Location :Depth-dependent Responses of Soil Organic Carbon under Nitrogen Deposition
In a study published in Global Change Biology, scientists from the Institute of Earth Environment and South China Botanical Garden, Chinese Academy of Sciences(CAS) have shed light on understanding the effects of nitrogen addition on soil organic carbon storage across soil profiles. Their results may help address the recently highly disputed topics on managing soil as carbon sink under enhanced nitrogen deposition.
Enhanced atmospheric nitrogen (N) deposition has greatly altered soil organic carbon (SOC) storage, thereby affecting carbon (C) cycling–climate feedback. Due to significant differences in external plant carbon input, microbial community structure, soil aeration and soil texture between topsoil and subsoil, the effects of N deposition on SOC at different depths likely vary or even contradict. However, there is a shortage of studies from subsoil.
To investigate whether the effects of N addition on SOC storage varied with soil depths, we conducted a comprehensive global data collection to examine the effects of N addition on SOC in both topsoil (0-30 cm) and subsoil (30-100 cm). They found that N addition significantly increased topsoil SOC, while did no significant affected subsoil SOC.
To explore the underlying mechanisms associated with the depth-dependent responses of SOC to N addition, they incorporated many ancillary variables into the model selection analysis, including N addition methods, vegetation type, mean annual temperature and precipitation, background N deposition rate and so on. They showed that the topsoil SOC increased significantly with N addition duration, whereas SOC in the subsoil initially increased with N addition but decreased over time.
Overall, this study highlights the importance of considering soil depth together with N deposition duration in predicting SOC storage under N addition. The lack of depth-dependent SOC responses to N addition in experimental and modeling frameworks has likely resulted in the overestimation of soil C sink capacity under future N deposition.
Contact: BAI Jie, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an, China. Email: baijie@ieecas.cn
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