Assessments of foliar functional traits of understory shrubs in two 13-year reforested plantations in subtropical China

Abstract Understory vegetation is crucial and necessary for the stability and biodiversity in plantation forests. However, the role of understory vegetation is easy to be neglected in traditionally intensity plantations. To date, the foliar functional traits of understory shrub in different plantation types are still in debate. Herein, a field–based restoration experiment with different plantation types was conducted to explore the variation of foliar functional traits of understory shrubs in two 13-year reforested plantations and assess which is the most suitable understory species for the plantation development and succession in subtropical China. The results showed that the foliar functional traits of the understory shrubs were species-specific. Both L. cubeba and I. asprella had higher specific leaf area (SLA) and photosynthetic pigments, suggesting that they can efficiently acquire and utilize light in the understory shade environment rather than M. candidum and R. tomentosa regardless of the plantation types. Also, the leaf N and P concentrations of L. cubeba and I. asprella were significantly larger than those of the other two species. Moreover, the SLA, leaf N and P concentrations were significantly positively related to the leaf photosynthetic pigments (chlorophyll and carotenoid) within the two plantations. These further supported that the L. cubeba and I. asprella can adapt well to the shade environment. Therefore, considering the higher SLA, leaf N and P concentrations, and photosynthetic pigments in L. cubeba and I. asprella, we strongly recommend that L. cubeba and I. asprella can be selective species for the understory management in the subtropical plantations of southern China.