Evidence and causes of recent decreases in nitrogen deposition in temperate forests in Northeast China

Yingying Wang; Feifei Zhu; Jin Li; Geshere Abdisa Gurmesa; Shaonan Huang; Xiaoming Fang; Dongwei Liu; Abubakari Said Mgelwa; Wenchao Wang; Kai Huang; Yihang Duan; Linlin Song; Xue Li; Zhi Quan; Ronghua Kang; Weixing Zhu; Erik A Hobbie; Yunting Fang

doi:10.1016/j.scitotenv.2024.172472

Evidence and causes of recent decreases in nitrogen deposition in temperate forests in Northeast China

Sci Total Environ. 2024 Jun 15:929:172472. doi: 10.1016/j.scitotenv.2024.172472. Epub 2024 Apr 19.

Authors

Yingying Wang¹, Feifei Zhu², Jin Li¹, Geshere Abdisa Gurmesa³, Shaonan Huang⁴, Xiaoming Fang⁵, Dongwei Liu⁵, Abubakari Said Mgelwa⁶, Wenchao Wang¹, Kai Huang³, Yihang Duan³, Linlin Song³, Xue Li¹, Zhi Quan³, Ronghua Kang³, Weixing Zhu⁷, Erik A Hobbie⁸, Yunting Fang⁹

Affiliations

¹ CAS Key Laboratory of Forest Ecology and Silviculture, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² CAS Key Laboratory of Forest Ecology and Silviculture, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; Qingyuan Forest CERN, National Observation and Research Station, Shenyang, Liaoning 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China. Electronic address: zhuff@iae.ac.cn.
³ CAS Key Laboratory of Forest Ecology and Silviculture, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China.
⁴ Key Laboratory of Geospatial Technology for the Middle and Lower Yellow River Regions, Ministry of Education, College of Geography and Environment Science, Henan University, Kaifeng 475004, China; Henan Key Laboratory of Air Pollution Prevention and Ecological Security (Henan University), Kaifeng 475004, China.
⁵ CAS Key Laboratory of Forest Ecology and Silviculture, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; Qingyuan Forest CERN, National Observation and Research Station, Shenyang, Liaoning 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China.
⁶ CAS Key Laboratory of Forest Ecology and Silviculture, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China; College of Natural Resources Management & Tourism, Mwalimu Julius K. Nyerere University of Agriculture & Technology, P.O. Box 976, Musoma, Tanzania.
⁷ Department of Biological Sciences, Binghamton University, The State University of New York, Binghamton, NY, USA.
⁸ Earth Systems Research Center, University of New Hampshire, Durham, NH 03824, United States.
⁹ CAS Key Laboratory of Forest Ecology and Silviculture, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China; Qingyuan Forest CERN, National Observation and Research Station, Shenyang, Liaoning 110016, China; Key Laboratory of Stable Isotope Techniques and Applications, Shenyang, Liaoning 110016, China. Electronic address: fangyt@iae.ac.cn.

PMID: 38642760
DOI: 10.1016/j.scitotenv.2024.172472

Abstract

High reactive nitrogen (N) emissions due to anthropogenic activities in China have led to an increase in N deposition and ecosystem degradation. The Chinese government has strictly regulated reactive N emissions since 2010, however, determining whether N deposition has reduced requires long-term monitoring. Here, we report the patterns of N deposition at a rural forest site (Qingyuan) in northeastern China over the last decade. We collected 456 daily precipitation samples from 2014 to 2022 and analysed the temporal dynamics of N deposition. NH₄⁺-N, NO₃^--N, and total inorganic N (TIN) deposition ranged from 10.5 ± 3.5 (mean ± SD), 6.1 ± 1.6, and 16.6 ± 4.7 kg N ha^-1 year^-1, respectively. Over the measurement period, TIN deposition at Qingyuan decreased by 55 %, whereas that in comparable sites in East Asia declined by 14-34 %. We used a random forest model to determine factors influencing the deposition of NH₄⁺-N, NO₃^--N, and TIN during the study period. NH₄⁺-N deposition decreased by 60 % because of decreased agricultural NH₃ emissions. Furthermore, NO₃^--N deposition decreased by 42 %, due to reduced NO_x emissions from agricultural soil and fossil fuel combustion. The steep decline in N deposition in northeastern China was attributed to reduced coal consumption, improved emission controls on automobiles, and shifts in agricultural practices. Long-term monitoring is needed to assess regional air quality and the impact of N emission control regulations.

Keywords: Ammonium; Bulk N deposition; Emission control; Nitrate; Northeastern China.