A simulation model of mire patterning – revisited

The development of regular, oriented hummock-hollow or string-flark patterns in boreal peatlands can be explained by a simple spatially explicit model in which hummocks have a lower hydraulic conductivity than hollows and are more likely to occur at lower water levels. Revisiting a previously published model, the function used to simulate water flow is shown to be faulty. Nevertheless, the corrected model confirms the general conclusions of the original paper, showing the robustness of the approach. Five phases can be discerned in the development of the pattern. Once the hummock strings reach from left to right across the grid, there is an increase in the volume of water stored in the system. The number of hummocks and hollows differs substantially from what would be expected based on the mean water level, showing that their arrangement is more important than the actual number of hummocks. Parameter settings at which a pattern develops are sharply delineated, indicating there is a positive feedback mechanism that enhances initial patterning. Like in natural mire systems, the patterns anastomose and merge. In contrast to what is generally assumed for natural systems, the patterns show a distinct downward movement.