Variation characteristics of nitrogen concentrations through forest hydrologic subcycles in various forests across mainland China

Abstract

Increased anthropogenic nitrogen emissions and more severe environmental issues (e.g. air pollution, soil acidification, and plant nutrient imbalances) are striking forest ecosystems. Data on concentrations in throughfall and stemflow were collected to estimate variation characteristics of nitrogen concentrations through forest hydrological processes across China. A typical study was carried out in the three forest types in the Jinyun Mountain region of Chongqing, from May to October 2012. Nitrogen concentrations in throughfall and stemflow are higher than those in atmospheric precipitation. DIN concentrations in atmospheric precipitation, throughfall, and stemflow, across China and in the Jinyun Mountain region, were 2.18 and 1.51, 3.19 and 3.88, and 5.14 and 3.92 mg N L⁻¹, respectively. concentration was higher than concentration, suggesting is the dominant nitrogen component in China. Additionally, across China, a linear relationship existed between DIN and , and between DIN and in atmospheric precipitation. DIN concentrations in throughfall and stemflow changed with the observed changes in precipitation, and DIN concentrations in precipitation positively correlated with those in throughfall and in stemflow were also observed. Moreover, average DIN concentrations in throughfall and stemflow varied in different forest types, resulting from differences in forest canopy structures and tree species characteristics. In the Jinyun Mountain region, both throughfall and stemflow DIN concentrations were the highest in the mixed broadleaved/coniferous forest, followed by evergreen broadleaved forest, and the lowest in moso bamboo forest. Monthly variations of concentrations, in throughfall and stemflow, were observed in the Jinyun Mountain region.

Keywords:

• ammonium
• nitrate
• throughfall
• stemflow
• forest types

Acknowledgements

We thank Prof. Y. J. Wang and Y. Q. Wang, Dr. H. L. Zhang, and others for their assistance with fieldwork. We also thank Dr. John S. Richardson and his lab team, Canada, for their help in writing this paper. We would like to acknowledge the two anonymous reviewers for their helpful comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Funding

This study was supported by the National Natural Science Foundation of China [grant number 31100515]; and by the China Scholarship Council (CSC) [grant number 20133050]; and by the CFERN & GENE Award Funds on Ecological Paper.