Chin J Plant Ecol ›› 2021, Vol. 45 ›› Issue (7): 790-798.DOI: 10.17521/cjpe.2021.0044

Special Issue: 全球变化与生态系统 生态化学计量

• Research Articles • Previous Articles     Next Articles

Responses of soil nitrogen in different soil organic matter fractions to long-term nitrogen addition in a semi-arid grassland

WU Yun-Tao1,2, YANG Sen1,2, WANG Xin1, HUANG Jun-Sheng1, WANG Bin1,2, LIU Wei-Xing1, LIU Ling-Li1,2,*()   

  1. 1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    2University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2021-02-03 Accepted:2021-03-30 Online:2021-07-20 Published:2021-10-22
  • Contact: LIU Ling-Li ORCID:0000-0002-5696-3151
  • Supported by:
    Chinese National Key Development Program for Basic Research(2019YFA0607302);Strategic Priority Research Program of the Chinese Academy of Sciences(XDA23080301);National Natural Science Foundation of China(31901138)


Aims Soil nitrogen (N) plays a vital role in regulating the structure and function of ecosystems and is affected by N deposition. Most previous studies focus on the responses of the N content in bulk soil to N deposition, but the responses of the N content in different soil organic matter (SOM) fractions remain unclear. We aimed to investigate how long-term N addition influenced soil N of different SOM fractions in a semi-arid grassland.

Methods A manipulated N addition experiment with 4 levels of N addition (0, 8, 32 and 64 g·m-2·a-1) has been conducted for 13 years in Duolun country, Nei Mongol. SOM was separated to particulate organic matter (POM) and mineral associated organic matter (MAOM) by density fractionation. The plant and soil properties were also measured.

Important findings The results showed that N addition had no significant effect on the carbon (C) content in bulk soil, POM, or MAOM. With increasing levels of N addition, the N content in bulk soil and in POM increased significantly. Furthermore, we found that the increased N content of POM was mainly associated with greater aboveground biomass following N addition. The N content of MAOM is mainly correlated with soil texture, but was not affected by N addition. These results suggest that continuous N addition can increase the soil N in bulk soil, but the increased N is mostly distributed in labile POM pools, which can be vulnerable to land use and climate change.

Key words: nitrogen addition, nitrogen content, particulate organic matter, mineral associated organic matter