Faded landscape: unravelling peat initiation and lateral expansion at one ofnorthwest Europe's largest bog remnants

On the mainland of northwest Europe generally only remnants offormer peat landscapes subsist. Due to the poor preservation of theselandscapes, alternative approaches to reconstruct peat initiation andlateral expansion are needed compared to regions with intact peat cover.Here we aim (1) to find explanatory variables within a digital soil mappingapproach that allow us to reconstruct the pattern of peat initiation andlateral expansion within (and potentially beyond) peat remnants, and (2) toreconstruct peat initiation ages and lateral expansion for one of thelargest bog remnants of the northwest European mainland,Fochteloerveen. Basal radiocarbon dates were obtained from the peatremnant, which formed the basis for subsequent analyses. We investigated therelationship between peat initiation age and three potential covariates: (1) total thickness of organic deposits, (2) elevation of the Pleistocenemineral surface that underlies the organic deposits, and (3) a constructedvariable representing groundwater-fed wetness based on elevation of themineral surface and current hydraulic head. Significant relationships werefound with covariates (1) and (3), which were then used for subsequentmodelling. Our results indicate simultaneous peat initiation at several lociin Fochteloerveen during the Early Holocene and continuous lateralexpansion until 900 cal BP. Lateral expansion accelerated between 5500-3500 cal BP. Our approach is spatially explicit (i.e. results in a mapof peat initiation ages), and it allows for a quantitative evaluation of theprediction using the standard deviation and comparison of predictions withvalidation points. The applied method based on covariate (1) is only usefulwhere remnant peat survived, whereas covariate (3) may ultimately be appliedto reconstruct peat initiation ages and lateral peatland expansion beyondthe limits of peat remnants.