PhD defence: Organic carbon mineralization and microbiology in subsoil

Zhi Liang has examined the fate of organic carbon inputs in deep soil ecosystems. This included laboratory studies of the carbon sequestration potential from deep-roted crops in relation to root chemical composition, soil nutrient availability, and microbial physiology.

2019.01.22 | Helene Uller-Kristensen

January 21, the PhD student Zhi Liang defenced her PhD thesis at AU Foulum.

Zhi has studied the carbon dynamics and microbiology in deep soil in potential response to the influence of deep-rooted crops. The specific objectives have been to:

  1. Investigate the role of root litter chemistry on carbon loss in different vertical soil layers amended with root materials from different plant species
  2. Study the effect of nutrient availability on fresh carbon turnover in subsoil compared to top soil
  3. Investigate how carbon input (root biomass, labile carbon substrate) in subsoils affect the diversity and functioning of the microbial community.

The results showed that plant nitrogen and ligning content were important factors regulating mineralization of fresh carbon inputs. Moreover, soil nitrogen availability interacted on control of microbial turnover of organic carbon. The PhD results have been synthesized into a conceptual model for deep soil carbon sequestration and further presented an operational methodology for analysis of labile carbon (glucose) in the soil.


Zhi is part of the Deep Frontier project. Deep Frontier is developing methods, facilities and ideas for future research into sustainable food production and improve understanding of deep rooting, i.e. what determines deep rooting, the activities of deep roots and which resources  from deep soil layers are utilized by plants. The project also studies cropping systems with deep rooted species.

With this research focus, the overall aim is to increase the exploitation of the subsoil resources by deep roots and thereby enhance food production in a sustainable way, as the need for resource input for food production and nutrient losses to the environment will be reduced. Additionally, the results are expected to contribute to climate change mitigation and improve soil biodiversity through the increased organic matter input to the soil.

The Deep Frontier project is carried out by University of Copenhagen, University of Aarhus and ICROFS (International Center for Research in Organic Food Systems). The project is funded by the Villum Foundation for the period of 1. September 2014 until 31. August 2020. 

Read about Zhi Liang's studies

Visit the website of Deep Frontier

Agriculture and food