Rising Temperature May Trigger Deep Soil Carbon Loss Across Forest Ecosystems

Area of Science:

• Soil Science
• Climate Change Research
• Biogeochemistry

Background:

• Deep soil horizons store significantly more carbon (C) than shallow ones.
• Understanding the temperature sensitivity of deep soil organic carbon (SOC) decomposition is crucial for predicting climate change feedbacks.
• Current large-scale predictions face uncertainties due to unexplored deep SOC responses.

Purpose of the Study:

• To investigate the short-term temperature sensitivity (Q10) of SOC decomposition across various soil depths in China.
• To determine how factors like climate and soil C quality influence Q10 at different depths.
• To assess the implications of depth-dependent Q10 for Earth system model predictions of C-cycle feedbacks.

Main Methods:

• Collected 540 soil samples from 90 upland forest sites across China.
• Analyzed SOC decomposition temperature sensitivity (Q10) at six depths within the top 1 meter.
• Examined the influence of climate and soil C quality on Q10 variations with depth.

Main Results:

• Q10 significantly increases with soil depth, indicating deeper SOC is more vulnerable to temperature increases.
• Climate primarily regulates shallow soil Q10, with its influence decreasing with depth.
• Soil C quality's influence on Q10 grows with soil depth, becoming more significant than in shallow soils.

Conclusions:

• Deep soil organic carbon is more susceptible to decomposition under rising temperatures than previously assumed.
• Earth system models must incorporate multilayer soil carbon dynamics and their controls for accurate climate change feedback predictions.
• Current modeling approaches that do not account for depth-dependent Q10 likely underestimate the impact of warming on soil carbon storage.