An improved method for measuring peatland soil oxidase enzyme activities

Phenol oxidase (PPO) and peroxidase (PO) are critical enzymes in peatland carbon cycling, facilitating the decomposition of recalcitrant compounds. Quantifying their activities is, therefore, an important method for assessing the condition of peatlands in a changing climate particularly following restoration from degraded states. To increase certainty in the method, the study in this short communication modified the enzyme assay control setup by incorporating both autoclaved controls and non-autoclaved samples with ABTS as the substrate in drained and restoration-to-bog peatlands. Specifically, the effects of autoclaved and non-autoclaved controls on enzyme assays were evaluated, alongside the influence of peatland treatments on soil properties such as soil moisture content (SMC) and pH. The results indicated significantly higher (p < 0.05) PPO and PO activities in non-autoclaved compared to autoclaved samples, emphasising the necessity of incorporating both soil conditions to account for abiotic oxidation. By subtracting the activity in autoclaved samples from that in non-autoclaved samples, this approach provides a more precise and biologically relevant measure of oxidative potential. Additionally, significant differences (p < 0.05) in SMC were observed among peatland treatments, with lower SMC associated with higher oxidase activity. Using this modified method (ABTS substrate, modified negative control), peroxidase was identified as the enzyme with the highest observed activity, underscoring the need for future research to focus on both PO and PPO to deepen understanding of peatland ecosystem processes.