Freeze-thaw cycles change pore-network regulating SOC and microbial communities

Area of Science:

• Soil Science
• Biogeochemistry
• Ecology

Background:

• Soil pore structure dictates microscale heterogeneity and influences soil organic carbon (SOC) and microbial community distribution.
• Limited data exists on soil pore scale biogeography under freeze-thaw cycles (FTCs) in alpine ecosystems.

Purpose of the Study:

• To assess soil pore structural changes due to FTCs.
• To investigate the regulation of SOC and microbial communities by soil pore structure under FTCs in alpine ecosystems.

Main Methods:

• Laboratory-simulated FTCs.
• Field observations of seasonal FTCs across three alpine ecosystems.
• Analysis of soil pore structure, SOC fractions (TOC, POC, MAOC), and microbial community indicators (PLFAs).

Main Results:

• FTCs increased soil porosity, macroporosity, and surface area density.
• FTCs led to significant decreases in total organic carbon (TOC) and particulate organic carbon (POC), with less impact on mineral-associated organic carbon (MAOC).
• Fungal PLFAs negatively correlated with soil porosity and macroporosity, while bacterial PLFAs were less affected. Microbial communities strongly influenced SOC fractions.

Conclusions:

• Reorganized soil structure from FTCs can mitigate SOC loss, with pore characteristics regulating POC and MAOC accumulation.
• Soil pore structure plays a crucial role in predicting carbon cycling under future climate scenarios.
• Integrating soil pore structure into Earth System models is vital for accurate permafrost carbon cycling predictions.