1. Background

Climate change is coming faster than we thought and is one of the greatest threats we face today. Recent rapid rise in temperature is considered the main driver of climate change and the global warming is mainly caused by increasing carbon dioxide (CO₂) concentration in the atmosphere.

CO₂ emissions from human activities from the industrial revolution are well recognized as an important source of CO₂ addition to the atmosphere, but soils, the largest reservoir of carbon in terrestrial ecosystems, also produce the dominant CO₂ emission flux through a natural process, the microbial decomposition of soil organic carbon (SOC). This CO₂ flux is estimated to be about 6 times that of CO₂ flux due to the use of fossil fuels. Therefore, even a small change in the CO₂ emission from soils due to global warming could have a significant impact on the atmospheric CO₂ concentration and the global carbon cycling, and thus the Earth’s climate.

However, it remains unclear how global warming affects CO₂ release from soils, mainly because of a lack of quantitative data of soil and SOC characteristics including degradability and its response to temperature. Radiocarbon (¹⁴C) analysis-based approaches have the potential to quantitatively understand the SOC dynamics, and this could be the key to predicting long-term impacts of global warming.

2. Purpose and goal

The overall objective of this project is to understand processes driving carbon cycling in terrestrial ecosystems (soils, in particular) and their sensitivity to rise in temperature, and thereby to predict carbon cycle feedback to global warming. Asia occupies one third of the Earth’s land area and is the world’s largest diversity in terrestrial ecosystems, covering the world’s widest climatic zones. Therefore, we aim to construct the Asian-scale database of SOC characteristics in forest soils and a soil CO₂ emission model by ¹⁴C analysis-based approaches through the FNCA collaboration.

The database of SOC characteristics has been constructed by ¹⁴C analysis using accelerator mass spectrometry (AMS) for some forest soils in the previous project. Further analysis for soil samples collected from a large variety of terrestrial ecosystems is necessary to improve our ability to predict future climate change. Therefore, we will expand the database into the Asian scale by compiling results of soil analysis by FNCA member countries following the Guideline for soil sampling and SOC analysis (output of the previous project).

The new soil CO₂ emission model will be developed based on field/laboratory experiments to reveal the relationship between CO₂ emission and SOC characteristics. In addition, research methods for field/laboratory experiments will be transferred to FNCA member countries, and basic data for the soil CO₂ emission model development will be obtained.