Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 15, issue 18
Biogeosciences, 15, 5621-5634, 2018
https://doi.org/10.5194/bg-15-5621-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Biogeosciences, 15, 5621-5634, 2018
https://doi.org/10.5194/bg-15-5621-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 20 Sep 2018

Research article | 20 Sep 2018

Microbial decomposition processes and vulnerable arctic soil organic carbon in the 21st century

Junrong Zha and Qianlai Zhuang Junrong Zha and Qianlai Zhuang
  • Department of Earth, Atmospheric, and Planetary Sciences and Department of Agronomy, Purdue University, West Lafayette, IN 47907, USA

Abstract. Various levels of representations of biogeochemical processes in current biogeochemistry models contribute to a large uncertainty in carbon budget quantification. Here, we present an uncertainty analysis with a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), into which detailed microbial mechanisms were incorporated. Ensemble regional simulations with the new model (MIC-TEM) estimated that the carbon budget of the arctic ecosystems is 76.0±114.8PgC during the 20th century, i.e., −3.1±61.7PgC under the RCP 2.6 scenario and 94.7±46PgC under the RCP 8.5 scenario during the 21st century. Positive values indicate the regional carbon sink while negative values are a source to the atmosphere. Compared to the estimates using a simpler soil decomposition algorithm in TEM, the new model estimated that the arctic terrestrial ecosystems stored 12Pg less carbon over the 20th century, i.e., 19 and 30PgC less under the RCP 8.5 and RCP 2.6 scenarios, respectively, during the 21st century. When soil carbon within depths of 30, 100, and 300cm was considered as initial carbon in the 21st century simulations, the region was estimated to accumulate 65.4, 88.6, and 109.8PgC, respectively, under the RCP 8.5 scenario. In contrast, under the RCP 2.6 scenario, the region lost 0.7, 2.2, and 3PgC, respectively, to the atmosphere. We conclude that the future regional carbon budget evaluation largely depends on whether or not adequate microbial activities are represented in earth system models and on the sizes of soil carbon considered in model simulations.

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This study used a detailed microbial-based soil decomposition biogeochemistry model to examine the fate of much arctic soil carbon under changing climate conditions. We found that the detailed microbial decomposition biogeochemistry model estimated a much lower carbon accumulation in the region during this century. The amount of soil carbon considered in the 21st-century simulations determines the regional carbon sink and source strengths, regardless of the complexity of models used.
This study used a detailed microbial-based soil decomposition biogeochemistry model to examine...
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