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Threshold and multiple indicators for nitrogen saturation in subtropical forests.
Journal article

Threshold and multiple indicators for nitrogen saturation in subtropical forests.

  • Yu Q State Key Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China.
  • Duan L State Key Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China; Collaborative Innovation Centre for Regional Environmental Quality, Tsinghua University, Beijing, 100084, China. Electronic address: lduan@tsinghua.edu.cn.
  • Yu L Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Box 5003, NO-1432 Ås, Norway; Laboratory for Air Pollution & Environmental Technology, Empa, Ueberlandstr. 129, CH-8600 Duebendorf, Switzerland.
  • Chen X Air Environmental Modeling and Pollution Controlling Key Laboratory of Sichuan Education Institutes, College of Resources and Environment, Chengdu University of Information Technology, Chengdu, 610225, China.
  • Si G State Key Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China.
  • Ke P State Key Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing, 100084, China.
  • Ye Z Air Environmental Modeling and Pollution Controlling Key Laboratory of Sichuan Education Institutes, College of Resources and Environment, Chengdu University of Information Technology, Chengdu, 610225, China.
  • Mulder J Faculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, Box 5003, NO-1432 Ås, Norway.
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  • 2018-06-15
Published in:
  • Environmental pollution (Barking, Essex : 1987). - 2018
Enrichment factor
N deposition
N isotope
N saturation
Subtropical forests
Ammonium Compounds
China
Ecosystem
Environmental Monitoring
Forests
Nitrogen
Nitrogen Cycle
Soil
Trees
English The influence of nitrogen (N) deposition on forest ecosystems largely depend on the N status. Developing threshold and practical indicators for N saturation in subtropical forests, with extremely high N deposition, would both enhance forest management and the assessments of global N balance and carbon (C) sequestration. Here, we quantified the N mass balance and assessed current N status at a number of subtropical forest sites in South China, using both N content, C/N ratio, and 15N natural abundance (δ15N) as potential indicators of N saturation. Among the studied sites, N deposition ranged from 13.8 to 113 kg N ha-1 yr-1 in throughfall, and was dominated by ammonium (NH4+). The threshold for N leaching in subtropical forest was first found to be 26-36 kg N ha-1 yr-1, which was 160% higher than in temperate forest (based on prescribed minimum). This indicates that critical parameter inputs in global models of the impact of N deposition are in need of revision, based on specific ecosystem characteristics. We found a critical C/N ratio of 20 for the O/A horizon as indicator of N saturation. Foliar N content and δ15N were positively correlated with N deposition and were well suited to indicate regional N status. The δ15N enrichment factor (Ɛfoli/So2, δ15Nfoliage - δ15NSoil2) was between -10‰ and -1‰, and had similar trend to those obtained from other regions with increasing N deposition. These suggest that the enrichment factor could be used to investigate the influence of N deposition in forest ecosystems, regardless of spatial heterogeneity in δ15N of N input, soil N availability and geomorphology.
Language
  • English
Open access status
closed
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Persistent URL
https://sonar.ch/global/documents/75509
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