A Thermodynamic Analysis of Soil Ecosystem Development in Northern Wetlands

The Maximum Power Principle (MPP) — a theoretical construct that argues that systems develop to maximize energy throughput, or power — is the subject of few empirical studies. We used the MPP to explore the thermodynamic basis for microbial processes and greenhouse gas fluxes in high latitude peat soils. Increasing temperatures cause extensive areas of permafrost degradation, which can lead to wetland formation, though permafrost degradation and aggradation can be cyclical under the right conditions. Differential ecosystem responses to permafrost degradation offer an opportunity to use the unifying approach of thermodynamics. We used adenosine triphosphate (ATP) production in peat soils as a soil-relevant proxy for power to test the MPP along a chronosequence of wetlands with time following permafrost degradation. We conducted soil incubation experiments and measured production rates of CO₂, methane (CH₄), nitrous oxide (N₂O), and ATP. ATP production was significantly lower (p < 0.05) in the young bog soils compared to the undisturbed permafrost bog soils; rates in the older bog soils were not different from either site. Our results suggest that power output increased following recovery from permafrost thaw. A unifying vantage point provided by thermodynamics may be useful in other investigations of wetland ecosystems with unpredictable responses to disturbance.