The Impact of Compaction on Porosity and Decomposition in Peat

The physical structure of peat, particularly porosity, regulates both biochemical and physical processes in drained peatlands. Porosity influences key subsidence mechanisms such as consolidation, creep, and organic matter decomposition. This study investigated how compaction alters porosity and how these structural changes affect decomposition rates in peat with two levels of degradation over the short term.

Intact peat samples were collected from a drained peat meadow in the Netherlands, representing less decomposed fibric peat (FP) from saturated depths and more degraded peat (DP) from unsaturated layers. The samples were subjected to controlled compaction under different stress levels (10 kPa and 40 kPa) in the laboratory to assess changes in porosity and decomposition through CO₂ emissions and ß-D-Glucosidase potential activities (PA).

The results showed that compaction reduced porosity in both peat types with this reduction leading to a decline in CO₂ emissions and ß-D-Glucosidase PA, which was more significant in fibric peat. The average CO₂ emissions decreased by 33.1% and 48.1% for FP, and by 11.2% and 14.4% for DP, when subjected to compaction of 10 kPa and 40 kPa, respectively. The reduction in ß-D-Glucosidase PA with compaction averaged approximately 30%.

These findings highlight the complex interplay between mechanical and biochemical processes in drained peatlands, where changes in the physical structure of peat can directly influence subsidence dynamics. By demonstrating how mechanical stresses alter porosity and, consequently, biochemical activity, this research underscores the critical role of soil structure in driving organic matter dynamics and overall peatland function.