Effects of understory vegetation and litter on plant nitrogen (N), phosphorus (P), N:P ratio and their relationships with growth rate of indigenous seedlings in subtropical plantations.

Jun Wang,Zhanfeng Liu,Hai Ren,Dafeng Hui,Long Yang,Ting Wang

doi:10.1371/journal.pone.0084130

Abstract

Establishing seedlings in subtropical plantations is very important for forest health, succession and management. Information on seedling nutrient concentrations is essential for both the selection of suitable indigenous tree species to accelerate succession of the established plantation and sustainable forest management. In this study, we investigated the concentrations of nitrogen ([N]), phosphorus ([P]), and N∶P ratio in leaves, stems and roots of seedlings of three indigenous tree species (Castanopsis chinensis, Michelia chapensis and Psychotria rubra) transplanted with removing or retaining understory vegetation and litter at two typical subtropical forest plantations (Eucalyptus plantation and native species plantation). We also measured the relative growth rate (RGR) of seedling height, and developed the relationships between RGR and leaf [N], [P] and N∶P ratio. Results showed that treatments of understory vegetation and associated litter (i.e. removal or retained) generally had no significant effects on leaf [N], [P], N∶P ratio and RGR of the transplanted tree seedlings for the experimental period. But among different species, there were significant differences in nutrient concentrations. M. chapensis and P. rubra had higher [N] and [P] compared to C. chinensis. [N] and [P] also varied among different plant tissues with much higher values in leaves than in roots for all indigenous species. RGR of indigenous tree seedlings was mostly positively correlated with leaf [N] and [P], but negatively correlated with leaf N∶P ratio. Considering the low [P] and high N∶P ratio observed in the introduced indigenous tree seedlings, we propose that the current experimental plantations might be P limited for plant growth.

Highlights

In South China, large areas of plantations established in the past several decades still have a simple structure with few typical zonal forest species in the understory[1,2]
Plant [N], [P] and N:P ratio At both the Eucalyptus plantation (EP) and the native species plantation (NP), no significant differences in leaf, stem and root [N] and [P] were observed between the vegetation and litter removed (VR) and the CK treatments for all species, except that root [P] of C. chinensis seedlings at the NP (Figure 1d)
By transplanting different indigenous tree species into subtropical plantations, we demonstrated that species selection could be an important factor determining leaf nutrient concentrations and potential survive ability in the subtropical Eucalyptus plantation and native species plantation

Summary

Introduction

In South China, large areas of plantations established in the past several decades still have a simple structure with few typical zonal forest species in the understory[1,2]. For this reason, there is always a need to promote environmental conditions for the established plantations to support species assemblages similar to natural forests. As indicated by previous studies, nutrient concentrations of plants mostly vary with their nutrient uptake capability among specie [9,10] From this viewpoint, to improve early seedling establishment and accelerate colonization of indigenous species into plantations, transplanting seedlings of species with a greater nutrient uptake potential or capacity is crucial

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Results

Discussion

Conclusion