Soil mixing and genesis as affected by tree uprooting in three temperate forests

Pavel Samonil, P. Danek, Randall J. Schaetzl, I. Vasickova, and M. Valtera

The purpose of this study was to identify general patterns of pedoturbation by tree uprooting in three different, forested landscapes and to quantify post-disturbance pedogenesis. Specifically, our study illustrates how the effects of ‘tree-throw’ on soils gradually become diminished over time by post-uprooting pedogenesis. We studied soil development within 46 pit-mounds in two regions of the Czech Republic, one on Haplic Cambisols and one on Entic Podzols. A third study site was in Michigan, USA, on Albic Podzols. Uprooting events were dated by using tree censuses, dendrochronology and radiometry. These dates provided information on several chronosequences of pedogenesis in the post-uprooting pits and mounds, dating back to 1816 AD (dendrochronological dating, Haplic Cambisols), 322 AD (median of calibration age, 14C age=1720±35 BP, Entic Podzols) and 4077 BC ( 14C age=5260±30 BP, Albic Podzols). Post-uprooting pedogenesis was most rapid in pits and slowest on mounds. Linear chronofunction models were the most applicable for pedogenesis, regardless of whether the soils were in pit or mound microsites. These models allowed us to estimate the time required for horizons in such disturbed sites to obtain the equivalent thicknesses of those in undisturbed sites. These ranged from 5 (O horizon in pits on the Haplic Cambisols) to >16 000 years (E horizon on mounds on the Albic Podzols). On the Albic Podzols, development of eluvial and spodic horizon thicknesses suggested that pathways involving divergent pedogenesis may occur at these small and localized spatial scales.