Prediction and Hypothesis Testing in Raised Peatland Morphology

Abstract:

Predictions of hillslope equilibrium morphologies often arise from geomorphic transport laws in which the divergence of horizontal transport of material is balanced by the rate of its production. In most cases, the sculpting of hillslopes towards this form occurs by mass-wasting processes and wear, where new mobile material is created by the mechanical and chemical breakdown of bedrock into erodable material. In contrast, in peatlands, material is built up through an entirely biological process in which plant matter is produced and then preserved from decomposition by a combination of cold temperatures and waterlogging. Further, in many settings this material experiences little horizontal displacement by erosive processes. Despite these differences in processes, theory and observation suggest that tropical peat domes approach equilibrium shapes with the same general forms predicted by geomorphic transport laws in erosional environments. Although the relief created by growth of raised peatlands is orders of magnitude smaller than in most other geomorphic systems, their morphology is important nonetheless because peat is built from carbon sequestered from the atmosphere, and this carbon is released by decomposition and fire when peatlands are drained. In this presentation, we discuss theory and observations supporting prediction of raised peatland morphology. In particular, we describe how LiDAR, ecosystem carbon flux, and radiocarbon data can be used to evaluate hypotheses about peatland morphogenesis despite the long time scales of peatland morphological equilibration.