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Plant function and evolutionary biology
RESEARCH ARTICLE

Specific responses of sap flux and leaf functional traits to simulated canopy and understory nitrogen additions in a deciduous broadleaf forest

Liwei Zhu https://orcid.org/0000-0001-5191-2868 A B , Yanting Hu A , Xiuhua Zhao A , Ping Zhao A C , Lei Ouyang A , Guangyan Ni A and Nan Liu A
+ Author Affiliations
- Author Affiliations

A Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.

B Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China.

C Corresponding author. Email: zhaoping@scib.ac.cn

Functional Plant Biology 46(11) 986-993 https://doi.org/10.1071/FP18277
Submitted: 24 October 2018  Accepted: 10 June 2019   Published: 8 July 2019

Abstract

To investigate the effects of atmospheric nitrogen (N) deposition on water use characteristics and leaf traits of trees, we performed canopy (C50) and understory (U50) N additions as NH4NO3 of 50 kg N ha–1 year–1 in a deciduous broadleaf forest of central China. We measured xylem sap flux, crown area : sapwood area ratio (Ca : As), specific leaf area (SLA), mass-based leaf nitrogen content (Nmass) and leaf carbon isotope ratio (δ13C) of Liquidambar formosana Hance, Quercus acutissima Carruth. and Quercus variabilis Blume. Functional traits under different N addition treatments and their responses among tree species were compared and the relationship between xylem sap flux and leaf functional traits under N additions were explored. Results showed that under U50 sap-flux density of xylem significantly decreased for three tree species. But the effect of C50 on sap flux was species-specific. The decrease of sap-flux density with N additions might be caused by the increased Ca/As. δ13C remained constant among different N addition treatments. The responses of SLA and Nmass to N additions were species- and N addition approaches-specific. The correlation of xylem sap flux with leaf traits was not found. Our findings indicate that the effects of canopy N addition on xylem sap flux and leaf functional traits were species-specific and it is necessary to employ canopy N addition for exploring the real responses of forest ecosystems to climate changes in the future researches.

Additional keywords: atmospheric nitrogen deposition, leaf nitrogen content, sap flux, specific leaf area, δ13C.


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