Carbon Dioxide Emission from Black Soil as Influenced by Land‐Use Change and Long‐Term Fertilization

Abstract

Land‐use change and soil management play a vital role in influencing losses of soil carbon (C) by respiration. The aim of this experiment was to examine the impact of natural vegetation restoration and long‐term fertilization on the seasonal pattern of soil respiration and cumulative carbon dioxide (CO₂) emission from a black soil of northeast China. Soil respiration rate fluctuated greatly during the growing season in grassland (GL), ranging from 278 to 1030 mg CO₂ m⁻² h⁻¹ with an average of 606 mg CO₂ m⁻² h⁻¹. By contrast, soil CO₂ emission did not change in bareland (BL) as much as in GL. For cropland (CL), including three treatments [CK (no fertilizer application), nitrogen, phosphorus and potassium application (NPK), and NPK together with organic manure (OM)], soil CO₂ emission gradually increased with the growth of maize after seedling with an increasing order of CK < NPM < OM, reaching a maximum on 17 August and declining thereafter. A highly significant exponential correlation was observed between soil temperature and soil CO₂ emission for GL during the late growing season (from 3 August to 28 September) with Q₁₀  =  2.46, which accounted for approximately 75% of emission variability. However, no correlation was found between the two parameters for BL and CL. Seasonal CO₂ emission from rhizosphere soil changed in line with the overall soil respiration, which averaged 184, 407, and 584 mg CO₂ m⁻² h⁻¹, with peaks at 614, 1260, and 1770 mg CO₂ m⁻² h⁻¹ for CK, NPK, and OM, respectively. SOM‐derived CO₂ emission of root free‐soil, including basal soil respiration and plant residue–derived microbial decomposition, averaged 132, 132, and 136 mg CO₂ m⁻² h⁻¹, respectively, showing no difference for the three CL treatments. Cumulative soil CO₂ emissions decreased in the order OM > GL > NPK > CK > BL. The cumulative rhizosphere‐derived CO₂ emissions during the growing season of maize in cropland accounted for about 67, 74, and 80% of the overall CO₂ emissions for CK, NPK, and OM, respectively. Cumulative CO₂ emissions were found to significantly correlate with SOC stocks (r  =  0.92, n  =  5, P < 0.05) as well as with SOC concentration (r  =  0.97, n  =  5, P < 0.01). We concluded that natural vegetation restoration and long‐term application of organic manure substantially increased C sequestration into soil rather than C losses for the black soil. These results are of great significance to properly manage black soil as a large C pool in northeast China.

Keywords:

• Black soil
• CO₂ emission
• land‐use change
• long‐term fertilization
• rhizosphere respiration

ACKNOWLEDGMENTS

This work was supported in part by a grant from the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2‐YW‐407), the Science Foundation of Heilongjiang Province, China (GB06B107‐2), and the Massachusetts Agricultural Experiment Station (Project No. MAS00860).