycling rate, which could lead to soil degradation.

Highlights

Bamboos(Poaceae: Bambusoideae) are perennial tree-like grasses widely distributed in tropical, subtropical and temperate forest ecosystems[1]
The averaged values of EBF biomass obtained in the present study was 201.2 t ha−1, a result that was higher than the mean value of EBFs in subtropical China (163.7 t ha−1)[23] but close to the EBF in east China (225.3 t ha−1) reported by Yang et al.[24]
The total biomass of the BDF was 205.5 t ha−1, which was in the range of 132.8–309.2 t ha−1 previously reported for equivalent vegetation in various regions of China and Japan[14,25,26]

Summary

Introduction

Bamboos(Poaceae: Bambusoideae) are perennial tree-like grasses widely distributed in tropical, subtropical and temperate forest ecosystems[1] These plants frequently expand into their neighboring forest ecosystems by clonal and sexual reproduction and become dominant species in the canopy or understory with human or natural disturbances[2,3,4]. Evergreen broadleaved forest (hereafter, EBF), the typical vegetation type in subtropical areas, is recognized as an important global vegetation type that contributes to both biodiversity and environmental protection[16]. Despite their formerly widespread geographical distribution, remnant EBFs next to bamboo forest are suffering from extensive expansion by bamboo[15,17]. Species Bamboo shoot (≤1 a) Bamboo shoot (>1 a) Castanopsis fargesii Castanopsis sclerophylla Symplocos laurina Schima superba

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