The Vulnerability of Particulate Soil Carbon to Climate Change

Soil organic matter is a significant reservoir of carbon, containing more carbon than both plants and the atmosphere combined. This has led to an increasing interest in the potential role of soil in mitigating climate change by sequestering carbon. However, recent research conducted by Lawrence Livermore National Laboratory (LLNL) and collaborators sheds light on the vulnerability of soil carbon to microbial decomposition under rising global temperatures.

The study focused on two distinct pools of carbon found in soil: mineral-associated carbon and particulate soil carbon. Mineral-associated carbon consists of organic compounds bound to clay minerals, which can persist for long periods of time. On the other hand, particulate carbon comprises partially decomposed plant fragments that cycle on shorter timescales. The research revealed that particulate carbon is significantly more sensitive to temperature increases than mineral-associated carbon, especially in cooler climates.

Analyzing global data on these two carbon pools, the researchers found that the temperature sensitivity of particulate carbon is almost 30% higher than that of mineral-associated carbon. This suggests that as temperatures rise, particulate carbon may be more vulnerable to decomposition, releasing carbon into the atmosphere. Lead author Katerina Georgiou emphasized the importance of understanding these differences in temperature sensitivity to predict the potential impacts of climate change on soil carbon.

One key finding of the study was the variability in Earth system models when it comes to the distribution of carbon among soil pools. While mineral-associated carbon constitutes the majority of global soil carbon, the proportion of this pool in different models ranged from 16% to 85%. This discrepancy has significant implications for estimating soil carbon ages and the responsiveness of ecosystems to climate change. Georgiou pointed out that half of the models underestimate the presence of carbon in slower-cycling, mineral-protected pools, highlighting the need for improved representations of soil carbon dynamics.

The vulnerability of particulate soil carbon to climate change underscores the importance of considering the dynamics of different carbon pools in soil. As global temperatures continue to rise, understanding how soil carbon responds to these changes will be crucial for developing effective climate mitigation strategies. By shedding light on the distinct temperature sensitivities of mineral-associated and particulate carbon, this research provides valuable insights into the potential impacts of climate change on soil carbon storage.