Consequence of litter removal on pedogenesis: A case study in Bachs and Irchel (Switzerland)

Abstract

In forests, soils contain at least twice as much carbon than plants that mostly grow in the upper layers. Litter at the interface between soils and the atmosphere regulates a variety of biogeochemical cycles, which are important for both plants and soils and have possible implications for other environmental components. We have compared leachates collected during an incubation experiment on: a) two deciduous leaves; b) organic and mineral horizons; c) treated with litter removal (and untreated) plots, to assess the changes in the chemical composition of the litter layers and leachates during weathering and their influence on the underlying horizons. Two different types of broadleaves - beech and oak - become indistinguishable when they experience weathering. As a litter horizon is altered, it becomes more stable and loses fewer elements, both in gaseous and liquid forms. The annual removal of litter represents a net loss of biomass from the system. Nevertheless, the effect on soil in the medium term is not significant. Leaves and litter horizons were incubated in micro-lysimeters, leached, and characterised by different analytical approaches, from elementary analyses (dissolved organic carbon, CO2 production, nitrogen forms, UV absorptivity) to solid state NMR spectroscopy. The results reveal that the removal of the litter does not degrade the underlying soils, in direct contrast to what was thought to be the case previously. Moreover, it extends previous knowledge that litter removal promotes an increase in fulvic acid activity in underlying horizons. The results demonstrate how this human disturbance, if not combined with other degradation factors, could promote podzolisation. In a wider outlook, if managed properly (for example, by burying litter removed after its use in animal husbandry), even the repeated removal of forest biomass contribute not negatively to the genesis of these soils.