Chin J Plant Ecol ›› 2024, Vol. 48 ›› Issue (2): 229-241.DOI: 10.17521/cjpe.2023.0148

• Research Articles • Previous Articles     Next Articles

Effects of nitrogen addition on soil active organic carbon in a temperate grassland of Nei Mongol, China

YAN Chen-Yi, GONG Ji-Rui*()(), ZHANG Si-Qi, ZHANG Wei-Yuan, DONG Xue-De, HU Yu-Xia, YANG Gui-Sen   

  1. State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
  • Received:2023-05-29 Accepted:2023-10-09 Online:2024-02-28 Published:2023-10-12
  • Contact: * (
  • Supported by:
    National Natural Science Foundation of China(32230065);National Key R&D Program of China(2022YFF1303404)


Aims Both the carbon cycle and the function of grassland ecosystem as a carbon sink are impacted by the rising nitrogen deposition. Active organic carbon content is an important measure that can reveal changes in soil carbon pool. For a thorough understanding of carbon cycling and the creation of sensible ecosystem management strategies, it is essential to investigate the impacts of nitrogen addition on the active organic carbon fractions of grassland soils.

Methods Five different nitrogen addition treatments were set up in a temperate typical steppe of Nei Mongol. Soil organic carbon fractions content, soil physical and chemical properties, aggregate stability, microbial activities and extracellular enzyme activities were measured. Pearson correlation and structural equation model (SEM) were used to examine the relationships.

Important findings Nitrogen addition reduced the contents of dissolved organic carbon (DOC), microbial biomass carbon (MBC), and easily oxidizable organic carbon (EOC). The contents of DOC, MBC, and EOC all decreased with the increases of soil depth. The treatment of 5 g·m-2·a-1 nitrogen addition significantly promoted the decomposition of active organic carbon fractions. The effect of nitrogen addition on soil active organic carbon fractions content was regulated by biotic (microbial biomass, extracellular enzyme activity, etc.) and abiotic (soil physical and chemical properties, aggregate stability, etc.) factors. Nitrogen addition reduced soil density, increased mean mass diameter and the proportion of large aggregates, increased the contact between organic matter and substrate, promoted the decomposition of active organic carbon, and reduced the contents of DOC and EOC. Nitrogen addition inhibited the activities of polyphenol oxidase and peroxidase, reduced the decomposition of difficult-to-decompose organic matter and the contents of EOC and MBC. Nitrogen addition increased the activities of β-glucosidase and cellulose hydrolase, promoted the utilization of DOC by microorganisms, and reduced the content of DOC. Our results indicated that nitrogen addition treatment can affect the decomposition process of active organic carbon by changing soil physicochemical properties and the secretion of extracellular enzymes from microorganisms, promoting the release of carbon in grassland soils. This provided a theoretical basis for further exploration of grassland soil carbon dynamics under nutrient addition in the future.

Key words: nitrogen addition, active organic carbon, soil aggregates, biotic factor, physicochemical properties