The relationship between surface topography and peat thickness on Tebing Tinggi Island, Indonesia

Peat and its substratum have different geology and parent materials. Studies on peat formation and spatial patterns of peat deposits have been widely reported, but little is known about patterns of peat thickness across tropical peat landscapes. We studied the relationship between surface relief and peat thickness on Tebing Tinggi Island (Indonesia) by considering peat surface altitude, peat thickness and substratum altitude. The research location is unique, being a small (~ 70 × 30 km) predominantly peat-covered island separated by a strait from the mainland of Sumatra and its more extensive peat deposits. Geomorphological features on the island were identified using a digital terrain model (DTM) developed from LiDAR data, together with observations on peat cores. The results indicate that the topography of the peat landscape does not reflect peat thickness. Thick peat can be found at the edge of a peat dome if it overlies a basin or valley in the substratum, while thinner peat can be found at the centre if it overlies a mound in the substratum. It is also important to note that the shapes of the peat surface and the substratum surface are not the same; a flat peatland surface may have an undulating substratum and vice versa.